Pipes, Pipe Fittings, and Piping Details

Pipes are available in a variety of materials, sizes, and weights. The type selected for a particular installation will depend on a number of factors, including government codes and standards, specifica­tions, system requirements, availability of materials, and cost. Some of these factors, such as codes and standards, will have priorities over others, but all should be given equal consideration before deciding which pipe to use. The purpose of this chapter is to offer some guidance for making these decisions.

Types of Pipe Materials

The materials used in the manufacture of piping and tubing for steam and hydronic heating systems include the following:

• Wrought iron

• Wrought steel

• Galvanized steel

• Copper, brass, and bronze Plastic

Synthetic rubber Composites

Steel piping leads in popularity and is available in the form of either wrought steel or galvanized steel. Wrought-iron and cast-iron pipe are also used, but less frequently because of their higher cost. Copper and brass are employed in the manufacture of both pipes and tubes and find their greatest application in radiant panel heat­ing, air-conditioning, and refrigeration systems. Other metals (for example, aluminum, bronze, and alloy metals) have also been used in the manufacture of this pipe, but with limited application due to cost, lack of availability, and other factors. In addition to steel and copper tubing, modern hydronic heating systems also commonly use plastic tubing (cross-linked polyethylene or polybutylene), synthetic rubber hose, and composite tubing.

Note

The terms pipe or piping and tube or tubing are sometimes used interchangeably, especially when referring to the piping/tubing systems of hydronic radiant panel heating systems. See Copper and Brass Piping and Tubing in this chapter.

This chapter concentrates on a description of iron, steel, copper, and brass pipes; the various types of nonmetal tubing; the pipe fit­tings used with them; and the methods employed in installing them.

Wrought-Iron Pipe

Wrought-iron pipe enjoyed widespread use in steam heating systems prior to World War II and was still being used, although on a much smaller scale, until 1968 when its production was discontinued in the United States.

Wrought-iron pipe has been shown to have an extremely long service life. Piping systems installed 50 to 80 years ago are still operating without any signs of deterioration. This is due not only to the internal grain structure of wrought-iron pipe, but also to its high resistance to corrosion.

Note

Some ferrous metals, such as black iron (ordinary steel), are subject to corrosion if oxygen is allowed to enter the pipes. Certain types of cast-iron pipe fittings, as well as some valves and fittings, are also sub­ject to corrosion if oxygen is present. The corrosion is irreversible.

Wrought-iron pipe differs very little in appearance from wrought — steel pipe. Indeed, were it not for special markings, the casual observer would not be able to distinguish between the two. Some wrought-iron pipe is stamped genuine wrought iron ’’on each length. More frequently, the distinguishing mark is a spiral line marked into each length of pipe. The spiral identification line may be painted onto the surface in some bright color (usually red) or knurled into the metal.

The pipe used in heating installations is manufactured for differ­ent pressures and is available in various rated sizes (also referred to as the nominal inside diameter). The three grades of wrought-iron pipe are as follows:

Standard

Extra strong (or heavy)

Double extra strong (or very heavy)

SIZE

STANDARD

EXTRA STRONG

DOUBLE EXTRA STRONG

12

O

O

O

34

1

O

O

O

P

O

O

Figure 8-1 Three sizes of standard, extra-strong, and double — extra-strong wrought pipe.

The pipe sections shown in Figure 8-1 are approximately half their actual size. Figure 8-2 illustrates their actual sizes, showing proportions of the three grades of wrought pipes.

The diameters given for pipes are far from the actual diameters, especially in the small sizes. Thus, a pipe known as Vi inch (rated size) has an outside diameter of 0.54 inch and an inside diameter of 0.364 inch. Dimensions for standard, extra-strong, and double — extra-strong pipe are given in Tables 8-1, 8-2, and 8-3.

Wrought-iron pipes are adapted to higher pressures by making the walls thicker, but without changing the outside diameters. It is the inside diameter that is reduced.

Pipes, Pipe Fittings, and Piping Details

358

подпись: 358

Nominal Weight per Foot Threaded and

подпись: nominal weight per foot threaded and

Nominal

подпись: nominalDiameter Nominal

Vs

0.405

0.269

0.068

0.245

Y4

0.540

0.364

0.088

0.425

Vs

0.675

0.493

0.091

0.568

V2

0.840

0.622

0.109

0.852

3/4

1.050

0.824

0.113

1.134

1

1.315

1.049

0.133

1.684

1V4

1.660

1.380

0.140

2.281

1V2

1.900

1.610

0.145

2.731

2

2.375

2.067

0.154

3.678

2Vi

2.875

2.469

0.203

5.819

3

3.500

3.068

0.216

7.616

3V2

4.000

3.548

0.226

9.202

4

4.500

4.026

0.237

10.889

5

5.563

5.047

0.258

14.810

6

6.625

6.065

0.280

19.185

Size External Internal

(in) (in) (in)

Thickness Coupled (in) (lbs)

Transverse Area

External

Internal

(in2)

(in2)

0.129

0.057

0.229

0.104

0.358

0.191

0.554

0.304

0.866

0.533

1.358

0.864

2.164

1.495

2.835

2.036

4.430

3.355

6.492

4.788

9.621

7.393

12.566

9.886

15.904

12.730

24.306

20.006

34.472

28.891

Length of Pipe per Square Foot

External

Surface

(ft)

Internal

Surface

(ft)

9.431

14.199

7.073

10.493

5.658

7.748

4.547

6.141

3.637

4.635

2.904

3.641

2.301

2.768

2.010

2.372

1.608

1.847

1.328

1.547

1.091

1.245

0.954

1.076

0.848

0.948

0.686

0.756

0.576

0.629

Length of Pipe

Containing

I Cubic Number of

Foot Threads

(ft) per Inch

2533.775

27

1383.789

18

754.360

18

473.906

14

270.034

14

166.618

HVi

96.275

IIV2

70.733

IIV2

42.913

IIV2

30.077

8

19.479

8

14.565

8

11.312

8

7.198

8

4.984

8

8

8.625

8.071

0.277

25.000

8

8.625

7.981

0.322

28.809

10

10.750

10.192

0.279

32.000

10

10.750

10.136

0.307

35.000

10

10.750

10.020

0.365

41.132

12

12.750

12.090

0.330

45.000

12

12.750

12.000

0.375

50.706

14

15.000

14.250

0.375

60.375

17

17.000

16.214

0.393

72.602

18

18.000

17.182

0.409

80.482

20

20.000

19.182

0.409

89.617

359

подпись: 359

58.426

51.161

0.442

0.473

2.815

8

58.426

50.027

0.442

0.478

2.878

8

90.763

81.585

0.355

0.374

1.765

8

90.763

80.691

0.355

0.376

1.785

8

90.763

78.855

0.355

0.381

1.826

8

127.676

114.800

0.299

0.315

1.254

8

127.676

113.097

0.299

0.318

1.273

8

176.715

159.485

0.254

0.268

0.903

8

226.980

206.476

0.224

0.235

0.697

8

254.469

231.866

0.212

0.222

0.621

8

314.159

288.986

0.190

0.199

0.498

8

Table 8-2

360

подпись: 360Diameter Nominal

Size External Internal

(in) (in) (in)

Vs

0.405

0.215

0.095

Y4

0.540

0.320

0.119

Vs

0.675

0.423

0.126

V2

0.840

0.546

0.147

3/4

1.050

0.742

0.154

1

1.315

0.957

0.179

1V4

1.660

1.278

0.191

1V2

1.900

1.500

0.200

2

2.375

1.939

0.218

2V2

2.875

2.323

0.276

3

3.500

2.900

0.300

3X/2

4.000

3.364

0.318

Dimensions of Extra-Strong Pipe

Weight Nominal per Foot Plain

Length of Pipe per Square Foot

Length of Pipe

Containing 1 Cubic

Transverse Area

External

Internal

Ends

External

Internal

Surface

Surface

Foot

(lbs)

On2)

(in2)

(ft)

(ft)

(ft)

0.314

0.129

0.036

9.431

17.766

3966.393

0.535

0.229

0.072

7.073

12.648

2010.290

0.738

0.358

0.141

5.658

9.030

1024.689

1.087

0.554

0.234

4.547

6.995

615.017

1.473

0.866

0.433

3.637

5.147

333.016

2.171

1.358

0.719

2.904

3.991

200.198

2.996

2.164

1.283

2.301

2.988

112.256

3.631

2.835

1.767

2.010

2.546

81.487

5.022

4.430

2.953

1.608

1.969

48.766

7.661

6.492

4.238

1.328

1.644

33.976

10.252

9.621

6.605

1.091

1.317

21.801

12.505

12.566

8.888

0.954

1.135

16.202

4

4.500

3.826

0.337

14.983

5

5.563

4.813

0.375

20.778

6

6.625

5.761

0.432

28.573

8

8.625

7.625

0.500

43.388

10

10.750

9.750

0.500

54.735

12

12.750

11.750

0.500

65.415

W

O>

подпись: w
o>

15.904

11.497

0.848

0.998

12.525

24.306

18.194

0.686

0.793

7.915

34.472

26.067

0.576

0.663

5.524

58.426

45.663

0.442

0.500

3.154

90.063

74.662

0.355

0.391

1.929

[27.676

108.434

0.299

0.325

1.328

Nominal

Size

(in)

Diameter

Nominal

Thickness

(in)

Nominal

Weight

Per Foot

Plain

Ends

(lbs)

Transverse Area

Length of Pipe per Square Foot

Length of Pipe

Containing 1 Cubic Foot (ft)

External

Surface

(ft)

Internal

Surface

(ft)

External

(in)

Internal

(in)

External

(in2)

Internal

(in2)

0.840

0.252

0.294

1.714

0.554

0.050

4.547

15.157

2887.165

3/4

1.050

0.434

0.308

2.440

0.866

0.148

3.637

8.801

973.404

1

1.315

0.599

0.358

3.659

1.358

0.282

2.904

6.376

510.998

M

1.660

0.896

0.382

5.214

2.164

0.630

2.301

4.263

228.379

11/2

1.900

1.100

0.400

6.408

2.835

0.950

2.010

3.472

151.526

2

2.375

1.503

0.436

9.029

4.430

1.774

1.608

2.541

81.162

21/2

2.875

1.771

0.552

13.695

6.492

2.464

1.328

2.156

58.457

3

3.500

2.300

0.600

18.583

9.621

4.155

1.091

1.660

34.659

4

4.500

3.152

0.674

27.541

15.904

7.803

0.848

1.211

18.454

5

5.563

4.063

0.750

38.552

24.306

12.966

0.686

0.940

11.107

6

6.625

4.897

0.864

53.160

34.472

18.835

0.576

0.780

7.646

8

8.625

6.875

0.875

72.424

58.426

37.122

0.443

0.555

3.879

362

подпись: 362

Wrought-Steel Pipe

Wrought-steel pipe is cheaper than wrought-iron pipe and conse­quently is used more widely in heating, ventilating, and air-condi­tioning than the latter. Depending on the method of manufacture, wrought-steel pipe is available as either welded pipe or seamless pipe. Seamless wrought-steel pipe finds frequent application in high-pressure work.

The wall thickness and weights of wrought-steel pipe are approximately the same as those for wrought-iron pipe. As with wrought-iron pipe, the two most commonly used weights are stan­dard and extra strong. Theoretical bursting and working pressures for wrought-steel pipe are listed in Table 8-4.

In some systems, steel piping has lasted as long as 80 years without showing signs of deterioration. When installed properly, steel pip­ing and tubing are not subject to leakage. Most problems with floor systems occur with steel pipe or tubing installed in a single-pour slab. The stresses that can develop in this type of construction can sometimes damage the pipes or tubing in the radiant floor panels. This does not seem to be the case if the pipes or tubing is installed between the two sections of a two-pour slab or above a concrete slab and beneath a wood floor.

Armco plastic-coated steel, cold-rolled or extruded steel, and stainless steel are among the types of steels currently used in the manufacture of tubing for hydronic heating systems.

Galvanized Pipe

Galvanized steel or iron pipe is covered with a protective coating to resist corrosion. This type of pipe is often used underground or in other areas subject to corrosion. The coating is not permanent, and care should be used when handling it to avoid nicks and scratches. If the surface coating is broken, corrosion will begin that much sooner. Galvanized pipe is cheaper than copper pipe but more expensive than either wrought-iron or wrought-steel pipe.

Caution

Galvanized pipe and galvanized fittings are not recommended for use in steam heating systems.

Copper and Brass Pipes and Tubing

Copper and brass are used in the manufacture of both pipes and tubes and find their greatest application in air-conditioning, refrig­eration, and hydronic radiant floor heating systems. One major advantage of using copper or brass is that both metals are corrosion resistant.

Table 8-4 Wrought-Steel PipeTheor etical Bursting and Working Pressures (pounds per square inch)*

Double Extra

Large O. D.

Standard

Extra Strong

Strong

Bursting

Working

Bursting

Working

Bursting

Working

Thick Bursting

Working

Thick Bursting

Working

Pressure

Pressure

Pressure

Pressure

Pressure

Pressure

Pressure

Pressure

Pressure

Pressure

Size

Size

Barlow’s

Barlow’s

Barlow’s

Barlow’s

Barlow’s

(in)

(mm)

Formula

Factor 8

Formula

Factor 8

Formula

Factor 8

Formula

Factor 8

Formula

Factor 8

364

подпись: 364

Vs

3

13,432

1679

18,760

2345

1/4

6

13,032

1629

17,624

2204

3/s

10

10,784

1348

14,928

1866

1/2

13

10,384

1298

14,000

1750

28,000

3500

3/4

19

8,608

1076

11,728

1466

23,464

2933

1

25

8,088

1011

10,888

1361

21,776

2722

114

32

6,744

843

9,200

1150

18,408

2301

11/2

38

6,104

763

8,416

1052

16,840

2105

2

50

5,184

648

7,336

917

14,680

1835

212

64

5,648

706

7,680

960

15,360

1920

3

76

4,936

617

6,856

857

13,714

1714

312

90

5,610

701

7,950

994

15,900

1987

4

100

5,266

658

7,480

935

14,970

1871

412

113

4,940

618

7,100

887

14,200

1775

5

125

4,630

579

6,740

842

13,480

1685

6

150

4,220

528

6,520

815

13,040

1630

7

175

3,940

493

6,550

819

11,470

1434

8

200

3,730

466

5,780

722

10,140

1267

9

225

3,550

444

5,190

649

10

300

3,390

424

4,650

581

12

300

2,940

368

3,920

490

14

350

2,680

335

3,570

446

15

375

2,500

313

3,333

417

16

400

2,340

293

3,120

390

18

450

2,080

260

2,770

346

20

500

1,870

234

2,500

313

22

550

1,700

213

2,270

284

24

600

1,560

195

2,080

260

*Butt-welded pipe was figured on sizes 3 inches and smaller and lap-welded pipe on sizes 3 !/2 inches and larger.

