08/09 Ed., Rev. B
Page 8of 16
Inspection
Once disassembled, the reusable components of the pump will need to be inspected for
damage. This includes the body, the rotor and the bypass.
1) Pump Body
:
Check the pump body for dents on or around the rim that may impair the insertion of the new
graphite. The rim or ports are the most likely areas for a pump to be dented, and dents can
crack graphite as it is being inserted or keep fittings from screwing in the ports. If the body is
dented, try tapping it out carefully with a hammer if possible. Sometimes a file can be used to
take down the remaining high points. If the ports look damaged, running a tap through the
threads sometimes cleans them up. Also check the body for dirt or debris which could keep
the pump from being assembled properly, or damage the pump when put back into service.
The body should be thoroughly washed out before proceeding.
2) Bypass:
The bypass acorn nut can be removed to check the condition of the bypass valve and seat.
Remove the nut and components, and start by checking the bypass valve. The tapered
portion on it which seats against the hole should be smooth and have very little or no wear on
it. Check the edge of the hole that the valve seats in. This should also be smooth and free of
wear or erosion. If either of these is worn, this could prevent the pump from priming properly,
and/or reduce the flowrate out of the pump. If the valve is worn, it should be replaced. If the
valve seat is worn, the body may not be reusable. If the damage looks minor and the body is
brass, you can try “reseating” it. Drop a 3/8” steel ball bearing into the hole and using the rod
(material #3) hit it several times with a hammer. This can sometimes smooth out the hole
enough to make it reusable.
3) Rotor:
The rotor should have a smooth surface finish. A rough surface will wear out the graphite
quickly as the rotor spins. A nicked or dented slot will prevent the vanes from sliding in and
