Entrapped slag between the backing ring and ID of the pipe

Date 09-09-2017 10:14

Hello all,

My question is regarding the SMAW of pipes using backing ring. One of the pipe has not very good roundness. So, there are gaps between the backing ring and ID of the pipe. Using SMAW on the root pass will cause the slag entrapment in that gaps which is almost impossible to remove. Will that slag appear on X-ray?

Thanx all in advance.

By 803056

Date 09-10-2017 17:08

Yes, there will be slight changes in film density. However, the film density through the weld should be less than that of the adjacent pipe since the weld reinforcement will increase the thickness along the centerline of the weld face. Slag trapped between the backing ring and the ID of the pipe will increase the "thickness" very slightly since the slag is more dense than the air that would otherwise fill the void. Since the slag is slightly more dense than air (but not as dense as metal), it will absorb more radiation so less radiation will strike the film thereby producing a slight decrease in film density.

Al