system pressure testing

[refaircon]

how do you do it, and what way is it meant to be done. Im really on about the gear you use, and how you do it.

just curious

[Rob White]

how do you do it, and what way is it meant to be done. Im really on about the gear you use, and how you do it.

just curious

Off the top of my head and in general Pressure Testing is........

BS EN 378 states that new systems, existing system that are undercharged,
or systems totally devoid of refrigerant should be tested to ensure they have no leaks.

Note: If a system is undercharged, always assume it has a leak.

Test pressures should be calculated as shown in BS EN378. There are two
categories of pressure tests; strength and leak pressure tests.

The Strength test is performed to prove that the system has sufficient strength
to withstand the pressures that could be generated within the system

The Leak test is performed to ensure that the system does not leak when
subjected to the pressures that could be generated within the system

Strength testing shall be between 1.0 and 1.43 times maximum working pressure
but must not exceed the individual test pressure of any component on the system.
This should only be used on initial construction or if substantial modifications have
been carried out.

It is permissible to test the low pressure and high pressure parts of the system
separately at different pressures, depending on the type of system. After testing,
all parts and pipe-work should be inspected for deformation.

Leak testing shall be between 1.0 and 1.1 times the maximum working pressure
of the system, and pressures should be maintained for at least one hour, or until
all joints have been tested for leaks.

The minimum value of allowable design pressure shall be determined by the minimum
specified temperature given to determine the saturated refrigerant pressure.

Rob

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[Brian_UK]

Tempted to say that you should know that having acquired your refrigerant safe handling ticket.....

Basic equipment is a bottle of oxygen free nitrogen, OFN, nitrogen pressure reducing regulator, test pressure gauge and hoses to connect with the system, safety goggles, risk assessment and method statement.

[The Viking]

With Brian on this one.

Sorry but if you have to ask then you are not qualified to carry it out.

Further more, engineers are regularly killed whilst carrying out pressure testing and there is no way we here in a thread on the net can teach you how to do it safely...

:cool:

.

[refaircon]

Tempted to say that you should know that having acquired your refrigerant safe handling ticket.....

Basic equipment is a bottle of oxygen free nitrogen, OFN, nitrogen pressure reducing regulator, test pressure gauge and hoses to connect with the system, safety goggles, risk assessment and method statement.

My question is how are others doing it, not me and what kit are they using

[Grizzly]

Hi refaircon.
Don't be to annoyed, yours does read as a rather simple question that can be taken as the guys above and myself did!
To answer your question on equipment used?

The most fundamental changes over the last few years that i can think of at present.
Are the need for dedicated manifolds and hoses when testing R410a systems. Because of their greatly elevated pressures.

Along with this BOC and others have raised their cylinder pressures / Volumes. Which coupled with new industry regs, requires the use of Date stamped nitrogen pressure regulators. These having to be replaced after 5 years!
Which is another industry conn in my opinion!
Much like the wire wrapped pressure hoses sold with the regulators as a "specialist kit ".

Many advocate the use of manifolds without sight glasses where that may even be a requirement, however newly purchased R410a manifolds are still supplied with sight glasses?

BOC do a regulator kit but I think others are now doing so as well.
Be advised some regulators don't have a range that can cover all applications. Harris do a nifty regulator.

The most important thing to consider is the age and condition of your kit.
I know of a experienced engineer who sliced part of his chin off recently.
Because he used his dads old "trusty" manifold (He now having retired). When the sight glass blew out catching his chin whilst on it's flight path!

These comments may not apply outside the UK and I hope others may dispute some, as we like you are all here to learn.
Grizzly

[The Viking]

Well said Mr Bear,

One thing I would like to add;
A manifold with a sight glass doesn't in itself stop you from pressure testing at high pressures.
There is a simple solution, just fit a 1/4" T piece on the high pressure connection of your manifold, connect both the OFN and the system to the T piece then pressure-test with the high pressure valve shut. The gauge will still read the pressure but the body of the manifold will not be exposed to any of it.

:cool:

.

[Grizzly]

Cool Solution Norseman!
Sadly the system says I have to spread some more love, before I can add you rep points.
Cheers Grizzly

[chemi-cool]

Agree with you guys. Since i do a lot of work for the biggest local gas manufacturer, www.maxima.co.il , I have gained a lot of experience with pressure testing, gas bottles are tested with water up to 250 bar.
i have tested condensers with OFN up to 40 bar to eliminate even the smallest leak, Helium is the best gas for detecting leaks because of its small molecules. been using Helium on vacuum insulated N2 tanks, its amazing the number of leaks i find after it was pressure tested with air.
My bottom line of the subject is: keep your OFN pressure regulators is a padded special box as your life may be depended on its condition. i do as the Viking do with 1\4 T (great minds think alike....). never use manifolds with sight glass anyway. replace my manifolds and hoses every two years, only use brass ones by Imperial.

[Grizzly]

Hi Chemi.
Can you advise me as to how you use the Helium, is it neat?
Or is it as I believe we can get over here mixed with OFN?
When you have pressurised the system, what means of leak checking do you use?
I have often heard that it is so good as the molecules are so small, especially for that pain in the arse gas R407.
I have not come across anyone who uses it before, so your advise would be appreciated.
Is there any truth that there are issues because it is flammable?
Cheers Grizzly

[chemi-cool]

I dont see any reason why not mix helium with ofn, helium is inert gas so no problems.
You will need to buy a small cylinder of helium and pressure regulator. they come here at 200 bar,
Vacuum the system, insert about 3 to 4 bars helium and the rest ofn. i only use liquid soap, the best stuff ever.
some people use "big blue" by refrigeration technologies, bubbles last longer and bigger.
i dont see any problems with the flame abilities of helium, once it is mixed with ofn i think it is safe.
look at all these kids with balloons full of pure helium, you can also inhale a bit and try to talk, makes your voice fanny.
bottom line, you in for surprise to see how many leaks you will find when you use it.

[install monkey]

What is helium leak testing?
Helium is used to find small leaks or possibly larger leaks in bigger volumes. The helium is used as a tracer gas and its concentration is measured. .
Why use helium for leak testing?
Helium is one of the smallest gas molecules and is inert, (remember your periodic table from Chemistry?). Being inert it is relatively safe to use (rather than hydrogen) and will not react with any of the materials within the part to be tested. In most helium leak testing applications, one uses a mass spectrometer tuned to detect helium although it is possible to use a residual gas analyser. Helium leak testing can be generally be between one thousand and one million times more sensitive than using pressure decay techniques.
What are the benefits of Helium Leak Testing?
Using this technique you can leak test to find smaller leaks than with other test processes, using a temperature stable, dry technique. This should result in a longer product life.
There are 2 basic techniques; high vacuum testing which allows leak test thresholds to be set down as low as 1x10-12mbar.l.sec-1, or sniffing which is generally used for helium leaks down to 1x10-6mbar.l.sec-1. For reference 1 cubic millimetre per second is approximately 1x10-3mbar.l.sec-1.
Most tests use readily available Balloon Gas (yes, this is what is put in kiddies balloons!). On rare occasions certifiably pure gas is used. On a safety note, please remember that helium contains no oxygen and is therefore an asphyxiant.
It is worth remembering that leakage is a flow of fluid from a higher pressure to a lower pressure through a fault in an assembly or manufactured part.
The high vacuum technique requires that the test volume to which the instrument is connected is at high vacuum i.e. less than 10mbar absolute pressure. Can the part or assembly withstand this pressure?
It is possible to test a part at high pressure and high vacuum at the same time. You need to arrange these pressures either side of the leaking boundary. This may mean putting the part under test inside a leak tight chamber.
When testing using helium it is possible to flood the mass spectrometer with helium if there is a large leak. In most instances, where there are many minutes between each test, this is not a problem, one just waits for the instrument to clean itself up.
One can also either sniff or spray helium. Sniffing is used where the part can be pressurised above atmospheric and a sniffing gun is manually positioned round the part. Spraying is where the part can be evacuated and helium is manually sprayed over the outside of the part.
Background Helium concentration.
Helium can and will get everywhere if it can. It gets quite difficult sometimes to determine where the helium is coming from.
There is approximately 5 ppm Helium in the atmosphere. If the part under test is filled with helium it is important that the test charge is taken away and not just released into the immediate area. For just a few tests, the helium can be diluted in the immediate area. For more frequent testing, this may mean piping the extracted test gas away to the outside of the building on the downwind side and well clear from doors or windows that could allow it back in.
To locate helium leaks one usually either sprays or sniffs, the latter being the norm in high volume testing. When sniffing one starts with 5 ppm and would usually look to detect an increase of a further 5 ppm.
One can use this detectable rise in helium concentration to test parts inside a shroud where the test pressure is at or near atmospheric pressure. By circulating the air within the shroud and passing it by a mass spectrometer in sniffing mode, you can set an alarm limit at say 8ppm. Again it is important to flush or extract away any contaminated air once the test has completed.
Helium leak testing at Lower Limits
When testing at 1 x10-9 and below one may need to do additional things to be able to complete a viable test. One may need to purge away and clinging helium left in the part to be tested or the test chamber. For example, with the chamber and part open to atmosphere before the test, they are exposed to a helium concentration of 5 ppm. The helium can cling to various surfaces and affect the results of the test. So, one may need to "wash" away any clinging helium in the chamber and part in a gas containing no helium.
The sequence might be:
1. evacuate both the part and chamber,
2. back fill the test volume with certified clean dry nitrogen
3. re-evacuate
4. fill the part with the test gas
Helium leak testing at high production rates.
When high volume production requires high vacuum, you must also consider the time taken to pump down to the required level of vacuum, this can be significant.
At higher production rates, having much shorter time to test a part, large leakers may be a problem. The flooding of the leak test instrument with helium may take several minutes for the helium to reduce to a level where testing can recommence. To reduce the effect of a large leaker one can; build up to the full test pressure in stages, build up to the full concentration, flush the mass spec with a gas with no helium present or pre-screen using an air decay technique before helium testing. Air decay pre screening willallow known larger leakers to be to be removed prior to helium leak testing.
When testing at high speed it is important to reduce the test time to its minimum. To do this one may have to employ a number of techniques to; reduce the test volume (by infilling voids and ensuring minimum pipe run volumes), nitrogen flush, etc. Of course at high speed the automatic handling of the product and automatic connection play a large part.
Tooling & Pipework
If one is intending to helium leak test a part it is important to note that the tooling and pipework used to create the test volume and helium gas supply must be leak tight to higher degree than the leak test threshold. This means that careful engineering of the seals is necessary, particularly where complicated seals are required (e.g. right angled seals for 2 perpendicular faces).
One must also use helium leak tight valves and pipework and pay particular attention to the sizing of the vacuum pipework
Helium mixing, helium recovery and helium re-use
When testing large volumes, at higher pressures and at high speed, the quantity of helium being used may become significant. There are a number of techniques to reduce the consumption of the helium gas.
First of these is to mix the helium with another lower cost gas either nitrogen or compressed air. This is only possible where the sensitivity of the test is not compromised by the mixing process.
The second of these is to re-use the gas from one test by extracting it from the device and then pushing it into the next device. This can often be implemented by a combination of a vacuum pump and simple air cylinder arrangement if the volume is not too large. Between cycles it is possible to use the mass spectrometer to monitor the concentration of helium that is being reused; when the concentration falls below an acceptable level it is dumped and a new charge of helium is used.
sourced via http://www.tqc.co.uk/

[MasterD]

Tempted to say that you should know that having acquired your refrigerant safe handling ticket.....

Basic equipment is a bottle of oxygen free nitrogen, OFN, nitrogen pressure reducing regulator, test pressure gauge and hoses to connect with the system, safety goggles, risk assessment and method statement.

Yup, I'm with Brian. I think if you have got the certificate, that should be evidence that you know what you're doing.

Make sure you use those safety Goggles as I've heard of some tragic accidents.

What's my experience? I work with Platinum AC (http://www.platinumac.com.au).

[r.bartlett]

Yup, I'm with Brian. I think if you have got the certificate, that should be evidence that you know what you're doing.

Make sure you use those safety Goggles as I've heard of some tragic accidents.

What's my experience? I work with Platinum AC (http://www.platinumac.com.au).


Having seen some of those who 'have the certificate' I wouldn't take that as any form of g.tee...

[MasterD]

Having seen some of those who 'have the certificate' I wouldn't take that as any form of g.tee...

Ha, you're telling me mate. They're much to easy to obtain.

[seadanzig]

leaks on a system
the last guy found the leak it was the schraeder valve leaking how many times have you heard that?

[WeNeedUnions]

A tip if you are nitrogen pressure testing especially when looking for a small leak use a digital gauge not analogue because the digital can measure in 1kpa increments so much easier than looking at a needle and saying to you self **** has it moved or am i seeing things lol? Btw dont use a sight glass manifold even with a nitro reg i know a guy who is blind in one eye cause it popped out of the manifold when he was nitro testing.