Help. Crane boom lattice repair

Date 02-06-2004 15:27

We are a bit slow now and have performing much needed maintenance around shop. I have been in my office quite a bit lately. Stretching legs this morning I found some shop personnel in the process of replacing a couple of damaged lattice tubes (bent lattice form material impact) on a boom of a crane in the material handling yard. Welds all look sound visually. I realize this repair is supposed to be performed by certified personnel. This is not really my business except as a safety item because I noticed it being done in our facility. It is not production oriented in other words. I mentioned this issue to shop superintendant. He says main fitter/welder charged with making the repair is capable of making repair. He is going to let him proceed. As far as this man being a highly qualified welder, I agree. One our best fitters/welders. In my mind, I am sure he can perform the work competently even if I don't have papers on him. Wish I did have a procedure for him to follow though. Apparently this boom has been repaired by our shop personnel at times in past and no apparent problems have arisen from those repairs. So compatibility of materials does not appear to be an issue. In other words, no unacceptable welds are apparent on other repairs using normal steels found in structural yard and 7018. So there is reason to believe we can perform this repair competently even if we do not have paper trail to back us up.

I do not have a copy of AWS D14.3 which apparently is code that would cover this repair. Does anyone have access? I realize there should be a procedure performed by certified welder. Is there any other special requirements to be considered? NDE (MT) of welds? I wish to see this done as competently as possible since we are already in the middle of performing this repair. Give me some guidance. Not trying to cause trouble, just want this done competently so no one will get hurt.

By CHGuilford (****)

Date 02-06-2004 15:54

Be very careful there!
We do a lot of boom repairs. We get the replacement tubes cut to fit directly from the boom manufacturer and follow their welding instructions to the letter, including NDE. Having a long history with those manufacturers, as long as we do as they indicate, they will maintain certification for the boom section.
A few times, we have increased the capacity of a boom by adding material to it. Again, all is per instructions but in those cases the manufacturer sends a rep to inspect and test everything before they certify the boom.

Key points to watch for, DO NOT replace boom tubes with A53 pipe. That is NOT what they are made of, they are high tensile strength materials. Welding on our booms is NOT done with 70K tensile strength electrodes. We have used 80K, 90K, 100K, and 120K all depending on the particular boom and welding instructions. Do not heat straighten anything.

There is some redundancy designed into the boom for safety. Maybe one lacing might not cause a problem (but maybe it will). But having made repairs in the past, at what point will the straw break your camel's back? I suggest someone should contact the manufacturer for guidance.

Chet Guilford

By G.S.Crisi (****)

Date 02-08-2004 14:45

I've been involved with crane boom repair in the past, and all I can say is that Mr. Guilford is absolutely right.
Crane boom lattices are made of high strength, heat treated steel. They aren't made of plain carbon steel, so you should buy the spare tube from the crane manufacturer and follow strictly his instructions for the weldment.
Scrap the bent tubes, do not attempt to straighten them.
Giovanni S. Crisi
Sao Paulo - Brazil

By jwright650 (*****)

Date 02-09-2004 16:16

Chet,
Just for my information, I was under the assumption that some of those crane booms were strung under tension. Interrupting any of those banjo runs required retensioning. I have never attempted any repairs on these items due to my ignorance of the subject. I was always scared to make any attempts after seeing a couple of very disturbing videos of those booms failing and people scrambling to get out of the way. Is this true about these booms being built with tension in the lattice work?(before loading the crane hook)
John Wright

By CHGuilford (****)

Date 02-09-2004 17:26

Hi John,
The booms we have (mostly Manitowoc, some American) don't have any preload that I am aware of. That doesn't mean there aren't any such as you described, just that I haven't run into any yet. The loading on a boom is mostly compression from what our engineers tell me. The stay cables are the tension members.

For distortion control, we always keep the boom well supported with blocking, and never take out any more than 1 lacing at a time in a given area. We skip around and roll the boom several times so that welding is in the 2F positions as much as possible. Welding isn't difficult, you just need the right electrodes, preheat and so forth. Most important is to realize when a boom is too far gone and needs to be cut up into small pieces. One accident could be far more costly than a new boom section.
Chet

By G.S.Crisi (****)

Date 02-10-2004 18:46

Mr Guilford is absolutely right again. Crane booms are not pre-loaded, in the way some concrete beams and slabs are. As he says, booms work under compression, so there's no need nor manner to pre-load them up.
He's also right at saying that the worn out boom sections are cut into pieces, so nobody will have the crazy idea of using them again.
Giovanni S. Crisi
Sao Paulo - Brazil

By jwright650 (*****)

Date 02-10-2004 19:21

Chet and Giovanni,
Thanks for the informative replies, I learn something new each day.

Doug,
I did read that the welders making the repairs should be qualified/certified under D14.3 and with 100ksi material. WPS' can be prequalified under D14.3.

John Wright

By thirdeye (***)

Date 02-06-2004 17:11

Chet's reply is right on the money, espically the involvement of the manufacturer regarding repair procedures, upgrades & modifications, inspections etc. Most manufactures will also assist you in development of your daily, weekly or monthly inspections as well. Hook and rigging manufactures (like Crosby) even have online forms you can download for this purpose.

By magodley (**)

Date 02-09-2004 14:55

That paper trail, including instructions from the mfg. and papers on the welder to weld the type material involved are essential to maintaining certification of the boom. Any shortcuts may leave you with all of the liability...from now on.
Andy

By thcqci

Date 02-11-2004 13:26

Thanks for all the replies. As is obvious by my original post, I know what the right thing to do is and believe we should be proceeding differently. But I do not have authority to override his orders to his personnel. Not production work. I have strongly expressed my opinion. Have given advise to shop superintendant and now will just have to wait to see what he does. I think I know how it will go, but time will tell. Been told we have done it before with no problems and our crane maintenance company was comfortable with previous repairs. Kinda makes you wanta say HUH! Will look closer next time to see the name on theide of the truck when they are here.

Thanks again all. I can't tell you guys how good it is to have a group of like minded people when dealing with quality as it is to "speak" with others in this forum!

By Shane Feder (****)

Date 02-16-2004 04:48

Greetings to all from Australia,
Quite a few years ago I was involved in the repair of damaged lattice piping on a Coles " Gargantua " crane which is a 100 ton mobile ( rubber tyred) crane originally made in England. After sending a section of the damaged 1.5" piping away for chemical analysis we were surprised to find out it was ordinary "black" mild steel tube. The 4" chord pipes were definitely high tensile. The weld repairs were conducted using a qualified welder, a qualified WPS and MT testing was conducted on completion of welding. We also did a mock up of the joint and ripped the weld apart to examine fusion prior to commencement.
thcqci,
You mentioned that the welds appeared "sound" visually. As a CWI and NDT technician of 8 years I can assure you that being acceptable to visual inspection is absolutely no guarantee of a "sound" weld.
The main thing to remember is that every time that crane is in service someones life could be at risk if repairs are not carried out correctly.
Consultation with the manufacturer regarding their recommended repair procedure should be first choice.
Secondly, and this is purely my opinion, a qualified welder / qualified WPS and NDT should be a minimum requirement.
Sorry if I have got carried away but I have seen some absolute shockers go back in to service when I have not had the power to do anything about it.
Kind regards,
Shane Feder