leak search in large refrigeration pipe system

[coldseeker2013]

Good evening and greetings to everyone. Thank you for allowing me in your forum. I`m a new user, just out of technical college, with almost a year of working experience. I hope I can eventually add something to the wisdom and knowledge contained in this site, but right now I can only seek to benefit from your superior experience, skills and intellect.
I´ve been contracted for the leak inspection of several sets of large refrigeration pipes being installed in a supermarket. The diameters of the pipes are 2-5/8 and 3 inches. The length of the sets are between 90 to 120 feet. I´ve used nitrogen for similar jobs in much smaller systems, but never before tried to tackle such a large system.
In the same building, there is a compressed air system used for pneumatic packaging machines. I see that the compressed air goes through a mechanically refrigerated drier and several stages of filtration. As the copper pipes, after being installed, are containing ambient air anyway, would it be possible to use dried/filtered air for leak testing ? Thank you for any comments.

[GT Jets]

Good evening and greetings to everyone. Thank you for allowing me in your forum. I`m a new user, just out of technical college, with almost a year of working experience. I hope I can eventually add something to the wisdom and knowledge contained in this site, but right now I can only seek to benefit from your superior experience, skills and intellect.
I´ve been contracted for the leak inspection of several sets of large refrigeration pipes being installed in a supermarket. The diameters of the pipes are 2-5/8 and 3 inches. The length of the sets are between 90 to 120 feet. I´ve used nitrogen for similar jobs in much smaller systems, but never before tried to tackle such a large system.
In the same building, there is a compressed air system used for pneumatic packaging machines. I see that the compressed air goes through a mechanically refrigerated drier and several stages of filtration. As the copper pipes, after being installed, are containing ambient air anyway, would it be possible to use dried/filtered air for leak testing ? Thank you for any comments.

Possible, but don't recommend it at all. Dry nitrogen or helium (helium would be expensive as hell).

[Capz]

Go to Airgas or similar gas supply house & get about (4)--250 cf cylinders. For really big pressure test jobs you can always get an (1)-LG45 liquid cylinder = to 22 cylinders. Helium is for really critical jobs flowing gases (such as hydrogen) with really small molecules but is the best pressure gas test and can always be used. Nitrogen is lighter than air too so is a good leak test gas for just bout everything. Both are obviously inert. Never use any gas with a moisture content.

[Capz]

What will you use for leak detection once pressurized? How long are you being asked to keep the system under pressure?

[Tommy knocker]

I would not do that. Ya it has a drier but that's only gonna get the air dryish. You will only add a lot of time to your evacuation trying to get the additional moisture out. Nitro is best bet, IMHO. Push it up and let it sit a few hrs and check for fall. If none start your evacuation. Get it down to 500 microns. If it will hold below 1000 microns for an hour you've got a tight dry system. Good luck.

[coolerik]

I would not do that. Ya it has a drier but that's only gonna get the air dryish. You will only add a lot of time to your evacuation trying to get the additional moisture out. Nitro is best bet, IMHO. Push it up and let it sit a few hrs and check for fall. If none start your evacuation. Get it down to 500 microns. If it will hold below 1000 microns for an hour you've got a tight dry system. Good luck.

I would think more than a few hours standing test...100feet of 3inch pipe might take some time to see a drop. I would say 24hours, but thats just me

[Tommy knocker]

I would think more than a few hours standing test...100feet of 3inch pipe might take some time to see a drop. I would say 24hours, but thats just me

Agreed

[coolerik]

[coldseeker2013]

Good evening and thank you all for your replies. In a few words:
1. Forget about dried/filtered pressurized air.
2. Use only nitrogen + refrigerant mixture up to maybe 150 psig (10 kg/cm2). The system is to be operated with R-404A. Is this Nitro/R404A the easiest detectable mix?
3. Check with electronic leak detector around joints for obvious leaks.
3. 24 hour pressure holding test time.
Am I missing something?

