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10-07-2011, 02:29 PM #1
Alternative leak testing technique
Boyles law states that P * V = constant.
When performing a pressure test or a leaktest, we mostly use a nitrogen bottle on 200 bar (2,900 psi) with a pressure regulator on it.
Say you pressurize your system to 25 bar (360 psi) like me mostly do.
You stabilize the flow until you notice a complete standstill in flow.
You then can have 25 bar in you system, your manifold and in the small expansion chamber of the pressure regulator/reducer.
But you still have 200 bar at the inlet tube and a small part of the pressure reducer.
You then shut off the valve of the nitrogen bottle.
You then have a system with a big V and a small P (cooling system, manifold, and ½ of the pressure regulator) compared to the high P and small V at the inlet of the pressure regulator.
You wait some time and the smallest pressure drop that will happen in your system will result in a very fast pressure drop at the 200 bar side because you regulator tries to maintain 25 bar but there’s in that part only a very small volume available to let stabilize the lost pressure again.
Does this make sense? Sorry if I explained this already in the past.
It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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10-07-2011, 02:57 PM #2
Re: Alternative leak testing technique
your saying that the regulator is allowing flow into the system if there is a drop in pressure within the system. it wouldnt be a problem if after allowing for stabilisation of the system then the regulator is disconnected from the system and a valve cap is fitted to the manifold.
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10-07-2011, 03:09 PM #3
Re: Alternative leak testing technique
Sounds like a good idea Peter, thank you, you rely on the regulator gauge to show the drop?
alecMostly found in the southern part of this green and pleasant land.
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10-07-2011, 03:35 PM #4
Re: Alternative leak testing technique
It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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10-07-2011, 03:36 PM #5
Re: Alternative leak testing technique
Last edited by Peter_1; 10-07-2011 at 06:17 PM.
It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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14-07-2011, 03:28 PM #6
Re: Alternative leak testing technique
Hello
My common sense tells me the point is the precision of the regulator. If its springs/ membranes' hysteresis is low, so reactance is quick , then "high" side would open when the P at the "low" side is, let's say 24.99 B, followed by pressures equalization. If the regulator is of a worse class, then the equalization may not take place till the "low" side is, for instance, 24.5 B (with "high" side showing 200B until the moment).
Should depend on the regulator.
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14-07-2011, 05:50 PM #7
Re: Alternative leak testing technique
Tried already with 3 different brands with same results. But you have a point.
We're just back from a service call on a big automated refrigerant filling system for harvester machines. There they pressurize the system for 30 seconds to 5 bar, then vacuum for 9 minutes and do a vacuumtest for 16 seconds.
All not that long and not very high pressures IMHO to find out if system is leaktight.Last edited by Peter_1; 14-07-2011 at 05:54 PM.
It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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15-07-2011, 08:21 AM #8
Re: Alternative leak testing technique
A very cunning use of Boyle's Law. Excellent Peter, thank you.
Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )