Pump shaft and flange misalignment

[stephelton]

I've had a couple march pumps for many years now and they've increasingly been unreliable. They symptom they exhibit is that they will start making a low rattling sound shortly before they turn into an alarming high pitched squeal, at which point they stop pumping.

I noticed last night that the flange that attaches to the main pump housing isn't quite aligned with the pump shaft/magnet. Consequently, when the pump head is attached to the flange, the impeller isn't quite aligned with the magnet. I think this problem has been getting worse; when I reattached everything last night, the pump housing was actually touching the magnet and preventing the shaft from turning altogether.

My guess at this point is that the main pump housing is warped or offset slightly, and thereby the flange and pump head that attach to it.

My setup is a bit unusual. I've had these pumps in a few different "pump boxes" over the years. When I started having severe problems with the pumps a couple weeks ago, I decided to build my third version of the pump box (pics below). However, the previous version (Pump Box 2.0) was a ghetto cardboard box (actually, a nice sturdy one from a Hops Direct shipment.) In this setup, I had the box between the housing and the flange, which made for a slightly uneven surface between the two -- I think this might have been part of the problem.

By the way, I'm using march pump bodies with chugger pump heads (I wanted to go all-stainless and/or spend extra money).

So... any thoughts on what might be wrong and what I might do to fix it?

pics:

3.0: https://www.dropbox.com/sc/pdd0qh62oh07vda/AADm_CDFVfHt1ykO17kD0wHla
2.0: https://www.dropbox.com/sc/7ip5cpe9oazoabq/AADx5pDwhcBzyw9plNfZVKzza

 

[WalterAtMarchPump]

Are you removing the motor bracket to mount this stuff up? If so you are probably messing up the alignment of the drive magnet in relation to the pump housing. We use a jig here at the factory to center up everything. Also you will need to off set the drive magnet the thickness of the separating wall.
As for the squealing...its usually a sign of lack of lubrication for the impeller....if you know for a fact you are flooded and not sucking in air bubbles off the bottom of the kettle during boil, then you may have a pump with tighter then normal tolerances. Easiest thing you can do is just drill out the bore of the impeller with a 17/64" drill bit and that will open it up a few thou and get more liquid between the impeller and shaft. While you in there make sure the teflon thrust washer is still there too

 

[stephelton]

Thanks for the reply, Walter. The newest pump box actually has no separating wall -- I suspected that was causing problems, so I wanted to avoid that this time around.

No, I never messed with the pump bracket.

After playing with it a lot, I found that there's a good bit of play in the flange mounting, and that without the separating wall to confuse things, it was easy to align that to make the pumps happier. Basically, I loosened the 4 screws connecting the flange to the pump bracket (body, I called it), then turned the pump on, primed it, and played with it while screwing the flange in.

The pumps are happily working now, but I do still see the squealing issue when they run dry (particularly pump #1). I have never replaced the washers/gaskets, so I may do well to replace those. If I continue to have problems, I'll consider increasing the impeller bore just a bit.

Thanks again for the tips.