End of Cruve Operation of Centrifugal Pumps

[Arshad Ahamed]

Hi,

Could someone kindly clarify what End of Curve operation means and what the limits are?

 

[Artisi]

Operating to the far right of BEP, under normal circumstances don't.

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.)

 

[MortenA]

You can describe it as the operating point where you cant increase flow rate if you lower the dischare pressure any further

 

[LittleInch]

Pump manufacturers supply pump curves which define the pumps operation.

They normally define a curve which stops at a certain point. That is the "end of curve" and operation beyond that point is beyond what the pump is designed for. The pump can physically operate beyond this point, but on any sort of extended basis will cause serious damage to the pump.

Even then operating at or close to the end of the curve leads to problems with

Reduced efficiency
Increased power requirement
Increased NPSH
Vibration
Increased wear on the impellor or pump in general

The limits are defined by the pump vendor.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TenPenny]

If you look at a pump curve, and follow it to the right of BEP, you'll see that it ends at some point. This is a point where the manufacturer determined that the curve should end; it's usually because the shaft deflection goes up steeply as you go to the right, and they set a limit on what the pump can handle.
However, sometimes, the point where the curve ends is determined more by standards; API and Slurry Pump best practices have different limits to what the %BEP can be, so sometimes especially with slurry pumps, you will find the curve ends abruptly about 5 or 10% beyond BEP. Sometimes, the manufacturer will show this limitation as a 'recommended operating range'.

Note, however, that the end of the curve is NOT a physical limitation; it's a point where the manufacturer decided to stop drawing a line, for whatever reason. theoretically, given enough NPSH, a pump with no discharge head requirement will run way out past the printed curve; it won't last long, but it will do it.

 

[chicopee]

As well as the above explanations, it can also mean free delivery (no back pressure) of the fluid.

 

[georgeverghese]

A typical solution for pumps that may go to EOC during hot start or other operating scenarios, is to install a max set FIC on the pump discharge which throttles a FCV (for fixed speed applications) or reduces pump speed. EOC operation on pumps can result in pump trip due to high current at the motor.
Refer to your pump curve to see if this could be the reason for your pump trip at EOC. Some times EOC operation may be suspected when in reality it could be that a denser fluid is being pumped due to loss of interface control at the upstream separator.