Field welding on hydro-carbon pipeline?
Field welding on hydro-carbon pipeline?
(OP)
I witnessed a field weld on a semi large hydro carbon pipe line (12" - 18") where the welders inserted a "balloon" on a lanyard, inflated it to isolate the hydro carbon vapors in the line, and to further isolate any vapors a synthetic-base mud was mixed and liberally spread at the edge of the balloon and pipe wall. I remember this mud was very slippery, and had a tenancy to fleck off as it dried (welding was done when the mud was wet). This was some time ago, and I have forgotten what the mud was? ...Drilling mud? ...or some specialty mud? Anybody know?





RE: Field welding on hydro-carbon pipeline?
If your future needs are just for a branch connection, it would be safer to use the procedure set forth in API-570, and do the welding with flow in the pipe.
Fumes plus air = explosion. Note that the 'mud' was drying out and loosing its seal during this operation. Too risky for me.
Welding heat on the OD of a line with flowing hydrocarbon [or any liquid] = cool, fast-freezing weld and no chance of going "BOOM".
RE: Field welding on hydro-carbon pipeline?
RE: Field welding on hydro-carbon pipeline?
If the buring whisper purge is too exciting for your Safety dept, you can use a Freeze Plug. Insert two inflatable bladders [plumbers drain plugs] into your line about 2-3 diameters apart. Leave a tube at the top and a hose at the bottom of the outer bag. Fill through the hose, until ALL the air is purged from between your bags -- 100% full of water. Now have somebody like TEAM Industrial put the freeze jacket and thermocouples on your line and freeze the water. As long as the thermocouples show 0-deg F or colder, the ice plug is structural, not just sealed. You should be able to hydro against a 3" Sch40 2-diameter freeze3 plug at 500 psig.
I have done 200 psig on a 20" line, and 3100 psig on a 1" line. Ice is amazing stuff.