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.

358

Nominal Weight per Foot Threaded and

Nominal

Diameter 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

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

Diameter 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>

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

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

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

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

CLOSE NIPPLE

RIGHT — AND LEFT-HAND CENTER NIPPLE

SHORT NIPPLE

THREADED END

‘ V w

SHOULDER END GASKET UNION SCREW RING

GOOD ALIGNMENT

GASKET

GROUND-JOINT UNION

BAD ALIGNMENT j

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

BLIND VARIOUS FLANGES

Figure 8-3 (Continued)

Short 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

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

Up 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

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

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

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,

F

А

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

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

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

LONG SWEEP ELBOW OR RUN OF STANDARD TEE

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

Branch

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

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 ‘

FLAT BAND COUPLING	OPEN RETURN — FOR NORMAL THREAD BEND ENGAGEMENT
CLOSE RETURN BEND
PLAIN COUPLING
REDUCING COUPLING

Size (in)

General dimentions of Crane standard malleable iron screwed fittings. The reference letters refer to the accompanying table.

395

Dimensions (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 —

…… c y ■

— ~1 C —

ALLOWANCE FOR THREADS

— —A— —■ DISTANCE BETWEEN CENTERS

D = A — 2B + 2C

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

Figure 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

Between centers of an installation.

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.

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.

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

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

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

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.

JAWS ON ■BITE’ Figure 8-13 Method of using a Stillson wrench.

Figure 8-14 Method of using a chain wrench.

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).

■SOFT’ JAW COVERS OF LEAD OR COPPER

Figure 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

Figure 8-19 Pipe cutting.

(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*

METAL UPSET BY CRUSHING ACTION OF PIPE CUTTER WHEEL

……………………. ‘

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

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.

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.

Figure 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

Size 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.

Irsw*n

Figure 8-24 Flange and pipe alignment.

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

T FITTING UNION 90°ELBOW

SEP m—»

MALE ADAPTER FEMALE ADAPTER FLARING TOOL

FEMALE ADAPTER RIGID PIPE

Figure 8-27 Double-seal flared joint fitting.

Figure 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

M

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	2У	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

		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).

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. 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

SUPPLY MAIN 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

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

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.

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 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.

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

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

DOWNFEED SUPPLY RISER TO RADIATOR 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 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 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

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

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

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

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