Pressure testing, anyone uses this method?

[Peter_1]

How you can see very fast if you have a leak?

Pressurize the system to let's say to 15 bar (215 psi) and let's assume we have a full OFN bottle on 200 bar (2900 psi)
The dials will show you 15 bar and 200 bar.
When pressurized at 15 bar, you shut the valve on the OFN bottle.
There's now 200 bar left only in a very small portion of the pressure regulator (piece of tube from the bottle to the inner chamber of the regulator)
If you have now a leak, then the remaining 200 bar will try to equalize the loosing pressure on the 15 bar.

Due to the very small volume at a very high pressure difference, you will notice very fast, sometimes in terms of 1 minute a pressure fall on the high presure dial.

Try once.

I never saw this method in a book.

[Brian_UK]

Good idea Peter, I will try it next time.

[nicolacozma]

I never use this method to check the leakage but I was wondered one time during pressure testing why the HP falls so quicly. And the reason was a smole leakage.
I will check this with a simulation next time.
Thanks for ideea.

[nike123]

What if pressure regulator leaks from high pressure side to low pressure side?
I suppose we should test it before for internal leaks.

[Peter_1]

Did this check already with 5 different regulators on a same small leaking system and always same result.
If you should have a leak from HP to LP, then pressure should rise on LP side and you should see this on your manifold.
We noticed this while doing the exams for the Belgium F-gas regulation. We supervise now for some time +/- 20 pressure test/week and we have time now to search for small changes.

Recovery on a system with 900 gr (28.9 ounce) R134a, you loose always at least 20 gr (0.643 ounce) but mostly something around 40 to 50 gr (1.607 ounce)
So you never can recover everything.

[Peter_1]

Someone noticed this already: in the new EN378-2008, all the requirements about vacuum are forgotten (vacuum level to achieve and stand time)

How long you need to perform a pressure test? 1 hour or 24 hours or 1 minute?
Nobody knows it for the moment.

[US Iceman]

How long you need to perform a pressure test? 1 hour or 24 hours or 1 minute?

This develops into an interesting problem.

If the vacuum is not low enough to remove all of the moisture, is the rise in pressure/vacuum due to a leak or to the moisture boiling off and raising the vacuum?

[nike123]

This develops into an interesting problem.

If the vacuum is not low enough to remove all of the moisture, is the rise in pressure/vacuum due to a leak or to the moisture boiling off and raising the vacuum?

I think you should do vacuum test ( for moisture presence purpose) after leak test is done.

[Peter_1]

Both are no longer described: leak and strength testing.
In the old regulations, there was a vacuum procedure description for systems containing less than 20 kg , vacuum till 290 Pa for at least 30 minutes and brake the vacuum with the refrigerant while filling.
More than 20 kg: vacumm the same as > 20kg, brake wit OFN and vacuum again for 6 hours where the pressure must remain 6 hours below 290 Pa.

You have a point about moisture in the system. What a coincidence you posted this now: moisture in the system.
I just posted a new thread http://www.refrigeration-engineer.co...ghlight=vacuum where a technician of a client performed a test this morning for me under a very high vacuum.
I see now I forgot to post the movie. It's uploading right now on Rapidshare.

[icecube51]

thats a nice trick Peter_1, never heard that one before.
but how do we find the leak itself? is there a trick to???
have to perform one on a Daikin VRV2 whit 11 indoor units. all tubes in sealing (gyproc).

Ice

[Peter_1]

Ice, just back from Austria in the snow.
I should say, use a good electronic sniffer.
I've used several and I heard now the opinions of +/- 140 technicians while doing exams and most go for the Inficon D-Tek.
I wish you a lot of luck. One advantage, your job will be mostly inside the building , better than those freezing temperatures outside
Noticed also just now the messages you've send me in my Public messages. Are those still valid?
Ben je al ergens ingeschreven om examens te doen?

[Bachuss]

This develops into an interesting problem.

If the vacuum is not low enough to remove all of the moisture, is the rise in pressure/vacuum due to a leak or to the moisture boiling off and raising the vacuum?

If there is moisture in the system at some point the pressure will lvl off, if indeed it is a leak then the pressure should continue to rise until it is equal to atmospheric pressure . Personally I leave both pressure test and vac test over night, though that is not often possible or convenient for the customer.

Love the idea of using the OFN reg to test pressure and will test out this when I get the chance, will test my gauges first

p.s. it is also possible to work out how low you need to bring the pressure in the system to boil off moisture by takeing the ambient temperature, I have a table some where if anyone would like it though don't expect a quick response as I'm hardly on line.

[frederik79]

How you can see very fast if you have a leak?

Pressurize the system to let's say to 15 bar (215 psi) and let's assume we have a full OFN bottle on 200 bar (2900 psi)
The dials will show you 15 bar and 200 bar.
When pressurized at 15 bar, you shut the valve on the OFN bottle.
There's now 200 bar left only in a very small portion of the pressure regulator (piece of tube from the bottle to the inner chamber of the regulator)
If you have now a leak, then the remaining 200 bar will try to equalize the loosing pressure on the 15 bar.

Due to the very small volume at a very high pressure difference, you will notice very fast, sometimes in terms of 1 minute a pressure fall on the high presure dial.

Try once.

I never saw this method in a book.

make sure the manifold does not leak , good idea on small units