Page 456 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

434 Major Process Equipment Maintenance and Repair

Note; It is preferable not to close the nozzles on shutdown, because slight
leakage from the shutdown valve sometimes causes ‘yet stream-
ing” which can make the expander rotate when the nozzles are
closed.

3. Shut off compressor gas flow.

Note: There must be a provision, such as a check valve, to prevent re-
verse flow through the CompressoI:

4. Shut down the lube oil system.
5. When the oil pressure reads zero, shut off the seal gas.

Emergency Shutdown

In the event of system malfunction, the safety devices will automati-
cally close the expander safety trip valve to shut off the process stream to
the expander. Under normal conditions, the seal gas and lube systems
will continue to function unless those systems are the cause of the emer-
gency shutdown.

Turboexpander Maintenance
In these procedures, every question obviously cannot be answered nor
every problem anticipated. The maintenance person must use judgment
in handling the parts, and be careful to follow the manufacturer’s draw-
ings. If maintenance must include disassembly of the turboexpander, dis-
connect all lube oil and seal gas piping and all instrumentation lines. Plug
all lines to prevent the entry of any foreign matter.
The manufacturer’s reference drawings should clearly indicate the at-
tachment of all assembled parts.

Field Removal

Refer to the manufacturer’s service assembly drawing and parts list.
Some of the components are heavy and a hoist should be made available
for support during field removal. Extreme caution should be exercised in
the handling of all internal parts. These have been precision machined
and dynamically balanced. Careless injury to parts may result in irrepa-
rable damage. Avoid marring any flange face or gasket face.