[Tommy knocker]

Good evening and thank you all for your replies. In a few words:
1. Forget about dried/filtered pressurized air.
2. Use only nitrogen + refrigerant mixture up to maybe 150 psig (10 kg/cm2). The system is to be operated with R-404A. Is this Nitro/R404A the easiest detectable mix?
3. Check with electronic leak detector around joints for obvious leaks.
3. 24 hour pressure holding test time.
Am I missing something?

A good micron guage.

[Capz]

I'd pressurize with all nitrogen to 150psi. Using accurate pressure gauge securely tapped into the system, allow to hold for 24hrs. Take note of ambient temps as temps could change pressure. If pressure drops after 24hrs, using soap & water, test all joints. Make repairs as necessary. We used Ivory liquid & water for years before leak check soaps were used. Using your fingers wet with the soapy solution, wrap your hands around the joints, this is a good way to discover leaks.

I agree with T. Knocker, for the evacuation stage of your project.

[coldseeker2013]

I suspect that your preference for all nitrogen (instead of nitro+refrigerant) and soap and water (instead of electronic leak detector) might be related to something I have heard from other techs but never really got to know if it is myth or fact: that the chemistry of the components the Armaflex type insulation is made of, interferes with the electronic detector´s sensor sensitivity. I already cut open and removed a length of about 1 feet of the insulation at all joints. Does the sensitivity of the detector still be compromised?

[Capz]

I don't see the need of electronic leak detection for large tubing runs. If you have good installation practices with trained installers, why should there be leaks in the first place? If you are sweating/brazing 2" & 3" copper, with sil fas, using a n2 purge, why would you need an electronic leak detector? You typically should not have leaks with a copper tubing installation. You could visually inspect the sweat joints too. The armerflex should be installed after the piping system has be approved, shouldn't it? Leak detectors are most valuable when used tracking down leaks on systems with many connections, valves, components, etc. already in service. Right?

[Tommy knocker]

I don't see the need of electronic leak detection for large tubing runs. If you have good installation practices with trained installers, why should there be leaks in the first place? If you are sweating/brazing 2" & 3" copper, with sil fas, using a n2 purge, why would you need an electronic leak detector? You typically should not have leaks with a copper tubing installation. You could visually inspect the sweat joints too. The armerflex should be installed after the piping system has be approved, shouldn't it? Leak detectors are most valuable when used tracking down leaks on systems with many connections, valves, components, etc. already in service. Right?

Agreed. The ELD will typically stay in the truck until I'm sure I have a leak that's not jumping out at me, on new set ups anyway. I will grab it before bubbles however. No particular reason it's just what I do. ELD to get me in the area and bubbles to pinpoint.

[coldseeker2013]

Good evening to everyone.
I have spent the last couple of days getting everything needed for the job: N2 cylinders, new sensors for the ELD, and a pair of bottles of a leak detection bubbling solution recommended by a counter salesman. I also assembled a mobile scaffold since most of the pipes are about 20 feet above the floor level. When I thought I was ready to go, the first thing I did was blow some N2 through the first pipe, and what I discovered was not very pleasant: lot of debris came through the other end of the pipe. To my understanding, this means that whoever did the welding, did not use an inert gas while brazing. I suggested to the project manager that pipes should be cleaned before looking for leaks. I have used N2 + R-141 as flushing agent in some much smaller pipe systems, but, would it be equally effective in this large volume piping?

[coolerik]

That sucks man, but you would need a crap load of flush to flush out lines of that size and length, if it were me I would blow out what I can with nitro and you should be fine, just document it so whoever is doing startup is aware of it, and they may be changing oil, drier cores and cleaning txv screens over the first bit of run time...I would say flushin is not a realistic option. What type of system is this anyway?

[coldseeker2013]

Good evening.
These large pipes belong to the refrigeration system of a large walk-in freezer being installed in a supermarket. The equipment has not being brought in yet, but I read in the specs that it will work with R-404a. I would like to just blow the pipes with nitrogen and leave the messy work you just described for someone else, but, do you know of any other better flushing procedure that I could use besides Nitro+solvent ?

[jpsmith1cm]

The system's filter-driers will catch the debris upon startup.

Not optimum, but it happens on almost every supermarket install I've been around.