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Up Topic Welding Industry / Processes / Fractured TC bolt
- - By rsx-s-02 (*) Date 02-23-2010 20:54
Has anyone had a 3/4" diameter TC bolt fracture during installation before the pintail snaps off?  I have never experienced this in my 20+ years in QA and this has happened twice now over the last week with different lot #'s and different length of bolt.   Bolts were purchased from a reputable supplier and made by a reputable manufacturer.  The supplier says that I am the only one who has complained thus far.  So far I have researched the TC gun and it seems unlikely that the gun is the problem.  The installer is a seasoned employee with over 25 year’s experience.  We do not lubricate or alter the bolts in any way.  They are kept in a protected storage in original containers.  The containers are kept closed.  One of the bolts was fractured during the pre installation testing and the other during fabrication.  All bolts with these lot #’s have been pulled and returned to the supplier along with the broken bolts.   All of which will be returned to the manufacturer for testing and examination.  Currently I am waiting for the manufacturer’s test results.  Just curious if this has happened to anyone else and if so, what was the outcome.
Parent - - By jwright650 (*****) Date 02-24-2010 12:42
I have been involved with the Pre-Installation verification of hundreds, if not thousands of kegs of bolts with various mfg's and lot numbers over the years, and have yet to have a single TC bolt fail pre-installation verification. <crosses fingers hoping that I didn't just jinx myself with that statement>...LOL

I guess that you were glad that you performed the pre-installation verification on that lot of bolts.....shudder to think what could have happened as a result of high strength bolts failing in service.

Please post up the results from the bolt mfg once that information is available. I'm curious what went wrong with those bolts....

BTW, were these galvanized fasteners by chance?
Parent - - By rsx-s-02 (*) Date 02-24-2010 14:19
Hi John,
No, these were not galvanized.  These were regular black 3/4" dia. A325 TC.  Yes, I was glad to have done the pre-installation verification test this time…….finally after all these years of testing bolts, I have proof that it IS necessary.   It make training the shop guys that much easier.  Gotta love visual aids!  :-)   

Ed
Parent - By jwright650 (*****) Date 02-24-2010 14:33
Yeah, you hate to see failures, but at the same time, it helps drive a point as to why all of this QC hooplah is required....

I guess it's kind of like wearing your seatbelt, wear it "all of the time" for "the one time" that you actually need it.
Parent - - By DaveBoyer (*****) Date 02-25-2010 02:44
What data do You have regarding the bolt that failed in testing?
Failure above or below working torque?
Failure above or below working tension?
Parent - By rsx-s-02 (*) Date 02-25-2010 14:51
Being that these bolts are short….1 ¾” and 2”, we can not test them in our skidmore.  We use a direct tension indicator (DTI squirters) to test the shorter bolts.  While testing the 1 ¾” that failed, the silicone from the squirters was present and at acceptable amounts.  The fabricator described the process as, the gun started to slow as always just before reaching appropriate tension, and then it just popped and sped up again.  Still waiting for the results from the manufacturer.
Parent - - By Joseph P. Kane (****) Date 02-24-2010 16:20
Did you take close up photos of the fractured surfaces?  I know a few Committee people who would like to have one of the fractured specimens!!!!

Joe Kane
Parent - By eekpod (****) Date 02-24-2010 19:41
Can you describe where it fractured?

I have never had this happen either.

I have heard during a bolting seminar that if the lubricant is too efficient that it will allow the nut to rotate with minimal friction and the bolt will break.  This is why it is critical that only the manufactures lubrication be used on TC bolts, because if a different type that is better than what the manufacturer uses, it will allow the bolt to overtighten itself past it's tensile point and the bolt will brake.

Chris
- - By rsx-s-02 (*) Date 02-24-2010 21:42
Joe Kane, Yes, I took close up pictures....at least as close as I can get.  Sorry, the broken bolts have been sent back to the manufacturer for examination and testing.

