Several ASTM specifications are followed by an “M” that denotes it being an equivalent metric standard. While there is actually an A193M Grade B7 specification which is applicable to metric fasteners, this is not the case with ASTM A193 Grade B7M. This is a different grade of material than A193 Grade B7. So how exactly does A193 Grade B7M differ from A193 Grade B7?
There are some significant differences in both the mechanical properties and the testing requirements of A193B7M and A193B7. For instance, A193B7M has a minimum tensile strength of 100 ksi for diameters under 4”. The minimum tensile strength for A193B7 is 125 ksi for diameters under 2-1/2”, and 115 ksi for 2-1/2” – 4” diameter. Hardness is probably the most significant difference between A193B7M & A193B7. The maximum hardness of ASTM A193B7M is 235 HB or 99 HRB, while the maximum hardness of A193B7 is 321 HB or 35 HRC. The most notable difference from a manufacturing perspective is that when providing A193B7M bolts, every individual bolt or stud in the lot must be hardness tested. A193B7M fasteners will also require a different grade of heavy hex nut than A193B7, which would be ASTM A194 Grade 2HM.
While A193B7 is specified relatively often in the construction industry, A193B7M is a specification that is not seen as regularly. This makes it important to understand the differences between the two specifications so that the correct material is ultimately provided.
are B7M Is it suitable for work in the sanitary lifting stations?
@Osama- We are sorry, but we are not familiar enough with the requirements of sanitary lifting stations to know if B7M bolts are allowed. Apologies.
Hi, Would there be an issue using B7M washers with B7M bolts & 2HM nuts?
@Neil- A193 B7M does not specifically cover washers, although I guess theoretically you could make them from the same material. I see no issues using the same bolting material to make washers for use here. That said, ASTM F436 washers are an off the shelf, very common washer that may provide the same benefit at a much lower cost.
At wellhead platform , B7 bolts used instead of B7M , is there any big issue .Enviornment is a little bit corrosive.
@Jayant- B7 and B7M bolts are chemically identical, so they would both have the same corrosion resistance, which is negligible. However B7 and B7M bolts re not mechanically identical. B7 bolts are stronger, but rated for lower temperatures than B7M. You will need to consult the project engineer and get their approval for the substitution.
Dear Sir,
May you help me about correlation Bolt Tensile Strength vs Pressure?
Right now I want to have high pressure valve test using test flange 10″1500# (standard no. of bolts is 12 ea) and the test pressure is 5,575 Psi.
At the moment I only have 6 bolts size 1-7/8″, it is permissible to test the valve with only 50% attached to the valve?
Is there any calculation about it?
Thank’s
Ramonz
@Ferry- Apologies, but we do not have any engineers on staff, and do not have the expertise to answer this. Sorry we could not help.
Dear Mr McKinnon
May you help me about difference between stud bolt & machine bolts , in fact about Mechanical properties , I think that the stud bolts will be used in piping components without washer , but the machine bolt use for structure with washer. At least Can We say the stud bolts are stronger than machine bolts?
Thanks a lot,
Ashkiani
@Ashkiani- The only difference is that the machine bolt has a head, and the stud bolt does not. Mechanically, assuming that they are the same grade, they will be identical. Machine bolts sometimes fare better during wedge tests due to the forged head, but we would not say that one is stronger than the other. It will depend on how they are being used and what the engineer designed for.