Cracking Reparation in fillet weld.

Date 10-13-2005 13:11

I have seen engine blocks fixed by drilling holes an the ends of the crack and then welding over the crack.and filling the holes.Not saying that it works though.
I work with structural steel.When we find a crack(if we are allowed to fix it),the crack is fixed by cutting(carbon arc or grinding)the crack out plus 2" past the point of where the crack stopped and then weld it up and grind it flat.

By JCaprarulo (**)

Date 10-13-2005 22:57

QCCWI.
OK, I agree with you too, but the million dolars answer is where is stated about prohibition of that explained procedure.
The same question has been done in ASME forum, but no response yet.

By QCCWI

Date 10-14-2005 10:56

I have never seen it in a code book that states you can or you cannot fix a crack by drilling holes at the ends.
Just ask the Engineer his/her opinion because he/she has the final say in how it gets fixed.

By - Date 10-14-2005 12:01

I agree with your answer. May I share how I used to recommend to our welding dept. how to fix cracks?

I recommended that no pre-grinding was done anywhere on the existing crack. Our practice was to start approximately 2" past the visible ending of the crack, on each end. Start the weld on what appeared to be good metal and weld toward the middle of the crack, stopping half way the length of the crack. We then started on the other end of the crack, again 2" from the visible end of the crack on good metal and welded toward the center joining the weld metal that we started from the other end. We did not ever drill holes. The practice we used worked very well on almost all circumstances. It was after we finished welding that we lightly and very carefully ground off the excess metal, although there was very little excess. Then, if critical, we x-rayed to make sure we got it. Thanks for letting me give my opinion on how we did it.

Chuck

By jwright650 (*****)

Date 10-14-2005 12:51

Hi Chuck,
Wouldn't your suggestion of welding over a crack be very dependant upon the thickness of the material?
0" - 5/16" = yes; over 5/16" = no
Even then welding process will dictate those thicknesses to some degree.

When using MT to locate the ends of cracks, I have found that the heat from cutting/gouging or welding can make the crack grow in length, so that can be another concern to watch for when repairing a crack. I understand what you are saying about starting a pass over on sound material and progress toward the middle for this reason.
I also work in structural steel so these pressure vessel codes are not at all familiar to me.
John Wright

By - Date 10-14-2005 13:19

Hey John,
Good to hear from you, my friend.

My recommendation to my welding dep. was referring to cracks we felt we could fix. Most definitely the thickness was a big factor on our decision whether we could do that. I was only stating the method that we used when we decided to fix one. There were many cracks that we did not attempt to fix. Trying to repair a crack, as most of us will probably agree, can be a touchy thing. We tried many methods, but the method I mentioned was one of our most successful on welds we attempted to fix. In virtually every instance a crack is heat induced anyway. Cutting, gouging, grinding, etc., if done incorrectly can make the crack propogate all the way through a weld. I have watched with amazement a welder chase a surface crack all the way to the root. Cracks are not something to be taken lightly.

Chuck

By jwright650 (*****)

Date 10-14-2005 17:12

"I have watched with amazement a welder chase a surface crack all the way to the root." - Chuck

Yeah Chuck, me too! We were repairing some fabricated material that came back from the galvanizer cracked, a few years ago. One of our welders thought it would be a good idea to take his torch and melt off the galvanized coating before he prepared the crack for welding. He found himself chasing a crack that started out being about 3" long and chased it all the way across the web of a W24x104. :)
John Wright

