Grinding of a gas pipeline

[Phelo]

We've got to do a strain gauge installation of a gas supply pipe to monitor it for stress changes due to subsidence. (about 8" dia)
As for normal strain gauge installations, we need to prepare the surface by grinding away paint and getting a nice smooth surface finish.
Problem for me is grinding sparks and gas don't mix very well.
The boss says we'll be fine, just bring a gas metre and it'll be alright.
I'm thinking adequate prepartaion for this is to write my will and get an extra life insurance premium.
Any thoughts?

 

[tbuelna]

The surface area required for a strain gauge installation is usually quite small. Use a hand scraper or wire brush to remove the loose surface debris and corrosion. Then use sand paper to finish the surface by hand. If you want to be extra-careful you can wet sand the pipe surface.

 

[Duwe6]

Boss is actually right. Proper procedure:
Ensure meter is currently calibrated, the 'bump' test it.
Walk the area your working in, looking for evidence of leakage, and watching the meter
Get in the hole, and test the air in the extreme bottom of the hole.
If no problems, go to work.

NOTE: unless you've been using a grinder many times a week, for many years, do not 'grind' on a live line; you won't have a delicate enough touch. Use something less aggressive, like a sanding disk or flapping pad [aka Tiger Pad] to ensure that only enough 'crust' gets removed to expose shiny metal. Don't remove any metal. Simple.

 

[brimmer]

Well, as long as all the gas is in the pipe there won't be any issue...

Sniff area first for LEL's, remove coating or with a wire wheel remove coating, get a fine disc for the grinder (80 grit or higher). Slowly polish surface. You will only need to take off a couple thousands of an inch material to get a polished surface. We do this all the time for installation of strain gauges, we also have other procedures for grinding out defects such as cracks on pipelines. As long as there is no issue in the area your grinding (such as severe wall thining) you'll be okay. You can take a wall thickness reading before you start grinding.

 

[jte]

As folks above said, this isn't unusual nor dangerous when done right.

Condisdering that we'll weld to operating hydrocarbon lines and vessels (patches, encapsulations, hot taps, etc), grinding in most conditions is easy.

 

[MJCronin]

Make sure that your boss is there in the trench with you......

MJCronin
Sr. Process Engineer

 

[Phelo]

Good advice MJ, good advice!!
I should have said that we're using sanding discs and not angle grinders, although we do start with 36 grade and work our way up to 120- there are still sparks.
Maybe I'll do it with a light touch

 

[racookpe1978]

Engineer should not be doing the grinding, the polishing, nor the welding. 8<)
But be there, with your boss! , when your tech's are doing it.