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Commentator

Join Date: Apr 2009
Posts: 68

### Bolts: SA193 B7 vs. SA 193 B7M

03/15/2010 10:06 AM

SA 193 B7 & SA193 B7M are asme specifications for bolts as per SECTION II part A.

Flange calculated thickness is lesser with SA193 B7M bolts than with SA193 B7 bolts

Why?

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Associate

Join Date: Sep 2008
Posts: 40
#1

### Re: Bolts: SA193 B7 vs. SA 193 B7M

03/16/2010 12:42 AM

In addition what u have asked when to use B7 & B7M?Is anything related to NACE requirement ?

Guru

Join Date: Feb 2007
Location: Cairo, Egypt
Posts: 1746
#2

### Re: Bolts: SA193 B7 vs. SA 193 B7M

03/16/2010 6:49 AM

• The bolt material Grades B7 and B7M are different grades for material ASME SA 193, and each grade has its different mechanical properties compared with the other grade, see Table 2 Mechanical Requirements of bolt material ASME SA 193.

• In design calculations of flanges as per ASME VIII, Div. 1, the total bolt load, W (for circular heads) shall be carried out per 2 scenarios: Operating Condition and Gasket Condition.

In gasket condition, the flange design bolt load W = 0.5(Am + Ab) Sa, where Sa is allowable stress of bolt material at atmospheric temp./bolt-up temp. So the load W is a function of Sa, and Sa depends on type of bolt material and/or grade type.

• And the thickness of blind flange (for example) shall be determined by t = d √ [(CP/SE)+(1.9WhG/SEd3)], which is a function of W.

• Also, in integral flanges, the load W is used to calculate the total flange moment in bolt-up condition (gasket condition), MO2 = HG hG = WA(C - G)/2 , and the thickness of flange is a function of flange moment. Therefore the thickness of flange in gasket condition depends on the allowable tensile strength of bolt material.

• For more details, free download the following PDF files: Flange_Design_Calculations & Blind_Flange_Design_Calculation.html.

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