Pressure Relief Valves 2

[dutchie]

I am working on a large concrete tank which will located in an area where the groundwater table is likely to be at or near grade a large portion of the time. I am going to install pressure relief valves in the bottom of the tank to ensure it doesn't float when emptied, but i am having a difficult time locating any definitive design information.

The tanks will be about 6m deep. I have located an old detail showing installation of the valves, but nothing to say how many and what spacing they should be installed.

Does anyone out there have any guidance.

Thanks much

 

[Focht3]

You need to discuss this with your geotechnical engineer...

Where will the tanks be located? (city, state)



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[dutchie]

He has been involved from the start. He has detailed backfill and so on, but hasn't been able to give me the awnsers I am looking for on the PVR's.

I have been cruising the net looking for some guidance, but as I stated, nothing great yet.

 

[ERV]

dutchie,

Here is a site for hydrostatic valves that I have used:

http://www.trumbull-mfg.com/hydrostatic.pdf

Some good info, hope this helps.

 

[Focht3]

You may need to treat the valves as pressure-actuated weep holes. If you use an oil sand or asphalt beneath the tank, the valves are worthless - the water can't get to them. If you use crushed rock, you should use a graded filter design - follow the gradation guidelines in the authoritative reference book on drainage, Seepage, Drainage & Flow Nets by Harry R. Cedergren. An excellent reference. Also look for COE dewatering manual - should be on-line by now. It was written by Charles (Charlie) I. Mansur -

If the valves actuate frequently - or with a significant pressure buildup - you could erode some of the soils from beneath the crushed rock (loss of ground) which would cause the tank to settle unevenly.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[dutchie]

Thanks ERV, that site helped a lot,

Focht3, we do have the filter designed below the tank, and I plan to dig up that reference just to familarize myself a little more. These valves would be little used, as they are to be in a bioreactor in a wastewater treatment plant.

Thanks to both of you for your input, it has been very helpful,

dutchie