ITW exit 1 module tank flange o ring has been replaced. the old o r-ing was completely flat in slot without elastic property.  tank flange, module flange, and o ring slot were clean by acetone and canister vacuumed. Raised up module 3 feet and pulled new o-ring over module top so new o ring could be  installed without moving module out. after new o ring installation, craned down module to flange and raised up module 2 feet again to confirm the o ring is properly sit in slot.