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Hydrostatic Testing Isuues

Hydrostatic Testing Isuues

Hydrostatic Testing Isuues

(OP)
I have a project where the client has a specified Testing Engineer that is required to witness the hydrostatic testing, in addition to the local AHJ. The Test Engineer has made us re-test every system we have installed, some as many as six times. At the start of the hydro test, he will report the pressure to the fraction of a psi. For example: "At 9:07AM we are at 207.5 PSI", or "207 psi heavy". He will then view the gauge at the end of the test and report something like: "At 11:07AM, we are 207.0 PSI. The system has lost 0.5 psi and the test has failed".

I have been in the sprinkler business 15 years, and I still don't have the ability to read 1/2 a psi change on a gauge that has 5 psi increments. I also realize that changes that small are subject to viewing angle.

Another problem we are having is with thermal expansion and contraction, especially on smaller systems. For example, we currently have a small, four head system with about 30' of pipe. where the gauge has risen considerably during the 2 hour test period. But even though it may rise by say 10 psi during the first hour and a half, if it drops to 8 psi above what it originally was at the start of the test, he will fail the test.

Please keep in mind that we have done EXTENSIVE pretesting of the systems to check for leaks, going so far as to check every fitting and joint of pipe one at a time from a lift or ladder.

We have already went over the section in the handbook about thermal expansion, but he is not satisfied with only that. He is going so far as to mention we may need to bring calibrated thermometers to the site and record the start and end temperatures during the test, and then calculate how much a one degree change in ambient temperature will raise/lower the pressure. I'm not joking when I say that I can see him requesting us to take samples of the water to check for dissolved elements that may affect the rate of temperature rise.

We are looking into digital gauges, but that still does nothing for the thermal issue.

Is anyone aware of any other published writings or documentation from a reputable source that may help my cause?

RE: Hydrostatic Testing Isuues

Not near the book but think it says something like 200 psi test 2 hours

No visible leaks

Never seen an inspector that bad

RE: Hydrostatic Testing Isuues

(OP)
Its the phrase "Without Loss" that he is hanging his hat on. in his eyes .01psi loss does not meet the code requirements. I have submitted the documentation from the handbook that explained the thermal side of it, but it had got me nowhere.

RE: Hydrostatic Testing Isuues

I have seen plenty of systems, that have leaks, increase pressure, because of temperature increase. I see gauges that stick (tap it, and it now reads different) I once installed a system with hundreds of 4'-0" sprig-ups, and it took my pump about a 45 minutes to pump up (you could have let out 2 gallons, without a noticeable decrease. Most contractors seem to pump to about 210 psi, and inspector is happy if psi is above 200 psi at time of inspection, and no visible leaks. I think inspectors are missing the point of the 200 lb test. To me the test is to verify that nothing leaks, and nothing blows apart at 200 PSI, when the pumper truck charges the FDC, in a fire. Leaks happen even after successful pressure tests, and are the responsibility of contractor (NOT THE INSPECTOR). My opinion

RE: Hydrostatic Testing Isuues

You know if you pump up the system, and shut the valve below the gauge. It will hold a steady pressure for a very long time!!!!

RE: Hydrostatic Testing Isuues

This is a fairly common problem in South Texas on hazardous materials piping. I don't apply these requirements on fire protection piping but we do apply it on piping conveying hazardous materials.

Here's a helpful explanation of compensating for temperature when dealing with flow. The same equations work for pressure. If you don't understand it you need to seek professional engineering assistance. This is an internet forum, not a on-line consulting service.

http://www.peconet.com/products/RootsBulletins/rm-...

RE: Hydrostatic Testing Isuues

25.2.1.7 Loss shall be determined by a drop in gauge pressure or visual leakage.


It does say OR in the base standard

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