Operating of reciprocating pump
Operating of reciprocating pump
(OP)
Please any expert explain when operating reciprocating pump. If the process require flow rate with lower pressure than discharge pressure from pump. Let's say required pressure = 5 barg but discharge from pump is 414 barg. How can we reduce pressure? Is it adjustable to achieve the desired value from reciprocating pump?





RE: Operating of reciprocating pump
I don't know the extent of your pump experience, but one basic fact about all pumps is: the pump doesn't set discharge pressure - the process does. The pump conforms its discharge pressure to suit the existing process pressure. This is true for all pumps.
If you are using a PD pump you have a wide range of available discharge pressures the pump can pump to. If you happen to be using a centrifugal type pump (which is not your case), then you are limited in achieving a discharge pressure by the characteristics of the performance curve and its dead head pressure.
Your reciprocating PD pump will have no problem in pumping liquid into your 5 barg system. Its discharge pressure will be the 5 barg you seek plus the pressure drop required to get it to the point you need it at.
RE: Operating of reciprocating pump
I have a little experience about reciprocating pump. Could you give suggestion?
Thanks.
RE: Operating of reciprocating pump
As I see it, PD reciprocating pumps, operating at constant speed, deliver approximately an average constant liquid volume flow rate independent of pressure levels, although with flow pulsations resulting from individual fluid displacements. The liquid is assumed incompressible.
The discharge pressure (within design limits) is determined by the system resistance and back pressure as Montemayor explained.
Thus I assume you'd have to look for flow control rather than pressure control.
RE: Operating of reciprocating pump
5 bar back pressure, and the pump is set/capable at 414 bar??
It needs one idiot to close a valve, to shoot the equipment to the moon..
How could you reduce the pressure? Just reduce the speed of the pump.
RE: Operating of reciprocating pump
Am I missing something or is 5 bar to 414 bar is a huge difference, no?
This is a bit simplistic, but, a different pump?
RE: Operating of reciprocating pump
Reducing the speed of a reciprocating pump will not reduce the pressure; it will only reduce the flow.
Cheers,
CanuckMiner
RE: Operating of reciprocating pump
But the application give the impression of gross over-dimensioning. Something like a Volkswagen with a jet engine...
RE: Operating of reciprocating pump
I wonder whether -in principle- the discharge valves of the high-pressure pump need higher discharge pressures to be properly activated.
RE: Operating of reciprocating pump
RE: Operating of reciprocating pump
1. It may waste energy to run a 414barg PD pump for the 5barg process. I assume it was a small flow application.
2. If your PD pump have a speed controller, you could adjust the speed to reduce the pump discharge head.
3. Based on the required flow you needed, you may adjust the pump stroke length to set new discharge flow.
4. You don't want to overpressure the new system. If cost effective, you could install a pressure reducing valve on the discharge to reduce the pressure.
5. Also, you may want to reset or replace the PSV valve on the PD pump discharge (for system protection).
6. You may review the pump manual for the PD pump you have to see how much you could do to this pump. if any double, you should check the pump dealer for more info.
Remember, the safety first and good luck.
RE: Operating of reciprocating pump
RE: Operating of reciprocating pump
Pressure
^ .
| .
| .
| . System Curve
|______________._____________________
| .
| .
| .
| .
| .
_|__.______________________________
| ---> Flow
|
The graph above shows the pressure-flow relationship for reciprocating pumps. As you can see, you can only change the flow by changing reducing or increasing the speed. The system curve is dependent on your operation, and the pressure P-414 is dependent on the pump design (your swept volume, the piston diameter etc).
The implication is that you cannot change the pressure profile unless you change the pump configuration/design itself. Changing settings on the pump may not be feasible as usually done with reciprocating compressors. Installing a flow control valve on the discharge only helps to control flow. A pressure control valve or relief dissipates the pressure to accpetable points, but can't see the practicality of this with a turndown of 414bar to 5 bars, so would only suggest a pump replacement to the acceptable point (for this kind of turndown).
RE: Operating of reciprocating pump
Positive displacement pumps give you constant flowrate any head and that is why the performance curve of a PD pump is a straight line parallel to ordinate (not abscissa).