cellulosic and low hydrogen electrodes 1

[sftyvlv]

Why can cellulosic electrodes (root,fill and cap) be used on natural gas transmission lines and not used in process or power piping. Why one and not the other. Hydrogen embrittlement comes to mind.....must be something else?
Sftyvlv

 

[stanweld]

Cellulosic electrodes can be used in power and process piping; however, many Engineers and Owners have precluded its use therein. At present we have great difficulty in hiring welders for our process and power projects who are adept in its use, especially when radiographic quality is required.

 

[sftyvlv]

Stanweld, I mean cellulosic rods used from the root pass right through to the cap. Why can they do this in NG piping and not process or power piping. If I misunderstood you please elaborate.
Thanks
Sftyvlv

 

[stanweld]

From a metallurgical point of view, the limiting of cellulosic electrode use and precludion of its use in fill pass welding were/are based on hydrogen embrittlement and weld metal toughness concerns. From a cost standpoint, elimination or reduction of preheating to mitigate hydrogen induced cracking and potentially additional PWHT and depostion rate are also a factor to be considered. From a aradiographic quality issue, slow speed fine grain films have been used in the process and power industries while high speed, course grain film had been used in the pipeline industry; the flaw resolution is greater with the slower speed, fine grain films. Tradition and engineering bias within the pipelining, power and process industries play their part as well. Finally, the pipeline industry and affiliated Union have maintained a high level of welder skill useing celulosics while the same cannot be said regarding the Contractors and Unions in the power and process industries.