major difference of B7& B7M

[Ali Asghari]

Dear All
What are differences between B7,B7M ?(except as torque value,yield strength)
In our specification usage of B7M confined under insulation.why?
When we can B7 replaced by B7M with regard to service condition?or is it possible with regard to dissimilar strength ?
Regards

[Rahul Singh]

Dear Ali,

Your specification calls the requirement for B7M to avoid the corrosion under insulation. B7M bolting is often opted for in corrosive environments due to its heat treatment & hardness.

B7  bolting also can be used if it is used for non exposed to corrosive environment which means we can substitute the B7 bolting with B7M for corrosive environment.

Regards

[nishant nair]

Dear rahul, I understand that normally b7m bolts are preferred in corrosive environments.. can u pls elaborate the difference on the account of corrosion resistance.I.e. why b7m has better corrosion resistance. . Thanks in advance; Regards, Nishant Nair Sent from Yahoo! Mail on Android

---

From: Rahul Singh <rahu...@gmail.com>;
To: <material...@googlegroups.com>;
Subject: [MW:18535] Re: major difference of B7& B7M
Sent: Wed, Aug 28, 2013 11:09:19 AM

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[binoy...@gmail.com]

Mr. Nishant,

Corrosion resistance of both b7 and b7 bolts are same.B7M is used for the lines where there is chances for embrittlement(sour service lines/H2S production areas). To avoid embrittlement, hardness of the bolts should keep minimum.B7M bolts are having hardness less than B7 bolts (percentage of carbon in B7M is slightly less than B7 )and every pieces of bolts are heat treated and hardness tested.Tensile strength and yield strength of the B7M bolts are less than B7 due to the %carbon difference.

binoy ravindran