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A325 vs. A193 Gr B7
2

A325 vs. A193 Gr B7

A325 vs. A193 Gr B7

(OP)
I have a contractor that has substituted A193 Gr B7 for the specified A325.  Both were galvanized.  Any problems that anyone might see with that?

Thanks as always!

RE: A325 vs. A193 Gr B7

In or on what and what is the environment?
 

RE: A325 vs. A193 Gr B7

(OP)
it is a structural application, on a pedestrian bridge tower that is exterior, inland and not exposed to a corrosive environment like salt air...

RE: A325 vs. A193 Gr B7

I'm going to defer to one of the more knowledgeable structural members for the answer.

Personally I would not allow the substitution without a written change order from EOR because of two words in your reply, "pedestrian and bridge". Normally B7 bolts aren't galvanized while A325's are. The 325's have a very definate product form with a specific length of threads to shank length, which isn't normally found in B7s'.  

RE: A325 vs. A193 Gr B7

Yes, I do have a problem. The answer is NO you cannot substitute materials because you need the approval of the Engineer that is going to sign and seal the drawing and bill of materials. Do you realize the liability if something happens and the smoking gun is a material substitution???

RE: A325 vs. A193 Gr B7

(OP)
I am the engineer of record, I'm asking the difference in the two types of bolts, both are galvanized, so corrosion resistance is the same.  The tensile and yield strengths are greater than A325.  Is there any other difference I should be aware of.  I can make them take the bolts out if necessary, so the question is, is it necessary?

RE: A325 vs. A193 Gr B7

The differences between the two are chemical composition and thermomechanical processing.  The A193 Grade B7 material is higher strength, and has a minimum tempering temperature that should avoid problems with 1) strength reduction due to hot dip galvanizing and 2) delayed fracture due to hydrogen embrittlement.  You should be able to approve this, but there is a slight risk if the wrong procedures are used during manufacturing.  You can read more here:

http://www.portlandbolt.com/faqs/galvanizing-high-strength-bolts

RE: A325 vs. A193 Gr B7

Here is a US manufacturer's (Portland Bolt) take on the subject.   You are correct as far as physical properties go in that both fasteners are on the same page.  The devil is in the details in the HDG process and how was the fastener treated to rid it of Hydrogen.  The vast of majority of HDG fasteners are coming from off shore no verifiable pedigree.   Things are being done  with fasteners in spite of the NFA that will scare the hell out of you .   
Again personally I would use a galvanized B7 fastener in any situation where I didn't have the history of said fastener from bar to box.

http://www.portlandbolt.com/faqs/galvanizing-high-strength-bolts
 

RE: A325 vs. A193 Gr B7

(OP)
thanks all, much appreciated.

RE: A325 vs. A193 Gr B7

Correcting the last sentence my previous post:

Again, personally I would not use a galvanized B7 fastener in any situation where I didn't have the history of said fastener from bar to box.
 

RE: A325 vs. A193 Gr B7

(OP)
just bearing connections

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