Calculate the flowrate through hoses all connected to the same high pressure pump

[pa5tabear]

We have a pump with spec'd at 60 gpm and 3000 hd-ft.

I measured the flowrate out of the high pressure nozzles on the hoses and found it to range between 6.5 and 7 gpm. I assume the difference is due to frictional losses based on location.

How do I calculate the change in flowrate if I were to turn on two/three/four/etc hoses at once?

I assume the flow change until the capacity of the pump is reached. Is that correct?

For the purposes of the questions, neglect frictional losses.

 

[Artisi]

60 gpm at what head?
Need more data re performance,
are you saying
1. the pump is rated to delivering 60 gpm at a pressure of 3000 ft head
or are you saying
2. the pump is capable of a maximum of 60 gpm
and
3. the pump is capable of generating a maximum 3000ft?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[pa5tabear]

"1. the pump is rated to delivering 60 gpm at a pressure of 3000 ft head"

Yes. That is the information engraved on the pump panel. My understanding is that the pressure right at the pump outlet is 3000 ft-hd and that the flow is 60 GPM. I understand how to calculate losses from friction and fittings in terms of ft-hd.

I'm confused about calculating the volumetric flow out of a nozzle, and how it is affected when an additional nozzle is opened on another line.

 

[LittleInch]

From your description I can only assume that the vast majority of the pressure drop is taken by the nozzle as opposed to the hose. In this instance the pump is effectively a constant pressure source until it reaches it's duty point (60gm) when it will start to reduce pressure/head. There will be some effect as additional hoses come on line, but probably less than 10%.

Vertical head will have more effect in differences between hoses, but without some more info, length, hose diameter (ID), pump curve, pressure drop along the hose vs pressure drop across the nozzle, there's not much more I can offer. Hope this helps.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[pa5tabear]

Okay, thanks.

In our system, the hoses have no net vertical head. The difference between each is frictional loss in horizontal pipes, and this is still much smaller than the pressure drop of the nozzle. I measured volumetric flowrates and the flowrate of the furthest hose from the pump was 11% less than that of the closest hose.

==================

If we added one "extra" hose that pushed us beyond the duty point, how would the flows out of each be affected? In our case, would you divide the capacity by the number of hoses (60 gpm divided among say 11 hoses ---> 5.5 gpm)?

 

[LittleInch]

Depends on your type of pump and how sensitive the flow through the nozzle is to pressure drop.

If it's a PD pump (piston etc) with a constant pressure re-cycle lien, then it will be 60 gpm / 11. If it's a centrifugal then the pressure will go down a bit and hence flow through your nozzles will go down a bit, but probably closer to 63/11. Too little data to give amore accurate answer, but will be lower than if at 60 gpm total, but not as much as 60 / 11. Sorry if that doesn't make sense but that's how it is sometimes....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way