Vent holes and patch plates 1

[virjil]

Are vent holes in patch plates needed when welding patch plates to areas with holed through portions? We usually do it as practice to provide vent holes in patch plates to have a way for trapped air to escape while welding the patch plates.We have experienced difficulty in closing the weld as trapped air pushes the molten weld metal thus preventing a complete fusion or the weld may crack.But in cases where the portion to be patched has a hole already, are vent holes in the patch plates necessary?

 

[deanc]

Try a threaded vent hole and a pipe plug.

 

[James01]

I dont know if the code you are working to states they are necessary, but I would definately recommed them.

 

[pablo02]

If a hole already exists, we didn't use the vent hole in the patch plate -- as you stated, the purpose was for an gases or vapors generated a place to escape without interferring with the welding process..