Repairing vacuum pump?

[cokeguy]

We have a damaged SIHI liquid ring vacuum pump, model LPH 60520, cast iron casing and ductile iron impeller. Inner surfaces are pretty worn out, with irregular "craters" throughout side covers and casing, some more than 5 mm deep.

What amazes me is that the pump worked OK, up until the day where we had to install the spare one because some of the "craters" were already leaking into the outside of the casing. This pump is used in a rotary vacuum filter where calcium sulphate is removed from a slurry. Due to misuse/abuse, calcium sulphate sometimes ends up inside the pump, which ultimately caused its demise.

My question is, can those pumps be repaired? I´m (probably obviously) totally illiterate regarding vacuum pumps, and our vacuum pump supplier told us (obviously)that it cannot be repaired. We´ll get a new one anyhow, besides the spare, but we have a pretty good machine tool shop that works for us and I´m sure they could coat and grind interior surfaces on the damaged one, if only I knew what tolerances it requires, and if those tolerances are critical or not to the correct operation of the pump. I always thought that since the liquid ring acts as seal between casing and impeller, mechanical tolerances weren´t critical. Any comments? Thanks.

p.s. we do need a good vacuum of at least 20 inHg vacuum in our process.

 

[TenPenny]

Yes, they can be repaired, but the question is whether or not it's economical to do so. There are many people who specialize in vacuum pump rebuilds; that's the way to go. If you have someone that you deal with for major rotating equipment rebuilds, talk to them, but but but make sure they can give you references - there are lots of people who claim they can do the work, but you want someone with a proven track record. You really want a shop that does vacuum pumps regularly to do this sort of work.

What region are you located in?

 

[Artisi]

You can repair anything if you have the expertise, time and money available.

You could metal or ceramic spray the surfaces and grind back to standard or it maybe possible to overbore the stator and shrink a sleeve into it, tolerance wouldn't be critical provided you have enough end clearance between rotor and stator.

 

[cokeguy]

Thanks, we are buying a new spare pump anyway, so Í don't mind experimenting with the damaged one. The machine tool shop we regularly deal with is willing to try even though they haven´t dealt with a vacuum pump before, and they are cheap when they are experimenting. However, we don´t know what the clearances between rotor and stator and between rotor and side covers should be, and whether they are critical or not. Thanks again for your comments.

 

[itsmoked]

Gonna buy a new spare? Open it and look.

If needed use modeling clay to find the clearance.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[pumpking]

Have a look at

http://www.pumpgroup.co.uk

who are specialists in vacuum pump manufacture and repair (in fact they have the largest test facility barring actual manufacturers) they do LOTS of work with a product called 'Belzona' for pump repairs - talk to a guy called Martin Cooper if you need more info.

They can re[air to real good tolerances to bring back to 'as new' and generate excellent vacuum levels.

They are our agents in the North of England !!

http://www.cdrpumps.co.uk

Ash Fenn

http://www.cdrpumps.co.uk