UCS-79 - Measured Thickness vs Specified 1

[bobracha]

Per UCS-79(d) we would need to perform heat treatment on heads when the extreme fiber elongation is greater than 5% unless none of UCS-79(d)(1-5) apply. My problem comes with a 1/2” thick (pre forming) head. The manufacturer of the heads would only guarantee and provide papers showing that the head met a 0.400” minimum thickness with a 1/2” (nom) straight flange.

The 0.400” min thickness satisfies our minimum thickness requirement per the calcs, but results in a reduction of thickness greater than 10% and an extreme fiber elongation greater than 5%, therefore we do not satisfy UCS-79(d)(4), and would be required to heat treat the heads.

As part of our QA/QC procedures, we take (3) measurements in the knuckle area of the heads when they arrive from the manufacturer. My understanding is that the knuckle will, almost certainly, be the area where the greatest reduction in thickness occurs. The heads in question have been measured to have thicknesses of .472”, .494”, and .457” on head “A” and .471”, .472”, and .493” on head “B”.

Clearly, the knuckle appears to have a far greater minimum thickness than the 0.400” guaranteed by the manufacturer. I’m not sure how to formulate a solid argument for heat treating or not per the UCS-79. If the true minimum thickness is greater than 0.450”, then I no longer have to heat treat. But, at what point can I be confident that the head min thickness is greater than 0.450”, short of measuring every point in the knuckle. Certainly 3 locations seems few, and my conservative nature makes me want to accept the minimum specified thickness, but I'm going to receive a bit of resistance moving forward with heat treatment, so I need confidence not gut feel.

42" ID and 516-70 if you need.

 

[weldtek]

weckesser,
I'd suggest you discuss this with your A.I. Ultimately, it is he or she you must satisfy.

 

[bobracha]

I have posed the question to them, was curious if anybody else had any experience.

I'm still fairly new to PV design, sort of surprised how many things can be left to the discretion of the AI...

 

[SnTMan]

weckesser, it is common for the head vendors to buy "green" (un-heat treated) plate, and form at normalizing temps, or normalize after forming. Check with your vendor. If so, the whole issue goes away.

Regards,

Mike

 

[vesselfab]

What SnTman said.

we do it every day and head manufacture puts te ug-79 statememt on thicknes guarantee sheet

 

[GenB]

Guarantee by mfr does not mean you cannot use it to top q.c. measured t. You are OK using your measurements to satisfy the Code you may take several t checks but it goes with the job. If your QC says 3 meas. Take 6 or 12.before releasing the mats and present for approvals. And again check if the HDS are been normalized as the prev. Post experts suggest. Genblr.