VS4 Sump Pump vibration

[longzul]

Hye experts,

Need your advise. Currently in my plant we have VS4 type pumps for waste water treatment. The pumps used to pump out the sludge from the pit. We use double arrangement bearing at the coupling side and carbon bushing at each pipe support in order to minimize vibration. The problem is that we always have the issue on the high vibration of the pump and when we open and check, we found the the shaft already bend and the bushing totally worn out. Some of the pump use external cooling(water) and some use internal cooling(from discharge) for the bushing.

I would like so seek for advise on the
1. cooling for the carbon bushing
2. minimize foreign solid material into impeller (currently we use basket cage strainer)

Thank you very much

 

[DubMac]

These cantilevered end suction pumps can be very troublesome if not matched to their service properly. You have not given much detail so it is hard to provide a very helpful answer..... can you tell us the brand, model, speed, HP, length, flow/head??? Any kind of diagram or picture of how you have the pump mounted is also helpful. The better info in, the better the answer out.

First thing I would ask is whether or not your pump is designed for sewage?? Mainly, do you have a non-clog type impeller?? If not, you surely will have imbalance problems as solids, both spherical and stringy, get caught in a traditional impeller.

Also, was the pump mounted properly....absolutely vertical?.....very secure foundation plate, or flimsy "get'er done" installation??

 

[LittleInch]

On the basis of info to date - it looks to me like you're using the wrong type of pump. "Sludge" is such a vague term that there's no way you can design a pump properly and I'm not surprised your shaft is bending - it's probably getting continuous shock loading each time the "sludge" varies in density, viscosity and solid content.

If I was you I'd try a progressive cavity pump or a specific sewage pump - basically an open impellor with terrible efficiency, but doesn't clog.

For this duty you should always use external clean water flushing down through the shaft. You are pumping dirty water so you can't filter out the grit as our filter would constantly block and then you've got no cooling water and maybe that's what happened here. As dub mac says, absolute vertical installation is required or the bearings will wear horribly.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[longzul]

Thanks for your reply guys. Pump spec is:
Sulzer TAN1130
Capacity: 12 m3/hr
speed: 2900 rpm
Head: 32m
NPSHr: 1.3m
Power: 2.2kw
length from base to bottom: 4.7m
sump pit length: 6m
impeller type: enclosed
impeller diameter: 178mm
pump mounted on rectangular base plate

Pump is actually used for waste water which contain mixture of hydrocarbon and water (I mistakenly referred it as sludge) The average MTBF for the pump is 3 months. Some of the pump has been modofied to use the external cooling for the bushing. We use Antimony carbon for the bushing material. currently we used enclosed type bushing.
How do I prevent this problem to occur and how to improve on the cooling of bushing?
Thanks

 

[LittleInch]

Have you asked Sulzer? Sounds to me like you also need to investigate shaft vibration and where the bushes are located and also make sure that you have some sliding mechanism to allow the shaft to expand and contract. As said, if you think you're getting dirt in the water, then all bearings / bushes should be flushed with clean water.

Has the duty of the pump changed form when it was ordered? Has it been moved about? Has it been "modified" or "improved" during its life time?

I think the answer lies in these questions.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way