By - Date 10-14-2005 18:57

John,
Having been in the trade for 35 years, I'm not really surprised at what I see anymore. My next statement is probably going to cause some flak, but we are all entitled to our opinions in this Forum, so I will say it any way. 20-30 years ago, when the welding technology was not as advanced as it is now, a welder was supplied with "not as modern" equipment as is the norm today. Then, it took a lot of pride and skill to produce really exeptional welds. Most welds were manually done, with equipment norm for those days. The welders of those days figured out ways to do things to get good results, knowledge was shared, new techniques were being developed using old technology. The welders of today, God bless them because they are great welders, but they don't realize how much more technology and modern equipment is available to make their job easier. I see welders in this later day and age that will absolutely refuse to pick up a grinder and grind his weld, but will gripe if his fitter does it less than what he likes. I have been in this trade for over 35 years, my father who is 26 years older than me was a welder in the Union as was his brother. I've seen, as many of the experts in this Forum, the great strides welding and welding technology have advanced just in the last 25 years. As a Welding Engineer, I have personally seen how much it has advanced, and even participated in developing some of that technology. My point is, the ability to produce good welds is much more expected today because of all the modern assets abailable to today's welders. When something less than perfect happens, a lot of today's welders are at a loss of repair methods. Hence, the example of this welder chasing the crack from Dallas to Houston. (extreme example) It is a fact that welding and welding technology has advanced more in the last 25-30 years than it has in the last 100+ years. The welders of today are great, but just hope that they all realize the dreams and desires to develope the industry of yesteryear, are what makes today's technology available. My compliments go out to all welders, old and new. I hope all of this makes sense. Sometime my brain and typing fingers don't always work in conjunction with each other. ;-)

By jwright650 (*****)

Date 10-14-2005 19:40

Chuck,
I hear what you are saying. ;) the SMAW and FCAW machines that we have and many of the welders themselves were here when I started here at this company 21 years ago. In fact the SMAW and FCAW machines that were here when I started, were already 10 years old then. I understand completely about how technolgy has past our shop by and left us in the dark ages. You know that old equipment, as old as it is, is still good running stuff. If you brought in new machines with all the bells and whistles, my poor guys wouldn't know how to even turn them on. When it comes to all those bells and whistles, I have to agree with Ed Craig, that less knobs, the better.
John Wright

By - Date 10-14-2005 19:50

You got it, John...It all boils down to one thing that is the biggest asset in this trade..DESIRE..desire to be the best when using less than the best..It all comes from within. God gave most all of us the equipment to be a good welder..2 eyes, 2 arms, 2 legs, a functioning brain..It's the desire that sets the good welder from the average welder. The best welding machine and the best technology in the world will not make a welder a good welder if the desire is not there. But, I hear what you're saying.

By medicinehawk (**)

Date 10-14-2005 21:44

What you witnessed (welder chasing a crack to the root) is why you need to grind out the crack and re-weld it.

By - Date 10-14-2005 22:14

That's exactly what he did...He ground it out and re-welded it. That's usually what happens when you start trying to repair a crack by grinding it out. But, there are other ways to repair a crack without grinding the whole weld out. In some Code cases you might have no choice but to remove the whole weld and re-weld.

By Jim Hughes (***)

Date 10-13-2005 18:09

Not here in America. If the vessel is built to Sec VIII there is no provision for stopping a crack by drilling a hole. There is a way of repairing this weld by grinding it completly out and re-welding it. If this is a National board stamped vessel then in most states you would need a repair stamp to do the weld repair.

Hope that helps
Jim

By JCaprarulo (**)

Date 10-13-2005 22:50

Jim.
First of all thanks a lot for your answer.
I agree with you about ASME VIII has not any provision about that procedure, but also is thrue that doesn't state anything prohibiting that one.

By BillC

Date 10-14-2005 22:34

Just remember that parts only fail because the stresses are too high... Make sure that you understand WHY you have an indication or you are destined to repeat your repair...

Regards,

By andy

Date 10-17-2005 08:34

Good point - I missed replying because of the weekend. Plates fillet welded to shells often crack due to stresses during operation - thermal are the most common.

Drilling holes to stop cracks in components like this can have two effects

Often the crack won't stop as the very act of drilling a hole is to concentrate stresses unless its big enough - I've seen this many times on baffle plate fillet welds.

Secondly, get the drilling wrong and you can end up drilling a hole into the vessel shell reducing thickness and threatening integrity.

If the cracks aren't propagating into the vessel wall then they're probably not too dangerous UNLESS there's a danger of the plate becoming completely detached and bouncing round the vessel interior.

Sounds like you need to talk to an structural engineer about this.

Andy

By JCaprarulo (**)

Date 10-17-2005 11:04

Andy.
Very clear your explanation, thanks a lot.