Pressure issue

[nanuuk]

I know I am getting off the subject a little but...............We have recently had a sprinkler system ( DRY ) system installed that is in one of our freezers. This job was done while the room was at temperature - 23C. We have done a series of pressure tests on the system the code requirements for this neck of the woods is when testing with air is 40 psi and must hold this pressure with no pressure loss for 24 hrs. We loose 6 psi when doing the tests over a 24 hr. period the installers have found a couple of small leaks but can't find any others. It is a 6 " header and is about 600 ft. long. The next step we did was to split the header in 1/2 then pressure tested both sides this time both sides lost 6 psi after a 24 hr. period. Will the environment that the pipe is in cause this problem when testing with air or do we just have more leaks that we haven't found yet?

[NH3LVR]

It may well be due to the temperature change.
See this link.
https://www.usfa.fema.gov/downloads/pdf/coffee-break/cb_fp_2013_18.pdf
N2 will show less change, but if you charge with air increase the pressure up to 46 six pounds or so, then wait two days for the pressure to stabilize.

[nanuuk]

Thank you for the info the temperature in the freezer may change 1 or 2C would you think that would make a change of 6 psi?

[NH3LVR]

I do not know how to make that calculation easily.
The issue is that if you apply compressed air to the system it will be quite warm in most cases. (Check the discharge temperature of the compressor)) It warms the piping and will take some time to cool down.
I would not think 1 or 2 C would make that much difference by itself. If it does not stabilize and continues to drop then you have a leak somewhere.

[Segei]

I know I am getting off the subject a little but...............We have recently had a sprinkler system ( DRY ) system installed that is in one of our freezers. This job was done while the room was at temperature - 23C. We have done a series of pressure tests on the system the code requirements for this neck of the woods is when testing with air is 40 psi and must hold this pressure with no pressure loss for 24 hrs. We loose 6 psi when doing the tests over a 24 hr. period the installers have found a couple of small leaks but can't find any others. It is a 6 " header and is about 600 ft. long. The next step we did was to split the header in 1/2 then pressure tested both sides this time both sides lost 6 psi after a 24 hr. period. Will the environment that the pipe is in cause this problem when testing with air or do we just have more leaks that we haven't found yet?
This is not refrigeration system. Why it should be absolutely tight? Every sprinkler system has small air leak. Air compressor will make up lost air.

[Magoo]

the air volume will change with temperature change ever so slightly may be enough for a pressure drop in large volume system. As per NH3LVR try nitrogen, will be less effected by temp change

[al]

The only part of the sprinkler system that should be in the freezer room is the outlet head, have they used suitable jointing sealant rated at -30 for this?

[nanuuk]

Thank you for your reply. When you say that only the outlet heads should be in the freezer do you mean that the 6" header should be on the outside of the room or in an area that is above freezing if so could you explain? As for the fittings what was used was Victaulic fittings with a rubber gasket and the threaded fittings for such things as the sprinkler heads they used the standard Teflon pipe tape.

[NH3LVR]

I did not tumble to the trouble until I read al's post. Having a header in a freezer room is asking for trouble.
I am no expert, but what happens when the system activates? Or at least shortly after.
Is this a Sprinkler Contactor doing this?

[al]

A factory i used to work in had a sprinkler system, the place had no heating but the machines kept it warm, shut down one christmas, temps dropped to -10, heads froze, no issues until they started the machines up, Niagara falls later that day. they've since wrapped heater tape around all the outlet heads and drain the system when shutting down.

[nanuuk]

In answering NH3LVRs question it is a contracted job in answering als remark on frozen heads it is a dry system so the heads should not freeze. I contacted the manufacturer and these sprinkler heads are rated for these types of temperatures. If the system trips well yes that would be a bad thing. As for the placement of the header I don't think they had any other option other than put it on the roof and we get negative temperatures up here in Canada.