A Fundamental Question Regarding Weep Holes

Angsi,
Weep holes serve more than one function. You noted one, others are to aid in release of gases produced during welding of the nozzle/rpad and another is to aid in detection of leakage from the nozzle/shell welds while under pressure. They should not be sealed while under operation.
Regards,
RLS

Thanks.

If I remember correctly, ASME actually states that they can be sealed, provided the seal isn't adequate to hold pressure. IE, seal it to keep air and moisture out.

Yes, see UG-37(g) (or UW-15(d) if you don't have the latest Div1 Addenda).
Cheers,
John

In our drawings, we mention a note that,

"X nos. of 1/4 inch NPT tell-tale holes (what you mentioned as weep holes)" to be provided. The holes shall be sealed with grease after pnuematic testing."

I hope this sounds adequate.

I had thought one of the reasons not to seal up the weep hole was that if there were leakage behind the reinforcing plate (at the nozzle), it could change the loading on the plate attachment welds.

The attachment plate provides additional strength in the longitudinal and circ directions to the shell (compensation) and the welds take that load. If there was a leak in the nozzle then you'd have fluid pressure acting on the reinforcing pad directly and the welds would have to take that force too (pressure times area of reinfocing pad) in a different direction (tending to force the pad radially off of the vessel).