Leak detection based on pressure

[darren000]

Could someone please help me with this??

I am working on a problem with 2 pipes, one 100mm and one 150mm in diameter. The shape of the pipeline is a square. Majority is the 100mm pipe and the other is 150mm pipe.

1.If entire pipeline is filled with water, no leak and no supply, is pressure the same through out the pipeline?

2. If no supply, and there is a leak point on the 100mm pipe at a rate of 1 L/min. what formula should I use to calculate the pressure difference?

 

[mfb]

1.If entire pipeline is filled with water, no leak and no supply, is pressure the same through out the pipeline?

Without flow and if the pipes are horizontal (or without gravity), yes.

2. If no supply, and there is a leak point on the 100mm pipe at a rate of 1 L/min. what formula should I use to calculate the pressure difference?

Depends on the setup. Bernoulli's principle might be useful, but you really have to take the setup into account.

 

[darren000]

Thanks for replying mfb,

Please help me little further. I have attached a drawing of this problem.

As you can see. My task is to determine if there are any leak in this pipe network.(sorry, 100mm PVC is on the left side of A until 50mm Blow-Off, rest is 150mm)

1.If I close valve C and A, can I calculate the leaking rate of the leak 3 and leak 1 using following steps? Since I have supply flow rate and pressure, I can calculate initial velocity, then I can use the pressure on the port to calculate the velocity at the outlet near pressure monitoring port. With velocity and pressure at the port, I can calculate the output flow rate.
I'm stuck here. if I minus outlet flow rate from inlet. Does that = to the rate of leaking??

2.Any idea how I can determine leakage on the left side of valve A? (Shut valve B and see if outlet flow is same as what we found before considering leak 3 and leak 1. If flow rate is the same, then there is no leaking on the left side of valve A). Is my thought on the right track?

Thank You very much for helping.

Very Appreciate

 

[mfb]

In setup 1, is there any flow apart from Supply->leaks1+3? If not, there is no flow at the 100mm<->150mm-transition and pressure is the same at both sides. If your flow meter measures flow itself, that should be the same as the flow through the leaks, right? If it just measures velocity, you can use the measured pressure to calculate flow.

2) Closing B and opening A C D should work - if you know the flow through leak 1+3 (as determined in 1), you can calculate the total leakage again and find the contributions from the other leaks. If flow is significant, you might have to consider pressure differences in the 100mm<->150mm-transitions or in the pipes itself (again, depends on the setup).