HDPE inserted pipe

[austsa]

HDPE pipe can be inserted into old underground steel or cast iron pipes used in water or gas distribution network, to save a total dig up and replacement. Other than checking of records, is there any other way of finding out whether a particular steel pipe has been inserted or not (eg say if some records are not 100% reliable)?

One way that I can think of is use a hot tap. If no water or gas is detected, then pipe has been inserted with HDPE pipe. But is there a better way?

Thanks in advance,
austsa

 

[BigInch]

Drain the line and see how much fluid it takes to fill it. Color the fluid and accurately measure the volume that has to be introduced until you see the color, change the temperature of the fluid being introduced and see when the outlet temperature increased, etc. From that data, calculate the volume in the pipe using its expecgted inside diameter. Consistantly lower volumes than what you expect using the assumed inside pipe diameter (of the exterior pipe) might give you an indication that some sort of a liner is present.

you might also try a pressure drop calculation, assuming that an HDPE liner at the same flow and roughly the same diameter would give only about 25% of the pressure drop you would get with an old steel inside surface.

I'd at least try those things before I hot tapped it.

From "BigInch's Extremely simple theory of everything."

 

[austsa]

Thanks BigInch.

 

[bimr]

It would be much less expensive to just check the pipe terminations than any of the methods proposed.

The cost of a hot tap will be at least several thousand dollars.

There are companies that can do internal inspections with water mains in services.

http://www.wachsws.com/services/pipeline-management/cctv-of-pressurized-water-mains

 

[BigInch]

More expensive than a pressure drop calculation?

From "BigInch's Extremely simple theory of everything."

 

[StephenA]

The HDPE lining is hard up against the steel pipe so you are very likely to damage or go straight through the lining if you do a hot tap.

If the pipe is a pressure pipe the lining is returned at the flange joints or at least there is a special flange. I would check those first.

Stephen Argles
Land & Marine

http://www.landandmarine.com