bmlxd40
Mechanical
- Oct 7, 2011
- 82
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?
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?