USE OF INSERT PLATES

[ferbus]

Good Afternoon to you all,

I’m wondering if any of you have used insert plates in lieu of Reinf. Pads. My client doesn’t allow Reinf. Pads. on the vessel I’m working on. Our intention is to use insert plates to increase the available area and avoid the use of expensive forgings.
The vessel is 4500mm I.D., Design pressure/Temp 3.5 bars/426 Celsius. Wall thickness is 18 mm and proposed insert plate is 30 mm
We have different Nozzle’s diameters from 24” to 48”.
What do you think about the use of insert plates? Does any body have any previous experience?
Any help is highly appreciated.
Best Regards,

 

[gr2vessels]

The use of insert plates is common and acceptable to the Code. The butt weld between the thinner shell and the insert is a lot stronger than any reo plate arrangement. Also, I should mention that in several services the reo plate could be a hazard (hydrogen accumulation, cracking of the reo plate fillet weld due to adverse environment, etc..).
Obviously, there are issues employing the inserts, to be resolved per the Code requirements, like taper of the edges to reduce the stress concentration, PWHT in some cases (check if it is your case), large diamenters for large nozzles like in your case brings fabrication issues.
If you need specific advice on any issue, just ask in this forum.
Cheers,
gr2vessels

 

[unclesyd]

As stated by gr2vesels there is no problem with the codes as long as you apply the proper rules.
We use insert plates on nearly all SS tanks and vessels due to the above stated reasons in that a reinforcing plate will cause us all manner of problems.

Another area where we use insert plates in SS vessel where we have very high rate thermal cycles. We use the plate as it creates less of a heat sink. This in turn helps mediate the differential thermal fatigue we would see if we had used a repad.

 

[jte]

ferbus-

Welcome to the forum! Don't forget to tell us a bit about your background in the "personal profile" part of the top left window which says "Hi ferbus". You can see my profile by clicking on the "jte" at the top of this post. Helps us to answer your question better if we know a bit more about your background and perspective - and it helps you to understand our perspective when you're reading our responses.

As already stated, insert plates come with several advantages, and I've yet to see anyone make a convincing argument against them - or even try. In addition to the advantages already listed by gr2vessels and unclesyd, consider the advantage of being able to monitor corrosion in service via UT vs not being able to determine what's happening without an internal inspection which is what you'll get with a repad. In addition, since the you are dealing with integral reinforcement, the F factor in Fig UG-37 can be used to reduce your area replacement requirements and save a dollar or two.

http://store.asme.org/product.asp?c...tegory_name=&product_id=PVP2006-ICPVT11-93596

As for "getting away from expensive forgings", I can understand getting away from fully self reinforcing forgings, but I'd encourage you to at least use long weld neck ("Straight Hub" in B16.5-2003 part 2.8 on page 3) style nozzle necks at least for the 24" connections and roll some heavy wall plate to form the nozzle necks for the larger nozzles. You're already have 3/4" and 1½" plate being used on this vessel so those thicknesses might be good candidates. By doing this you're distributing the reinforcement a bit between the shell and nozzle, rather than making the shell/insert plate quite a bit stronger/stiffer than the nozzle.

Let us know how you wind up proceeding... just to satisfy our curiosity!

jt