365

подпись: 365

Sometimes the terms copper tube and copper pipe are used inter­changeably as if they were synonymous. Another semantic idiosyn­crasy is to refer to the same product as tube or tubing when still on the inventory at the supply house, but as pipe or piping when installed. Both usages can be confusing because there are differences between the two. For example, copper pipe is often made thicker than tubing because it can be used with threaded fittings if soldering is not desired for making the joint connection. Another point to remember is that copper pipes have the same outside diameters as standard steel pipes. Copper tubing, on the other hand, is standardized on the basis of use into three standard wall-thickness schedules (see Table 8-5): (1) Type K, (2) Type L, and (3) Type M. Type L and Type M are used in heat­ing, ventilating, and air-conditioning systems.

Copper tubing is available as hard-grained (drawn) copper tubes or soft (annealed) copper tubes. The former is subject to freezing, which can cause the tubes to twist in almost the same way as steel pipes. On the other hand, the stiffness of hard-grained copper tubes enables them to hold their shape better than the softer ones. They are, therefore, often used for exposed lines such as mains hung from the ceiling.

The soft-tempered Type L copper tubing is recommended for hydronic radiant heating panels. Because of the relative ease with which soft copper tubes can be bent and shaped, they are espe­cially well adapted for making connections around furnaces, boil­ers, oil-burning equipment, and other obstructions. This high workability characteristic of copper tubing also results in reduced installation time and lower installation costs. Copper tubing is produced in diameters ranging from V8 inch to 10 inches and in a variety of different wall thicknesses. Both copper and brass fittings are available. Hydronic heating systems use small tube sizes joined by soldering.

The DIN Rating System

Oxygen from the outside air can permeate the tubing material and enter the hydronic system where it will corrode iron and steel com­ponents (boiler, fittings, valves, and so on). In the early 1990s, American tubing manufacturers decided to adopt the German DIN Standard 4726 as a uniform rating system. DIN stands for Deutsche (German) Industry Norm. The DIN Standard 4726 requires that hydronic systems not permit the entry of more than one-tenth of a milligram of oxygen per liter of water per day when the water is 104°F (40°C). All of the tubing used in hydronic heating systems must meet this standard.

Pipes, Pipe Fittings, and Piping Details 367 Table 8-5 Sizes and Dimensions of Copper Water Tubes

For General

For

Plumbing and

Underground

House Heating

Services and

For General

Purposes, with

General

Plumbing and

Normal Water

Plumbing

House Heating

Conditions.

Purposes, Used

Purposes, Used

Used with

With Solder or

With Solder or

Solder Fittings

Flared Fittings

Fittings

Only

Type Hard or

Type Hard or

Type Hard

Sizes

K

Soft

L

Soft

M

Nominal Size (in)

Outside

Diameter

(in)

Wall

Thick­

Ness

Pounds

Per

Foot

Wall

Thick­

Ness

Pounds

Per

Foot

Wall

Thick­

Ness

Pounds

Per

Foot

Vs

0.250

0.032

0.085

0.025

0.068

0.025

0.068

1/4

0.375

0.032

0.133

0.030

0.126

0.025

0.106

3/s

0.500

0.049

0.269

0.035

0.198

0.025

0.144

1/2

0.625

0.049

0.344

0.040

0.285

0.028

0.203

5/s

0.750

0.049

0.418

0.042

0.362

0.030

0.263

3/4

0.s75

0.065

0.641

0.045

0.455

0.032

0.328

1

1.125

0.065

0.839

0.050

0.655

0.035

0.464

11/4

1.375

0.065

1.04

0.055

0.884

0.042

0.681

11/2

1.625

0.072

1.36

0.060

1.14

0.049

0.94

2

2.125

0.0s3

2.06

0.070

1.75

0.058

1.46

212

2.625

0.095

2.92

0.080

2.48

0.065

2.03

3

3.125

0.109

4.00

0.090

3.33

0.072

2.68

31/2

3.625

0.109

5.12

0.100

4.29

0.083

3.58

4

4.125

0.134

6.51

0.110

5.38

0.095

4.66

5

5.125

0.160

9.67

0.125

7.61

0.109

6.66

6

6.125

0.192

13.87

0.140

10.20

0.122

8.91

S

S.125

0.271

25.90

0.200

19.29

0.170

16.46

10

10.125

0.33s

40.26

0.250

30.04

0.212

25.57

12

12.125

0.405

57.76

0.280

40.36

0.254

36.69

Plastic Tubing

Both cross-linked polyethylene tubing and polybutylene tubing are used in modern hydronic radiant panel heating systems. The former is by far the more popular of the two. The tubing is available in coils.

Some plastic tubing may become hardened and brittle after long use. If the tubing is then subjected to sudden unusual high pressures,

Such as those caused by boiler, valve, or other system component failures, cracks form and leakage occurs. Long cracks or fractures along a tubing circuit are not considered repairable to code.

Normal temperature differences in a hydronic system will cause the plastic tubing to expand and contract. This expansion and con­traction over a long period of time eventually causes cracks or frac­tures to develop in the tubing, especially if it is already weakened by age or other factors. Expansion and contraction at the joints and connections between the tubing and the system boiler and mani­folds may also cause leakage.

Cross-Linked Polyethylene Tubing

Cross-linked polyethylene (PEX) tubing is commonly used indoors in hydronic radiant heating panels or outdoors embedded beneath the surface of driveways, sidewalks, and patios to melt snow and ice. It is made of a high-density polyethylene plastic that has been subjected to a cross-linking process. It is flexible, durable, and easy to install. There are two types of PEX tubing:

Oxygen barrier tubing Nonbarrier tubing

Oxygen barrier tubing (BPEX) is treated with an oxygen barrier coating (EVOH) to prevent oxygen from passing through the tubing wall. It is designed specifically to prevent corrosion to any ferrous fittings or valves in the piping system. BPEX tubing is recommended for use in hydronic radiant heating system.

Nonbarrier tubing should be used in a hydronic radiant heating system only if it can be isolated from the ferrous components by a corrosion-resistant heat exchanger, or if only corrosion-resistant system components (boiler, valves, and fittings) are used.

PEX tubing is easy to install. Its flexibility allows the installer to bend it around obstructions and into narrow spaces. A rigid plastic cutter tool, or a copper tubing cutter equipped with a plastic cut­ting wheel, should be used to cut and install PEX tubing. Both tools produce a square cut without burrs.

Caution

PEX tubing is not resistant to ultraviolet (UV) rays. It should not be allowed to remain unprotected outdoors for long periods of time.

Polybutylene Tubing

Polybutylene tubing is offered in diameters and lengths comparable to PEX tubing but is more expensive, less durable, and not as easy to install.

Synthetic Rubber Hose

Synthetic rubber hose is very flexible and highly temperature resis­tant, but it is less durable than PEX tubing and has a low pressure rating. A number of different rubbers have been used to produce synthetic rubber hose for use in hydronic systems. Cross-linked EPDM is one of the most popular types.

Composite Tubing

Some manufacturers are producing composite tubing for hydronic heating systems. Composite construction commonly involves the combination of aluminum sandwiched between layers of plastic (PEX) or synthetic rubber.

PAX tubing is a typical three-layer composite tubing consisting of an inner layer of PEX tubing, a middle layer of aluminum, and an outer layer of PEX tubing. The aluminum middle layer, which provides an effective barrier to oxygen penetration through the tub­ing walls, is bonded to the inner PEX layer. PEX tubing is very flex­ible and, because of its aluminum middle layer, will retain its shape after bending much more easily than standard PEX tubing or BPEX tubing. PAX tubing is recommended for use in hydronic floor panel heating systems.

Brass tube and brass pipe should also be distinguished from one another. Brass tubing is generally manufactured from yellow brass (about 65 percent copper, 35 percent zinc). Brass piping is more frequently a red brass (about 85 percent copper, 15 percent zinc) and is much stronger than the tubing. As a result, brass pipe is sometimes used in heating, ventilating, and air-conditioning sys­tems, particularly when it is necessary to use a pipe material that strongly resists corrosion.

Pipe Fittings

Pipe cannot be obtained in unlimited lengths. In most pipe installa­tions, it is frequently necessary to join together two or more shorter lengths of pipe in order to create the longer one required by the blueprints. Furthermore, in practically all pipe installations there are numerous changes in directions and branches that require join­ing the pipes together in special arrangements. Pipe fittings have been devised for the necessary connections.

A pipe fitting may therefore be defined as any piece attached to pipes in order to lengthen a pipe, to alter its direction, to connect a branch to a main, to connect two pipes of different sizes, or to close an end.

Classification of Pipe Fittings

The pipe fittings used in heating, ventilating, and air-conditioning installations are most commonly either screwed or flanged types. Screwed pipe fittings use a male and female thread combination, which tightens together to form the joint. Screwed pipe fittings are designated as either male or female, depending on the location of the thread. A female thread is an internal thread, and a male thread is an external one.

A flanged pipe fitting has a lip or extension projecting at a right angle to its surface. This lip is bolted to the facing lip of the adja­cent fitting for additional strength. As a result, flanged fittings are generally recommended for 4-inch pipe and above.

Screwed and flanged pipe fittings are used to make temporary joints. If soldering, brazing, or welding is used in joining the sepa­rate lengths of pipe, the joint is considered a permanent one. The advantage of a so-called temporary joint is that it can be easily dis­assembled for repair.

The great multiplicity of pipe fittings can be divided on the basis of their functions into the following six general classes:

Extension or joining fittings

• Reducing or enlarging fittings

• Directional fittings Branching fittings

• Union or makeup fittings Shutoff or closing fittings

Extension or Joining Fittings

Nipples, locknuts, couplings, offsets, joints, and unions are all examples of extension or joining fittings. With the possible excep­tion of an offset, these fittings are designed to join and extend (but not change the direction of) a length of pipe. An offset is used to reposition a length of piping so that it is parallel but not in align­ment with another section of its length. The offset itself constitutes a change of direction; however, its function is to create a piping run parallel but not in alignment with the rest of its length.

Nipples

Nipples are classified as close, short, or long (see Figure 8-3). Standard lengths of nipples are listed in Table 8-6. The length of close nipples varies with the pipe size, it being determined by the length of thread necessary to make a satisfactory joint. There is one length of

A

/«1 111,1,1m 1UW

LONG NIPPLE

подпись: 
long nipple

CLOSE NIPPLE

подпись: close nipple
 
Pipes, Pipe Fittings, and Piping Details

RIGHT — AND LEFT-HAND CENTER NIPPLE

подпись: right- and left-hand center nippleSHORT NIPPLE

Pipes, Pipe Fittings, and Piping Details

THREADED END

подпись: threaded end‘ V w

SHOULDER END GASKET UNION SCREW RING

GOOD ALIGNMENT

подпись: 
good alignment
GASKET

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

GROUND-JOINT UNION

подпись: ground-joint unionBAD ALIGNMENT j

Pipes, Pipe Fittings, and Piping Details

Figure 8-3 Various pipe fittings used in heating and air-conditioning installations.

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

BLIND VARIOUS FLANGES

Figure 8-3 (Continued)

Pipes, Pipe Fittings, and Piping DetailsShort nipple for each size of pipe. Long nipples are made in many lengths up to 12 inches. Anything over 12 inches is known as cut pipe.

Locknuts

Locknuts are commonly used on long screw nipples that have cou­plings (see Figure 8-3). A recessed or grooved end on the locknut fitting is used to hold packing when a particularly tight joint is required. If at all possible, a union is preferred to a locknut because a much tighter joint is obtained.

The standard length for all sizes of locknut (or tank nipples) is 6 inches. They are made from standard-weight pipe threaded (for lock — nut) 4 inches long on one end and with regular pipe thread on the other. Tank nipples longer than 6 inches are made-to-order only.

Couplings

A coupling is a pipe fitting used to couple or connect two lengths of pipe. They are available in numerous sizes and types. The standard coupling (see Figure 8-3) is threaded with right-hand threads. Others are available with both right-hand and left-hand threads. The exten­sion piece coupling illustrated in Figure 8-3 has a male thread at one end. Couplings used as reducers (see Figure 8-3) are also common.

Offsets

An offset fitting (see Figure 8-3) is used when it is necessary to pass the pipeline around an obstruction that blocks its path. The new path will be parallel to the old one, but not aligned with it.

Joints

A joint (also referred to as an expansion joint or bend) is a pipe fit­ting designed to accommodate the linear expansion and contraction of the pipe metal caused by the temperature differences between the water or steam inside the pipe and the air on the outside of it. The

Size (in)

Standard Black, Right Hand

Kind of Nipples

V8 to V2

Close, short, then by

Vi-inch lengths from 2

Inches long to 6 inches long

Then by

1-inch lengths from 6

Inches long to 12 inches long

% and 1

Close, short, then by

V2-inch lengths from 2V2

Inches long to 6 inches long

Then by

1-inch lengths from 6

Inches long to 12 inches long

LVito 2

Close, short, then by

V2-inch lengths from 3

Inches long to 6 inches long

Then by

1-inch lengths from 6

Inches long to 12 inches long

21/2 and 3

Close, short, then by

V2-inch lengths from 3V2

Inches long to 6 inches long

Then by

1-inch lengths from 6

Inches long to 12 inches long

3V/2 and 4

Close, short, then by

V2-inch lengths from 4V2

Inches long to 6 inches long

Then by

1-inch lengths from 6

Inches long to 12 inches long

5 and 6

Close, short, then by

V2-inch lengths from 5

Inches long to 6 inches long

Then by

1-inch lengths from 6

Inches long to 12 inches long

8

Close, short, then by

V2-inch lengths from 5V2

Inches long to 6 inches long

Then by

1-inch lengths from 6

Inches long to 12 inches long

10 and 12

Close, short, then by

1-inch lengths from 8

Inches long to 12 inches long

376

подпись: 376

Up to and including 8-inch size, same lengths as black, right hand

Standard Black, Right and Left Hand

Up to and including 4-inch size, same lengths as black, right hand

Extra Strong Black, Right Hand

377

подпись: 377Up to and including 2-inch size, same lengths as standard, black, right hand

Amount of expansion or contraction at different temperatures for a variety of metals used in steam pipes is listed in Table 8-7.

