Reinforcing Pads

[AllHandlesTaken]

I am not involved in a specific design/problem right now but I have read in a couple places the two following points and was wondering if some light could be shed on them:

1. Apparently some/most companies do not allow reinforcing pads with long weld neck nozzles. Why would that be?

2. Again, I gather that some/most companies do not allow reinforcing pads for vessels in hydrogen service.

Does anyone know the issues/reasons?

Thanks in advance.

 

[vesselfab]

Hydrogen can be ""captured"" in the area between pad and shell. NOT GOOD

I have never heard of someone not allowing pads on Long Weld Necks. Not a smart economic practice to use pads on them, but if as an afterthought to meet design requirements after installed.....

 

[SnTMan]

vesselfab is right. For H2 it is best to avoid pads and attachement details using other than full penetration welds so as to avoid unvented spaces.

The idea with LWN's and other forged nozzles is to get integral reinforcement, adding a pad defeats that.

Regards,

Mike

 

[MJCronin]

All...


Discussion in Appendix #5.

http://h2bestpractices.org/docs/Doc15_06GaseousHydrogenStations.pdf

-MJC

 

[Shmulik]

This subject is well explained and illustrated in Bednar's Pressure Vessel Design Handbook, chapter 11.6