Welding to seal tube

Question

We are manufacturing metal parts that requires to have a center tube and on both of the tube ends, we weld 2 plates that seals off the tube. Some manufacture require to punch holes on the tube in order to allow gas and water to flow out, but some says they don't need this hole, and since it is sealed on both ends, water can not get into the tube. Does anyone have experienced this type of welding? Do we really need this hole on the tube?

Answer 1

The air and humidity that was in the tube when you started will still be there unless you evacuate the tube somehow.  This will expand and contract as well as evaporate and condense as the temp changes.  So much will depend on what the part has to do and how long it is expected to last.

Answer 2

You don't need to punch a hole on the tube or the plate seal. When you weld your last seal plate, any expansion of the air inside the tube will just go through  whatever remaining gap between the unwelded edge of the seal plate and the tube. The last portion of your first pass of weld is not sufficient to create a large increase in the pressure of the air trapped inside the tube. Besides, if you punch a relief hole, you still have to weld this hole later, The effect of this would be the same as the effect of the last segment of your first pass on the weld of the seal plate if there was no relief hole.