Relief hole & tell-tale hole in PV 1

[BPVFEA]

Hi....
1)What is the basic difference between relief hole & tell-tale hole?
2)Compensation pads are provided with tell-tale holes & not with relief holes.Is it right? Please describe.
3)What is the recommended size of tell-tale hole?
Please let me know about useful information available on the internet regarding the same.
Thanks in advance for reply.

 

[prex]

A tell tale hole is used for testing the welds of the compensation pad with pressurized air and soap. Hence it should be tapped, possibly at 1/4".
The relief hole is intended for releasing the inner pressure build up during welding. Of course a tell tale hole is also a relief hole.
prex
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