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M A I N T E N A N C E
TYPE D OR F SEALS - EXTERNAL BALANCED
GENERAL
WARNING
Before servicing the pump, disconnect electrical power
source, carefully relieve all pressure, and drain all fluids
from the pump and connected piping.
The D and F balanced seals are identical except that the F seal has a water cascade provision.
The DG and FG types are similar, but incorporate a replaceable clamped-in stationary seal seat.
The FG has a water cascade.
A balanced design utilizes pump internal pressure to aid the seal spring in maintaining seal
contact with the backplate.
The seal is centered on the pump shaft by a recess that pilots on the nose of the drive collar. The
recess also accommodates an o-ring that prevents fluid leakage from the rear of the seal.
Torque is transmitted by tabs on the seal cup that engage slots on the seal periphery and by
another slot that engages a lug on the drive collar.
The seal should be replaced when the clearance between the carbon seal face and the stationary
seal surface is less than
1
/
32
" or when leakage is observed.
DISASSEMBLY
1.
Disconnect piping.
2.
Remove the casing clamp, casing and impeller.
3.
Rotate the backplate to disengage the hooks that secure it to the pump frame and remove.
The seal rotating components will now be accessible.
INSPECTION
Examine the seal rotating and stationary sealing surfaces for nicks, scratches or other damage
and replace as necessary.
Inspect the o-ring for abrasions, cuts and resiliency. Replace if defective.
The pump shaft should be unworn and free of nicks and scratches, especially in the area of the
seal o-ring contact.
