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khuff
27 Posts |
 Posted - 07/11/2012 : 20:09:38
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Tanks and stp several hundred feet elevation above dispensers, what is the best way to regulate excessive line pressure at dispensers in a marina environment? Playing havoc with valves and nozzles, not to mention hard to get leak detectors to work properly. Any input?
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bigbadjohn
Canada
2163 Posts |
Posted - 07/12/2012 : 05:51:58
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| 52 valve under dispenser. |
Don't learn safety by accident.
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bigbadjohn
Canada
2163 Posts |
Posted - 07/12/2012 : 05:53:01
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| Several hundred feet above? OY VAY! |
Don't learn safety by accident.
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hardworking
USA
506 Posts |
Posted - 07/12/2012 : 09:51:43
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quote:
Originally posted by bigbadjohn
52 valve under dispenser.
I thought you needed a vacuum source on the outlet side of a 52 valve for it to work. If that's correct, this job would require a switch to suction pumps (to use a 52 valve). |
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bigbadjohn
Canada
2163 Posts |
Posted - 07/12/2012 : 10:04:53
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Yeah I missed the STP part.
With a couple hundred feet of static head you wouldn't need a pump for anything besides priming the line, a suction pump would be a better solution I'd think, that's a lot of pipe holding against a lot of pressure. |
Don't learn safety by accident.
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hardworking
USA
506 Posts |
Posted - 07/12/2012 : 10:05:58
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I think what you need is a pressure reducing valve. They use them in water systems. Finding one rated for gas/diesel will be the trick.
Rough estimate is you have a little over 100#s of head pressure to deal with (based on 300' and specific gravity of .8). What's the inlet pressure limit on a 52-valve? |
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hardworking
USA
506 Posts |
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hardworking
USA
506 Posts |
Posted - 07/12/2012 : 10:20:00
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One more thing. Get a PE involved, one that has experience in fuel systems. You will have to deal with pressure relief down at water level. Typically, excessive pressure is relieved through the submerged pump, but with all that head it won't work that way.
The fix for this problem is not cheap (assuming the customer wants a 1st class job). |
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pumpologist
USA
99 Posts |
Posted - 07/12/2012 : 19:57:48
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Is there a solenoid valve in the line preventing the functional element from doing its job? I've seen that scenario before. Some times there will be a hidden swing check under a dock that previously had suction pumps, when converted to stp system over pressure conditions would exist. If there is a solenoid valve there must be a tee plumbed around valve to return thermal expansion back to stp to bleed off thru functional element.
Hope this helps |
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hardworking
USA
506 Posts |
Posted - 07/12/2012 : 20:18:09
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| I'm curious, what kind of piping is installed now? How is the piping making the 300' drop (steep angle, straight down,??)? Is the pipe underground or above ground? |
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hardworking
USA
506 Posts |
Posted - 07/14/2012 : 07:28:48
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quote:
Originally posted by pumpologist
Is there a solenoid valve in the line preventing the functional element from doing its job?
Over the years I've heard this statement many times. The majority of solenoid valves will only block pressure in one direction (check the directional arrow on the valve). Since the majority of solenoid valves will not block pressure from the outlet to the inlet side, a solenoid valve typically will not block pressure relief through the functional element.
Of course a check valve will block the pressure relief.
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