Hydrogen line welding

[all2win]

Hi All,
I have a situation here.we have to do welding on a line whose upstream is connected to the hydrogen system and the downstream is connected to a tank which is also blindedand the line is isolated with valve and tail blinded with teflon sheet. Now During welding the earth rod will be connected to the line which is being welded.Is there any possiblity that the earthline connected can cause any problem to the hydrogen system which is live as there is a metal to metal contact in the flange bolts?

tnx

 

[unclesyd]

We weld on H2 lines as required by using the essenitally the same isolation procedures that you describe. The whole process should be carried out under a Peer reviewed "Breaking Into Process Procedure". We have checkoff sheets that are mandatory. All our procedures are area specific and process directed.
You didn’t mention any purging of the line requiring the repair, this is an essential procedure and should be carried out before and continued during welding if feasible. Purge from the middle toward the blanks if possible. Make sure that you have an Explosimeter in service around the weld area during the welding procedure. In reality preparing and welding on H2 lines properly prepared for welding isn't as bad as welding on lines that have carried hydrocarbons.

Just a few things to lookout for. I want tell why I mention these particular ones.

Make sure the equipment and tank grounds are in good condition.
Have the welder ground his machine as close to the site of welding as possible. This should be routine.
Make sure your blanks are designed for any pressure that they could possibly see from the process.
Don’t trust the valves to hold the H2, the blank and gasket is the ultimate stopper.
Watch for lateral lines, like drain or vents tied togather.
Watch the initial venting of the subject line.
Make sure the local or field operator stays involved and talks to the control, especially at a shift break.
If anything unusual happens make damn sure everyone involved is notified, where no one will assume anything..