HDPE for casing of a steel pipe?
HDPE for casing of a steel pipe?
(OP)
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?
That being said, is there ever a case where HDPE is a better alternative than steel for casing?





RE: HDPE for casing of a steel pipe?
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: HDPE for casing of a steel pipe?
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
RE: HDPE for casing of a steel pipe?
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 ( Fen + 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.
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RE: HDPE for casing of a steel pipe?