Page 454 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

432 Major Process Equipment Maintenance and Repair

ings. See manufacturer’s data for maximum permissible thrust meter dif-
ference.
For reference purposes a third meter, the center one, reads the con-
trolled pressure behind the compressor impeller.
A thrust balance valve is generally furnished. The adjustment of this
valve is set at the factory and readjustment is not needed unless:
1. The operating conditions change.
2. There is a major deterioration of one of the seals, as by erosion
from dust particles entrained in the gas.
3. Deposits of ice or the like collect in the vent passages. An unex-
plained, significant change should be investigated.

On modern turboexpanders, adjustments are made automatically at all
speeds. An alarm switch is installed to warn the operator, should pres-
sure reach a preselected pressure on either thrust bearing. The unit will
shut down automatically when the pressure reaches a higher, preselected,
shutdown pressure on either thrust bearing. If activated, an investigation
of wear on seals or wheels should be made immediately.

Normal Operation and Periodic Service
Normal operation requires only routine monitoring of system controls
and gauges.

1. The following should be checked frequently:
a. Reservoir oil level
b. Seal gas flow
c. Lube oil pressures
d. Lube oil temperature
e. Thrust meters

2. The lube oil should be changed as often as found necessary by indi-
cations of lube oil contamination. However, frequent checks, espe-
cially of oil viscosity, should be made.
3. Filter elements should be changed with each lube oil change.

Filter or Heat Exchanger Servicing While In Operation (Caution!)

If a filter or heat exchanger is taken out of service and drained, it must
be refilled manually before being placed back in service. Otherwise, the
filling of it may take excessive oil from the bearing supply. Also, the dis-
placed air may be forced through the bearings.