Bored, cased pipe cathodic protection

[jbraud]

I have a situation where an 8" insulated, cased line will be installed via boring and jacking +/- 600 feet. The pipe will only be accessible where it exits the ground on each end. Can someone recommend which method to look at for cathodic protection?

 

[LittleInch]

In general insulated pipes do not get any protection from cathodic protection. who is telling you that it actually needs CP?

What type of insulation?

What do you mean by "cased?"

got a cross section you can share?

If this is inserted into a casing pipe which is bored and jacked what are the plans for the annulus - leave it open or grout it?

 

[jbraud]

In general insulated pipes do not get any protection from cathodic protection. who is telling you that it actually needs CP?

What type of insulation?

What do you mean by "cased?"

got a cross section you can share?

If this is inserted into a casing pipe which is bored and jacked what are the plans for the annulus - leave it open or grout it?

The client wants an 8" steam line installed under a right-of-way from one facility to another. I'm not even sure if it is feasible or not yet and just exploring all aspects of a buried line. The line is proposed to be insulated and cased in at least a 12" casing. I was thinking more of the casing needing protection.

 

[jbraud]

The client wants an 8" steam line installed under a right-of-way from one facility to another. I'm not even sure if it is feasible or not yet and just exploring all aspects of a buried line. The line is proposed to be insulated and cased in at least a 12" casing. I was thinking more of the casing needing protection.

I am not sure of the insulation type that will be proposed yet. 500# superheated steam.

 

[SJones]

Some recent thinking

 

[LittleInch]

Well 50mm of insulation isn't going to work to any decent extent and you will lose a lot of heat and heat up the ground a lot, not to mention the thermal expansion of both the inner pipe and the casing.

What's the temp of the 500 psi steam?

CP of a 200m long line is prob ok with sacrificial anodes at each end, but if you have a load of other pipes there I would just cross bond it on one of the others.

You'll want a decent outer coating on your casing pipe and maybe add some rock guard, but a lot depends on your soils, resistivity and other lines in the ROW.

 

[jbraud]

Temp is estimated to be around 650F. Thermal expansion calculated to be about 60". It has BAD written all over it, and we are attempting to sway the client towards another solution. Thanks for your input.

 

[LittleInch]

Wow, 350C!

If you bury something anything over about 85 to 90 c starts causing huge problems.

If this is a pipe wrapped or covered in some sort of insulation sitting with an annulus of a few mm inside a casing and the casing is pretty straight it might work, but you will be getting a whole lot of expansion as there will be very little friction.

But its the casing which will really cause you problems as it heats up and if it is buried it will still have very significant expansion. If you're close to any other pipes they really won't like having something which could easily get to 100C plus given that thermal conductivity in the soil is relatively low.

So the CP bit is easy compared to the that.