ASME Sec VIII UCS Impact Test Exemption for Backing Band

[syagla]

Anyone know how to calculate an impact test exemption for a backing band (Type 2 Joint)? Looking for guidance on determining a required thickness to use in calcs.

 

[SnTMan]

syagla, first you'd need to know the Code of Construction.

I'll ASSume Sec VIII, Div 1. You'd need to know the material. Then, based on the (governing, if applicable) thickness, exempt (or not) per the relevant Part: UCS, UHA, UNF, etc. Required thickness would not likely be needed unless applying UCS-66(b).

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[syagla]

Section VIII Div 1 UCS. Been using SA36 backing bands on 516-70 vessels for 40 years, now inspector says backing bands need to be impact tested for vessels under -20F. I can try to take exemption by calculating ratio but calculation requires “required” thickness. Since backing band isn’t considered when determining vessel thickness the “required” thickness should be zero but my inspector won’t allow that reasoning. Nobody at One CIS is interested in helping us and not having luck finding a supplier that can provide 1/16” backing band in 516-70N. Hope this better explains my problem.

 

[david339933]

Just because you have done something for 40 years, does not make it correct. UCS-66(h) clearly states the exemption temp. for A36 (Curve A) backing strip is -20F. I would be more concerned of what else these so called "inspectors" missed in 40 years.
Why not increase thickness of backing strip to one that is available? You don't state shell thickness, but 1/16" seems quite thin as it is.....

 

[SnTMan]

syagla, see if you can cause your inspector to read and comprehend Part UCS-66(d), exempting Part UCS materials 0.10" and thinner to -55 F.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[syagla]

Thanks SnTMan - yes I think we will be good there as we can use that thin of a backing band on our smaller (24" diameter and under) vessels. Above 24" our backing bands go above 0.10".
We have been working with our steel suppliers for backing bands in a Curve C or D material but not having much luck.

 

[SnTMan]

Well, can the backing band itself be a roll & weld? Make it yourself.

Alternate: Learn to make welds without the backup. Done all the time.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[syagla]

If we don't use a backing band the inspector needs to see both sides and our vessels are not designed with internal access to allow that. In order to compete in our industry we cannot add manways to our vessels without pricing ourselves out of business.
Thank you for the ideas!