Rotary Vane Vac pump, sudden odd noise

My converted Masterwood Speedy 207 has a 1.1 kW dry rotary vane vacuum pump.

The machine is practically brand new, even though it was built in 1999...long story. The pump probably has about 6 hours of operating time.

I was running my first longer program, and after about 15 mins the pump suddenly got twice as loud, it's normally very quiet. I (stupidly) let it run another 5 minutes hoping to finish the program but the 6A breaker tripped.

I found 2 damaged vanes (see photos). I turned the motor manually and ran it without vanes and there is a squeak like a dry rubber seal. Otherwise the motor seems OK.

Questions:
1) What caused the vanes to be damaged? The motor did run backwards a couple times due to wiring the phases backward.

2) Should I try to quiet the seal with lubricant or just let it break in?

3) What caused the motor to draw enough current to trip the breaker?

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Most rotary vane pumps have cast iron housings. If your's stood for any length of time, rust may have developed on the surface the vanes run against. Wouldn't take long for a corroded surface to destroy the graphite vanes. While you've got it apart, you may want to change out the shaft seals as well. They're nowhere near as expensive as the vanes.

Thanks Marv, that’s probably the case. There is some rust on the mating surfaces of the housing so there is probably more in the cylinder. Hope that rotor is easy to get off the shaft, it has two tapped holes on the face that tell me it might need a special tool to pull it.

Can I just flip the vanes that are chipped? Or do they need to be chamfered?

I just replaced the vanes in our two pumps, and the new vanes come with the beveled edge. You can probably flip them, but you'd probably get a lot less vacuum until they wear in.
I would expect any light rust in the cylinder to wear off pretty quickly.

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Originally Posted by kmagyoyo

1) What caused the vanes to be damaged?

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a) vanes break when they are worn beyond the limit (not your case though);
b) vanes break when a foreign particle finds its way into the cylinder (check the air filter);
c) vanes break when they get stuck in the slots (again, check for dirt);
d) sometimes they just break for no apparent reason.
Running the pump backwards for a couple of seconds (to check the motor phasing) does not damage the vanes.

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2) Should I try to quiet the seal with lubricant or just let it break in?

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You have a 20 year old rubber seal. I would replace it if it shows any signs of aging. The bearings should also be checked and replaced/lubricated if necessary.

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3) What caused the motor to draw enough current to trip the breaker?

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Broken vanes = increased friction = increased current.

Replacing the vanes is no big deal. Just be sure to clean the cylinder from any debris, and check the air filter. If the vanes have a beveled edge, make sure you install them the right side up (refer to the pump service manual). New vanes may run louder than usual until they break in, that's normal.

P. S. I had one (Chinese made) vacuum pump fail after just a few hours because of a factory defect - some burrs or metal shavings inside the cylinder. This could be your case as well.

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New vanes may run louder than usual until they break in, that's normal.

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Ours were actually much quieter. I guess ymmv.

Thanks all for the informed and well considered replies. I think it’s very interesting the way both vanes broke in almost the exact same pattern, this leads me to believe I will find a patch of rust or irregularity in the bore the same width as the fracture. I’ll try to pull the rotor today and see.

I can't believe that rust would have caused that, especially after 15 minutes of run time. If it was rough enough to break them, it would have been very loud from the start.

I inspected the bore as best I could with the rotor in place, saw no rust. The rotor will need a special tool to pull it, so I decided “if it ain’t broke, don’t fix it”. I tried to get a shot of silicone spray on the seal, but it still squeaks a bit. It may have hardened slightly but I doubt that it is crumbling after 20 years in a cool, dark place.

I flipped the chipped vanes and reassembled, tested for 5 minutes and seems to work fine.

You are lucky that the vanes only got chipped. They usually shatter into unusable shards when they break - although that probably applies more to larger pumps where the vanes are wider and much longer.

Anyway, time to order a new set of vanes to keep as spares.