Book on centrifugal pump control

[eeprom]

Hello,
I am looking for a book(s) which may explain the different methods of centrifugal pump control, especially with respect to using a variable frequency drive. I have The Pump Handbook, and it makes no significant mention of this topic.

I work with lots of systems which have a pump on a VFD and a pressure control valve in front of the pump. Some people recommend running the VFD at 60 Hz (using the VFD as a soft start) and then using the valve for flow control. Others say to use the VFD for flow control and use the valve to maintain a minimum back pressure on the pump. And yet others say to use the VFD for flow control and use the valve to keep the pump at or near its BEP.

I would like to find a book which discusses these options and the benefits/costs of each.

EE

 

[bimr]

Try Pumping Station Design by Garr Jones.

http://store.elsevier.com/Pumping-Station-Design/Garr-M_-Jones-PE-DEE/isbn-9780080560052/

 

[BigInch]

It can depend on the type of system (is it pipeline, or plant use, fire engine, etc.), the unit's specific function, the system hydraulics and the econommics as how you might want to control any given pump. In general there is little physical necessity to control flow via pump speed in most situations, unless you need to run multitudes of different flow rates and there are economic advantages to do so via VFD. Most often pump systems are best designed to run at one optimum flow rate, so if that is the case, VFD adds too much unnecessary cost and maintenance. Sometimes both flow rate control and control valves at the end of a pipeline can be desirable.

Some examples were recently discussed here,

http://www.eng-tips.com/viewthread.cfm?qid=400478

 

[eeprom]

Thanks for the pumping station reference. As for variations in flow, the work I have been doing is for pipelines, and the system characteristics and flow change greatly from day to day, depending on line usage and pumping direction.

EE

 

[BigInch]

Why exactly do you think you have to flow at a certain flow rate in one direction, but another flow rate in the other direction. Shouldn't you be pumping at the maximum possible flow in any direction until a tank(s) is full? If you don't it will take you longer.

That means that in no matter which direction you flow there are only two real constraints, 1 you should keep the pump suction above NPSHR and 2, keep discharge pressure below the maximum pressure allowed in the downstream pipeline(s). That may represent two different flow rates in each direction, so hopefully the pump(s) capacity and configuration should have been designed with those system hydraulic conditions in mind.

If the required pressures are different for each pipeline, then either a VFD, or a pressure control valve might be provided in order to keep discharge pressures below maximum allowed pressures of the downstream pipelines.

If the pump curve and system curve do not intersect at a convenient flow rate for either or both flow directions, then you might want to control the pump discharge pressure (on a discharge pressure signal) such that you can hold a convenient flow rate using a pressure reference. Alternatively you can add a flow meter and provide exactly the same control ability, but it would be based on a set flow rate reference signal, rather than a corresponding pressure reference signal. If you use a flow rate reference, then you may still need to provide a pressure signal as a safety feature override on that flow contol which would trip the pump if discharge pressures were to go over max allowables, or when suction pressures were to go below NPSHR level.