Tank Anchor Chair Bolt Specifications 1

[Chap123]

Hello Great Brainers,

I have little concern related to bolting specifications for tank anchor bolt chairs.

As per API 650 and our client specifications, we are required to use ATM F1554 for anchor bolts.Our client is stressing me to use ASTM 193 B7 threaded rod and A194-2H nuts ( which is for higher bolting strength applications like flanges, bars, piping etc)


My question here is that; can we really use A193 B7 for anchor chairs from an engineering point of view? Moreover API 650 section 4.7 b says that bolts with minimum specific yield strength 55 ksi is prohibited. I think A193 B7 has yield strength of 93 ksi.

So we can use A193 bolts ?


P.S our anchor chair is a36 .

 

[BJI]

You don't get any advantage by going to higher strength bolts because you are still limited by the strength of the concrete. I don't see any issues using higher strength bolting provided you don't design it relying on the higher strength. So Your client is incorrect, what is in API 650 is appropriate.

 

[JStephen]

I was thinking API-650 had a provision for use of other materials as well, but don't have the standard in front of me.
One requirement that comes up, I think in the seismic, is that chairs are designed for the yield strength of the bolt, and if you arbitrarily use a much higher yield strength, you can come up with unreasonable anchor chair loads from that.
Typically, a heavy hex nut embedded in concrete is adequate to restrain a bolt of that size. If you increase the bolt strength without increasing the nut size, that may not be the case, in which case, some form of additional anchor plate is required.

 

[Chap123]

Thanks for the reoly .

Do we think using sane yield strength nut with the stud can resolve any issue that may arise .

ASTM 193 B7 threaded rod and A194-2H nuts.

Should I be worried for the plate material that has low yield strength I.e 36 ksi

 

[JStephen]

Yield strength of the plate usually isn't an issue, you adjust the thickness per your design anyway.

 

[Chap123]

Thanks,


As per API-650 Table 5.21, the yield strength is limited to 55000 psi and A193 B7 has yield strength of 93000psi. Moreover code says that yield strength of bolt material shall not exceed minimum yield strength of shell.
Can we use A307 in place of A193 B7?

 

[JStephen]

The item about yield strength not exceeding yield strength of the shell is for anchor straps, not anchor bolts.
But the restrictions about not exceeding 55ksi should answer your question.