Unions

A union is another form of extension fitting used to join two pipes. The two most common types of unions are (1) the ground-joint union and (2) the plain or gasket union.

A ground-joint union (see Figure 8-3) consists of a composition ring pressing against iron or both contact surfaces of composition. A joint using a ground-joint union is characterized by spherical contact. Because no gasket is used, perfect alignment of the two pipes is not as important in making up the joint as it is when a plain or gasket union is used.

A disassembled plain or gasket union fitting is shown in Figure 8-3. It consists of three basic parts and a gasket. In assembling, the gas­ket (A) is placed over the projection on the shoulder so that it is in contact with its surface (B). The ring is slipped over the shoulder end and the threaded end placed in position so that the flat surface (C) of the threaded end presses against the gasket. The ring is then screwed firmly into the threaded end. Since the shoulder on the shoulder end cannot back off the ring, the two ends are pressed firmly together against the gasket by the ring, thus securing a tight joint.

The limitations of the plain or gasket union are also illustrated in Figure 8-3. The alignment must be good to secure a tight joint. In the illustration, the ring section is omitted for clearness. If both ends are in line and firmly pressed together against the gasket by the ring, the gasket will bear evenly over the entire contact surface and the joint will be tight. If the two ends are out of alignment when the ring is screwed tight, it will bring great pressure on the gasket at point A, and the surfaces will not come together at the opposite point B, thus causing a leak.

Reducing or Enlarging Fittings

Both bushings and reducers are examples of reducing or enlarging fittings. Their function in pipe installations is to connect pipes of different sizes.

Bushings and reducers may be distinguished by their construc­tion. A reducer is a coupling device with female threads at both ends (see Figure 8-3). A bushing has both male and female threads.

A bushing (see Figure 8-3) is a pipe fitting designed in the form of a hollow plug, and it is used to connect the male thread of a pipe end to a fitting of larger size. Bushings are sold according to the pipe size of the male thread. Thus, a V4-inch bushing (or, more specifically, a

Table 8-7 Expansion of Pipe (Increase in Inches per 100 Feet)

Temperature

(°F)

Cast

Iron

Wrought

Iron

Steel

Brass

And

Copper

Temperature

(°F)

Cast

Iron

Wrought

Iron

Steel

Brass

And

Copper

0

0.00

0.00

0.00

0.00

450

3.89

4.28

4.08

6.18

50

0.36

0.40

0.38

0.57

475

4.20

4.62

4.41

6.68

100

0.72

0.79

0.76

1.14

500

4.45

4.90

4.67

7.06

125

0.88

0.97

0.92

1.40

525

4.75

5.22

4.99

7.55

150

1.10

1.21

1.15

1.75

550

5.05

5.55

5.30

8.03

175

1.28

1.41

1.34

2.04

575

5.36

5.90

5.63

8.52

200

1.50

1.65

1.57

2.38

600

5.70

6.26

5.98

9.06

225

1.70

1.87

1.78

2.70

625

6.05

6.65

6.35

9.62

250

1.90

2.09

1.99

3.02

650

6.40

7.05

6.71

10.18

275

2.15

2.36

2.26

3.42

675

6.78

7.46

7.12

10.78

300

2.35

2.58

2.47

3.74

700

7.15

7.86

7.50

11.37

325

2.60

2.86

2.73

4.13

725

7.58

8.33

7.96

12.06

350

2.80

3.08

2.94

4.45

750

7.96

8.75

8.36

12.66

375

3.15

3.46

3.31

5.01

775

8.42

9.26

8.84

13.38

400

3.30

3.63

3.46

5.24

800

8.87

9.76

9.31

14.10

425

3.68

4.05

3.86

5.85

Note: Expansion given is approximate but is correct to the best known information.

The linear expansion and contraction of pipe, due to difference of temperature of the fluid carried and the surrounding air must be cared for by suitable expansion joints or bends. In order to determine the amount of expansion or contraction in a pipeline, Table 8-8 shows the increase in length of a pipe 100 feet long at various temperatures.

The expansion for any length of pipe may be found by taking the difference in increased length at the minimum and maximum temperatures, dividing by 100, and multiplying by the length in feet of the line under consideration.

379

подпись: 379

V^inchXVs-inch bushing) is one used to connect a Vi-inch fitting to a Vs-inch pipe. This may be less confusing if you remember that a bush­ing has one male and one female thread and that the female thread of the bushing must be tightened into the male thread of the pipe end.

Ordinary bushings are sometimes used when a reducing fitting of proper size is unavailable. If the reduction is considerable, it may be necessary to use two bushings. A common application of eccentric bushings is to avoid water pockets on horizontal pipelines. This appli­cation is illustrated in Eliminating Water Pockets later in the chapter.

Directional Fittings

Directional fittings such as offsets, elbows, and return bends are used to change the direction of a pipe. Because of an overlap in function, offsets also may be considered to be a type of extension or joining fitting.

Elbows

An elbow (see Figure 8-3) is a pipe fitting used to change the direc­tion of a gas, water, or steam pipeline. Elbows are available in stan­dard angles of 45° and 90, or special angles of 22 V20 and 60° (see Figure 8-3).

Return Bends

A return bend (see Figure 8-3) is a U-shaped pipe fitting commonly used for making up pipe coils for both water and steam heating boilers. They are commonly available in three patterns (close, medium, and open) with female threads at both ends. It is impor­tant to know the dimensions between centers when making up heating coils in order to avoid possible interference.

Branching Fittings

As the name implies, a branching fitting is used to join a branch pipe to the main pipeline. The principal branching fittings used for this purpose are as follows:

Tees

Crosses

• Y branches

Elbows with side outlets

• Return bends with back or side outlets

Tees

Tees (see Figure 8-3) are made in a variety of sizes and patterns and represent the most widely used branch fitting. As the name suggests, a tee fitting is used for starting a branch pipe at a 90° angle to the main pipe.

A tee fitting is specified by first giving the run and then the branch. The run of a tee refers to its body with the outlets opposite each other (that is, at 180).

Tees are available with all three outlets the same size, with the branch outlet a size different from the two outlets of the run, or with all three outlets different sizes. Whatever the size configura­tion of outlets, the run is always specified first. Tee specifications generally take the following form:

• 1" (1-inch outlets on run and tee)

• 1" X V2" (1-inch outlets on run; V^-inch tee outlet)

• 1" X Vx (outlets of 1 inch and V2 inch on the run; y2-inch tee outlet)

Crosses

A cross fitting (see Figure 8-3) is simply a tee with two branch out­lets instead of one. The branch outlets are located directly opposite one another on the main pipe so that the fitting forms the shape of a cross (hence its name). Both branch outlets are always the same size, regardless of the size of the outlets.

Y Branches

A Ybranch (see Figure 8-3) is a pipe fitting with side outlets located at 45° or 60° angles to the main pipe. Y branches are available in a number of pipe sizes. They may be straight or reducing, and single — or double-branching.

Elbows with Side Outlets

An elbow with three outlets is classified as a branching rather than a directional fitting because the third outlet serves as the connection for a branch pipeline (see Figure 8-3). The branching outlet should be at a 90° angle to the plane of the elbow run.

Return Bends with Back or Side Outlets

An ordinary return bend is a U-shaped fitting with two outlets (see Figure 8-3). Some return bends are designed with three outlets, the third outlet being located on either the back or the side of the fitting and used for connecting to a branch pipeline. This type of return bend is more properly classified as a branching fitting.

Shutoff or Closing Fittings

Sometimes it is necessary to close the end of a fitting or pipe. This is accomplished with a shutoff or closing fitting, and the following two types are used for this purpose:

• Plugs

• Caps

Plugs

A plug (see Figure 8-3) is used to close the end of a pipe or fitting when it has a female thread. In other words, it is designed to be inserted into the end of the pipe or fitting. Plugs are made in a vari­ety of sizes (V8 inch to 12 inches), designs (hexagon, square head, or countersunk heads), and materials (for example, iron, brass).

Caps

A cap (see Figure 8-3) performs the same function as a plug except that it is used to close the end of a pipe or fitting that has a male thread. They are also available in a variety of sizes, designs, and materials.

Union or Makeup Fittings

Union or makeup fittings (see Figure 8-3) are represented by union elbows and union tees. This type of pipe fitting combines both a union and an elbow or tee in a single unit. They are available with female or both male and female threads.

Flanges

Flanges (see Figure 8-3) are pipe fittings used to close flanged pipelines or fittings. They are manufactured in the form of cast-iron discs and are available in many sizes, thicknesses, and types.

Pipe Expansion

The linear expansion and contraction of pipe due to the surround­ing air must be provided for (especially in the case of long lines) by suitable expansion joints, bends, or equivalent provisions.

In order to determine the amount of expansion or contraction in a pipeline, Table 8-8 shows the increase in length of a pipe 100 feet long at various temperatures.

The expansion for any length of pipe may be found by taking the difference in increased length at the minimum and maximum tem­peratures, dividing by 100, and multiplying by the length in feet of the line under consideration. See Table 8-8.

Expansion of Steam Pipes (Inches Increase per 100 Feet)

Steel

0

0.15

0.30

0.45

0.60

0.75

0.90

1.10

1.25

1.45 1.60 1.80 2.00 2.15 2.35 2.50

2.70

2.90 3.05

3.25

3.45

3.70

3.95

4.20

4.45

4.70

4.95

5.20

5.45

5.70 6.00 6.30 6.55

6.90

подпись: steel
0
0.15
0.30
0.45
0.60
0.75
0.90
1.10
1.25
1.45 1.60 1.80 2.00 2.15 2.35 2.50
2.70
2.90 3.05
3.25
3.45
3.70
3.95
4.20
4.45
4.70
4.95
5.20
5.45
5.70 6.00 6.30 6.55
6.90

Temperature

(°F)

0

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

540

560

580

600

620

640

660

Wrought Iron

0

0.15

0.30

0.45

0.60

0.80

0.95

1.15

1.35

1.50

1.65

1.85

2.5 2.20

2.40

2.60

2.80

3.05

3.25

3.45

3.65

3.90

4.20

4.45

4.70

4.90

5.15

5.40

5.70

6.00

6.25

6.55

6.85

7.20

Cast Iron

0

0.10

0.30

0.40

0.55

0.75

0.85

1.00

1.15

1.30

1.50

1.65

1.80

1.95

2.15

2.35

2.50

2.70

2.90 3.10

3.30

3.50

3.75

4.00

4.25

4.45

4.70

4.95

5.20

5.45

5.70

5.95

6.25

6.55

Brass and Copper

0

0.25

0.45

0.65

0.90

1.15

1.40

1.65

1.90

2.15

2.40

2.65

2.90

3.15

3.45

3.75

4.05

4.35

4.65

4.95

5.25

5.60

5.95

6.30

6.65

7.05

7.45

7.85

8.25

8.65

9.05

9.50

9.95

10.40

(continued)

Temperature

(°F)

Steel

Wrought Iron

Cast Iron

Brass and Copper

680

7.20

7.50

6.85

10.95

700

7.50

7.85

7.15

11.40

720

7.80

8.20

7.45

11.90

740

8.20

8.55

7.80

12.40

760

8.55

8.90

8.15

12.95

780

8.95

9.30

8.50

13.50

800

9.30

9.75

8.90

14.10

Valves

Some authorities regard a valve as simply another type of pipe fit­ting and distinguish it from others by its capacity to control the flow of steam or hot water through the pipe. Be that as it may, the subject of valves is so extensive that it warrants a chapter of its own (see Chapter 9 of Volume 2, V alves and Valve Installation)’.

Pipe Threads

The threads used on pipes are referred to as pipe threads. The dis­tinguishing characteristic of pipe threads is that they are tapered. This results in a greater number of turns when screwing the pipe to another length of pipe or pipe fitting. When properly done, this will result in a tight, leak-free joint. Care must be taken, however, not to exceed the elastic limit or the joint will leak.

The total taper used on pipe threads in % inch per foot. The total number of threads per inch will vary from 27 threads for V8-in pipe to 8 threads for 2y2-in pipe and larger sizes. Standard pipe threads are listed in Table 8-9.

Pipe Sizing

Pipe sizing refers to the procedure of determining the projected capacities of a piping installation and selecting the pipe sizes most capable of meeting these capacities. Most methods used for deter­mining pipe sizes are only approximate calculations, and they should be considered as such when you are using them.

Both the American Society of Heating, Refrigerating, and Air — Conditioning Engineers (ASHRAE) and the Institute of Boiler and Radiator Manufacturers (IBR) issue publications that contain consid­erable data for designing the piping arrangements of various steam and hot-water space heating systems. Manufacturers of proprietary heating systems, pipes, pipe fittings, and valves also provide data for sizing pipes and valves. Examples of these data are illustrated in Tables 8-10 and 8-11. Methods for pipe sizing are explained in detail with accompanying examples. These publications can be obtained by writing to these organizations. Their addresses are given elsewhere in this book. Sometimes copies are also available at a local library.

Because pipe sizing is specific to the piping arrangement and other variables within a system, no attempt is made in this chapter to cover the subject with the detail it requires. The basic principles of the methods used for sizing steam and hot-water heating pipes, along with recommendations for their application, are described in the sections that follow.

Sizing Steam Pipes

Many manufacturers of proprietary or patented steam heating sys­tems provide their own pipe-sizing schedules. For nonproprietary systems, the projected capacities of the piping installation must be determined by a number of sizing calculations.

