Does ASME require a weep hole for slip on flanges?

By Kix

Date 07-08-2009 10:46

Another question would be, do you always have to weld both sides of a slip on flange per ASME? Someone told me that you are supposed to leave a weep hole when welding both sides of a slip on flange. I have never done this while in the trade and was just wondering what the correct practice was. I have also seen slip on flanges seal welded from the inside and stitch welded on the outside. Is that just an engineering call or improper practice?

Thanks,
Kix

By G.S.Crisi (****)

Date 07-08-2009 14:24

Yes, slip on flanges should be wholly welded on both sides, with no weep holes. The weld should be complete, no stitch.
Now, this apply to pressure vessels and piping. If there's another application that allows slip on flanges to be stitch welded and contain weep holes, I frankly don't know.
Giovanni S. Crisi
Sao Paulo - Brazil

By aevald

Date 07-08-2009 16:22

Hello Giovanni, I had been told at one time that the weep holes were tattletales(a way to indicate leaks as they develop). Is this completely off base, or is this just something that someone has come up with on their own and outside of what code would indicate? Would appreciate your input. Best regards, Allan

By RANDER

Date 07-08-2009 17:56

ASME B31.3 2004 Appendix F - Precautionary Considerations

F308 FLANGES AND GASKETS
F308.2 Specific Flanges
Slip-On Flanges. The need for venting the space
between the welds in double-welded slip-on flanges
should be considered for fluid services (including vacuum)
that require leak testing of the inner fillet weld,
or when fluid handled can diffuse into the enclosed
space, resulting in possible failure.

This is not a code requirement however and I dont recall having seen this in the field.

By Arctic 510 (**)

Date 07-08-2009 20:43

All of the slip-on flanges I have seen/welded/dealt with have been double welded. The precautionary statement mentioned earlier is of some value. I would also direct you to B31.3, Section 308.2.1:

(a) A slip-on flange shall be double-welded as shown
in Fig. 328.5.2B when the service is
(1) subject to severe erosion, crevice corrosion, or
cyclic loading
(2) flammable, toxic, or damaging to human tissue
(3) under severe cyclic conditions
(4) at temperatures below −101°C (−150°F)

(b) The use of slip-on flanges should be avoided
where many large temperature cycles are expected, particularly
if the flanges are not insulated.

Hope this helps.

By Kix

Date 07-09-2009 12:42

Thanks guys!!! That was exactly what I was looking for.

Thanks again!
Kix