2 replies to this topic

[mmole]

i have been given a project to investigate the rusultant failure of a centrifugal pump and come up with alternatives to solving the problem of failure.

so far i have gathered that cavitation is one of the major causes of failure, and also what has come to my attention is that operation personnel cool the pump with water which might damage the pump.

a pressure pack is one of the devices that doesnt cavitate, and i was just wondering how it operates and how viabe and effective it might be as opposed to a centrifugal pump.

how else can we cool down the pump without damaging it and not affecting production.

how does the incline of the suction line affect the pump?

hoping for a reply. thanks

[Art Montemayor]

MMole:

You mention some items related to centrifugal pump operations and ask help in others. I can respond as follows:

• You should be specific as to what caused your centrifugal pump to fail – and in what manner. If you don’t know, at least tell us all the details of the operation and the sequence of events – such as fluid identification, pressures, temperatures, fluid vapor pressures, make and type of pump, capacity controls employed, etc. etc.
• Yes, cavitation is one culprit that hampers pump operation. But what has it to do with your operation? Can you definitely put your finger on cavitation as your problem? What is the reason your personnel are putting water (spraying it directly on?) on the pump? Have you asked them for a justification? This can cause material damage to any pump operation in various ways and is definitely not the proper, engineering manner of resolving a problem. Find out and tell us.
• What is a pressure pack? I have only been specifying, purchasing, installing, and operating centrifugal pumps for over 45 years and so I have never heard of such a thing (device?) or machine. Can you be specific and describe what you mean?
• You can cool down the fluid entering a pump using a heat exchanger.
• I can’t imagine how the slope of the suction line to a pump affects its operation. I can readily see how it can help to drain the line when the pump is shut down. But other than that, I don’t see any advantage unless you feel you can save on a slight piping length.

When you respond, an isometric sketch on a spread sheet would be a great help in defining just exactly how your pump installation looks like and what are the piping dimensions and layout.

You should also, by now, have developed a NPSH availability to the pump suction eye and be able to compare it to the pump’s NPSH requirements. You should also have calculated and developed a system curve for your pump’s installation and operation. All this would be helpful if included in the same workbook with the sketch.

Await your response.

[pawan]

I fully agree with Art,

We dont know, on what basis, u have concluded the cavitation as a problem. This might be ur own justification, but anyway U must have all NPSH figures in that case.

Pressure pack is not suitable for process fluids, It is useful only for hot condensate due to higher wear & tear in case of Centrifugal pumps. Its a mechanical device pumping liquid out of the vessel by sudden injection of live steam. See more details on my Blog - Click Here

Reg Inclination, it is definitely going to reduce NPSH due to some extra losses, so avoid it if U can.