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# siphon collapse

## siphon collapse

(OP)
I'm designing a large diameter siphon to dewater a deep mine pool. I am currently considering 12" diameter DR 11 HDPE Pipe with fused connections.

My first question is this "If I break or lose siphon will the pipe have a good potential to collapse?"

Secondly, the siphon will be operating at a minimum pressure of about negative 11 psi. Are there adjustable vacuum release valves available which can be set to operate at a negative pressure of 11 psi and release the vacuum at a setting of say negative 15 psi?

Thanks in advance for any responses.

### RE: siphon collapse

If DR is the diameter divided by the wall thickness, the 50 year critical buckling pressure for unsupported PE80B is 476kPa. This gives a reasonable safety factor over the full vacuum differential of 100kPa. A safety factor of 2 to 2.5 is often recommended, and in this case it is 4.76 So it wont suck flat.

Bleeding air in to control vacuum is dodgy at best; unless velocities are high enough to sweep away the air, you run the risk of losing prime.

Cheers

Steve

### RE: siphon collapse

1PE,

Check out our website, www.performancepipe.com.  Request an engineering CD.  There are some calculations for unconstrained buckling on the CD plus many more design calcs.  If you have questions call me.

Kevin Deal
Performance Pipe
936-321-8940

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