L7M bolting over 2.1/2" diameter

[mombutto]

Hi all,

I wonder if someone could share with me if had experience with L7M (grade M) bolting over 2.1/2" in size with ASME VIII Div.1 code and stamped heat exchangers

The ASME II Part. D limits the allowable stresses to 2.1/2" although the ASME II Part.A for the SA 320 L7M bolting (table 1 - Mechanical requirements) states that this limit shall not intended as absolute limits beyond which bolting material could not be certified to the specification.
So, it seems to me that there would be the possibility to use L7M bolts eben with diameter over 2.1/2" inch, so admitted by the code also for stamped heat ngers.

I would appreciate if you could support me on this field.

thanks a lot to everybody in advance

 

[SnTMan]

mombutto, double posting is frowned upon. Go red flag the other one, then maybe an answer will be offered.

(Hint: see this thread: thread725-341276)

Regards,

Mike

 

[mombutto]

Thanks Mike.

I did not know double posting was nota good behaviour.

thanks for let me know.

 

[SnTMan]

mombutto, welcome to the site, the breadth and depth of knowledge available here is unbelievable.

As to your original question, the problem becomes one of finding a supply(er) that can quarantee the properties in the larger diameters.

Most likely you will have to do the legwork to find it.

Regards,

Mike

 

[jamesl]

I agree that you may be able to stamp the bolting material as SA-320 L7M. However I am not sure you can use it on a ASME Div 1 vessel. According to UG-4(e), you can use a material outside of size /thickness limit of a material spec assumuing there is no size/thickness limit given in the stress tables. Allowable stress Table 3 of Section II, part D does have a limit of 2 1/2" for L7M.

 

[mombutto]

Dear Mike, jamesl,

thanks for your support.

I am investigationg through and asked to our AI and our qualified bolting suppliers.
It seems that, from the calculation and stamping point of view, the note A of SA 320 L7M bolting (table 1 - Mechanical requirements) gives reasons to allow it. About the material supply, our sub-suppliers said that they normally manufacture L7M bolting over 2.1/2" in size. That's important is to perform the heat treatment in the right way; the rest is done by the good quality of material now-a-days the mills supply.
It is funny tolearn that, the limit we kept for years in our design/manufacturing is not the same for our qualified suppliers. Life is strange sometimes!!

Thanks again

Mombutto