Page 462 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Steam Turbines and Turboexpanders 439

Varlable Nozzle Assembly

The actuator rod (224) should be positioned to relieve the force on the
pin in the nozzle adjusting ring (90) in order to ease removal of nozzle
assembly. Care must be exercised in removal to ensure that actuator rod
or pin does not become bent. Support nozzle assembly with a hoist.

1. To remove nozzle assembly from expander case (61), release shoul-
der screws. Threaded holes are provided for jack screws. Take
component to a clean work area for further disassembly. Be aware
of piston ring inserted in part (90). If it does not fall off, remove it.
2. Position housing horizontally on a workbench with nozzle assembly
end up. Remove shoulder screws and nozzle assembly clamp. Lift
off nozzle adjusting ring (90) and nozzle segments with pins from
nozzle cover.
3. Nozzle fixed ring and shims may be removed from expander case
by releasing exposed screws. 'ho threaded holes are usually pro-
vided for jack screws. To remove the expander case diffuser you
will have to release a mounting screw.
Note: To reinstall nozzle assembly, the following procedures are carried
out in a clean work area:

1. Place nozzle segments on pins of nozzle cover in closed position.
Place adjusting ring (90) over nozzle segments and engage segment
pins in slots of adjusting ring. Install shoulder screws and nozzle
assembly clamp to hold adjusting ring and nozzle segments to noz-
zle cover.
2. The nozzle assembly may now be installed in expander case by
carefully engaging adjusting ring pin in actuator rod (224). This
may require some manipulation of adjusting rod. Care must be
taken to avoid bending the pin. When the pin is fully engaged, re
place shoulder screws.

Cleanlng and Reassembly

After disassembly, the parts should be thoroughly cleaned. Parts other
than those of expander housing should be coated with a thin film of lubri-
cating oil to protect them against rusting.
Reassembly of the unit is in the reverse order of disassembly. Ensure
that the expander end of the unit is not tilted below a horizontal position,
which could allow coating oil to leak into the labyrinth seal housing.
If prevention of gas seepage is imperative, all gaskets should be coated
with a viscous sealant.