Which of the following is a method to weld on a tank that contained flammable materials?

• A. Purge With Inert Gas
• B. Boil in Caustic Soda
• C. Steam and Weld While Full of Hot Steam
• D. Sandblast

Answer: (A)

Welding on a tank that has held flammable materials is dangerous because heat or an arc can ignite remaining vapors. The safest approach is to purge the tank with an inert gas, which displaces flammable vapors and reduces the oxygen level, creating an atmosphere that won’t support ignition during welding. This purge should happen before and continue during welding, with gas detectors used to verify the atmosphere stays within safe limits (low enough flammable vapors, adequate inertness).

Other options don’t remove the vapors or create an inert environment, so they don’t address the real risk. Boiling caustic soda introduces chemical hazards rather than solving vapor ignition risk. Steam-filled conditions don’t reliably remove vapors and still leave heat and moisture that can cause problems. Sandblasting can create sparks and dust, which is itself hazardous around flammable residues.