What kind of tests for bare pump?

[hubert88]

Hi All,

I have a pump which designed to ISO 5199.
To avoid prolong downtime and long lead time, I would like to purchase ONLY a bare pump to keep as spare.

Just to check, do I need to ask vendor to include: hydrostatic test, performance test and NPSH test?

 

[QualityTime]

I assume a bare pump means a pump without a motor? Not sure you can do any performance tests without a motor. If it does come with a motor do a hydrostatic test, get a performance test done, get a NPHSr curve, get a power curve

 

[hubert88]

Hi QualityTime,

Yes, you are right. A bare pump means a pump without motor.

Actually we can use shop motor if it is available from vendor to perform all the tests.

My concern is the necessity to perform the performance test and NPSH test since its operating condition would remains the same as existing pump.

Hydrostatic test maybe should be included to make sure there is no leakage.

 

[QualityTime]

if the pump is all that important to you, I would think you would want to do the tests just to make sure. The testing also ensures that it runs smoothly. Mistakes are made by equipment manufacturers. You would be suprised. It is the same for anything. Even engineers make mistakes...LOL. This will be your only chance to catch and correct it


I would also think you would need a spare set of bearings if this pump is going to sit on the shelf. On large pumps waiting in storage for installation we have the contractor rotate the shaft on a periodic basis

 

[JohnGP]

Agree with QT that testing should be requested for your spare pump, as there is no guarantee that it will be the same as any other pump coming through production. It should not be a problem for supplier to test with a shop motor, and some prefer to do it that way anyway (but perhaps more common with larger power motors). As a further aside, the manufacturer should have recommendations for specific preservation and programmed maintenance activities for the stored pump.

 

[Artisi]

As the purchaser you can ask for what ever you want- just be prepared to pay extra.
Hydro test, performance test to a nominated duty, vibration test and prepared for storage would be the norm.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[TenPenny]

It's up to you to decide what you want. I expect that the 'components', ie, casing, seal chamber, will be hydrotested as standard during manufacturing. If you want the assembled pump hydrotested, ask for it. If you want a performance test, ask for it.

Personally, I see no need for that, assuming you're buying from a reputable vendor.

 

[JohnGP]

Well you can take your chances with not testing, but when the time comes to install the pump, and it doesn't meet expected performance, and it's critical (because that's why you had a spare pump on the shelf), then it's a bit late to wish you had tested. I once had to witness a pump pull down (litigation claim because it didn't meet duty requirement, and this was a "name" pump) - as I now vaguely recall it was something simple like impeller installed the wrong way (must have been on a keyed shaft).
Upshot is I would always want to see performance testing performed on any pump I specified.

 

[QualityTime]

Agree with JohnGP. Don't assume that just because it is a brand name pump that there will be no mistakes made. Look at my previous posts. I can give you plenty of examples

http://www.eng-tips.com/viewthread.cfm?qid=417235

http://www.eng-tips.com/viewthread.cfm?qid=418631

 

[DubMac]

Depends on what you are using the pump for. A simple water pump used to occasionally fill a tank would not require anything near what a multistage boiler feed pump would require.

Hydrostatic tests are always performed by the manufacturer whether you want it or not.

Most manufacturers run a performance test anyway, they just charge you to provide the results of the test. The charge is always nominal and should be paid for.

An NPSH test can be useful if there is a close margin; your call.

For critical service pumps you may want to evaluate necessity of:

- mag particle or similar test for casting quality, or even request mill certificates.
- record vibration data (added onto performance test)
- performance test using job mechanical seals.

Ask the manufacturer what all they offer, they'll be happy to tell you.

As Artisi says, you can have whatever you want, if you're willing to pay for it.