Re: [PipingDesign] Reinforcement Pad Weep hole

From: <harihara.v>
Date: Thu Oct 07 2004 - 09:26:00 EDT

Thank you Chris. As per ANSI/ASME 31.3 this is intended to facilitate both the escape of gases during welding and to detect any leaks during the hydrostatic test. This hole is also used to pneumatic test the integrity of the shell to pad welds and is mandatory. It is mandatory to keep this open in API 650 to detect any leaks even while in operation. Since the reinforcement pad is not designed as a pressure part and not in contact with the inner fluid at normal operations seal welding of the hole is recommended after the equipment hydrostatic testing as per one designer standard
The real concern is what can be done if a leak develops while the exchanger/vessel is in operation in this area either due to a hole in the shell or some defect in the nozzle welding. Since the pad thickness and material is same as the shell the pad can take the shell design pressure. But the integrity of the shell to pad welding is not sure since this is pnumatically tested to only 15psi. Can the exchanger/vessel be operated by plugging the hole and dP all the welding joints to avoid an immediate shut down of the plant? In this case the repad need to be designed and tested as a pressure part which is not done presently.

Cheers

HVR
--- Christopher Wright <chrisw@skypoint.com> wrote:

>
> On Oct 6, 2004, at 4:55 AM, harihara.v ramanan
> wrote:
>
> > Weep holes are provided in nozzle reinforcement
> pads
> > of branch connections in piping and nozzles in
> > pressure vessels, tanks and heat exchangers to
> vent
> > out the gases during welding.
> Actually they're used to give notice of leaks, which
> might take place
> during hydrotests. There's no way gas can be trapped
> inside during
> welding. It is permissible to plug the holes after
> hydrotesting with
> caulk or some other non-structural material. I can't
> cite chapter and
> verse, but I recall that provisions for such a weep
> hole were in
> Section VIII Div 1 of the ASME Code, including
> plugging the hole. I
> don't recall that such holes were mandatory, but
> they seem like a good
> idea. You're not allowed to weld on a Code vessel
> after hydrotest, so
> for Div 1 at least seal welding the weep hole won't
> go. If the vessel
> is used out doors, it makes sense to keep moisture
> out of the space
> between the pad and the vessel wall by caulking and
> painting over the
> caulk. Autobody filler (Bondo) is probably as good a
> material as any
> on=ther for this purpose, especially if you're going
> to paint the
> vessel candy apple red. ;->
>
> Christopher Wright P.E. |"They couldn't hit an
> elephant at
> chrisw@skypoint.com | this distance" (last words
> of Gen.
> ...................................| John Sedgwick,
> Spotsylvania 1864)
> http://www.skypoint.com/~chrisw/
>
>



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