Dust pump 2950 Removed from EX Failed to turn over when plugged in on the test bench.
After we opened it up following the procedure dcc.ligo.org/LIGO-T2100415dcc.ligo.org/LIGO-T2100415in T2100415-v1 we found the vanes were broken and had Jammed the pump, stopping it from rotating. See pictures attached.  
When we tested the pump after the rebuild it had excellent performance on the test bench. But once again when we redeployed the unit it seemed to have a hard time pumping down.
After adjusting the tightness of the plastic black filter caps and seals on the front of the pump housing, I noticed that it was leaking from the exhaust seal. Once I realized that the there wasn't anywhere that the exhaust could easily be expelled from, it all made sense. The brass manifold muffler was clogged and installing a new one resolved the issues of the pumps not being able to pump down properly when deployed. The reason that the pumps work on the test bench and not when deployed is that the volume of air that needs to be pumped down when deployed is much greater than the volume of air they pump down during testing.

Dust pump from CS 1194 was opened up. The filters had holes in them and there was a lot of black fuzz on the inside. Vanes looked good though. We rebuilt it anyways because it hadn't been rebuilt in a while.
While on the test bench, I made a cable to power it from AC Power. This pump seemed to lurch forward and then sputter out, lurch then sputter. Kinda sounded like a lawn mower that was running out of gas. I think the extention cablewe used in the welding shop may not be able to provide enough energy to run this particular pump as it's much bigger than the corner station pumps. But the vacuum pressure was good during the sputtering. So we took it to the Corner Station tested in place and decided to leave it running. The Brass Manifold Muffler was replaced on this pump.
3238 was removed from duty and placed on the floor as it likely needs a new Brass Manifold like all the others. 

I updated the maintenance log.

Documents:
LIGO Document T2100415-v1 Checking Dust Monitor Vacuum Pumps
LIGO Document E1600132-v4 Gast Rotary Vane Vacuum Pump rebuild procedures (note: I have not yet modified this document to denote the replacement of the Brass Manifold Muffler) 
LIGO Document Q2200010-v4 Dust Monitor Pump History & Rebuild Maintenance Log