40
STATIONARY RING
Step 1. Determine outer diameter of stationary seal ring.
The top stationary seal ring is a
shrink fit in the headcover. The amount of interference between the ring and the headcover
should be sufficient to prevent the ring from becoming loose when the unit is watered up. The
stress in the zing should be checked, but the limiting factor on the amount of interference will be
the required installation temperature. The required installation temperature should not be lower
than -109
should be sufficient to prevent the ring from becoming loose when the unit is watered up. The
stress in the zing should be checked, but the limiting factor on the amount of interference will be
the required installation temperature. The required installation temperature should not be lower
than -109
o
F, the temperature of dry ice. Lower temperatures are attainable with other cooling
mediums such as liquid nitrogen, but this is not practical with large rings. A strain of 0.0005 inch
per inch should provide a fit that is sufficiently tight and attainable with dry ice.
per inch should provide a fit that is sufficiently tight and attainable with dry ice.
Step 2. Determine stress in ring caused by shrink fit.
Step 3. Check effect of watering up.
Assuming a worse case of unit being dry and at a
temperature of 70
o
F and being watered up suddenly with 40
o
F water, determine whether ring will
remain tight.