CMMS Fleet Maintenance
Software for Fleet, Vehicle, & Equipment Maintenance
Step 1. Determine inner diameter of rotating seal ring. The stress induced in the seal ring by
the shrink fit (i.e., the difference between the inner diameter of the seal zing the outer diameter of
the turbine runner) in most cases should not be more than one-third of yield strength of ring
material. The desired unit deformation, or strain, is calculated based on one-third of the yield
strength. The amount of shrink fit is then determined by multiplying the strain by the diameter of
the runner. This value is subtracted from the diameter of the runner to obtain the inner diameter
of the seal zing.
Step 2. Determine stress in ring caused by centrifugal force. The stress in the ring caused by centrifugal
force will be maximum at runaway speed. Compare this value to the shrink fit stress. If the stress caused
by the centrifugal force is greater than the shrink fit stress, the ring could become loose on the runner.
This Information is Reprinted From UNITED STATES DEPARTMENT OF THE
INTERIOR BUREAU OF RECLAMATION