Multi-stage Pump Discharging into a Loading Barge/Vessel 1

[asade]

Dear All,

Please, I need your insight. We have a 7-stage Centrifugal pump, fixed speed type that is used to deliver crude into the pipeline to the Storage Terminal some kilometers away.

At the moment, the pipeine network is not functioning due to damage to the main export pipeline, which would take some months to fix due to the magnitude of the damage. In order to ensure that we produce from the flow station, we planned alternative evacuation of the crude via barging from the facility. It is expected the pump to deliver 18,000 bpd.
My concern is that is it possible to use the existing pump to deliver the crude into the barge. It is assumed that the operating pressure of the loading barge would be within 1 - 2 barg.

See attached the pump curve.

Your response is highly appreciated.

I am what I am by His grace

 

[ashtree]

asade,

Maybe but the pump would running well off the end of the curve and is outside the allowable operating range. Because the head is much lower than what i assume the normal head the pump will try to pump a much higher flow and impeller damage due to cavitation is certainly possible.

A couple of options.

Use a VFD and operate at reduced speed so that flow is never greater than the allowable operating range
Throttle a discharge side valve to artificially increase the system head so that flow is in the allowable operating range.
Do something else or use a different pump.



Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[ashtree]

asade,

I forgot to include that its also possible that you may cause the drive motor to overload. Despite operating at a lower head the great increase in flow will certainly mean an increase in power required.


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[LittleInch]

Ashtree is genrally correct.

The items are quite clear.
1) You cannot use this pump as it is without some significant modifications to it or the downstream system
2) Your pump will produce something like 50bar at the flowrate you want, but your loading system ( presumable only a few km if that) only requires approx. 5 barg
3) You can throttle 45 bar across a new control valve but waste a lot of energy and possibly heat up the crude by 10 C?
4) You could remove probably 6 of the 7 stages and put dummy stages in (contact the vendor) to reduce these losses
5) You could use or fit another pump for the duration of the outage of the pipeline

I would go for a mixture of 3 & 4


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

 

[1gibson]

I'd use a VFD if possible. Head drops off to the square of the speed difference, flow drops off at 1:1 ratio. It may reduce the flowrate a little more than you prefer, but there is no modification to the pump required, and the big pressure reduction does lend itself to use of a VFD.

Say 1/2 speed, 1/4 the head, and you can run out further on the curve at the reduced speed, so additional reduction in head there.