11 replies to this topic

[shvet1]

Good day, forum

As we know there are a lot of documents that define pump upstream and downstream piping (please expand the list if you know more):
- ANSI/HI 9.6.6
- API 686
- CEN/TR 13932

All of these documents state that any pump shall have proper inlet and outlet piping geometry to work properly. All this is Ok and well understood. My question is - what will happen if I don't follow one of these document? Let's say suction pipe slope, gas pockets and straight run. I'm not a young engineer and understand that fotos of eroded impeller and vibrating bearings are not so terrible if fotos were made after 10-20 years of nonstop work. 2 months and 2 years online is a big difference. Can you share a good report, survey or research which states why proper piping is so important and what consequence are?

[Bobby Strain]

Why not install piping correctly?

 

Bobby

[shvet1]

Because vendor has already installed improper pump skid. See fotos.

Edited by shvet1, 01 September 2017 - 02:00 AM.

[Pilesar]

  Many pumps have a long and useful life with theoretically improper piping. You will have difficulty quantifying 'potential' harm, but when you look back in three to four years you can say 'I said the piping was improper and would cause this extra maintenance.' If the pumps don't have more problems after several years, then no one will remember anyway. If the pumps are already installed and spared, then in my opinion it is not worth changing at this point.

  Some engineer representing the plant should have been responsible to oversee the vendor's work. If the responsible person was you, then you are too late to do much about this. If the responsible person was someone else, then you might quietly teach them so they can do a better job next time. If there was no responsible plant engineer, then this is an example of failure of management and the client company is risking future problems if they do not oversee vendor's work.

[Bobby Strain]

I didn't see any particular problem with the piping. The discharge pipe routing could have been better, but the suction piping is most critical. The suction piping looks OK from your photos.  I can't see any pump discharge check valves, but maybe they are wafer checks. Your operators will need to take care during startup. But operators will always find a way to make things work OK.

 

Bobby

[shvet1]

I didn't see any particular problem with the piping.

Suction side:

- no slop (can't be seen on fotos)

- no straight run

- gas pockets

- concentric reducer instead of excentric

- no vortex breaker, not enough submergence depth (can't be seen on fotos)

- tees instead of long radius elbows

- no temporary strainers

- pipe spool between pump and valve can't be removed

 

Discharge side:

- check valves downstream of valves

- gas pockets

- spillback is routed straight to suction instead of vessel

 

  Many pumps have a long and useful life with theoretically improper piping.

This is my idea. Is or is not there a problem? Straight run and other requirements - what is it? A fairy tail to scare young process engineers or it is a real problem that shall be solved before facility start?

 

 

  If the pumps are already installed and spared, then in my opinion it is not worth changing at this point.

Thanks for your opinion.

 

 

    Some engineer representing the plant should have been responsible to oversee the vendor's work. If the responsible person was you, then you are too late to do much about this. If the responsible person was someone else, then you might quietly teach them so they can do a better job next time. If there was no responsible plant engineer, then this is an example of failure of management and the client company is risking future problems if they do not oversee vendor's work.

I was asked for help by a client's person who is resposible to oversee EPC-contractor work. I'm just trying to be as helpfull as I can. And it is a good engineering challenge for me to understand the real causes and consequences.

Edited by shvet1, 04 September 2017 - 01:21 AM.

[gegio1960]

my 2 cents...

what about the pumped fluid and its conditions?

at bubble point?

with solids?

velocity?

......

anyway, who has designed in this way is not a professional

good luck!

[shvet1]

 what about the pumped fluid and its conditions?

It is cooling water circuit. Reverse cooling water is chilled in cooling tower by air. Water is pumped from water pool by 2 parallel pumps. Cooling tower and pumps are moduled in 2-3 FEU ISO-containers by manufacturer. Actually I don't know is it subcontractor or EPC-contractor scope of supply.

 

 at bubble point?

 

Water 30-40°C. Ambient air is -35°C and a lot of snow during winter. Skids are installed outdoor.

 

 

with solids?

Froth, scales, sludge, dust. Range is as in usual refinery cooling water with cheap water treatment. Nothing special. Water make-up is a river water.

 

 

 

velocity?

Unknown. There is no flowrate control. Flowrate is controlled by hydraulic system. My estimation:

- suction ~1 m/s

- discharge 1.5-2 m/s.

Edited by shvet1, 04 September 2017 - 04:24 AM.

[gegio1960]

the good new is that CW is a "cold service", not very critical under the cavitation point of view.

in fact, a lot of the recommendations are mainly generated by the need of avoiding gas formation in the pumped liquid.

the bad new is that "brakish" water is a not a very clean service.

moreover and positively, the fluid velocity seems well within the ranges suggested by the industrial practices for this service.

it shouldn't be very difficult to try the following:

- put the temporary strainers on the pump suction

- install the check valves just downstream of the pump discharge

- install the vortex breakers

Edited by gegio1960, 04 September 2017 - 07:27 AM.

[breizh]

Hi,

hope this is helping the OP and others.

my 2 cents,

Breizh

 

[Bobby Strain]

I guess your client got what they paid for. Since you have a tank, I assume that the fluid is the chilled water.  Like I said, operators will find a way to make it work. But the pump suction should have a strainer. Good luck.

 

Bobby

[shvet1]

I guess your client got what they paid for.  

How properly installed pumps depends on money paid for? Does process facility engineering quality depend on money spent? If there would be a link 3d world countries have much better process industry.

No. I have another point of view. There is no or weak bond between money and quality. It more relies on sound competition and business.