Chris, The bolt fractured about half way down the shaft.  I too have heard that additional lubrication could cause this to happen.  (Maybe I’ll conduct a little impromptu experiment and grease or WD-40 some bolts and see if the pintail snaps off or they break.)   I examined the bolt at the pintail and there are some diagonal lines at the base of the pintail possibly indicating it started to twist, but the bolt broke before the pintail.  In my opinion, the bolt actually looks dryer (less lubricated) than normal.
Parent - - By eekpod (****) Date 02-25-2010 11:17
interesting.
I've tried the WD-40 thing, it didn't work.
We have some crazy special stuff for a special anchor bolt system and the lubricant is $80 for about 16oz.  I'm trying to find that to try it, I bet that would allow it to brake the bolt because it's so slippery.
Parent - - By rslif Date 02-25-2010 16:05
Interesting post. I have always had some question/concerns about tc bolts and their lubrication or lack of. I just emailed the manufacturer of the tc's we use regarding relubrication, whether or not they sell some product to relubricate with and/or the effects of too much lubrication and received this reply:

"ASTM specifications will not allow any change to lubricating by any other than the manufacturer. My quality supervisor said that if there is a lubrication process done to a TC other that what is provided by the manufacturer can cause the bolt to strip and or break. We are not aware of anything that can be done to accommodate your situation. Please let me know if I can assist you with anything else."

Now I want to respond with "Why yes you may be able to assist me a little more in fact. Would you mind answering my original questions w/o beating around it?" but thought it best not to. I'm sure I can get more info from this forum on the subject.
Parent - By swnorris (****) Date 02-25-2010 18:33
rsx-s-02,

Not that this has anything to do with your problem, but does your contract documents require you to comply with the 2004 RCSC? Did you get EOR approval to use A325 TC? RCSC requires the use of ASTM F1852 unless the EOR approves an alternative, such as A325.   Also, is the method of testing approved? Squirters typically aren't associated with twist off bolts.
Parent - - By eekpod (****) Date 02-25-2010 18:50
Basically I have never tried to have a TC bolt re-lubricated from the manufacturer, and only becasue I always figured that the cost to relubricate say 100 sets of TC bolts would be more than the cost to replace them with new ones.

I am curious what would happen if I did ask if it could be done so I just called out biggest supplier and he said that he has never had anyone ask to relubricate.  He is calling corporate to see if it is an option.

So the catch here is to NEVER allow the lubrication or cleanliness of stored TC bolts to be comprimised, and that's because once that happens, they can't be relubricated by you (or the manufacturer in your case) so your stuck.  You will need to replace them with clean bolts assemblies.

Chris
Parent - - By rsx-s-02 (*) Date 02-25-2010 20:40
Scott,
We follow the contract drawings and specs.  If we would prefer to do something different, we would seek approval from the EOR.   Since our Skidmore can not accommodate short bolts such as 1 ¾” and 2” we verify them using the squirters.  Squirters are first checked in the Skidmore with longer bolts.  There is a procedure we follow, but that’s the gist of it.

Chris,
I hate to think of how many bolts we have discarded/replaced because of contamination.  (an erector leaving the keg open and it rained, or someone was grinding and shooting sparks all over an open keg)  Now our bolts are practically under lock and key.  Our fabricators are allowed to remove only as many bolts as are needed to complete the pieces they are working on.
Parent - By eekpod (****) Date 02-26-2010 11:18 Edited 02-26-2010 12:04
Yes, I agree, we to over the years have ended up tossing kegs of bolts, after 5 or 6 years in the shop, no matter how hard we try to keep the lids on the dust and dirt gets in there and the lubrication goes away.

Now I actually called and spoke to my TC distributor and he called corporate.  He and I were surprised to find out that they have never relubricated TC bolts for their customers.
I guess I just assumed that since the manufacturer is the only one who can lubrucate the bolt, that only the manufacturer can RELUBRICATE it as well, but that is not a service they offer.

So the moral of the story is to keep them clean and tight until needed.

