Commissioning and start-up

General

Many fan units are supplied with large quantities of operating and maintenance manuals and other paperwork such as Certif­icates of Conformity and the like. It is a particular gripe of the au­thor that they are rarely available to the process operators or site maintenance staff. These people need such information on a daily basis, but instead the manuals reside in a project file, gathering dust.

Whilst they may be of interest when the plant is duplicated, this is not their purpose. Even worse is the situation where the con­tractor takes out what he thinks is the essential information to give the operators!

The transition from installation to operation is commissioning and start-up. Commissioning can often be performed by site staff but if they are unfamiliar with any features of the fan then they should seek information from the manufacturer. It is often then possible to combine commissioning with staff training.

Start-up

When erection is complete, shafts and impellers should be checked for freedom of rotation. As erection proceeds care should be taken to ascertain that no tools, pieces of packing etc, are left in the fan or ducts to cause obstruction or damage when the machine is started up.

When direct motor-driven, the direction of rotation of the motor should be checked with the fan, preferably before connecting up to impeller, coupling, or vee belt drive. This is important where special thrust bearings may be employed. The correct impeller rotation is shown by an arrow on the fan casing.

When the machine is driven through a coupling it is particularly important that correct alignment of the two shafts be achieved by checking the coupling by recognised methods for the partic­ular type; levelling up for this purpose is obtained by interposing steel packing between the underside of the bedplate and the top of the foundations. See Chapter 12, Section 12.11.

Alignment should be re-checked at the running temperature of the machine after the set has been run sufficiently long to allow for possible foundation settlement.

When the machine is indirect-driven the pulleys should be checked for correct alignment and spacing, and the driving and driven shafts must be parallel to each other to ensure that the vee belts run truly in the grooves and with recommended ten­sion of the vee belts. Excessive tension will overload bearings and cause possible damage to shafts and vee belts; conversely slack tension can result in slip leading to excessive wear on ropes and pulleys.

Precautions and warnings

Make sure that the guarding requirements outlined in Section

18.3 have been met and that the recommendations detailed in ISO 12499 have been complied with.

Before starting up check especially that the storage, installation and lubrication instructions have been followed. Then close dampers, on the inlet and/or outlet of the fan. Start and run up to full speed with dampers closed, then open gradually until the re­quired duty is obtained. These precautions will minimise start­ing time and avoid excessive load on the driving motor.

Note: An electric motor may be overloaded if a fan is allowed to run up to speed with inlet and outlet fully open. The set should be connected to the ductwork system, or the inlet or outlet dampered. Where shaft seals are pro­vided, adjustment may be necessary. If circumstances necessitate the fan being on site for a considerable time before erection and starting up, the lubricant it the bearing should be replaced. If it has been subjected to vibration from other machinery while standing, the bearings themselves may have suffered from indenta­tion of the races by the roller and they should be exam­ined and if necessary replaced before putting to work.

Remember:

1 Ensure that no tools, pieces of wood, etc, are left in the fan casing or associated ductwork.

2 Check freedom of rotation of shaft assembly.

3 Check vee belt drive alignment and tension (or coupling

Gap and radial alignment).

4 Check lubrication of bearings (and coupling if fitted).

5 Check that air connections are correctly made.

6 Check that shaft and cooling fan guards are correctly fitted and adequate clearances are maintained with rotating parts.

7 Fully close inlet and/or outlet damper.

8 Check motor and fan rotation by a flick of the starter on first start. Rotation should agree with rotation arrow on fan cas­ing. If incorrect consult the motor manufacturer’s manual.

9 Start motor and allow to run up to speed.

10 Gradually open any damper(s) ensuring that motor am­

Peres do not exceed duty figures.

Posted in Fans Ventilation A Practical Guide


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