Problems with Galvanized A325 bolts 1

[AlwaysAnAggie]

Is anyone aware of potential problems with ASTM A325 galvanized bolts? We are specifying them on a project, which is new for this company, and they are very leary of doing so. Do any of you know of typical problems with these bolts, uses that they are not good for, etc?

 

[gtaw]

The nuts and bolts should be galvanized by the same supplier and the threads "chased" to ensure the galvanizing does not muck up the threads.

The can only be tightened once, i.e., they can not be reused.

Best regards - Al

 

[connectegr]

Provided they are installed and inspected per RCSC spec., this is a common practice. Galvanized bolts and nuts are considered an "assembly", so they should come from the same supplier/manufacturer, as noted above.

http://www.FerrellEngineering.com

 

[bradleyelwood]

I built power transmission towers using lots of galvanized bolts and I dont know of any problems.

Their practice was to torque the bolts to a much smaller value than you would in typical structural steel.

 

[qcrobert]

Have you considered coated bolts & nuts like a Magna coat?

 

[dik]

They typically use male and female threads that have different tolerances to accommodate the added thickness.

Dik

 

[AlwaysAnAggie]

no, we have not tried that, but i think they are sufficiently comfortable with galvanized A325 bolts and prepared to use them on this project.

thank you for all of the comments.

 

[paddingtongreen]

As long as they fresh from the factory with the oiled surfaces they are no problem but dry zinc surfaces, moved over each other, under pressure tend to gall. I've seen it when someone tried to use some left over galvanized bolts, left out in the weather for years and very dry and perhaps a little corroded..

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[pipedreamer01]

Regarding the A325 bolt (galvanized finish): Does anyone know if the F436 hardened washers are required to be furnished with the bolt/nut assembly? My customer is indicating this is required by code. I understand the requirements of the nut and bolt since A563-S1 requires the testing of the lubricated nut with the bolt to confirm ability to rotate.

thanks
Bryan

 

[Duwe6]

Like any other A325 bolting application, a washer is only required for using torque to install the bolts, vs. turn-of-the-nut or 'snug tight'. Washers are also required to cover slotted holes. Period.

RCSC A325 & A490 requirements are attached.

 

[connectegr]

The requirement for hardened washers are relative to the hole type. And therefore may not be part of the "assembly". SEE attached

http://www.FerrellEngineering.com

 

[connectegr]

Duwe6 attached the previous issue of the RCSC spec.

FYI - attached the 2009 Spec

http://www.FerrellEngineering.com

 

[Guest102023]

bradleyelwood,
I doubt your application is nearly as critical as most applications for machine screws.

 

[cybo11]

I don't want to sound alarmist but Buy domestic. We had several thousand 1/2" A325's on a snug-tight pedestrian bridge job that guys were stripping out by hand. Got back to the shop, put them through some torque tests and found out they barely made spec. The domestics were capable of almost twice the load. From that experience I realized some manufacturers will use whatever voodoo they can to hit the numbers.

 

[REGRUMBLE]

We have had engineers specify that A325 assemblys not be galvanized due to concerns about the process making the bolts brittle. I have attached one link that details the problem. these bolts are used on thousands of structures but once in a while some enginner will refuse to accept them. As stated above the problem migh just be offshore stuff but it still is a problem.

 

[HgTX]

The link says A 490 bolts can't be galvanized. Not A 325.

Hg


Eng-Tips policies: faq731-376

 

[connectegr]

Hydrogen embrittlement is an issue with hot dip galvanizing of A490 bolts. However research found no embrittlement issues with Zn/Al Inorganic coating of A490 bolts. Additional information is available in the RCSC Spec commentary.

http://www.FerrellEngineering.com