Pressure testing with ofn

[Shussey1]

Hi all
I may be dumb but I have been having this argument at work dose it state in f gas regulation how long you have to leave a system on pressure test.

I have been told it needs to be on test overnight ie 12 to 24 hours, but one of the guys at work said it only needs a hour or 2.

Please help

[cadwaladr]

I guess you could leave it for infinity but and a big but clearly label it for safety sake,yes you should be able to find your leak within two hours,some new equipment comes charged with nitrogen I think to stop moisture ingress.

[nike123]

Depending on what pressure test you are conducting.
Leak test=> at least 12 hours, normally 24hours. You are establishing leak rate here. Longer is better.

Pipe work strength test (1.1 to 1.43 times PS) => reasonable long (15 min). You are determining strength of joints, and by doing so, you are also stressing them. Shorter is better.

https://www.coolconcerns.co.uk/imagelib/pdfs/CS_3_Pressure_testing.pdf

[Tycho]

I can't really tell you what the rules are,

usually, we do 1.5X max working pressure for 5-10-20 minutes and the surveyor is happy, he says "Nothing exploded, very good" and then we can continue to vacuum the system.

What is the point of keeping the pressure for 24 hours? if it wasn't leaking in 5 minutes, it's not going to leak after 10 hours.

And then there is the other surveyor who wants 1.5X pressure for 24 hours.
I will put the pressure up, with an external manometer for the surveyor to monitor.
Then I will give him my small note book and say "if you want the pressure to hold for 24 hours, here is a note book, please note any decrease in the pressure every 30 minutes, I am going home now"

[nike123]

And then there is the other surveyor who wants 1.5X pressure for 24 hours.


Yet another surveyor who is confused with strength and leak test!:)

[Brian_UK]

Some say 6 hours minimum and others state 30 minutes. To date I can't find an f-gas document that gives time limit.

If you do long time periods don't forget to record the ambient temperature at the start and end of your test.

[nike123]

And what type of test you are referring now Brian?:confused:

What is the point of leak test if time is insufficient to show leakage which has small leak rate but still big enough to consider it unacceptable!

Also, what is the point in long time stressing joints with overpressure of 1.5 times max working pressure if it is enough only short time to establish that joints are strong enough to whithstand max working pressure and 50% more for short period needed for protective devices to function and stop pressure to rise more than max working pressure.


Obviously, it is confusion of these two separate tests (which can be conducted in one combined procedure) which is giving us this theme for discussion.

Since you are doing strength test, and if it is successful it is most economical to perform leak test right after that strength test by lovering pressure and leaving equipment 12-24 hours pressurized to its maximum working pressures.

And there is source for confusion about times for each test.

Correct times are 10-15 minutes strength test immediately followed by at least 12 hours leak test (assuming that there are no weak joints and big leaks).

[Rob White]

.

There are 2 tests one after the other.
The first is a strength test to prove integrity of joints and fittings.
The second is the tightness test to prove the system is gas tight.

Strength test is done at x1.1 to x1.43 of the working pressure (Ps)
at 32degC for the low side and 55degC for the high side (air cooled
condensers only), manufacturers instructions used to find max
pressures of individual components and test is completed to the
lowest component pressure. This test is done for the shortest
possible time required to visually check the entire system. This
test should never be done for more than 1hour so if it requires
2 or more other engineers to ensure this test is done in as short
a time as possible then that should be done. Out of hours working
is also a consideration?

The gas tightness pressure is the working pressure 32degC or
55degC (Ps) on air cooled condensers only. The tightness pressure
is held for as long as possible 2 hour minimum, 4 hours is better
and 12 to 24 hours is ideal, remember returning the following
morning may mean the ambient temperature has changed and
that will affect the final pressure.

Some tests may have to be done in front of an independent witness
who will sign it off as complete for insurance purposes and these
test might be completed over days or even a week.

All this information is contained within the BS EN 378 part 2, 2016.

Rob

.

[Brian_UK]

Thank you Rob.

Usual problem nowadays I suppose, employer should have these documents to hand for employees to check against, but I'm no longer employed so don't have access anymore.

[frank]

And all assuming that no inline components will not be damaged by the test, i.e. EPR's