The principal factors used in determining pipe sizes for a given load of steam in a heating system are the following:

Initial pressure

Total pressure drop allowed between the boiler and the end of the return line

Equivalent length of run from the boiler to the farthest radia­tor or convector

• Pressure drop per 100 feet of equivalent length

The total pressure drop should not exceed the initial gauge pres­sure of the system. As a general rule, it should not exceed 50 per­cent of the initial gauge pressure.

The equivalent length of run equals the actual measured length of pipe plus the equivalent straight pipe length of the fittings and valves. Table 8-12 lists equivalent lengths of the more common fittings and valves and is an example of the data provided by the ASHRAE for sizing pipes.

The pressure drop in pounds per square inch per 100 feet is determined by dividing 50 percent of the initial pressure by the equivalent length of the longest piping circuit.

For the sake of illustration, assume that you must calculate the pressure drop and determine the pipe size for a steam heating

A

B

E

F

G

H

P

Nominal

Pitch Dia. at

Pitch Dia. at

Length

Of

Normal Engagement by Hand Between Male and

Outside

Actual

Inside

Number

Of

Threads

Pitch

Depth

Size

End of

Gauging

Effective

Female

Dia. of

Dia. of

Per

Of

Of

Of Pipe

Pipe

Notch

Thread

Thread

Pipe

Pipe

Inch

Thread

Thread

(in)

(in)

(in)

(in)

(in)

(in)

(in)

(in)

(in)

Vs

0.36351

0.37476

0.2638

0.180

0.405

0.269

27

0.0370

0.02963

X/4

0.47739

0.48989

0.4018

0.200

0.540

0.364

18

0.0556

0.04444

3/s

0.61201

0.62701

0.4078

0.240

0.675

0.493

18

0.0556

0.04444

12

0.75843

0.77843

0.5337

0.320

0.840

0.622

14

0.0714

0.05714

3/4

0.06768

0.98886

0.5457

0.339

1.050

0.824

14

0.0714

0.05714

1

1.21363

1.23863

0.6828

0.400

1.315

1.049

11V2

0.0870

0.06954

L1/4

1.55713

1.58338

0.7068

0.420

1.660

1.380

11V2

0.0870

0.06954

11/2

1.79609

1.82234

0.7235

0.420

1.900

1.610

11V2

0.0870

0.06956

2

2.26902

2.29627

0.7565

0.436

2.375

2.067

111/2

0.0870

0.06956

2V2

2.71953

2.76216

1.1375

0.681

2.875

2.469

8

0.1250

0.10000

386

подпись: 386

3

3.34063

3.38850

1.2000

0.766

3V2

3.83750

3.88881

1.2500

0.821

4

4.33438

4.38713

1.3000

0.844

4V2

4.83125

4.88594

1.3500

0.875

5

5.39073

5.44929

1.4063

0.937

6

6.44609

6.50597

1.5125

0.958

7

7.43984

7.50234

1.6125

1.000

8

8.43359

8.50003

1.7125

1.063

9

9.42734

9.49797

1.8125

1.130

10

10.54531

10.62094

1.9250

1.210

12

12.53281

12.61781

2.1250

1.360

14 O. D.

13.77500

13.87262

2.250

1.562

15 O. D.

14.76875

14.87419

2.350

1.687

16 O. D.

15.76250

15.87575

2.450

1.812

18 O. D.

17.75000

17.87500

2.650

2.000

20 O. D.

19.73750

19.87031

2.850

2.125

22 O. D.

21.72500

21.86562

3.050

2.250

24 O. D.

23.71250

23.86094

3.250

2.375

Data abstracted from the American Standard for Pipe Threads A. SA.-B2—1919.

3.500

3.068

8

4.000

3.548

8

4.500

4.026

8

5.000

4.506

8

5.563

5.047

8

6.625

6.055

8

7.625

7.023

8

8.625

7.981

8

9.625

8.941

8

10.750

10.020

8

12.750

12.000

8

14.000

8

15.000

8

16.000

8

18.000

8

20.000

__

8

22.000

8

24.000

8

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0.1250 0.10000

0. 1250 0.10000

0. 1250 0.10000

0. 1250 0.10000

— IMPERFECT — THREAD DUE TO LEAD OF DIE

NORMAL ENGAGEMENT BY HAND BETWEEN MALE AND FEMALE THREAD

LENGTH OF EFFECTIVE THREADS ———————————— E—————————-

I

■3os,

Pipes, Pipe Fittings, and Piping Details

F

 

А

 

Pipes, Pipe Fittings, and Piping Details

TAPER 1 IN 16 MEASURED ON DIAMETER

 

.. p.

 

H

 

G

 

A

PITCH DIAMETER OF THREAD AT END OF PIPE

 

B

PITCH DIAMETER OF THREAD AT GAUGING NOTCH

 

PITCH

 

ACTUAL INSIDE DIAMETER

 

OUT SIDE DIAMETER OF PIPE

 

Pipes, Pipe Fittings, and Piping Details Pipes, Pipe Fittings, and Piping Details

A = G — (0.05 G + 1.1)P B = A + 0.0625 F E = P (0.8G + 6.8)

DEPTH OF THREAD = 0.8P TOTAL TAPER ^"-IN. PER FOOT

Illustration for Table 8-9.

System in which the initial pressure is 2 psig. In order to do this, the following steps are necessary:

Pipe

Size

(in)

Internal

Diameter

D

(in)

Pipe Size

In Inches

D5/‘

1 8

1 4

3 8

1 2

3 4

1

1 [3] 4

1 1 2

2

21 2

3

31 2

4

5

6

8

10

12

Vs

0.269

0.037530

1.0

V4

0.364

0.079938

2.1

1.0

3/8

0.493

0.17065

4.5

2.1

1.0

12

0.622

0.30512

8.1

3.8

1.8

1.0

3/4

0.824

0.61634

16

7.7

3.6

2.0

1.0

1

1.049

1.1270

30

14

6.6

3.7

3.7

1.0

1/4

1.380

2.2372

60

28

13

7.3

3.6

2.0

1.0

11/2

1.610

3.2890

88

41

19

11

5.3

2.9

1.5

1.0

2

2.067

6.1426

164

77

36

20

10

5.5

2.7

1.9

1.0

21/2

2.469

9.5786

255

120

56

31

16

8.5

4.3

2.9

1.6

1.0

3

3.068

16.487

439

206

97

54

27

15

7.4

5.0

2.7

1.7

1.0

31/2

3.548

23.711

632

297

139

78

38

21

11

7.2

3.9

2.5

1.4

1.0

4

4.026

32.523

867

407

191

107

53

29

15

9.9

5.3

3.4

2.0

1.4

1.0

5

5.047

57.225

1526

716

335

188

93

51

26

17

9.3

6.0

3.5

2.4

1.8

1.0

6

6.065

90.589

2414

1163

531

297

147

80

40

28

15

9.5

5.5

3.8

2.8

1.6

1.0

8

7.981

179.95

4795

2251

1054

590

292

160

80

55

29

19

11

7.6

5.5

3.1

2.0

1.0

10

10.020

317.81

8468

3976

1862

1042

516

282

142

97

52

33

19

13

9.8

5.6

3.5

1.8

1.0

12

12.000

498.83

13292

6240

2923

1635

809

443

223

152

81

52

30

21

15

8.7

5.5

2.8

1.6

1.0

The figure that lies at the intersection of any two sizes is the number of smaller-size pipes required to equal one of the larger. Example: How many 2-inch standard pipes will it take to equal the discharge of one 8-inch standard pipe? Solution:Twenty-nine 2-inch pipes; the figure in the table that lies at the intersection of these two sizes is 29.

389

подпись: 389

Table 8-11 Diagram Showing Resistance of Valves and Fittings of the Flow of Liquids

ORDINARY ENTRANCE

■ -45° ELBOW

48-

42-

36-

30

30

24—’

22

■20

20 — 1-—- 16 —

14

12

10

10

INSIDE DIAMETER, INCHES

9

8

SUDDEN ENLARGEMENT d/D-1/4 d/D-!/2

D/D-

7

6-

5

41/2

4

3

3

<

CD

<

21/2

2-1

2

SUDDEN CONTRACTION d/D-M d/D-V2 d/D-5’4

11/2

11/4

; 1000

-500

■ 300 — 200

100

LL

LL

■" 50 “

— Q

* Q

-30 h 20,

-10

-5 ;

. I

■3 ;

-2 ;

I

-■1

" 0.5

" 0.3 -0.2

-0.1

50

Example: The dotted line shows that the resistance of a 6-inch Standard Elbow is equivalent to approximately 16 feet of 6-inch Standard Pipe.

Note: For sudden enlargements or sudden contractions, use the smaller diameter, d, on the pipe size scale.

-3000 — 2000

 

подпись: inside diameter, inchesPipes, Pipe Fittings, and Piping Details

LONG SWEEP ELBOW OR RUN OF STANDARD TEE

 

Pipes, Pipe Fittings, and Piping Details

Table 8-12 Length of Pipe in Feet for Fittings to Be Added to Actual Length of Run in Order to Obtain Equivalent Length

Size of

Pipe

(in)

Length

In Feet to Be Added to Run

Standard

Elbow

Side

Outlet Tee

Gate Valve*

Globe Valve*

Valve*

12

1.3

3

0.3

14

7

3/4

1.8

4

0.4

18

10

1

2.2

5

0.5

23

12

L1/4

3.0

6

0.6

29

15

1V2

3.5

7

0.8

34

18

2

4.3

8

1.0

46

22

21/2

5.0

11

1.1

54

27

3

6.5

13

1.4

66

34

31/2

8

15

1.6

80

40

4

9

18

1.9

92

45

5

11

22

2.2

112

56

6

13

27

2.8

136

67

8

17

35

3.7

180

92

10

21

45

4.6

230

112

12

27

53

5.5

270

132

14

30

63

6.4

310

152

*Valve in full open position.

Example of length in

Feet of pipe to be added

MEASURED LENGTH = 132.0 FT.

To actual length of run.

4 IN. GATE VALVE = 1.9 FT.

— ——————- 132′-0» — — —

4-4 IN. ELBOWS = 36.0 FT.

—M———————————————— K

, EQUIVALENT LENGTH = 169. 9 FT. ‘ i

, 1

‘ X

6. Check the pressure drop by calculating the equivalent length of run of the longest circuit from the pipe sizes determined. The pipe size determined in step 5 will be correct if the calcu­lated pressure drop is less than the assumed pressure drop.

A steam supply main should not pitch less than Vi inch per 10 feet of run, and its diameter should not be smaller than 2 inches. In

Gravity one-pipe systems, the diameter of the supply main at the farthest point should not be smaller than 50 percent of its largest diameter.

A rule-of-thumb method for determining the size of steam mains is to take the total amount of direct radiation and add to it 25 per­cent of the total for the piping allowance. Next, find the square root of this total and divide by 10. The result will be the size steam main to use for a one-pipe system. For a two-pipe system, one size smaller is generally sufficient for the supply main, and the return can be one or two sizes smaller than the supply main. A steam main should not decrease in size according to the area of its branches but much more gradually.

The aforementioned method for sizing steam mains can be illus­trated by using a structure with an assumed direct radiation of 500 square feet. Adding 25 percent for piping allowance gives 625. The square root of 625 is 25, which divided by 10 gives 2V2, or the size of the steam main (2V2 inches). For reference and practical use, refer to Table 8-13 when making calculations.

The pitch of runouts to risers and radiators should be at least V2 inch per foot toward the main. Runouts over 8 feet in length but with less than Vi-inch pitch per foot should be one size larger than specified in the pipe-sizing tables.

Table 8-13 Size of Steam Mains

Radiation (ft2)

One-Pipe Work (in)

Two-Pipe Work (in)

125

11/2

114 X 1

250

212

11/2 X 114

400

3

2 X 1V2

650

3V2

2V2 X 2

900

4

3 X 212

1250

4V2

31/2 X 3

1600

5

4 X 3V2

2050

5V2

41/2 X 4

2500

6

5 X 41/2

3600

7

6 X 5

5000

8

7 X 6

6500

9

8 X 6

8100

10

9 X 6

Sizing Hot-Water (Hydronic) Pipes/Tubing

Simplified pipe-sizing tables for hot-water heating systems are also available from organizations such as the ASHRAE.

Pipe sizing hot-water lines is similar in some respects to the cal­culations used in duct sizing because the pipe sizes are selected on the basis of the quantity and rate of water flow (expressed in gal­lons per minute, or gpm) and the constant friction loss. This fric­tion loss (or drop) is expressed in thousandths-of-an-inch per foot of pipe length.

The velocity of water in the smaller residential pipes should not exceed 4 fps (feet per second), or there will be a noise problem.

In forced hot-water heating systems, the problem of friction drop in the pipes can be overcome by the pump or circulator. In this respect, a forced hot-water heating system is much easier to size than a steam heating system.

The rule-of-thumb method used to size steam mains (see previous section) can also be used to determine the approximate sizes of hot — water mains; however, certain important differences should be noted.

When sizing hot-water mains, the mains may be reduced in size in proportion to the branches taken off. They should, however, have as large an area as the sum of all branches beyond this point. It is advisable that the horizontal branches be one size larger than the ris­ers. Returns should be the same size as the supply mains. Table 8-14 lists sizes of hot-water mains and the equivalent radiation ranges in square feet. Sizes for mains and branches are given in Table 8-15.