Chris
Parent - - By jwright650 (*****) Date 02-26-2010 12:43
"Now our bolts are practically under lock and key.  Our fabricators are allowed to remove only as many bolts as are needed to complete the pieces they are working on."-quote

That is exactly what we do here. There is one person with a key to the "bolt room". This person is responsible for handing out the bolts as the fitters need them, and he is also in charge of keeping the inventory straight(but that is a piece of cake now that he is the only one who messes with the bolts). He also lets me know when a new keg is delivered and we take care of the pre-installation verification and get that out of the way. I like our system and hope that we keep it for as long as I am involved with the QC here. It makes my job a bit easier when people take their job serious and do a good job.
Parent - - By rsx-s-02 (*) Date 03-01-2010 20:46
Hi everyone,
Just an update on one of the bolts.   After being tested along with multiple samples from the same lot, the broken bolt tested within acceptable range as did all the sample bolts.  The tests that were done were a twist off clamp load test as well as an inadequate hardness test.  All came out within acceptable range.  I also received a statement that ""....the "normal" reason for F1852 assemblies to break prior to the spline twisting off would be due to overlubrication""   As stated earlier, we never lubricate our TC bolts.  So unfortunately I do not have a reason that it broke, only information that the lot and broken bolt are within acceptable range.   Still waiting on results from the second bolt.
Parent - - By welderbrent (*****) Date 03-02-2010 03:13
rsx-s--02,

Is it possible that the fracture was either a result of bad practice utilized while installing the bolt assymbly or improper pre-tensioning before reaching the final tightening to reach the twist off point? 

If bad installation practices were used by the installer the bolt could have been damaged as a result of 'forcing' it into the hole using the bolt to 'line up' the hole.  In many of these cases the twist of would break before the bolt was properly set because of added thread friction.  But, it is possible that the damage caused the bolt to break because it was weakened in the thread area.

If improper pre-tensioning was employed it also could have damaged the integrity of the bolt and caused premature breakage.

Just my two tin pennies worth.  Have never experienced this problem.

Have a Great Day,  Brent
Parent - By rsx-s-02 (*) Date 03-03-2010 17:53
some helpful information:

TC BOLT INSTALLATION PROBLEMS
A) Bolt breaks at the threaded portion before the pintails shears off?
Answer: Most likely the torque co-efficiency value has become lower.
Possible Causes:
1) Storage conditions allowing exposure to rain, water, moisture, high humidity, temperatures over 140°F or
similar environmental conditions.
2) Lubrication of the product beyond “as delivered” condition from the factory. (Use of oil, grease, or wax on
the product components at the job site)
3) Adhesion of oil, paint, mill scale, dirt burrs, or foreign material on the faying surfaces which may allow
rotation of the bolt, or rotation of the washer with the nut during the tightening operation.
4) Not properly making the connection “snug” tight before final wrench tightening which may allow the bolt
to rotate.
(Same as common hex bolt)
5) Possible misalignment of the connection surfaces that may prevent proper contact of the head
and faying surface.
6) Exposure to the environment over an extended period before final tightening.
- - By rsx-s-02 (*) Date 03-02-2010 15:00
photo of 3/4"x2" A325 TC
Attachment: DSC02910.JPG (581k)
Attachment: DSC02909.JPG (569k)
Parent - - By rfieldbuilds (**) Date 03-14-2010 18:29
Thanks for the pictoral posting !!!
RF
Parent - - By ziggy (**) Date 05-21-2010 15:40
if one is concerned with the condition of the tc bolt and that the torque might be suspect, rather than throw away the tc bolts consider installing them using turn of the nut (t-o-n) method.

regardless of their condition (within reason and code allowances of course), they remain a high-strength bolt. a skidmore test using the t-o-n method will determine if they are sound. so, if the engineer of record permits, save your money and install them using the t-o-n method.

just a thought,

ziggy
Parent - By Bob Garner (***) Date 05-21-2010 17:28
St Louis Bolt Co. said not tightening the bolts to a snug tight condition before using the TC wrench can cause rupture at the threads before the pin breaks.
Up Topic Welding Industry / Processes / Fractured TC bolt

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