pump reserve rotation rate

[sunloco]

I would ask you a question about our double suction pump , I didn’t understand one term ,I feel it is diffcult to explain clearly. we first call it : pump reverse rotation rate .
In my point this rate means relation between pump reverse rotation speed and pump regular speed .when pump is stopped suddenly ,normally the water will flow back and make pump reverse rotate if check valve doesn't work .so ,who can tell me if double suction pump design standard in US has this rate or actually pump and motor doesn't allow to reserve ,even a short time ?
In the pumpstation design criteria of China ,pump reserve rotation rate must be smaller than 1.2 ,and doesn't last 2 minutes .
I don't know if i have explain clearly .please advise.

 

[Artisi]

You need to get information from the pump designer / manufacturer as to the pumps performance when driven as a turbine from reverse flow. Only they have this information.

" In the pumpstation design criteria of China ,pump reserve rotation rate must be smaller than 1.2 ,and doesn't last 2 minutes ."

Is 1.2 = 1 point 2 or ratio 1:2
I assume what ever it is - they do not want the reverse speed to exceed the driven direction speed by more than 1.2.

As for 2 minutes - again I assume they do not want the pump to run in reverse for more than 2 minutes - however, this is a function of the volume of product down stream of the pump and its potential to run the pump in reverse.

Phitsanulok
Thailand

 

[Artisi]

Forgot to include - you need the four-quadrant performance data of the pump/s you are discussing. This gives you all the data needed.

Phitsanulok
Thailand

 

[BigInch]

The two minutes might also refer to a closing time of any valve used to lock off the pump to positively stop any reverse flow in a system without a check valve, or perhaps as a backup for a damaged check valve. If the discharge line's head and reverse flow is not isolated by a functioning check valve or a shut-down valve, the pump would continue to reverse rotate, as long as the discharge line's pressure was sufficient to overcome the pump's internal friction.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[sunloco]

Thanks for above all
I have communicated with engineer in power plant ,they explained to me about the reversal rotation speed ratio.
As you all know that normally water hammer will be created when power off or stopping a liquid flow suddenly. The results of a water hammer will reverse the pump in a short time before check valve works. then enduser will request that pump and motor can reverse in a short time(about 20-50seconds) , pump will not be destroyed even when the reverse rotation speed reach 120% -160% of rated speed . so the ratio can reach 1point 2 or 1 point6 .
I selected double suction pump for this application case.I also have asked the pump manufacture ,hope I can get a answer ASAP.