5 replies to this topic

[R NESAMANI]

Hi all,

I am working in natural gas pipeline network & terminal.

We are planning to weld a steel plate with the support(Steel) of the gas pipeline.
1) What are the risks associated with this job?
2) Any hazard & how to prevent during this job?

[TS1979]

Is the gas pipeline alive?

[kkala]

Having no practical experience, following link is judged useful http://www.groupsrv....bout474966.html '> http://www.groupsrv....bout474966.html .

[R NESAMANI]

Is the gas pipeline alive?

Yes the pipeline is alive, gas flow exists. I want to weld on the support of the pipeline.
My doubt is the arc welding process, has the current flow on the metal body (support). So current will flow thru the pipeline.
Will that cause any fire?

[breizh]

Hi ,

How many supports are you talking? if one, you may use another way than welding - like cradling, which is more expensive but safer .


Breizh

[kkala]

Having no practical experience, following link is judged useful http://www.groupsrv.com/science/about474966.html.

Please read mainly post by SteveB in mentioned link. Situation here looks much simpler (no need for hot tap or welding directly on the pipe).
Despite lack of experience, possibilities of main risks seem to me as follows. Advice on other risks, or comments, welcomed.
1. Explosion / fire externally of the line from a welding spark, in case of gas leakage near by. This is more probable if pipe parts are connected through flanges, less if welded. Checked by explosivity meter, inspection (and probably other means).
2. Local overheating of the metal due to welding, resulting in loss of its strength. Welding electrical current could "travel" through the pipe. Loss of metal strength could result in pipe rupture, casual internal spark (*) could decompose sensitive compounds, if any (C2H2?). But these risks might be assessed in API 1104 (unknown to me), reported in above link.
Besides effective earthing of any equipment to bear welding is known to be important, so I would assure it concerning the relevant support. This is responsibility of the Electrical Engineer.

(*) Fire inside the pipe cannot be caused by a spark, seeing that there is no oxygen in the gas. If overheating creates a bore on pipe wall, gas can escape out and create a fire.

Edited by kkala, 04 October 2012 - 07:38 AM.