What happened to this brand new motor? Tomas from the Lifco content/media team here; this PGM511 came in with a blown out shaft seal. Upon inspection, nothing out of the ordinary was noted.
Video: PGM 511 Gear Motor
Tomas: On the PGM511 video with Russel (linked above), I've never seen a pump or motor on our channel that looked so new (besides the blown shaft seal of course). Why did this motor look so good on the inside, despite failing? Did they only run it for a second?
Fraser: System problem. Nothing wrong with the motor but it needed a proper way for the housing to drain. It might've slowly leaked out the shaft seal at first. But the large rupture would've been sudden. (See pictures below for diagram of the motor)
Tomas: Did we ever figure out what was preventing the housing from draining in this system? If not, what's your best guess for why this happened?
Fraser: No, details were limited. But there is something impeding the flow from the motor to the tank. My guess was a filter that was clogged. There should be a bypass on the return line filter that opens if the pressure gets too high.
Tomas: Are gear pumps more susceptible to shaft seals leaks/blow-outs than other types of pumps? Seems like we see more gear pumps with this problem than other types, is this the case?
Fraser: This one was a gear motor, the distinction is important because it has to be able to spin both rotations. That's why it has valving to drain it through whichever side is low pressure (not "lower" pressure, but an actual low pressure that is below the pressure of the shaft seal). The uni-directional pumps don't have this problem: they spin just one direction and so the internals of the gear pump drain the leakage right back into the pump’s inlet. I see lots of piston pump shaft seal blowouts. Piston is common when there is high internal leakage from something like a dry start. I don't see many vane ones. When I do, vanes seem to be more about fluid compatibility and fluid viscosity creating pressure. It would be an interesting article on "What has a case drain, and what doesn't