Closed Piping

[GeorgeMech]

Hi, I have a simple problem but I don’t know if I'm using the correct formula or procedure.
I have a fire pump rated at 14 bar with a churn pressure of 16 bar, the consultant wants to give the pressure at each tapping point for each building (16 buildings in site), the piping runs straight from the pump discharge line to the last building, so the question is, if the pressure in the discharge outlet of the pump is 16 bar, is the pressure at the inlet of the furthest building is also 16 bar during non-fire condition or should I consider hazen william formula to calculate the friction loss in piping from the discharge header up to the inlet point of that building.


Thanks!

 

[LittleInch]

This depends on two bits of data which you need to confirm. If there is no elevation difference, plus or minus from the pump discharge to the farthest building (did you mean flat when you said "straight"? ) and flow, assume no flow, then static flow pressure at the far building will be the same as the pump discharge pressure.

Only when you have flow will it be different or a change of elevation.

My motto: Learn something new every day

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

 

[GeorgeMech]

thanks littleinch, im worried that i need to consider friction loss in the system, however it is very clear that since there is no flow so velocity is zero and thus, no friction loss in the system even the piping is 1000m away from the pump discharge (without ups and downs).

 

[LittleInch]

Correct.

I'm worried that your consultant actually wants to know (or should want to know) is the pressure at the furthest building when that building is using fire water on a continuous basis. Static pressure is one aspect, but operating pressure is what really matters....

My motto: Learn something new every day

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