Preinsulated Piping Corrosion

[jonasinc]

Does anyone have experience with preinsulated piping installed underground in a wet environment (high water table)? What materials are recommended for the insulation, conduit and outer shell?

Have you experienced ID corrosion of the steel conduit due to water ingress into the insulated annulus around the carrier pipe?

If so, what were the sources of the water ingress?

 

[stanier]

If a thermoplastic pipe material can do the job I recommend that you consider K Flo ABS from Tyco. There is no chance of corrosion because the pipe and outer sheath are in ABS. Used extensively for chilled water reticulation in the middle east and on the sub continent. This ABS is not the same as the grade used in the USA plumbing industry that caused all those problems. It is a pressure pipe grade used in SE Asia and Europe for over thirty years.

http://www.tycoflowcontrol.com.au/t...ine_systems/Overview/plastic_products#ABSKFLO

The other problem with water ingress into the insulation is loss of heat. A foamed insulation reduces a the flow path considerably.

No matter how hard you try with steel there will always be apenetration of the insulation vapour barrier and corrosion will result leading to loss of availability of the asset.

 

[jonasinc]

The piping is used for steam distribution (400F), so plastic pipe would not be applicable.

 

[gmorin]

For insulation, look into cellular glass, like stanier suggests. It doesn't absorb water & stays on the pipe if it does get wet. One mfr:

http://www.foamglasinsulation.com/

I'm sure you'll get some horror stories posted here, but a steel sleeve pipe would be my default choice. It would take a long time to corrode through the sleeve from the inside - especially if you can seal it up well enough such that the 400 degree steam inside the annulus will evaporate any minor infiltration you do get.

Make sure you consider thermal expansion effects for the sleeve as well as the pipe. You have a 400 degree heat source. The only mechanism to remove heat is conduction through the soil, so it'll be pretty hot.

Greg

 

[kenvlach]

You made need stainless steel shell (and good stuff if brackish water).
What pH & chloride, etc. of the ground water?
What is the ground & fill?

Once, on a totally different project (hazardous waste cleanup), I backfilled with crushed limestone to groundwater depth to convince a regulator nothing bad would happen (at least, before they retired!).