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.leaning and Flushing
Serious mechanical damage to turbomachinery can result from operation with dirty oil systems. It is essential that an oil system be thoroughly cleanedprior to the initial startup of a new machine， and after each overhaul of an existing machine.
Preliminary steps for the initial startup and startup after the overhaul aresimilar， except for the reservoir and oil requirements on the machine after an overhaul. For anoverhauled machine， the oil is drained and tested forcondition. If there is no water or metalchanges， the oil may be used again.
Inspect the reservoir interior for rust and other deposits. Remove any rustwith scrapers and wirebrushes， wash down the interior with a detergentsolution， and flush with clean water. Dry the interior by blowing the surfaces with dry air and use a vacuum cleaner to remove trapped liquids.
Install all new five-micron pleated-paper elements in the filters. Connect steam piping to the water side of the oil coolers for heating the oil during the flush. Remove the orifice and install .umpersat the bearings，coupling，controls，governor， and other critical parts to prevent damage from debris during the flush. Make provisions for 40-mesh telltale screens at each.umper. The conical-shaped screen is preferred， but a flat screen is accept-able. Ad.ust all control valves in the full-open position to allow maximum flushing flow. The effectiveness of the flush depends to a large extent on high flow velocities through the system to carry the debris into the reservoir and filters. It may be necessary to sectionalize the system to obtain maximum velocities by alternately blocking off branch lines during the flush.
Fill the reservoir with new or clean used oil. Begin the flush without telltale screens by running the pump or pumps to provide the highest possible flow rate. Heat the oil to 160 .F (71 .C) with steam on the oil cooler. Cycle the temperature between 110 .F (43 .C) and 160 .F (71 .C) to ther-mally exercise the pipe. Tap the piping to dislodgedebris， especially along thehorizontal sections. Flush through one complete temperature cycle， shut-down and install the telltale screens， and flush for an additional 30 minutes. Remove screens and check for the amount and type of debris. Repeat the preceding procedure until the screens are clean after two consecutive inspections. Observe the pressure drop across the filters during the consecutive operation. Do not allow the pressure drop to exceed 20 psig (1.4 Bar).
When the system is consideredclean， empty the oil reservoir， and clean out all debris by washing with a detergent solution followed by a freshwaterrinse. Dry the interior by blowing with dryair， and vacuum any freestanding water. Replace the filter elements. Remove .umpers and replace orifices. Return controls to their normal settings. Refill the oil reservoir with thesame oil used in the flush if lab tests indicate it is satisfactory. otherwise， refill with new oil.
Because of the high flow velocities obtained during the flush， the previous procedure will allow the fastest possible cleanup of the oil system. The ob.ective is to carry the debris into the reservoir and filters. The turbulencefrom the highflows， along with the thermal and mechanical exercising of thepiping， are the main factors necessary for a fast and effective system cleanup.
.oupling Lubrication
Couplings are a very critical part of any turbomachinery. They must be carefully designed and proper lubrication must be applied. The mostcommon methods of lubricating gear-type couplings are: (1) grease-packed，
(2)oil-filled， or (3) continuous oil flow.
The grease-packed and oil-filled couplings offer similar advantages and disadvantages. The main advantage is simplicity of operation. They are alsoeconomical， easy to maintain， and the grease type resists the entry of con-taminants. In addition， high tooth leading can beaccommodated， since lubricants with heavy-bodied oil can be used. An important requisite for the oil-filled type is that the coupling must have an adequate static oil capacity to provide the required amount of oil to submerge the teeth when the coupling is in operation. The greatest disadvantage of these couplings is the possible loss of lubricants during operation due to defective flangegaskets， loose flange bolts， lubricantplugs， and flaws in the coupling flanges and spacers.
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燃气涡轮工程手册 Gas Turbine Engineering Handbook 3(4)
