When to use casing pipe?

[s0eebuch]

This seems an obvious question, but I can't seem to confirm the obvious answer....

In my mind, a casing pipe would be required when the anticipated loads (soil + road bed + traffic) exceed the maximum allowable which the carrier pipe can support.

So, I assume casing pipe requirements are a function of depth? Say I specifiy an increased carrier pipe thickness? Could I then omit the need for a carrier pipe? At what depth does the anticpated load become a concern?

Anyone with VDOT experience or Railroad experience, feel free to chime in.

Thanks!

 

[BigInch]

The best time to use casing is never. Casings tend to accumulate water, no matter how hard you try to keep it out and water comes just before corrosion, which in a casing, is hard to detect. They need to be isolated from the pipeline, they tend to block CP fields, they need to be tested for short circuits ... they're nothing but trouble.

There will be times when you must use a casing, usually because some railroad requires them (they try to make it difficult for pipelines since we're their main competition), but 999 out of 1000 times turn out to be better to bury deeper. If soil stress becomes a problem, then go to a thicker wall carrier pipe. Casing is my last resort. Did I say, "last"? I meant, "very last".

"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics

http://virtualpipeline.spaces.msn.com

 

[s0eebuch]

Word.

Thanks, BigInch. I just got off the phone with VDOT - they're approving my open-cut trench which (I think - I'm still researching) may eliminate my requirement for a casing pipe across the roadway.

 

[BigInch]

It might not, but that depends on the clear cover you have over the pipe and the road load classification. If they're letting you open cut, it must be a relatively light loaded rural farm road. What clear cover did you ask for?

BTW, what is VDOT? Vermont or Virginia? I guess Vermont.
And what's the pipe diam, wt and material?


"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics

http://virtualpipeline.spaces.msn.com