Page 455 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Steam lirrbines and Turboexpanders 433

To replace a fdter element, turn the switching valve to opposite fdter
from the one to be serviced.

1. Close equalizing valve.
2. Carefully remove drain plug of the filter housing to drain the oil.
3. Open the filter housing to remove the used element.
4. Insert new filter element.
5. Replace drain plug in the filter housing.
6. Manually fill the filter housing with clean lube oil.
7. Reassemble the filter housing. Make certain it is closed securely.
8. Open the equalizer valve.
9. Open the bleed valve.

After it is purged for ten minutes, the bleed valve should be closed and
the switching valve cautiously and gradually returned to a desired posi-
tion. Be camful not to significantly reduce the pressure ofthe oil to the
bearings during the switching process.

Note: The equalizing valve always remains open except when changing
filter elements.

Annual inspections of the expander-compressor are not essential, un-
less damage is suspected.
On units furnished with bladder-type accumulators, periodically check
accumulator bladder pressure. To do this, isolate the accumulator from
the system pressure by closing the block valve. Then drain the accumula-
tor by carefully opening drain valve.
Cazuion: The accumulator is under high pressure and some method
must be devised for receiving the high pressure of the oil to be drained.
Connect charge kit to the filling valve located on top of the accumula-
tor, and add nitrogen gas to achieve the pressure recommended by the
manufacturer.
'Ib place the accumulator back in service while the machine is in opera-
tion proceed as follows:
1. Close the drain valve.
2. Open the block (isolating) valve very graduulZy to fill the accumula-
tor to its capacity. Make sure this step is done gradually to avoid a
sudden pressure drop in the lube system which could nigger a shur-
down andperhaps cause damage to the bearings.

Normal Shutdown

1. Close the expander inlet block or safety trip valves.
2. Observe the expander to determine that rotation has stopped.