weld puddle blown out

by henry
(warri,delta,nigeria)

i have experience this twice when welding an ss schedule pipe, during hot passing at certain point the weld puddle just get blown out and splatter off. some colleagues of mine said it is due to porosity in the root but i have tried to verify that by welding a root with porosity and hot passing but nothing happened. any help please?

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henry,

in my experience, pressure built up inside the vessel or pipe is the culprit.

its especially pronounced on small parts but can happen on pipe joints too. also, when the inside is purged with no vent, pressure will build and expel a hole.

good luck

jody