Table 8-14

Sizes of Hot-Water Mains

Radiation (ft2)

Pipe (in)

75 to 125

114

125 to 175

11/2

175 to 300

2

300 to 475

21/2

475 to 700

3

700 to 950

31/2

950 to 1200

4

1200 to 1575

41/2

1575 to 1975

5

1975 to 2375

51/2

2375 to 2850

6

Main

подпись: mainBranch


1 inch will supply 1V4 inch will supply 1V2 inch will supply

2 inch will supply

2 V2 inch will supply

3 inch will supply 3V2 inch will supply

4 inch will supply 4V2 inch will supply

5 inch will supply

6 inch will supply

7 inch will supply

8 inch will supply

2, 3/4 inch 2, 1 inch 2, 1V4 inches 2, 1V2 inches

2, 1V2 inches and 1, 1V4 inches, or 1, 2 inches and 1, 1V4 inches

1, 2V2 inches and 1, 2 inches, or 2, 2 inches and 1, 1V2 inches

2, 2V2 inches or 1, 3 inches, and 1, 2 inches or 3, 2 inches

1, 3V2 inches and 1, 2V2 inches, or 2, 3 inches and 4, 2 inches 1, 3V2 inches and 1, 3 inches, or 1, 4 inches and 1, 2V2 inches 1, 4 inches and 1, 3 inches, or

1, 4V2 inches and 1, 2V2 inches

2, 4 inches and 1, 3 inches, or

4, 3 inches or 10, 2 inches

1, 6 inches and 1, 4 inches, or

3, 4 inches and 1, 2 inches

2, 6 inches and 1, 5 inches, or

5, 4 inches and 2, 2 inches

WIDTH OF ROOM 22 21 20 19 18 17 16 15 14 13 12 11

Pipes, Pipe Fittings, and Piping Details

YBRANCH

, * THREAD fi-. s

‘d3EngagemenT^;v,^|

SERVICE TEE CROSS

&A ^ Ja

10° ELBOW 45° ELBOW 90° STREET ELBOW45° STREET ELBO’" omw. nr-rrr

□W. Lui w ‘_j! j ‘

Pipes, Pipe Fittings, and Piping Details

FLAT BAND COUPLING

 

OPEN RETURN — FOR NORMAL THREAD

BEND ENGAGEMENT

 

CLOSE RETURN BEND

 

PLAIN

COUPLING

 

REDUCING

COUPLING

 

Pipes, Pipe Fittings, and Piping Details Pipes, Pipe Fittings, and Piping Details

Size (in)

подпись: size (in)General dimentions of Crane standard malleable iron screwed fittings. The reference letters refer to the accompanying table.

395

подпись: 395Dimensions (in)

Vs

“/16

3/4

1

7/8

11/16

31/32

14

13/16

3/4

13/16

15/16

11/4

11/16

11/16

3/8

15/16

13/16

17/16

11/32

11/4

11/16

123/32

215/32

15/32

V2

11/8

7/8

13/4

17/8

15/8

15/32

13/8

25/32

11/8

11/2

123/32

215/32

111/32

3/4

15/16

1

21/32

25/16

17/8

15/16

17/16

11/32

13/8

2

21/16

27/8

11/2

1

11/2

11/8

25/16

225/32

21/8

115/32

111/16

17/32

13/4

21/2

27/16

33/8

111/16

1V4

13/4

15/16

213/16

35/16

27/16

123/32

21/16

19/32

21/8

3

215/16

43/32

115/16

11/2

115/16

17/16

33/16

311/16

211/16

17/8

25/16

111/32

21/2

31/2

39/32

417/32

25/32

2

214

111/16

37/8

41/4

31/4

77/32

25/8

17/16

23/4

4

4I/32

517/32

217/32

21/2

211/16

115/16

55/32

4

31/16

2

41/2

43/4

61/2

27/8

3

31/16

23/16

513/16

411/16

39/16

21/8

5

511/16

73/4

31/2

31/2

327/32

219/32

4

23/16

4

313/16

25/8

615/16

511/16

43/8

25/16

6

615/16

9

45/16

5

51/2

31/16

615/16

51/8

217/32

6

51/8

315/32

57/8

211/16

General dimensions of Crane standard malleable iron screwed fittings.

DISTANCE CENTER TO FACE

-■bZ

72222m^2222222222222222222222222222222222222222222.

ACTUAL LENGTH OF PIPE D —

Pipes, Pipe Fittings, and Piping Details

…… c y ■

 

— ~1 C —

 

ALLOWANCE FOR THREADS

 

— —A— —■

DISTANCE BETWEEN CENTERS

 

Pipes, Pipe Fittings, and Piping Details Pipes, Pipe Fittings, and Piping Details

D = A — 2B + 2C

Figure 8-4 Diagram showing how to obtain the actual length of a pipe connecting two fittings.

Pipes, Pipe Fittings, and Piping DetailsFigure 8-5 Joint made up showing length of thread on pipe

(A) screwed into fitting.

Pipe Fitting Measurements

Pipe fitting may be done either by making close visual judgments or entirely by measurements scaled on a drawing. The first method is a hit-or-miss process and requires an experienced fitter to do a good job; the second method is one of precision and is the better way. In actual practice, a combination of the two methods will, in some cases, save time and give satisfactory results.

Working from a drawing with all the necessary dimensions has certain advantages. Especially in the case of a big job, all the pipe may be cut and threaded in the shop so that at the place of installa­tion the only work to be done is assembling.

In making a drawing, the measurements are based on the dis­tances between the centers of fittings. The data necessary to locate these centers are given in a more general dimension drawing with an accompanying table such as the one illustrated in Table 8-16. These dimension drawings and tables should be the ones corresponding to the make of fittings used; otherwise, there might be the possibility of
slight variation. In general, however, the different makes are pretty well standardized.

Figure 8-4 illustrates how the actual length of pipe connecting the two fittings is obtained. The actual length of pipe is equal to the distance between centers (of fittings) minus twice the distance from the center of the face of the fittings plus twice the allowance for threads. This is expressed by the following equation:

D = A — 2B + 2C

The allowance for the length of thread that is screwed into the fit­ting (dimension C in Figure 8-4) is obtained from a table furnished by the manufacturer. This allowance (called A in Figure 8-5) corresponds to the values given in the accompanying table (see Table 8-17). Note that the dimension A in Figure 8-5 is the same as dimension C in Figure 8-4.

A working drawing showing centerlines and distances between centers of an installation is shown in Figure 8-6. This gives all the information except the actual length of the pipes.

Problem

Find the length of the pipe connecting the 2-inch elbows in Figure 8-7. Using Figure 8-4 as a guide, the following dimensions are provided: A = 12 ft, B = 21/4 in, and C = n/16 in. The problem is solved as follows:

1. D = A-2B + 2C

2. D = 12 ft—2 X 2V4 in + 2 X 11/16 in

3. D = 12 ft-4Vi in + 22/32 (or 13/8) in

4. D = 11 ft 7V2 in + 13/8 in

5. D = 11 ft 8% in

Calculating Offsets

In pipe fitting, an offset is a change of direction (other than 90°) in a pipe bringing one part out of (but parallel with) the line of another.

An example of an offset is illustrated in Figure 8-8. As shown here, the problem is an obstruction (E), such as a wall, blocking the path of a pipeline (L). It is necessary to change the position of pipeline L at point A to some parallel position such as line F in order to move around the obstruction. When two lines such as L and F are to be piped with elbows other than 90° elbows, the pipe fitter is confronted with the following two problems: (1) finding the length of pipe H and (2) determining the distance BC. By determining the distance BC, the pipe fitter will be able to fix point A so that the two elbows A and C will be in alignment.

Table 8-17 Length of Thread on Pipe

Dimension

Dimension

Dimension

Dimension

Size (in)

A (in)

Size (in)

A (in)

Size (in)

A (in)

Size (in)

A (in)

Va

X/4

1

9/i6

3

1

6

1V4

V4

3/s

1V4

5/a

31/2

11/16

7

11^4

3/s

3/s

11/2

5/a

4

11/16

A

15/16

3

12

1/2

2

“/16

41/2

11/a

10

11/2

3/4

1/2

21/2

15/i6

5

13/16

12

15/a

398

подпись: 398

Pipes, Pipe Fittings, and Piping Details

Between centers of an installation.

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Figure 8-8 Pipeline connected with two 45° elbows illustrating offsets and method of finding length of connecting pipe H.

Of course, in the triangle ABC, the length of pipe AC and either offset (AB or BC) that may be required are quickly calculated by solving the triangle ABC for the desired member, but this involves taking the square root, which is not always easily understood by the average worker. Alternative methods are suggested in the fol­lowing sections.

First Method

If, in Figure 8-8, the distance between pipelines L and F is 20 inches (offset AB), what length of pipe H is required to connect with the 45° elbows A and C?

Based on the triangle ABC, the following equation is offered for solving this problem:

1. AC2 = AB2 + BC2 from which:

2. AC = VAB2 = BC2 or substituting:

3. AC = V202 + 202 = V800 = 28.28 inches

It should be remembered that when 45° elbows are used, both offsets are equal. Therefore, if offset AB is 20 inches long, offset BC also must be the same length.

Note that the value (that is, 28.28 inches) for the length of pipe H obtained by the aforementioned equation is the calculated length and does not allow for the projections of the elbows. In other words, pipe H (as calculated by this equation) is too long and must be shortened so that the elbows will fit.

Pipes, Pipe Fittings, and Piping Details

Figure 8-8 illustrates the difference between the calculated length (that is, the measurement from point A to point C) and the actual length of connecting pipe H when used with elbows other than 90°. Actual length is obtained by deducting the allowance for projection of the elbows from the calculated length.

Second Method

Another method of calculating the connecting pipe length (that is, the length of pipe H in Figure 8-9) is by multiplying the offset by 53/128 inch and adding the product to the original offset figure. Thus, if offset AB is 20 inches, the following calculations are possible:

. 53 1060 „ 9

‘ X 128 = 128 = 32

99

2. 20 + 8— = 28— in.

32 32

Third Method

The pipe fitter will often encounter elbows of angles other than 45°. For these, the distance between elbow centers (points A and C) can easily be calculated with the following procedure:

1. Determine the angle of the elbow.

2. Determine the elbow constant equivalent to its angle.

3. Multiply the elbow constant by the known offset.

Pipes, Pipe Fittings, and Piping Details

In Figure 8-10, even though only offset AB is known, it is possi­ble to determine the length of the other offset (BC) and the distance between elbow centers (AC). In order to do this, the following equations must be used:

AC = offset AB X constant for AC BC = offset AB X constant for AB

Assume that the distance between pipelines L and F (offset AB) in Figure 8-10 is 20 inches and the angle of the elbow is 22y2°. In Table 8-18 you will find that for a 22V20 elbow, the elbow constant for AB is 2.41. Substituting values in the second equation, you have the following:

BC = 20 X 2.61 = 48.2 inches

The constant for the elbow centers of 221/2° elbows is 2.61. Substituting values in the first equation gives the following results:

AC = 20 X 2.61 = 52.2 inches

Table 8-18 Elbow Constants

Angle of Elbow

Elbow Centers AC

Offset AB

60°

1.15

0.58

O

1.41

1.00

3

O

O

2.00

1.73

221/2°

2.61

2.41

11V4°

5.12

5.02

538°

10.20

10.15

Fourth Method

Offsets may also be calculated by using basic trigonometry. Using the example given in Figure 8-10, determine the length of the offset AB if AC is 8 feet and the angle ^ = 60°. From Table 8-19, sine 60° = 0.866:

Length of offset AB = 0.866 X 8 = 6.93

Pipe Supports

If piping is to be run along the wall or ceiling, it should be attached to the surface with pipe supports (for example, hangers, straps, clamps). The type of pipe supports used and their spacing will be regulated in accordance with approved local standards.

Pipe straps (perforated metal straps) are used to support small size pipes (see Figure 8-11). Larger pipes require various types of hangers (for example, rod, spring), chains, or other devices capable of supporting the heavier weight.

Vertical pipe is best supported with a shoulder clamp attached to the flooring at the point through which the pipe passes, or by clamps attached to adjacent walls or columns.

Pipe hangers and anchors are also used for supporting suspended piping or securing it (as in the case of anchors) to adjacent surfaces. Hangers are similar in appearance and function to pipe straps (see previous).

Joint Compound

Joint compound (also referred to as pipe dope) is a substance applied to the male thread when making up screwed joints. The purpose of applying a joint compound is to lubricate the threads so that tightening is made easier. By lubricating the threads, the fric­tion and heat produced by the tightening operation are greatly

