HDPE for casing of a steel pipe?

[HiProGlo]

I understand that HDPE isn't recommended as the casing material for a steel transmission natural gas pipeline that's cathodically protected. I guess the seals could end up leaking with time, and there's a shielding affect that could block cathodic protection to the steel carrier pipe.

That being said, is there ever a case where HDPE is a better alternative than steel for casing?

 

[zdas04]

I think that it would fail every purpose that I can think of for roadbore casing. It isn't even good in cyclical loads.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[LittleInch]

CP hasn't got anything to do with it - any casing pipe will shield the CP current which is why the latest versions of the pipeline codes all state that the best way is to use the main pipe itself.

PE sleeves tend to be used for smaller diameter (<8") as the strength is much less than steel, they tend to suffer a bit when you get bigger diameter, but water lines and gas lines cross roads all the time and don't collapse. If you have a particularly aggressive soil you might want to consider PE, but the key issue is probably the maximum length you can pull / push in which suffers due to the lower yield stress.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

Good point LittleInch.
I do wish everyone would throw away all the CP myths they have been letting fill thier heads with over the last 10 years. It doesn't matter at all if the carrier pipe inside a casing is shielded, as it is impossible for any electrical circuit (the one that drives electro-chemical corrosion) to be completed into a carrier pipe inside a casing, as long as the casing is full of dry air and not touching the casing. It doesn't matter if the casing is HDPE, PVC or STEEL. Air is a very good insulator. Corrosion due to chemical reduction ( Fe_n + O₂ = rust) may occur if you allow the casings to fill with water and oxygen from air, which is why casings used to have vents, spacers and were often filled with parafin, so casings are no longer the recommended way to install crossings (since the last 30 years or so), but shielding in an air environment is like Rusian troops in Crimea; it simply doesn't exist.



I hate Windowz 8!!!!

 

[cvg]

PE pipe (corrugated HDPE, corrugated/smooth lined HDPE and also PE pressure pipe such as driscopipe) is used extensively in right of ways for puclic roads, without any adverse effects. and not all casings are installed by jack and bore. so there may be an instance where it could be allowed and might be cheaper or beneficial. However, in public road right of ways, I have never heard of a road department allowing anything other than steel for a casing, so it might be a hard sell to get the encroachment permit approved for HDPE casing.