A325 BOLT ASSEMBLY WITH A194 GRADE 7L NUT 2

[PT99]

Is this grade of nut acceptable for a A325 bolt assembly. RCSC allows for A194 Grade 2H (see footnote c in Table 2.1), it says nothing about 7L.
I have a project where this 7L nut was used. I have said no but this is being disputed? The bolt is OK.

 

[ajh1]

The allowance for the swap of A194 2H nuts for A563 DH nuts in RCSC is due to a similar statement in ASTM A563 Table X1.1 Footnote A. The statement given is a question on availability of the A563 DH nuts for 3/4" diameter and larger. Whether that statement is still valid (as I suspect it's been in the standard for many years) is unknown to me. In reviewing the A194 7L nut, it appears to be the low temperature version of the A194 Grade 7 nut. As such it has the same mechanical property requirements as the A194 2H nut. Chemically it has a requirement for chrominum, making it an alloy steel rather than a carbon steel. As such it would likely not be viewed as a normal nut to use with an A325 bolt. That said there does not appear to be an obvious reason why it would not be acceptable.

 

[PT99]

Thanks ajh1,
Any corrosion issues between the 2 metals. This structure is completely exposed to the elements.

 

[ajh1]

If it's fully exposed, then I would assume that all of the bolts, nuts, etc. should be galvanized, overcoated with a good epoxy paint, or some other means to resolve long-term corrosion issues. I wouldn't anticipate that bolt to nut corrosion would be an issue simply due to the addition of chromium.

 

[bridgebuster]

The Portland Bolt Company has a lot of useful information, including a nut compatibility chart and mechanical properties of nuts and bolts.

http://www.portlandbolt.com/technical/nut-compatibility-chart/