Pipes, Pipe Fittings, and Piping Details

Deg

Sin

Cos

Tan

Sec

Deg

Sin

Cos

Tan

Sec

0

0.00000

1.0000

0.00000

1.0000

46

0.7193

0.6947

1.0355

1.4395

1

0.01745

0.9998

0.01745

1.0001

47

0.7314

0.6820

1.0724

1.4663

2

0.03490

0.9994

0.03492

1.0006

48

0.7431

0.6691

1.1106

1.4945

3

0.05234

0.9986

0.05241

1.0014

49

0.7547

0.6561

1.1504

1.5242

4

0.06976

0.9976

0.06993

1.0024

50

0.7660

0.6428

1.1918

1.5557

5

0.08716

0.9962

0.08749

1.0038

51

0.7771

0.6293

1.2349

1.5890

6

0.10453

0.9945

0.10510

1.0055

52

0.7880

0.6157

1.2799

1.6243

7

0.12187

0.9925

0.12278

1.0075

53

0.7986

0.6018

1.3270

1.6618

8

0.1392

0.9903

0.1405

1.0098

54

0.8090

0.5878

1.3764

1.7013

9

0.1564

0.9877

0.1584

1.0125

55

0.8192

0.5736

1.4281

1.7434

10

0.1736

0.9848

0.1763

1.0154

56

0.8290

0.5592

1.4826

1.7883

11

0.1908

0.9816

0.1944

1.0187

57

0.8387

0.5446

1.5399

1.8361

12

0.2079

0.9781

0.2126

1.0223

58

0.8480

0.5299

1.6003

1.8871

13

0.2250

0.9744

0.2309

1.0263

59

0.8572

0.5150

1.6643

1.9416

14

0.2419

0.9703

0.2493

1.0300

60

0.8660

0.5000

1.7321

2.0000

15

0.2588

0.9659

0.2679

1.0353

61

0.8746

0.4848

1.8040

2.0627

16

0.2756

0.9613

0.2867

1.0403

62

0.8820

0.4695

1.8807

2.1300

17

0.2924

0.9563

0.3057

1.0457

63

0.8910

0.4540

1.9626

2.2027

18

0.3090

0.9511

0.3249

1.0515

64

0.8988

0.4384

2.0503

2.2812

19

0.3256

0.0455

0.3443

1.0576

65

0.9063

0.4226

2.1445

2.3662

20

0.3420

0.9397

0.3640

1.0642

66

0.9135

0.4067

2.2460

2.4586

21

0.3584

0.9336

0.3839

1.0711

67

0.9205

0.3907

2.3559

2.5593

404

подпись: 404

22

0.3746

0.0272

0.4040

1.0785

23

0.3907

0.9205

0.4245

1.0664

24

0.4087

0.9135

0.4452

1.0846

25

0.4220

0.9063

0.4663

1.1034

26

0.4386

0.8938

0.4877

1.1126

27

0.4540

0.8910

0.5095

1.1223

28

0.4695

0.8829

0.5317

1.1326

29

0.4848

0.8746

0.5543

1.1433

30

0.5000

0.8660

0.5774

1.1547

31

0.5150

0.8572

0.6009

1.1666

32

0.5200

0.8480

0.6249

1.1792

33

0.5446

0.8387

0.6494

1.1924

34

0.5592

0.8290

0.6745

1.2062

35

0.5736

0.8192

0.7002

1.2208

36

0.5878

0.8090

0.7265

1.2361

37

0.6018

0.7936

0.7536

1.2521

38

0.6157

0.7880

0.7613

1.2690

39

0.6293

0.7771

0.8098

1.2867

40

0.6428

0.7660

0.8391

1.3054

41

0.6561

0.7547

0.8693

1.3230

42

0.6691

0.7431

0.9004

1.3456

43

0.6820

0.7314

0.9325

1.3673

44

0.6947

0.7193

0.9657

1.3902

45

0.7071

0.7071

1.0000

1.4142

405

подпись: 405

68

0.9272

0.3746

2.4751

2.6695

69

0.9330

0.3586

2.0051

2.7904

70

0.9397

0.3420

2.7475

2.9238

71

0.9455

0.3256

2.9042

3.0715

72

0.9511

0.3090

3.0777

3.2361

73

0.9563

0.2024

3.2709

3.4203

74

0.9613

0.2756

3.4874

3.6279

75

0.9650

0.2588

3.7321

3.8637

76

0.9703

0.2419

4.0108

4.1336

77

0.9744

0.2250

4.3315

4.4454

78

0.9781

0.2079

4.7046

4.9007

79

0.9816

0.1908

5.1446

5.2406

80

0.9848

0.1736

5.6713

5.7588

81

0.9877

0.1564

6.3128

6.3924

82

0.9903

0.1392

7.1154

7.1853

83

0.9925

0.12187

8.1443

8.2055

84

0.9945

0.10453

9.5668

85

0.9962

0.08716

11.4301

11.474

86

0.9976

0.06976

14.3007

14.335

87

0.9986

0.05384

10.0811

19.107

88

0.9954

0.03490

28.6363

28.654

89

0.9903

0.01745

57.2900

57.299

90

1.0000

Inf.

Inf.

Inf.

Reduced. Moreover, the joint compound forms a seal inside the screwed joint, which prevents leakage and ensures a tight joint.

Joint compounds are commercially available, or they may be made on the job from a variety of different materials. Red lead, white lead, or graphite have frequently been used as a joint com­pound. Red lead produces a very tight joint, but it hardens to such an extent that it is difficult to unscrew the joint for repairs.

A tape material has also been developed for use in making up screwed joints. It functions in the same manner as a joint com­pound. The tape is made of Teflon and is so thin that it will sink into the threads when wrapped around them.

An old toothbrush is an excellent tool for applying joint com­pound to the thread. It is important to remember that the joint compound must be applied to the male thread only. If it is applied to the female thread, some of it will be forced into the pipe where it will lodge as a contaminating substance.

Pipe Fitting Wrenches

The numerous wrenches used in pipe fitting may be listed as follows:

Monkey wrench

Pipe wrench

• Stillson wrench

• Chain wrench Strap wrench

Open wrench

The important point to remember in pipe fitting is to select a suitable wrench for the job at hand. Each of the aforementioned wrenches is designed for one or more specific tasks. No wrench is suitable for every task encountered in pipe fitting.

A monkey wrench has smooth parallel jaws that are especially adapted for hexagonal valves and fittings (see Figure 8-12). Not only does it fit better on the part to be turned, it also does not have the crushing effect of a pipe wrench.

The operating principle of a pipe wrench is simple. The harder you pull, the tighter it squeezes the pipe. The pipe wrench was designed for use on pipe and screw fittings only. On parallel-sided objects, its efficiency is not up to that of a monkey wrench, and its squeezing action can do a great deal of damage.

Many inexperienced fitters have learned from experience that using a pipe wrench too large for the job can cause the fitting to

Figure 8-12 Using a monkey,-Lk wrench.

&

C

Stretch or crack. The result is a leaking joint that will require a new fitting to remedy the damage.

A Stillson wrench has serrated teeth jaws that enable it to grip a pipe or round surface in order to turn it against considerable resis­tance. The correct method for using a Stillson wrench is illustrated in Figure 8-13. Adjust the wrench so that the jaws will take hold of the pipe at about the middle part of the jaws. To support the wrench and prevent unnecessary lost motion when the wrench engages the pipe, hold the jaw at A, with the left hand pressing it against the pipe. At the beginning of the turning stroke B, with the jaw held firmly against the pipe with the left hand, the wrench will at once bite or take hold of the pipe with only the lost motion nec­essary to bring jaw C in contact with the pipe.

Figure 8-14 shows a chain wrench (or pipe tongs) and the method in which it is used. Although they are made for small sizes up, they are generally used for 6-inch pipe and larger.

A strap wrench (see Figure 8-15) is used when working with plated or polished-finish piping in order not to mar the surface. It also comes in handy in tight places where you cannot insert a Stillson wrench.

Open-end wrenches (see Figure 8-16) are used for making up flange couplings. The right size should be used in order to prevent wearing of the bolt heads or slippage that can cause bruised knuckles.

Pipes, Pipe Fittings, and Piping Details

JAWS ON ■BITE’

Figure 8-13 Method of using a Stillson wrench.

Figure 8-14 Method of using a chain wrench.

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Pipe Vise

Either a pipe vise or a machinist vise (see Figure 8-17) can be used in pipe fitting. The pipe vise is used for pipe only. The machinist vise, on the other hand, has square jaws or a combination of square and gripper jaws, making it suitable for pipe as well as other work.

Several precautions should be taken when using a pipe vise. It exerts a powerful force at the jaws, which in some cases can do dam­age to the pipe. That is why experienced fitters never put a valve or fitting into a vise when making up a joint at the bench. There is too much danger of distorting the part by oversqueezing it or of putting the working parts of a valve out of line. The correct and incorrect methods of connecting a valve to a pipe are illustrated in Figure 8-18. Always hold a valve between lead — or copper-covered machinist vise jaws while unscrewing the bonnet (see Figure 8-18).

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details Pipes, Pipe Fittings, and Piping Details

■SOFT’ JAW COVERS OF LEAD OR COPPER

подпись: ■soft' jaw covers of lead or copperFigure 8-18 Correct method of using the pipe and machinist vise.

Installation Methods

Pipe fitting may be defined as the operations that must be per­formed in installing a pipe system made up of pipe and fittings. These pipe fitting operations can be listed as follows:

1. Cutting.

2. Threading.

3. Reaming.

4. Cleaning.

5. Tapping.

6. Bending.

7. Assembling.

8. Making up.

Figure 8-19 illustrates the principal operations in pipe fitting. After being marked to length by nicking with a file, the pipe is put in a vise and cut with a pipe cutter (or hacksaw) as shown in Figure 8-19A. Any external enlargement is removed with a metal file (see Figure 8-19B). The thread is next cut with stock and dies as in Figure 8-19C. After carefully cleaning the thread with a hard toothbrush and applying red lead or pipe cement to the freshly cut thread, the joint is made up with a Stillson wrench (see Figure 8-19D).

Pipe Cutting

Pipe is manufactured in different lengths varying from 12 to 22 feet. Accordingly, it must be cut to required length for the pipe

Pipes, Pipe Fittings, and Piping Details

Figure 8-19 Pipe cutting.

Pipes, Pipe Fittings, and Piping Details Pipes, Pipe Fittings, and Piping Details Pipes, Pipe Fittings, and Piping Details

(B)

подпись: (b)Installation. This may be done with either a hacksaw or a pipe cut­ter. The latter method is generally quicker and more convenient.

When a length of pipe is being cut or threaded, it is held firmly in a pipe vise. The pipe vise should be adjusted just tight enough to prevent the pipe from slipping, but not so tight as to cause the jaw teeth to unduly dig into the pipe.

A pipe cutter is a tool usually consisting of a hoop-shaped frame on whose stem a slide can be moved by a screw. On the side and frame, several cutting dies on wheels are mounted. In cutting, the
pipe cutter is placed around the pipe so that the wheels contact the pipe. The tool is rotated around the pipe, tightening up with the screw stem each revolution until the pipe is cut.

The operating principles of a three-wheel cutter and a combined wheel and roller cutter are illustrated in Figure 8-20A. The cuts show the comparative movements necessary with the two types of cutters to perform their functions. The three-wheel cutter requires only a small arc of movement and is recommended for cutting pipe in inaccessible locations. The wheel cutter has a greater range than the roller cutter and is therefore preferred for general use.

The major disadvantage of a pipe cutter is that it does not cut but crushes the metal of the pipe, leaving a shoulder on the outside and a burr on the inside. This does not apply to the knife-type pipe cutter designed to actually cut (not crush) the pipe.

Figure 8-20B shows the appearance of pipe when cut by a hack­saw or knife cutter and when cut by a wheel pipe cutter. When the latter is used, the external enlargement must be removed by a file and the internal burr by a pipe reamer.

Pipe Threading

A pipe thread is cut with stock and dies. Adjustable dies are used in pipe threading because of slight variations in fittings, especially cast — iron fittings. Figure 8-21 illustrates an adjustable pipe stock and dies for double-ended dies. As shown, each pair of dies has one size thread at one end and another size at the other end. Thus, the two dies in the stock are in position for cutting ^-inch thread, and by reversing them they will cut %-inch thread. The cut shows plainly the reference marks, which must register with each other in adjust­ing the dies by means of the end setscrews to standard size.

A vise is used in conjunction with the pipe stock and dies when threading a pipe. After securing the pipe in the vise, use plenty of oil in starting and cutting the thread. In starting, press the dies firmly against the pipe until they take hold. After a few turns, blow out the chips and apply more oil. This should be done several times before completing the cut. When complete, blow out the chips as cleanly as possible and back off the dies. When drawing in your breath pre­liminary to blowing out the chips, turn your head away from the die to avoid drawing the chips into your lungs.

A nipple is short piece of pipe 12 inches in length or less and threaded at both ends. Nipples are properly cut by using a nipple holder designed for use with hand stock and dies. The holder is double ended and holds two sizes of nipples, one being for ^-inch nipples and the other for 3/4-inch nipples. In construction, there is a

FLOOR

 

PIPE

 

I I

ROLLER CUTTER /

I

/

/

/

/

 

NOT WITHIN RANGE

 

NECESSARY MOVEMENT 360°

DC*

 

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

METAL UPSET BY CRUSHING ACTION OF PIPE CUTTER WHEEL

……………………. ‘

Pipes, Pipe Fittings, and Piping Details

Figure 8-20 The appearance of a pipe cut by a hacksaw and a pipe cut by a cutter wheel.

Pipes, Pipe Fittings, and Piping Details

Pin inside the holder having a fluted end that digs into the nipple end when pressed forward by driving down the wedge. In opera­tion, the nipple is screwed by hand into the holder as far as it will go, and then the wedge is driven down sufficiently to firmly secure the nipple. The holder is arranged in such a way that when the thread is cut, the nipple can be removed by simply starting back the wedge, which loosens the inner part of the holder and allows the nipple to be easily unscrewed by hand. The holder can be used for making either right or both right and left nipples.

Pipe Reaming

The burrs should be removed with a reamer to avoid future trouble with clogged pipes. This is a job that should be done thoroughly.

The correct way of removing the shoulder (that is, external enlargement) left on a pipe end after cutting it with a pipe cutter is by using a flat file. Obviously at each stroke, the file should be given a turning motion, removing the excess metal through an arc of the circumference. The position of the pipe is changed in the vise from time to time until the excess metal is removed all around the pipe. When the operation is done by moving the file in a straight line, it will result in a series of flat places on the surface. A good pipe threader will also remove the external enlargement of the pipe end caused by using a pipe cutter.

Pipe Cleaning

Dirt, sand, metal chips, and other foreign matter should be removed from pipelines to prevent future problems. When a new pipeline is installed, flush it out completely with water to remove any loose scale or foreign matter.

Check the threads for any dirt or other foreign matter. It is impor­tant to be thorough about this because dirt in the threads can also get into the lines when the joints are made up. Dirt can also cause tearing of the metal when screwing up a connection. It increases fric­tion and interferes with making a tight joint.

Flanged faces should also be cleaned thoroughly. Manufacturers usually coat flanges with a heavy oil or grease to prevent rusting. A solvent will easily remove this coating. Special precaution should be taken against dirt on gaskets. Dirt on any part of a flanged joint tends to cause leaks.

Pipe Tapping

An internal or female thread is cut by means of a pipe tap, a conical screw made of hardened steel and grooved longitudinally. A pipe tap and pipe reamer are illustrated in Figure 8-22.

Table 8-20 gives drill sizes that permit direct tapping without reaming the holes beforehand. Table 8-21 gives drill sizes for both the Briggs, or American Standard, and the Whitworth, or British Standard.

Figure 8-22 A typical pipe tap and pipe reamer.

подпись: 
figure 8-22 a typical pipe tap and pipe reamer.
Pipe Bending

With the proper tools, pipes may be bent within certain limits without difficulty.

An example of a pipe-bending tool is illustrated in Figure 8-23.

Pipes can also be bent by hand with­out the use of special tools. One method involves the complete filling of the pipe with sand and capping both ends so that none of the sand will be lost. Heat the part to be bent and then clamp the pipe in a vise as close to the part to be bent as possible. Now cool the outside with water so that the inside, being hot and plastic, is compressed as the bend is made.

Pipes, Pipe Fittings, and Piping DetailsFigure 8-23 Pipe-bending tool.

Assembling and Make-Up

Assembling is the operation of putting together the various lengths of pipe and fittings used in an installation.

