UCS-67

[Cobra17]

I have a vessel with 1.75" thick heads and shell made out of SA-516 70N. The material is impact test exempt (MDMT = -20°F) per fig. UCS-66.1. All the nozzles are HB or LWN made out of SA-350 LF2 Cl.1. 'Everyone' is telling me they always do production impact testing above 1.375" thick material and can't understand why I'm saying this doesn't have to be.

my view is that UCS-66(j) says that curve D materials coldest MDMT is -20°F if you don't meet UCS-67(a)(3), but since it's -20°F and no impact testing is required on the curve D material, production impact testing isn't required.

the closest interpretation I can find is:

VIII-1-01-46

Question(s) and Reply(ies):

Question: Are impact tests per UG-84 of welds made with filler metal required for welded components constructed using Fig. UCS-66 Curve A or Curve B base material that have been exempted from impact testing by the rules illustrated in Fig. UCS-66.2 of Section VIII, Division 1?

Reply: No.

Am I missing something?

 

[SnTMan]

Cobra17, I'm working from the 2017 Ed, I'm getting, from Table UCS-66, Curve D, 1.75" thk, MDMT -8F. A 12F reduction per Fig UCS-66.1 yields MDMT of -20F for base metal.

Impact testing of base metal is not required per UCS-66(a). Production impacts are not required per UG-84(i)(2). So, no, I don't think you're missing something.

Where your colleagues are getting their 1.375 limit I don't know, except if you disregard UCS-66(b) and kind of squint at Fig UCS-66, 1.375 thk & Curve D looks like -20F.

Regards,

Mike

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

 

[GD2]

Cobra17,
Impact test exemption rules are based on material, thickness and design MDMT.
Material manufacturer doesn't know where the material application will be and what the design conditions conditions will be.
ASTM A516 is a manufacturing standard that the mill has to follow with standard inspection and tests. A516 requires thickness over 1.5 in normalized. Thickness below 1.5in is required to be specified by the customer if normalizing is required. Otherwise, it comes in as-rolled condition.

A516 are not impact tested by the material standard/specification.

UCS-66 provides impact test exemption rules for carbon and low alloy steels.
UCS-67 provides impact test exemption rules for welding procedures.

You need to determine the governing thickness for welded assembly such as head and shell, nozzle and shell etc. The warmest MDMT shall be used after adjustment of any reduction due to thickness ratio for application of the exemption rule.

'Everyone' is telling me they always do production impact testing above 1.375" thick material and can't understand why I'm saying this doesn't have to be. - try to not fall to heresay. Read yourself to confirm it.

GDD
Canada

 

[weldstan]

There is no requirement to do so unless specified in the contract specs. We used to require impact testing and production impact testing for heavy wall materials and one client mandated such at 2.5" and above. But I never heard such a standard practice as you described.

 

[Chumpes]

Cobra17, I'm working from the 2017 Ed, I'm getting, from Table UCS-66, Curve D, 1.75" thk, MDMT -8F. A 12F reduction per Fig UCS-66.1 yields MDMT of -20F for base metal.

Impact testing of base metal is not required per UCS-66(a).

hello
I understand that tabulated D curve values in table UCS-66 give MDMT_D_curve= -8F for 1.75" thk.
Thus, having MDMT = -20F, and as -20F < -8F, the combinaison of (MDMT;thk)=(-20F;1.75") is below the D curve...
And I would conclude that impact testing is required as per Figure UCS-66.

why would a combinaison of (MDMT;thk) below the D curve not lead to application of impact testing ? where those 12F allowed reduction under the D curve without impact testing would come from ?

I have a vessel with 1.75" thick heads and shell made out of SA-516 70N. The material is impact test exempt (MDMT = -20°F) per fig. UCS-66.1

no, i see your point (MDMT;thk) = (-20F;1.75") below the D curve and impact testing required, am i wrong ?

 

[david339933]

why would a combinaison of (MDMT;thk) below the D curve not lead to application of impact testing ? where those 12F allowed reduction under the D curve without impact testing would come from ?

UCS-66(b) and Fig UCS-66.1

 

[Chumpes]

ah ok yes understood if using stress ratio for temperature reduction fig. 66.1, thx david
i guess they just don't want to apply result from fig. 66.1 and apply raw D curve as it is (as i ve done) without considering fig. 66.1

 

[Cobra17]

Thanks for the input. I think the "we've always done it this way" mentality made me question it. Guess they've always been doing it wrong.

 

[Chumpes]

I would not say it is wrong because it will also work this way =) it is just not exactely the minimum ASME requirement and it will be a bit more expensive.
i know some licensors of process units that does not believe in fig. 66.1 for standard designs, which maybe too conservative

 

[SnTMan]

I think in the "old days" there were enough grey areas in UCS-66(b) that people were reluctant to persue it. It's gotten better over the years. My opinion

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

 

[GinBread]

You may run into customers that don't care about UCS exemptions and they will tell you that you must impact test, regardless.

Like others have said, ASME is just the bare minimum requirements. Doing extra work isn't necessarily a bad thing, per se.

Is there enough cost wrapped up in the testing and do the customers even stipulate anything about IT to justify changing their methods?

Do you do enough other jobs to where it benefits you to have IT crop to use in the future?

You don't have to outright answer these questions, I'm just asking as more food for thought.