Inspection of process drain piping

[morganwx]

I've got perhaps an easy question on a topic I have little experience with. A project to replace drain piping in my plant found sections of pipe with material loss, and in one instance, failure of the pipe. Because we have multiple drain lines throughout the facility, I'd like to inspect other lines to determine if we have the same conditions elsewhere. Is there an effective way to determine pipe integrity in this situation? Some pertinent details:

The pipes are all cast iron, and some have been borescoped. The video from that inspection showed heavy scale accumulation, which obscured the pipe wall from view.
There are areas under the concrete we excavated that had sunk away from the floor. The condition seemed isolated to a few places, maybe 10% of the area excavated for drain line replacement.
All remaining drain piping in the plant is buried under 12-24" of concrete slab.
I can access the piping by removing an existing drain in each line (the drains have a strainer and trap that would need to be removed first, which requires chipping away the concrete).
The piping was installed between 20-50 years ago, depending on the section of the plant. The area we excavated was ~30 years old.

Can the pipe wall loss be measured internally, especially with the amount of scale present?

Any and all help appreciated.

 

[bimr]

It is possible, but depending on the pipe size involved, may not be practical. For a pipeline, you can get this information through the use of pigging. Pigging is not economical for floor drains.

Floor drains are usually tested by plugging the drainage outlet, filling the drainage system with water, and then watching for a drop in water level that indicates leakage.

 

[morganwx]

I forgot to include the pipe size in my earlier post. The drains are 4" dia.

 

[bimr]

Drainage inspection and cleaning is generally limited to pipe 6" and greater.

The inspection would start with cleaning the drains, which will be very difficult with 4" piping.

 

[LittleInch]

My challenge would be why are you bothering?

You can spend a lot of time and money inspecting something and then find it needs replacing, but if you just decided to replace it all the overall cost would be much cheaper.

Can you internally line the drains either with PE pipe or a spray coating?

If the runs are long without connections then it might be better to just do the sleeving anyway.

There are lots of sewer and cast iron pipe replacement technologies - though many are only suitable for buried lines not in concrete or much bigger, but the grundomat is one of many pipe bursting tools.





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Also: If you get a response it's polite to respond to it.

 

[morganwx]

Your challenge is a valid one. The cost to the plant in replacing the lines involves shutting down the process while drains are replaced. That downtime is difficult to arrange (plant is running at capacity), but would be required if the line needs replacement (the initial evidence suggests that it does). My hope was to find a low-impact/cost means of knowing for sure prior to shutting down the process area to do the drain work. In the absence of such a method, I believe we will proceed with proactive replacement. Thanks for the input on this; I appreciate the help!

 

[LittleInch]

Ok, that's fair enough.

The only other option I can see is possibly guided wave UT - the normal issue is that they don't like going beyond changes in wall thickness or discontinuations - is your drain pipe push fit?

If it's very corroded it might only do 10-15m

http://www.twi-global.com/capabilit...dt-techniques/guided-wave-ultrasonic-testing/

https://www.guided-ultrasonics.com/

plus an idea of the limitiations

https://www.irisndt.com/us/specialized-ndt/guided-wave-gul/

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.