Parallel Operation of the Pumps 2

[SENGUTTUVAN]

The Operational data of the NGL shipping pumps is as follows: 1. Base case:Flow: 605m3/hr Diff Head: 875m
Diff Head at runaway condition when one pump trips: 560m
2.Future case: Flow: 605m3/hr Diff Head: 1100
Diff Head at runaway condition when one pump trips: 800m .

When one of the pump trips the other pump have to run to meet the runaway conditions. Vendors have indicated that they cannot quote for such a huge difference in the range of Head and cannot guarantee for the runaway conditions.

Any technical solution and advise please.

 

[BigInch]

I would think your solution involves consideration of the length of time between present and future conditions.

I would evaluate the lifetime cost of operating 2 x 1100 m head pumps with heads cut back to 875 m, probably using control valves (at least for the initial study), during the initial time period and then operating them efficiently for the remainder of their lifetime,

Verses

the lifetime cost of installing 2 x 875 m head pumps now, running them at BEP during the same interim time period, plus the cost of installing and operating 2 x 225 m head pumps in future.

I would expect that, if the interim time period is not too long, that the energy use inefficiency of operating at reduced head would be easily made up over the lifetime of the facility, but you must know how long the inefficient operation of these 1100 m head pumps will need to persist.

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[SENGUTTUVAN]

Thank U Biginch . Keeping aside the meeting for future conditions for time being , the prime requirement is to meet the run away conditions which is not confirmed by any vendors either in present or in future cases. Since system head is constituted by means of discharge pipe frictional head, shut down of one pump is causing huge drop in the system head. And hence the pumps are pushed in to the run away conditions. Our concern is to design the pump / motor to meet that run away condition, if not possible then to protect the pump/motor from the run away conditions. pl suggest any suitable solution.

 

[BigInch]

Can you design those control valves I suggested above to hold back the runout, ie. something like for a flowrate of 605 m3/h, or whatever actual flowrate you need, while the valves cut the output head from 875 m to 560 m? That would take a 315 m dH across the valve. Then flow would enter the discharge piping at 560m?

Another possibility would be to have a VSD in there, but I hesitate to suggest a VFD, since its primary usefullness would only occur when you cut back the flow at runnout conditions. I believe a VFD would not be used economically, if your usual operating flowrate is almost always 605 m3/h and you only need a VSD to control unusual conditions. If you wanted to vary flowrates widely within normal operating conditions, then OK, it might be worth looking into using a VFD, but for now stick with thinking about those control valves.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[BigInch]

What flow do you have when one pump is tripped?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[dcasto]

get an 8 stage case in install 6 for now and 8 in the future.

 

[BigInch]

I like that.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/