Locally thickened shell area - Can you do it?

[brandonb73]

Has anyone had any experience with using a locally thickened area of the shell around a large diameter nozzle so it meets reinforcement requirements? This would be like a flush patch with thicker material then the rest of the shell. Sec. VIII Div. I

Is this a common practice? How far around the nozzle do you extend the thickened area?

Thanks

 

[vesselfab]

YES WE'VE DONE IT

EXTEND ENOUGH FOR IT TO BE GOOD IN CALCS PLUS ENOUGH FOR THE 3:1 TAPER .

 

[brandonb73]

Thanks....have you found it easier to align to the ID, OD or split the difference?

 

[vesselfab]

I'm sorry, don't understand the question

 

[jte]

brandonb73-

Its called an "insert plate". I've typically seen the ID kept the same (don't want to get the process engineeers fussy about the ID) so the excess thickness is on the outside, similar to a repad. Make sure you put a 3:1 taper on the transition.

Insert plates are commmonly used on large nozzles as well as high temperature and in fatigue service and I've seen some cases where multiple nozzles were in close proximity so rather than use several repads a single large insert plate was used.

jt

 

[LOUDOG]

Keep the ID's the same, it should help with internal corrosion. Or if it is being coated there will be less prep work.

 

[rajat84]

Well if I am understanding it correct than UG-37 under ASME VII Div. 1 should provide with the limits of enforcement showing how far the pad is allowed togo around the nozzle.

It is good engineering practice to have material for pad to be of equivalent strength as shell or greater.

Does same limits of reinforcement applies on insert plates ?

 

[SnTMan]

rajat84, yes, the limits apply, however you are able to restrict the limits if you want to limit the size of the insert, providing that you still have enough area.

Regards,

Mike

 

[jte]

... And the on the other hand, there is no limit as to the size of an insert plate or a repad. The limit is strictly on the extent to which you get to take credit for the extra reinforcement.

Thus, it is not unusual to see rectangular (with radiused cornes insert plates which far exceed the limits on area availale for reinforcement.

jt