If no mistakes have been made in cutting the pipe to the right length or in following the dimensions on the blueprint, the pipe and fittings may be installed without difficulty. In other words, the last joint (either a right or left union, or long screw joint) will come together smoothly or, as they say in the trade, make up.

Table 8-20 Drill Sizes for Briggs Standard Pipe Taps (For Direct Tapping Without Reaming)

416

подпись: 416Size of V8 !4 3/a 3/4 1 11/4 11-2 2 2V2 3 31/2 4

Pipe

Size of 21/64 7/16 9/16 45/64 29/32 19/64 131/64 14%4 213/«4 25/8 3V4 34%4 415/64

Drill

Table 8-21 Drill Sizes for Pipe Taps

Size Taps (in)

Briggs Standard

British (Whitworth) Standard

Thread

Drill

Thread

Drill

Vs

27

21/64

28

5/16

V4

18

2%4

19

7/16

3/s

18

9/16

19

9/16

12

14

N/16

14

23/32

5/8

14

25/32

3/4

14

29/32

14

29/32

7/s

14

11/16

1

1114

11/8

11

15/32

114

1114

115/32

11

112

112

1112

123/32

11

123/32

134

11

131/32

2

1114

23/16

11

23/16

214

11

213’32

212

8

29/16

11

225/32

23/4

11

31/32

3

8

33/16

11

39/32

314

11

312

314

8

3n/16

11

33/4

33/4

11

4

4

8

43/16

11

414

412

8

411/16

11

43/4

5

8

514

11

51/4

512

11

53/4

6

8

65/16

11

614

7

8

75/16

11

75/16

8

8

85/16

11

8%6

9

8

95/16

11

95/16

10

8

107/16

11

105/16

Screwed joints are put together with red or white lead pigment mixed with graphite and linseed oil, or with some standard com­mercial joint compound.

It is unnecessary to put much material on the threads because it will be simply pushed out and wasted when the joint is screwed up.

It should be put on evenly and cover all the threads, with care being taken not to let any touch the reamed end of the pipe where it may get inside. The red lead is preferably obtained in the powder form and mixed with oil and a little dryer at the time the pipe is to be made up. Get a clean piece of glass on which to prepare the lead. The toothbrush should be laid on the glass after applying the lead in order to avoid getting grit on the brush and paint on the table. When grit becomes mixed with the lead, it prevents close contact of the filling and pipe, thus making the joint less efficient.

The following steps should be taken before making up a screwed joint:

1. Ream the pipe ends.

2. Remove burrs from both the inside and outside of the pipe.

3. Thoroughly clean the inside of the pipe.

4. Thoroughly clean the threads.

Clean threads, a suitable joint compound, and proper tightening (neither too much nor too little) are all necessary for a satisfactory screwed joint.

There are four requirements for satisfactorily making up a flanged joint. In the proper order of sequence, these four require­ments are as follows:

Thorough cleaning Accurate alignment

• Using the proper gasket

Tightening bolts in proper order

Thoroughly clean the flange face with a solvent to remove any grease, and wipe it dry. The alignment must be accurate for satis­factory makeup. This is particularly important where valve flanges are involved. If the alignment is poor, a severe stress on the valve flanges may distort the valve seats and prevent tight closure (see Figure 8-24).

Selecting a suitable gasket for the service is also very important. Using the wrong gasket may result in a leak.

Figure 8-25 illustrates the recommended method of tightening the bolts with a wrench. This must be done not in rotation but in sequence as indicated by the numbers. This is the crossover method. Do not fully tighten on the first round but go over them two or preferably three times to fully tighten.

Pipes, Pipe Fittings, and Piping Details

Irsw*n

Figure 8-24 Flange and pipe alignment.

Pipes, Pipe Fittings, and Piping Details

Nonferrous Pipes, Tubing, and Fittings

Both brass and copper are used as materials for this type of pipe and tubing. The construction may be either cast or wrought, and the methods of joining include screwed, flared, and soldered.

The technique used with screwed fittings is the same as with ordinary malleable-iron fittings. This has already been described in the first part of this chapter.

The fittings used for flared soft tube end joints are cast fittings. These are usually used on oil burner construction and supply lines. Flared joint fittings include elbows, tees, couplings, unions, and a full range of reducing and adapter combinations in all standard sizes and combinations of sizes from 1/8 inch to 2 inches inclusive (see Figure 8-26). A double-seal type of flared joint fitting is illus­trated in Figure 8-27.

The sequence of operations required to make a flared joint are as follows:

1. Cut the tube with a hacksaw to the exact length, using a guide to ensure a square cut.

2. Remove all burrs and irregularities by filing both inside and outside.

3. Slip the coupling nut over the end of the tube and insert the flanging tool.

4. Drive the flanging tool into the tube with a few hammer blows, expanding the tube to its proper flare.

5. Assemble the fitting and tighten it by using two wrenches, one on the nut and the other on the body of the fitting.

Soldering Pipe

Solder fittings usually come in cast bronze and wrought copper. The two kinds of fittings used are the edge-feed fitting and the hole — feed fitting (see Figure 8-28).

The basic principle of solder fittings is capillary attraction. Because of capillary attraction, solder can be fed vertically upward between two closely fitted tubes to a height many times the distance required to made a soldered joint, regardless of the size of the fitting.

Either a 50-50 tin-lead solder or a 95-5 tin-antimony solder is rec­ommended for joining copper tube. The former is generally used for moderate pressures with temperatures ranging up to 250°F. The 95-5 tin-antimony solder is used where higher strength is required, but it has the disadvantage of being difficult to handle. Pressure ratings for soldered joints using these two solders are listed in Table 8-22. A suitable paste-type flux is recommended for use with these solders.

®®> @7

Pipes, Pipe Fittings, and Piping DetailsT FITTING UNION 90°ELBOW

SEP m—»

MALE ADAPTER FEMALE ADAPTER FLARING TOOL

Pipes, Pipe Fittings, and Piping Details

FEMALE ADAPTER RIGID PIPE

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Figure 8-27 Double-seal flared joint fitting.

Pipes, Pipe Fittings, and Piping DetailsFigure 8-28 Edge — and hole-feed solder fittings.

Table 8-22 Safe Strength of Soldered Joints Pressure Ratings, Maximum Service Pressure (psi)

Water*

Solder Used in Joints

Service

Temperatures

(°F)

‘A to 1 1 ‘A to 2 Inch Inches Incl.* Incl.*

2 ‘/2 to 4

Inches

Incl.*

50-50 tin-lead^

100

200

175

150

150

150

125

100

200

100

90

75

250

85

75

50

95-5 tin-antimony

100

500

400

300

150

400

350

275

200

300

250

200

250

200

175

150

Brazing filler metal

250

300

210

170

Melting at or above 1000°F§

350

270

190

155

*Standard copper water tube sizes

+ASTM B32, alloy grade 50A

*Including refrigerants and other noncorrosive liquids and gases §ASTM B260, brazing filler metal (Courtesy Copper & Brass Research Assoc.)

The series of operations necessary in making a solder fitting joint are as follows:

1. Measure the tube to proper length so that it will run the full length of the socket of the fitting.

2. Cut the tube end squarely.

3. Clean tube end and socket of fitting.

4. Apply soldering flux to the cleaned areas of tube and fitting socket.

5. Assemble the joint.

6. Revolve the fitting if you can, to spread the flux evenly.

7. Apply heat and solder.

8. Remove residual solder and flux.

9. Allow joint to cool.

With a hole-feed fitting that has a feed hole for the solder and a groove inside, the procedure is just the same as for an edge-feed fit­ting except that solder is fed into the feed hole until it appears as a ring at the edge of the fitting. Be sure the hole is kept full of solder, as it shrinks on cooling and solidifying.

Do not select fittings that are oversize because they will result in a loose fit. The capillary action is dependent on a fairly tight fit, although a certain amount of looseness can be tolerated. A loose fit causes the greatest difficulty when working with large-size copper tubes.

A thorough cleaning of the tube surface and the fitting socket is absolutely essential for a strong, tight, and durable joint. This can­not be emphasized too strongly.

Brazing Pipes

Brazing is rapidly taking the place of many operations formerly performed by soldering because it is simpler and quicker and results in a stronger joint. Like soldering, the brazing alloy is applied at temperatures below the melting point of the metal being brazed. In this respect, both brazing and soldering differ from welding, which forms a joint by melting (fusing) the metal at temperatures above its melting point.

During the brazing process, the brazing alloy is heated until it adheres to the pipe surface and enters into the porous structure of the metal. The brazed joint is almost always as strong as the brazed metal surrounding it.

Brazing can be used to join nonferrous metals, such as copper, brass, or aluminum, or ferrous metals, such as cast iron, malleable iron, or steel. The brazing alloy used in making the joint depends on the type of metal being brazed. For example, aluminum requires the use of a special aluminum brazing alloy, whereas a low-temper — ature brazing alloy or a silver alloy is recommended for brazing copper and copper alloys. A local welding supply dealer should be able to provide answers to your questions about which alloy to use.

The procedure for brazing consists essentially of the following operations:

1. Clean both surfaces.

2. Apply a suitable flux.

3. Align and clamp the parts to be joined.

4. Preheat the surface until the flux becomes fluid.

5. Apply a suitable brazing alloy.

6. Allow the surface time to cool.

7. Clean the surface.

The pipe surfaces must be thoroughly cleaned, or the result will be a weak bond or no bond at all. All dirt, grease, oil, and other surface contaminants must be removed, or the capillary attraction so important to the brazing process will not function properly.

Select a flux suited to the requirements of the brazing operation. Fluxes differ in their chemical compositions and the brazing tem­perature ranges within which they are designed to operate. Apply the flux to the joint surface with a brush.

Align the parts to be joined, securing them in position until after the brazing alloy has solidified. Preheat the metal to the required brazing temperature (indicated by the flux reaching the fluid stage).

After the flux has become fluid, add the brazing alloy. If conditions are right, the brazing alloy will spread over the metal surface and into the joint by capillary attraction. Do not overheat the surface. Remove the heat as soon as the entire surface has been covered by the brazing alloy. Allow time for the joint to cool and then clean the surface.

Braze Welding Pipe

Braze welding is another bonding process that does not melt the base metal. In this respect, it resembles both soldering and brazing.

Brazing and braze welding operate under essentially the same basic principles. For example, both use nonferrous filler metals that melt above 880°F but below the melting point of the base metal. They differ primarily in application and procedure.

The braze-welding process follows most of the steps previously described for brazing but will differ principally as follows:

1. Edge preparation is necessary in braze welding and is essen­tially similar to that employed in gas welding. The edges must be prepared before the surfaces are cleaned.

2. A suitable filler metal is used instead of a brazing alloy.

The filler metal will flow throughout the joint by capillary attrac­tion. Flanges that are to be brazed to copper pipes must be of copper or what is known as brazing metal (98 percent copper and 2 percent tin), as gunmetal flange would melt before the brazing alloy ran.

Welding Pipe

Oxyacetylene welding (gas welding) is probably the most common welding process used for joining pipe and fittings, particularly on smaller installations. Arc welding is also very popular.

Pipe welding should be done only by a skilled and experienced worker. The equipment and the procedure used are much more com­plicated than those used with soldering, brazing, or braze welding.

Welding forms a joint by melting (fusing) the metal at tempera­tures above its melting point. The filler metal, electrodes, or welding rods used must be suitable for use with the base metal to be welded, and the procedure used should be such as to ensure complete pene­tration and thorough fusion of the deposited metal with the base metal. The welding process is employed in many piping installa­tions, but especially those in which large-diameter pipes are used.

Manufactured steel welding fittings are available for almost every conceivable type of pipe connection. These steel welding fit­tings can be divided into the following two principal categories:

Butt-welding fittings

• Socket-welding fittings

Butt-welding fittings (see Table 8-23) have ends that are cut square or beveled 371/2° for wall thicknesses under 3/i6 inch. Wall thicknesses ranging from 3/i6 inch to 3/4 inch are beveled 37V20. For walls ranging from 3/4 inch to 13/4 inches thick, the bevel is U — shaped.

Socket-welding fittings (see Table 8-24) have a machined recess or socket for inserting the pipe. A fillet weld is made between the pipe wall and the socket end of the fitting. The fillet weld is approx­imately triangular in cross-section, the throat lying in a plane of approximately 45° with respect to the surfaces of the part joined. As shown in Figure 8-29, the minimum thickness of the socket wall (L) is 1.25 times the nominal pipe thickness (T) for the designated schedule number of the pipe. Socket-welding fittings are generally limited in use to nominal pipe sizes 3 inches and smaller.

In addition to butt- and socket-welding fittings, flange fittings are also available for welding in sizes ranging from inch to 24 inches.

