Before starting welding work at an existing flammable gas facility, nitrogen substitution is the first step to do. Flammable gas inside the facility has to be replaced by nitrogen, in order to move its concentration beyond its explosion limit or explosion range.

Explosion limit data should be referred to MSDS of the flammable gas. It is described in MSDS in terms of Lower Explosion Limit (LEL) and Upper Explosion Limit (UEL). (more…)