5 replies to this topic

[Rahimzadeh]

Dears:
Please tell me progressive cavity pump can have recirculation line in pocess.
thanks

[Art Montemayor]

This is an easy query to resolve because it involves the application of simple and basic engineering knowledge: A progressive cavity pump is basically a Positive Displacement (PD) type of device.


Although you fail to state your reason(s) for your query, I am assuming that it is based on trying to achieve a controlled, variable pumping capacity on a progressive cavity pump.

In operation, progressive cavity pumps are fundamentally fixed flow rate pumps – such as piston pumps. This type of pump needs a fundamentally different understanding to the types of pumps to which people are more commonly first introduced - namely ones that are thought as generating a pressure (i.e., centrifugal pumps). This can lead to the mistaken assumption that all pumps can have their flow rates adjusted by using a throttle valve attached to their outlet. However, with PD pump this assumption is a serious and potentially hazardous problem, since a throttling discharge valve will have practically no effect on the flow rate and completely closing it will involve very high, probably damaging, pressures being generated. In order to prevent this, PD pumps’ discharges are fitted with cut-off pressure switches, pressure relief valves, bursting disks (deliberately weak and easily replaced points), or a recycle valve that allows an amount of discharged fluid to return back to the pump’s suction source. With a recycle flow fitted, a fixed flow rate type of pump is effectively converted to a variable net flow rate producer.

[GS81Process]

Mr. Montemayor offers a good explanation. Flow rate of a PD pump is commonly controlled by recycling flow.

It is also common to control PD pump flow using a variable frequency drive (VFD). The flow rate of the pump will be proportional to the pump speed (RPM), which is in turn proportional to power frequency (Hz).

[Rahimzadeh]

Dear Mr. MONTEMAYOR &GS81Process:

Thank you so much for your nice response

[kkala]

An example of PD pump recycling can be seen on the attached diagram "FO.bmp". It concerns a rotary pump transferring (heavy) fuel oil to a boiler. Of course recycling does not substitute PRV, having to be placed at the immediate discharge of the PD pump, as noted on the diagram.

Attached Files

•  FO.bmp   350.06KB   61 downloads

[Florentina]

This is an easy query to resolve because it involves the application of simple and basic engineering knowledge: A progressive cavity pump is basically a Positive Displacement (PD) type of device.


Although you fail to state your reason(s) for your query, I am assuming that it is based on trying to achieve a controlled, variable pumping capacity on a progressive cavity pump.

In operation, progressive cavity pumps are fundamentally fixed flow rate pumps – such as piston pumps. This type of pump needs a fundamentally different understanding to the types of pumps to which people are more commonly first introduced - namely ones that are thought as generating a pressure (i.e., centrifugal pumps). This can lead to the mistaken assumption that all pumps can have their flow rates adjusted by using a throttle valve attached to their outlet. However, with PD pump this assumption is a serious and potentially hazardous problem, since a throttling discharge valve will have practically no effect on the flow rate and completely closing it will involve very high, probably damaging, pressures being generated. In order to prevent this, PD pumps’ discharges are fitted with cut-off pressure switches, pressure relief valves, bursting disks (deliberately weak and easily replaced points), or a recycle valve that allows an amount of discharged fluid to return back to the pump’s suction source. With a recycle flow fitted, a fixed flow rate type of pump is effectively converted to a variable net flow rate producer.

Dear Art,

do you have the steps to design a progressive cavity pump? I need this design urgently.

Thank you and kind regards,
Florentina