Page 464 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Steam Turbines and Turboexpanders 441

Labyrinth Seal Clearance

Should it become necessary to ascertain if the heat barrier labyrinth
bore is worn, proceed as follows:
1. Remove heat barrier wall (102) with dust free seal. Measure and
record shaft axial end play.
2. Loosen expander side bearing screws and pull the bearing (137)
away from the housing. Remove compressor impeller (170). Re-
place heat barrier wall and dust-free seal. Measure and record shaft
end play to heat barrier wall.
3. If the reading from Step 2 exceeds the reading from Step 1 by more
than .030 in., replace the heat barrier wall.
Similarly, check the labyrinth bore of the compressor seal and replace
if the reading exceeds .030 in.
To set the clearance between the expander rotor and the nozzle fixed
ring, and the impeller follower and impeller, pull the shaft toward mini-
mum clearance and check with clay on the face of the blades. The clear-
ance should be a nominal .020 to .025 in., measured between the contour
surfaces. Adjustment is made with shims.

References
1. De Lava1 Engineering Handbook, edited by H. Gartmann, Mc-
Graw-Hill, New York, third edition, page 5-6.
2. Handbook of Loss Prevention, Allianz Versicherungs-AG, Berlin/
Munchen, Germany. Springer Verlag, New York, 1978, page 164.
3. Bloch, H. P. and Geimer, E K. Machinery Failure Analysis and
Troubleshooting, Gulf Publishing Co., Houston, Texas, 1983,
pages 289-476.
4. Bloch, H. P. Improving Machinery Reliabiliry, Gulf Publishing
Co., Houston, Texas, 1982, pages 38-47.
5. Reference 3, pages 268-275.
6. Cowgill, T., and Robbins, K., “Understanding the Observed Ef-
fects of Erosion and Corrosion in Steam Turbines,” Power, Septem-
ber 1976, pages 66-72.
7. LaLena, P. and Glaser, F., “Consider Foam Cleaning for Turbines,”
Power, March 1980, pages 66-68.