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Testing with water under pressure
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Posted by: scandle

05/18/2005, 14:51:27

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I have a sprinkler head under pressure (500psi). I generated the pressure with a teledyne pump. I have a transducer (4-20 ma) made by GEMS 1200BGG6002A3UA and an Automation Direct PM24-200-AC tied into the piping. I also have 2 isolation ball valves to shut off the water before and after the transducer. I have verified there are no leaks in this system. I screwed a sprinkler head into the open ball valve and opened the valve. This frame is leaking around the bellville washer on the seat. The pressure is dropping as expected. My problem with this is I thought it should loose pressure at a much faster rate since the volume of water is less when the space it occupies remains the same. Should the pressure drop almost instantly to 0 psi with a loss of water?






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Re: Testing with water under pressure
Re: Testing with water under pressure -- scandle Post Reply Top of thread Forum
Posted by: Cragyon
Bart
05/21/2005, 22:58:07

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Another possibilty is that the pipes, pump, housing and valves are realizing expansion due the applied pressure of the water. In effect, the hardware is expanding under pressure and acting like a hydraulic accumulator or a spring untill the distortion due to thepressure is removed. Another example, is a very weak and flexable garden hose under pressure. Even with the water supply removed the hose will store energy due the expansion of the hose along the entire length.






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Re: Testing with water under pressure
Re: Testing with water under pressure -- scandle Post Reply Top of thread Forum
Posted by: zekeman

05/19/2005, 21:23:23

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When you isolate the water and it is still under the 500psi, the only way this happens is that there is entrained air in the fixed volume. Otherwise an infintesimal amount of water leakage would render the system to the vapor pressure of the water, which would be relatively small.






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Re: Testing with water under pressure
Re: Re: Testing with water under pressure -- zekeman Post Reply Top of thread Forum
Posted by: scandle

05/20/2005, 10:29:40

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That's what I thought. There is small air bubbles, from cavitation maybe, I don't know. In the Navy submarines used a check valve that eliminated the water from air lines during the emergency blow of ballast tanks. The Thresher is believed to have sank on sea trials when water in the line froze. Is it possible to measure this water loss another way or remove the air from the tested parts? Each part is void of water when entering the test fixture. I need to sense the leak in 7 seconds or less.
Thanks for your help.
steve out






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