L L(minimum) = 1.25 T Figure 8-29 Filletweld

BUT NOT LESS THAN 5/3

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

M

427

подпись: 427

Nominal Pipe Size

Long Radius Elbows

ISO Returns

Straight Tees

Outside Diameter at Bevel

Center to End

Outside Diameter at Bevel

Center to Center O

Back to Face K

Outside Diameter at Bevel

Center to End

900

Elbows A

45°

Elbows B

Run C

Outlet M

1

1.315

1У2

78

1.315

3

2У16

1.315

1У2

1%

1У4

1.660

17/8

1

1.660

33/4

23/4

1.660

17/8

17/8

1У2

1.900

21/4

1У8

1.900

41/2

31/4

1.900

21/4

21/4

2

2.375

3

13/8

2.375

6

43l6

2.375

21/2

21/2

2У2

2.875

33/4

13/4

2.875

71/2

5З16

2.875

3

3

3

3.500

4У2

2

3.500

9

61/4

3.500

33/8

33/8

3У2

4.000

51/4

21/4

4.000

101/2

71/4

4.000

334

33/4

4

4.500

Б

4.500

12

81/4

4.500

41/8

41/8

5

5.563

7У2

31/8

5.563

15

105/16

5.563

4%

47/8

Б

6.625

9

33/4

6.625

18

125/16

6.625

55/8

55/8

8

8.625

12

5

8.625

24

165/16

8.625

7

7

10

10.750

15

61/4

10.750

30

203/8

10.750

81/2

81/2

12

12.750

18

7У2

12.750

36

243/8

12.750

10

10

14

14.000

21

83/4

14.000

42

28

14.000

11

16

16.000

24

10

16.000

48

32

16.000

12

Not

Standard

18

18.000

27

111/4

18.000

54

36

18.000

13Ь

20

20.000

30

121/2

20.000

60

40

20.000

15

24

24.000

36

15

24.000

72

48

24.000

17

From American Standard for Butt-Welding Fittings, ASA BI6.9-l958.All dimensions are in inches. Dimension A is equal to V2 of dimension O. (Courtesy I960ASHPAE Guide)

428

подпись: 428 Pipes, Pipe Fittings, and Piping Details

Center to Bottom of Socket

Socket Wall Thickness, Min

Bore Diameter of Fitting

Sched 40

Sched

Sched

Sched

Sched

Sched

Sched

Sched

Depth of

And 80

160

Bore Diameter

40

80

160

40

80

160

Nominal

Socket,

Of Socket, Min

Pipe Size

Min

A

B

C

D

Vs

3/8

7/i6

0.420

0.125

0.125

0.269

0.215

X/4

3/8

7/i6

0.555

0.125

0.149

0.364

0.302

3/s

3/8

1732

0.690

0.125

0.158

0.493

0.423

V2

3/8

5/8

34

0.855

0.136

0.184

0.234

0.622

0.546

0.466

3/4

1/2

3/4

%

1.065

0.141

0.193

0.273

0.824

0.742

0.614

1/2

12

7/s

11/16

1.330

0.166

0.224

0.313

1.049

0.957

0.815

L!/4

V2

11/16

1V2

1.675

0.175

0.239

0.313

1.380

1.278

1.160

1V2

V2

1V4

11/2

1.915

0.181

0.250

0.351

1.610

1.500

1.338

2

5/8

11/2

15/8

2.406

0.193

0.273

0.429

2.067

1.939

1.689

2V2

5/8

21/4

2.906

0.254

0.345

0.469

2.469

2.323

2.125

3

5/8

21/4

21/2

3.535

0.270

0.375

0.546

3.068

2.900

2.626

(Courtesy I960ASHRAE Guide)

Gas Piping

The gas pipe installations in which gas-fired furnaces, boilers, heaters, or other gas appliances are used deserve special attention because of the volatile and highly flammable nature of the fuel. Special attention should be given to the installation of gas piping to ensure against leakage.

The installation and replacement of gas piping should be done only by qualified workers who have the necessary skills and experience.

The following recommendations are offered as a guide for installing and replacing gas piping:

All work should be done in accordance with the building, heating, and plumbing codes and standards of the authorities having local jurisdiction. These take precedence over national codes and standards.

In an existing installation, the gas supply to the premises and all burners in the system must be shut off before work begins. When installing a system, size the pipes according to the amount of gas to be delivered to each outlet and at the proper pressure. The length of pipe runs and number of outlets are the main determining factors.

Use a piping material recommended by the local authorities having jurisdiction. Never bend gas piping because it may cause the pipe walls to crack and leak gas. Use fittings for making turns in gas piping. Take all branch connections from the top or side of horizontal pipes (never from the bottom).

• Locate the gas meter as close as possible to the point at which the gas service enters the structure.

Make certain all pipes are adequately supported so that no unnecessary stress is placed on them.

• Offsets should be 45° elbows rather than 90° fittings in order to reduce the friction to the flow of gas.

• Check for gas leaks by applying a soap-and-water solution to the suspected area. Never use matches, candles, or any other flame to locate the leak.

Insulating Pipes

Insulating the supply pipes in a low-pressure steam or hot-water space heating system will reduce unwanted heat loss and improve the heating efficiency of the system. The return pipes in a hot-water heating system should also be insulated so that the water reaches the boiler with a minimum of heat loss. Do not insulate the return pipes in a steam heating system. Uninsulated pipes will aid in the condensation of any steam that has succeeded in bypassing the thermostatic traps and entering the returns.

The pipe insulation material must be noncombustible, durable, and resistant to moisture. Furthermore, it should be able to retain its original physical shape and insulating properties after becoming wet and drying out.

Fiberglass is used to insulate steam or hot-water heating pipes. It can be easily applied to the pipe, requiring little more than ordinary cutting shears or a sharp knife.

Another effective pipe-insulating material is expanded polystyrene (see Figure 8-30).

Pipes, Pipe Fittings, and Piping Details

Figure S-30 Expanded polystyrene as a pipe-insulating material.

(Courtesy Dow Chemical Co.)

Your local building supply dealer should be able to answer any questions you may have about pipe-insulting materials. The manu­facturers of these materials also generally provide detailed instruc­tion about how to apply them. You should not have any difficulty if you carefully read and follow these instructions.

Piping Details

Each piping installation will have design or layout problems that the fitter must solve. Many of these problems, such as installing dirt pockets or siphons, are quite simple for the pipe fitter to handle.

More-complicated layout problems are solved by calculating and installing lift fittings, swivels and offsets, and drips. These and other piping details are described in the sections that follow.

Connecting Risers to Mains

Many steam fitters connect risers directly to mains with a tee; although this method saves on extra labor and expense, it results in a more inefficient operation of the installation. When a tee is used, the condensation falls directly across the path of the steam flowing in the main and will be carried along and finally arrive at the radia­tor or convector with excess moisture. This problem is avoided with a 45° connection.

Using a 45° connection very effectively drains the condensation from the main, the path of the condensation being along the metal of the pipe and fittings instead of dripping directly into the steam.

The proper method of connecting a riser to a main where the riser has a direct connected drip pipe is by using a 45° connection downward. If the riser has no drip, the riser should be connected to the main with the leadoff being 45° upward connecting with a 45° elbow. The runout should pitch V2 inch per foot. Runouts over 8 feet in length, but with less than 1i2 inch per foot pitch, should be one size larger than specified in the pipe sizing tables.

If the condensation flows in the opposite direction to the steam, the runouts should be one size larger than the vertical pipe and pitched Vi inch per foot toward the main. If the runouts are over 8 feet in length, use a pipe two sizes larger than specified.

Connections to Radiators or Convectors

The connections to radiators and convectors must have a proper pitch when installed and be arranged so that the pitch will be main­tained under the strains of expansion and contraction. These con­nections are made by swing joints.

In two-pipe systems, radiators are connected either at the top and bottom opposite end or at the bottom and bottom opposite end. The top connection is not recommended for best performance. Short radiation may be top-supply and bottom-return connected on the same end.

Additional information about radiator and convector connections can be found in Chapter 2 of Volume 3 (“Radiators, Convectors, and Unit Heaters”).

Lift Fittings

The lift fittings illustrated in Figure 8-31 are adapted for use on the main return lines of vacuum heating systems at points where it is desired to raise the condensation to a higher level. In operation, the

NOTE: Cold-water line connected to opposite side.

Pipes, Pipe Fittings, and Piping Details

Place gate valve & check valve in this connection.

Figure 8-31 Typical installation of lift fittings.

Momentum of the water is maintained and assists in making the lift with minimum loss of vacuum. The lift fitting is constructed with a pocket at the bottom of the lift into which the water drains. As soon as sufficient water accumulates to seal this pocket, it is drawn to the upper portion of the return by the vacuum produced by the pump. The shape of the fitting is such that dirt and scale are usually swept along by the current. Cleanout plugs are provided for use if necessary. A second fitting in a reversed position is recommended for use at the top of the lift to prevent water from running back while the pocket is filled.

Drips

A steam main in any steam heating system may be dropped to a lower level without dripping if the pitch is downward with the direction of the steam flow. By the same token, the steam main in any system may be elevated if properly dripped.

Various piping arrangements for dripping the main and riser are illustrated in Figures 8-32 through 8-39. Figure 8-39 shows a con­nection where the steam main is raised and the drain is to a wet return. If the elevation of the low point is above a dry return, it may be drained through a trap to the dry return in a two-pipe vapor, vacuum, or subatmospheric system.

Figure 8-32 Dripping end of main into wet return.

TRAP

Pipes, Pipe Fittings, and Piping Details

SUPPLY MAIN

Pipes, Pipe Fittings, and Piping Details

Figure 8-33 Dripping end of main into dry return.

A horizontal steam main can be run over an obstruction if a small pipe is carried below for the condensation with provisions for draining it.

In vacuum steam heating systems, drip traps for steam mains should be either thermostatic or combination float and thermo­static protected by dirt strainer or dirt pockets. Typical methods of making these connections are illustrated in Figures 8-40 through 8-43. The bases of supply risers are dripped through drip traps as

Pipes, Pipe Fittings, and Piping Details

Shown in Figures 8-44 and 8-45. Methods of connecting return risers are also shown.

In vapor steam heating systems, runouts to supply risers should be dripped separately into a wet return.

Dirt Pockets

On all systems employing thermostatic traps, dirt pockets should be located so as to protect the traps from scale and muck, which will interfere with their operation. Dirt pockets are usually made 8 to 12 inches deep.

Siphons

A siphon (see Figure 8-46) is used to prevent water from leaving the boiler due to lower pressure in a dry return. Condensation from the drip pipe falls into the loop formed by the siphon and, after it is filled, overflows into the dry pipe. The water will rise to different heights (G and H in the legs of the siphon) to balance the difference in pressure at these points.

If a dry return is used without a siphon, then water would be drawn from the boiler in sufficient amounts to balance the low pressure in the riser, filling the return and drip to approximately point M (see Figure 8-46).

Hartford Connections

Another method employed to prevent water leaving the boiler is the Hartford connection (or loop) on the wet return (see Chapter 15 of Volume 1, “Boilers and Boiler Fittings”).

Making Up Coils

In putting together lengths and return bends to form a coil heating unit, there is a right way and a wrong way to do the job. The essential requirement for the satisfactory operation of the coil is providing

Pipes, Pipe Fittings, and Piping Details

Figure 8-35 Method of dripping short steam main and discharging condensation into pressure wet return near floor.

For proper drainage. To obtain this, the pipes should not be parallel but should have a degree of pitch.

A pitch fitting should be used to obtain pitch in the coils rather than the so-called drunken thread method (see Figure 8-47). The drunken thread is obtained by removing the guide bushing from the stock and cutting the thread out of alignment. This gives a
poor joint—one that will eventually break because of corrosion. The corrosion is caused by the deep cut on one side of the pipe resulting from cutting the thread out of alignment.

Pipes, Pipe Fittings, and Piping Details

Figure 8-36 Method of dripping long steam main and discharging condensation into pressure wet return near floor.

подпись: 
figure 8-36 method of dripping long steam main and discharging condensation into pressure wet return near floor.
Relieving Pipe Stress

Long runs of rigidly supported piping carrying steam or hot water, especially when they are at high pressures and temperatures, are

UP TO RADIATOR RETURN TRAP

Pipes, Pipe Fittings, and Piping Details

Figure 8-37 Alternative method of dripping end of supply main through dirt pocket to pressure wet return near floor and venting to overhead dry return.

Pipes, Pipe Fittings, and Piping Details

Figure 8-38 Method of dripping base of main supply riser of downfeed system through dirt strainer and drip trap.

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Figure 8-40 Method of dripping steam mains with drips on end of main.

Pipes, Pipe Fittings, and Piping Details

DOWNFEED

SUPPLY RISER TO RADIATOR

Pipes, Pipe Fittings, and Piping Details

Figure 8-42 Method of installing drip connection at base of downfeed supply riser to overhead return main through cooling leg, dirt strainer, and return trap.

DOWNFEED SUPPLY RISER

Pipes, Pipe Fittings, and Piping Details

Figure 8-43 Method of installing drip connection at base of downfeed supply riser to overhead return main.

Often subject to stresses caused by the expansion and contraction of the pipe. These pipe stresses can be relieved in a number of ways, including the installation of either a U-expansion bend or an expan­sion joint.

Swivels and Offsets

Another method of providing for pipe expansion in steam mains is through the use of swivels and offsets (see Figure 8-48). Allow at least 4 feet of offset for each inch of expansion to be taken up in the line. The offsets should be placed far enough apart to minimize any strain on the threads when expansion or contraction occurs.

RISER RISER RISER riser

Pipes, Pipe Fittings, and Piping Details

Figure 8-44 Method of connecting drips from upfeed risers into a wet return and discharging some through a trap into overhead vacuum return main.

Eliminating Water Pockets

Water pockets (that is, the tendency for water to collect in pipes) are caused by incorrect pipe installation methods (see Figures 8-49 and 8-50). Not only do these water pockets have the potential dan­ger of freezing and damaging the pipes when the boiler is shut down, but they also cause that loud and disagreeable hammering in the pipes known as water hammer. Water hammer is caused by a sudden rush of steam picking up this undrained water when the radiator or convector is opened and forcing it against any turn in the direction of the main. Hammering in steam lines can be stopped by providing for the proper drainage of the condensation. This can be accomplished by installing eccentric fittings or by installing traps of suitable capacity. For example, the water pocket shown in Figure 8-50 can be avoided by using an eccentric reduc­ing tee (see Figure 8-51).

Water trapped in a supply line can sometimes be the cause of radiators failing to heat properly. In this case, the trapped water is

Pipes, Pipe Fittings, and Piping Details

Figure 8-45 Method of connecting drips from downfeed risers into wet return and discharging some through a trap into overhead vacuum return main.

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Figure 8-47 Right and wrong ways of making up coils.

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Pipes, Pipe Fittings, and Piping Details

Usually caused by an improperly pitched supply line, rather than fit­tings. You can create a slight pitch in the line by slipping wedges under the radiator. Space the wedges so that the radiator remains level (check it with a carpenter’s level); otherwise, the radiator will not operate properly.

Pressure Tests

ECCENTRIC REDUCING FITTING

подпись: 
eccentric reducing fitting

Figure 8-51 Using an eccentric reducing fitting to eliminate water pockets.

подпись: 
figure 8-51 using an eccentric reducing fitting to eliminate water pockets.
Pressure tests are performed on hydronic heating systems on a peri­odic basis to determine the condition of the piping/tubing and sys­tem components. These tests are described in Chapter 1 (“Radiant Heating Systems”) in Volume 3.

Posted in Audel HVAC Fundamentals Volume 2 Heating System Components, Gas and Oil Burners, and Automatic Controls


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