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Page Title:
Mechanical seal and alignment test |
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|  MIL-P-17840C(SH)
The mechanical seal and align-
4.6.5 Mechanical seal and alignment test.
ment test shall be as follows:
(a)
The mechanical seal on one pump of each size on the contract or
order shall be installed and aligned precisely in accordance
with the procedures stated in the proposed pump technical manual.
Packing shall not be installed during this test. The amount of
force required to axially position the mechanical seal onto the
impeller hub, the shaft sleeve, or whatever it rests on in the
assembled condition shall be measured and recorded. If the
mechanical seal includes an adhesive or setting compound on the
elastomer that seals between the mechanical seal and the impeller
hub or shaft sleeve, and if there is a maximum allowed time
between initial wetting of that compound and final positioning
of the mechanical seal in the pump, then do not perform that
final positioning until the maximum allowed time has clasped.
After installation, the mechanical seal shall be run in and the
(b)
pump operated for at least 4 hours at maximum rated speed with
the pumped fluid at maximum operating temperature and with pump
suction pressure as high as feasible without requiring pump
test loop modifications. The seal leak rate shall then be
measured and recorded. Also, the dynamic balance shall be
measured and recorded using a vibration indicator of the neon
tube or similar type capable of measuring vibrations of 0.001
inch or less. During subsequent pump disassembly, the final
axial position of the mechanical seal shall be measured and
recorded if the pump design permits.
Acceptance criteria: Mechanical seal leakage shall not exceed 5 drops per
minute. The pump and drive shall exhibit no abnormal noises or roughness of
operation. Vibration shall not exceed the limits specified in MIL-STD-167-1,
type II, measured on the bearing caps. The mechanical seal shall have been
positioned at the axial position recommended by the mechanical seal vendor to
generate the proper amount of mechanical seal spring force. The mechanical
seal vendor shall provide in writing his recommendation regarding the axial
position and his concurrence that the mechanical seal alignment test results
demonstrated proper positioning of the seal. If it was not practicable to
measure the axial position of the mechanical seal, then the seal vendor shall
concur that the recorded force used to position the seal during assembly was
acceptable and shall state the technical basis for considering that force
acceptable. A copy of these mechanical seal vendor documents shall be provided
as part of the test report.
4.6.5.1 Packing and alignment test. The mechanical seal shall not be
installed during this test. The pump shall be packed and aligned precisely in
accordance with the procedures stated in the proposed technical manual. The
packing shall then be run in the pump and operated for at least 4 hours at a
maximum rated speed with the pumped fluid at maximum operating temperature and
with pump suction pressure as high as feasible without requiring pump test loop
modifications. The time of day of each packing leakage measurement and of each,
packing adjustment shall be recorded. The dynamic balance shall be checked
with a vibration indicator. After the tests, the packing and shaft sleeve
shall be inspected and the results recorded. If the rated maximum operating
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