SA/A 240 316L 60 mm thick plate - which stress value

[XL83NL]

Hi all,

Im designing a small pipe component, a lateral tee, which will be custom made of 60 mm thick plate SA/A240 316L.
From this plate a block will be cut. This block (overdimensioned) is 60 x 100 x 100 mm.
The run and branch will be drilled into the block making the lateral tee.
2 corners of the block will be chamfered/beveled to reduce excessive material and thus weight.

The design code is B31.3.

If I look up the stress value for this material at 148 deg C and 200 bar(g) (the design conditions),
I find that B31.3 gives me 115.14 MPa as max value, while ASME II part D gives me 87.4 MPa.
Im confused what to use, since Im having doubts whether or not the B31.3 listed value of 115.14MPa is applicable for 60 mm thick plate (hence I looked up the values in ASME II part D).
Any help would be appreciated.

Regards

 

[XL83NL]

Anyone?

 

[StevenHPerry]

If B31.3's entry in appendix A is limited to a certain thickness, it will be noted. (I presume that there's nothing in SA-240 that limits the thickness.)

If it's giving you heartburn though, nothing says you have to design to the full allowed stress value.

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[Latexman]

If you are sure these values are apples-to-apples in every way, I recommend you contact ASME for an explanation.

Good luck,
Latexman

 

[XL83NL]

Thanks for the replies. The reason Im asking is that, although B31.3 doesnt mention anything about the thickness of a A240 316L plate being limited w/ respect to stress values, I believe Ive seen specs before where,
beyond a certain thickness, the max allowable stress decreases (since for thicker plates, other metallurgical aspects come to play a role which might decrease allowable stress values.)

Now I looked up if the A240 spec is perhaps limited somwhere, but I cant find any info on thickness ranges.

I guess Ill just take the lower stress value to be certain.

 

[racookpe1978]

Well, the metal will be a good or strong as it is secified, but 60 mm is very thick. Can you buy it as a forged block instead of just plate? That pressure of forging should reduce the tendency of plate to strip or separate at weak points in the crystal structure.

Make sure your machining fab instructions prohibit the presence of stress risers in the internals when everything is finished: no sharp corners, undercut intersections or notches, require blended radius or fillets - not corners and chamfers, use rolled thread if you can, etc. A standard fitting bought "off-the-shelf-catalog" will have these little details done automatically.

 

[XL83NL]

hi racookpe1978, I informed the fabricator with some instructions regarding your last reply. Im afraid the the lateral tee will be made out of plate, since that's probably all he got.

however, thnx for the good recommendations, I think it'll work now.

 

[unclesyd]

I don't have a late edition of the ASME Code but in the older editions there are two values for SA240 316l plate. The higher value is to used when temperature is between 200F and 1050F as the yield gets above 62.5% and you can stand a little distortion. The higher values are not to be used or flanges and pipe.