Common issues with pumps (in general, not exclusive to centrifugal or PD)

[Arshad Ahamed]

Hi Everyone,
I was preparing a presentation covering the broad classification of pumps. I was considering adding a section detailing the common issues encountered with a pump during its operation. The information available from the internet is mostly exclusive to a single category (i.e, issue with centrifugal pumps, issues with diaphragm pumps and on).

I'm a fresher in this industry and would deeply appreciate insights from the experts here.

Thank You,
Regards,
Arshad Ahamed.

 

[SandCounter]

It is strange to me that you would be preparing a presentation on something in which you have little knowledge.

In the broadest sense, issues with pumps result in them not adequately performing their designed duty. Again, broadly, a pump's purpose is to convert rotational power to water power. Since water power has two components, pressure and flow, issues will concern input power, pressure, and flow. The symptoms may be as follows:

[ul]
[li]Higher than expected outlet pressure[/li]
[li]Lower than expected outlet pressure[/li]
[li]Higher than expected flow[/li]
[li]Lower than expected flow[/li]
[li]Reverse flow[/li]
[li]Cavitation[/li]
[li]Higher than expected inlet vacuum[/li]
[li]Vibration[/li]
[li]Higher than expected power demand[/li]
[/ul]




I used to count sand. Now I don't count at all.

 

[Artisi]

And what is important, if the pump fails to produce or over produces the design flow, don't blame the pump for the over / under performance without firstly undertaking a full analysis of the system.

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.)

 

[hydtools]

Leaks. For various reasons

Ted

 

[mk3223]

Give some thought to your topics:
- Selection of the specific pump type for the application
- Proper pump sizing based on operation vs, design conditions
- Material selections based on the process fluids
- Selection of the different pump drivers
- Maintenance work, if special pump type selected

 

[pennpiper]

Please be aware, when there is poor pump performance, it is not always the Pumps fault.
Case in point: Real case, I was involved in the original design and (5 years later) I was involved in identifying the problem.

The symptoms; The pump was cycling minor to violent vibrations (up and down, up and down, etc) thus, not delivering required discharge performance.

The Owner/Operator blamed improper Piping Layout and Stress Analysis by the EPC.

Two people from the Original Engineering and Design Team were available and assigned to be Investigators to look into the situation.

Copies of the original design and stress analysis were available.

The Design Supervisor and the Pipe Stress Engineer took copies and made a trip to the Plant site.

After a through investigation it was determined that:
a) There was nothing wrong with the Pump
b) There was nothing wrong with the layout of the piping
c) There was nothing wrong with the Pipe Stress Analysis
d) There was nothing wrong with the Pipe Fabrication
e) there was nothing wrong with the piping Installation

The problem, the Investigators found was a malfunction of the Level Control Circuit.
The Liquid Level was supposed to be at a certain "Normal Liquid Level" This level was supposed to be indicated on the Main Control Panel in the Control Room.
Plant Operators were supposed to "Trust but Verify" all readouts during the day.

In this case the the actual liquid was below the "Low-Low" Liquid Level but the Level Instruments all indicated the level was at the "High Liquid" Level. This was a 15'-0" difference in the actual NPSHa.

The Plant Operators who pointed the finger at the Engineering Company were proven to be the guilty party in not doing their jobs properly.




Sometimes its possible to do all the right things and still get bad results

 

[MortenA]

they suck (could not resist)

 

[Longinthetooth]

I remember being told by a pump guru that 90% of all pump problems were on the suction side of the pump.

 

[Artisi]

Not sure about 90% being being suction side, but can count for many of the so-called pump problems, followed closely by over estimation of head requirements based on actual operating conditions - which of course leads to suction side problems.
It is fair to say that many so called "pump" problems are actually wrong pump selection based on incorrect head conditions - both suction side and discharge side.

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.)