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6-1
Chapter 6
Fault Finding
Poor PCU Spin/Sensitivity
The clean pneumatic piston/weight carrier assembly will rotate freely, without additional
weights, slowing down gradually to a complete stop. If the rotation stops quickly, then
the PCU may be dirty and require cleaning. If the piston “squeaks” when rotated, it must
be cleaned immediately, see Chapter 5, Maintenance & Servicing.
To check the freedom of the PCU, open the Exhaust valve and hold the weight carrier.
Lift the piston vertically, gently up and down. It should slide freely within the cylinder, if
any resistance is detected, it must be cleaned immediately.
W
Caution
Do not rotate the piston if it is dirty as permanent damage can
occur.
If the spin/sensitivity of a recently cleaned PCU deteriorates quickly, then it is likely that
the hydraulic system has become contaminated. If this is the case, the system must be
completely dismantled, thoroughly cleaned and rebuilt before further calibration is
carried out.
During the normal operation of a deadweight tester, gas flows slowly through the tiny
gap between the piston and its cylinder. If the system has become contaminated, any
particles will tend to move towards the PCU and thus affect its performance, and possibly
damage it.
System Will Not Pressurize
1. Ensure that Inlet and Exhaust valves are closed.
2. Ensure for missing or dirty seal in test port.
3. Ensure that the sealing face of the DUT is not dented or scratched, and is correctly
contacting the seal in the test port.
4. Ensure that the external supply is correctly connected and functioning correctly.
5. Ensure that the selector valve(s) are correctly positioned (if fitted).
6. Ensure that the safety valve (models with vacuum PCU only) is seated correctly.
7. Ensure that the DUT is not leaking.
1.888.610.7664 sales@GlobalTestSupply.com
Fluke-Direct.com
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