ASTM A193 B7/B7M material in place of ASTM A320 L7M

[Iyer S]

We have a Fuel Gas line, 60", Design Temp (93 Deg C Max. (-)19 Deg C Mini), Design Pressure 40 Bar.
One Flange joint is originally having ASTM A320 L7M Stud Bolt.
Can we use ASTM A193 B7 stud bolts for this service, in place of original ASTM A320 L7M?

 

[XL83NL]

I dont think an A193 would be an issue, compared to the cold temperature variation of A320, for a -19 °C application.
However given the designator M Im not sure if sour serivce is involved and if as such you'd be better of with B7M rather than B7.

 

[metengr]

I concur with XL83NL. However, you need to review the code of construction and, if applicable, contact the Engineer responsible for design regarding material substitutions.

 

[Iyer S]

thanks for the inputs..however, my thought process is like this
ASTM A320 L7M grades mandatorily goes through Charpy Impact test (due to its low temperature service applications).
As you are aware, this test determines the total amount of Energy that is absorbed by a material during fracture, thereby improving material’s notch toughness and resistance to embrittlement.

ASTM A193 does not specify Charpy Impact testy by default….its a supplementary requirement (S2).
Hence have my own apprehension in using A193 B7 for the intended service..

Any comments?

 

[EdStainless]

If it meets the same impact requirement then it is just as good.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

That is true that SA 193 does not mandate impact testing because the application is for moderate to elevated temperature service. However, keep in mind your minimum design temperature of only -19 deg C exempts material from mandatory impact testing.