Designing a Blind

[MetricNinja]

Hi,

I was hoping I could get some help. I was verifying the design of a blind for RTJ flange that a contractor proposed to us using B31.3 calculations. The material they're proposing to use is 44W steel. I don't see 44W in Table A-1 to get the S value. I know the yield strength is 44ksi from other structural books I'm using, but wasn't sure if I was allowed to substitute the value from there or if Table A-1 using more conservative values for the same material.

Similarily, please correct me if I'm wrong, the E value even though it's not shown there would just be 1.0 as it's a plate (therefore seamless) and the W value would also be 1.0.

thank you.

 

[LittleInch]

Don't understand why you are doing this. why not just use a blind as designed and supplied in accordance with ASME B 16.48?

The stress value S in table A-1 is NOT the yield stress, but something considerably less than that. If you look at the table you will see a column showing yield strength and then the values for S. You will see a considerable difference.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MetricNinja]

Sorry, it's understandable that you don't understand why I'm doing this. I didn't give enough info.

It's a 16" 2500# RTJ Pancake Blind.

B16.48 only goes to 12", I believe for that chart.

thanks.

 

[LittleInch]

WOW, that will be something special to see....

A simple search found examples like this which seems to offer #2500 flanges to 24"

http://www.redearthsteels.com/flang...s/asme-b16.5-flange-class-2500lb-flanges.html

I would trust a blind from someone like this rather than a contractor, especially if he's using material which isn't listed.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MetricNinja]

thanks for your help, I'll take a look at the website.

It was also pointed out to me that ASME Section II-D has the required S value for this plate.

 

[LittleInch]

That was just an example. Don't mix values from different codes, they may not be the same thing.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jte]

As LittleInch said, II-D is not the place to be looking for allowable stresses for B31 designs. Section II-D has allowable stress values in tension for at least six standards... and none of 'em are B31. It is, after all, Section II Part D of the ASME Boiler and Pressure Vessel Code. Not piping.