boiler repair

Date 12-29-2006 21:42

Had my first go at a big boiler on a nat. gas rig here in Colorado. The internal burner tubes were coming apart at the factory welds. I knew I was only going to buy some time before a truck showed up with a new boiler unit. After several attempts with both Low Hy and 5p, my efforts were in vein. I preheat before each weld around the outside of the tubes, but I found that once I was succesfull stopping one tube from leaking, the one next to it would spring a leak. The only thing I think I could have done any different or "better" would have been to use an ln-25 for the whole welding process. Unfortunatly some affable fella decided to take mine out of the back of my pick-up last month, so I didn't have one on this job.
As a last ditch effort, I made some templates and cut some patterns out of 3/16" plate to actually try and isolate 24 of these leaking tubes at one time. Needless to say, I got halfway home at 1am and they called me back out to try again. Long story short, I told them they were sol, because there just wasn't anything I could do, beyond what I had, that would take us forward with the repair. I suggested they turn the pressure down way low, and nurse it along until the new unit showed up the next day. That's what they did, and they had enough steam to keep everything from freezing solid.

I suppose I'm asking for some sort of validation that I did everything I could to save the remaining volume of the boiler. Believe me, I would have liked to be the hero of the day by making that thing purr, but I'm convinced I did everything I could for them. Please share your thoughts on this subject - Sourdough

By yorkiepap (***)

Date 12-30-2006 02:41

Hey SD,
Out of curiosity, could you have employed brazing rod or wire since you were only repairing weld cracks? I know there are brazing rods for stick and brazing wire for MIG. Quite a lower heat parameter. Just wondering....Denny

By Sourdough (****)

Date 12-30-2006 04:33

Denny, it was a mess. I was standing on my head half the time, and the other half I was trying to get stood up on my head to weld. The tubes actually were cracking at the factory welds and the actual tube flange. Basically this thing was plumb wore out. Brazing was an option, but I would have been there till the cows came home. These guys just wanted to get by any way they could. I have a feeling someone was gonna get run off over it.
I told them we needed to get a wire machine, but they were out of time. Preventive maintainence doesn't exist in the oilfield, it seems.

Good talking with you Denny!

By CWI555

Date 12-30-2006 16:12

Doesn't seem to me that there was much more you could do. Your last statement in regards to preventive maintenance says it all.

By MDG Custom Weld (***)

Date 12-30-2006 16:18

.SD,
How old was the unit?? What bothers me is the factory welds were letting go in the first place. I could see the tubes getting corroded and cracking, but the welds first has me puzzled. Maybe they are running the thing beyond its intended pressures, or even further, maybe the original material or welding process is the problem. I really don't think you failed, I think you were set up to fail because of factors out of your control. Just a thought.

By Sourdough (****)

Date 12-30-2006 17:15 Edited 12-30-2006 17:18

Well, when you're talking about big rigs you're talking about making holes as fast as possible. These outfits are making up to 25k a day when they are running, 0 -when they're not. They nurse everything they can until they can't anymore.

The boiler was definately a vintage, but i think that on these huge boilers your dealing with a detrimental combo of heat and pressure. When the toolpushers and hands push it beyond its recomended volume for years, it's just not good for anything.

Another issue is that a "certified" vessel shop made this unit. I have seen the most hideous welds come frome a "certified" vessel shop, so it's possible that the welds weren't up to code in the first place. I worked for a guy a few years ago, and his primary clientelle were people who had failing vessels from a "certified" vessel shop. I guess it's just hard to get anything that is of genuine quality these days. . . .?

I think mainly this boiler failed, prematurely, due to it running beyond its capacity too long. I'll tell you though, I don't like things that I can't fix! I like going home with a signed ticket, and everyone happy.

By MDG Custom Weld (***)

Date 12-30-2006 17:33

Yep, I hear ya on that. I like to be the one that gets called when everyone else couldn't fix it too. It's few, and hopefully far between, when I go home with my head down being beat by some little (or big) piece of metal that I could not fix. Each time, it all goes into that ever growing bag that we call "Experience", and makes us better welders. At lease we never stop getting better!!

By Sourdough (****)

Date 12-31-2006 02:09

Darn straight, man! I don't know how many times I am doing geometry in my sleep. Not getting any sleep just, well. . . .SUCKS!

By MDG Custom Weld (***)

Date 12-31-2006 12:26

You got it, no sleep sucks, but then unless you know something I don't....I don't make any $$$$ sleeping!!!!!!
Anyway, I have many years to sleep when I kick the bucket. Then maybe I can leave the kids with something and they can get some sleep and not have to work so hard.
Hay SD, congrats proud papa. I read in another post you just had a little curtain climber yourself.
Mark

By Sourdough (****)

Date 12-31-2006 22:09 Edited 12-31-2006 22:22

Thanks, brother! Yeah, I'll sleep when i'm dead, I guess!

SLEEP, yikes man!!

By CWI555

Date 01-01-2007 23:11 Edited 01-01-2007 23:14

The welds failing without the tubes base metal having the same problem in parallel or before would be a concern. It implies that the original factory welds were of a lesser grade metallurgically, mechanically, or both, than the parent metal in the tubes. That goes against the grain imho, as it's typically the tubes that fail first, not the welds. I've worked in a lot of boilers, from package up to 950mw units, I've seen a few cases were the welds failed first. I have no idea if it applies, but I'll list the failure analysis of some that were looked into that I have reports on.

1. tubes in a power boiler/reheat welds were determined to have been originally welded with the wrong filler in excess of 400 welds mislabeled materials at fault.
2. tubes in a package boiler - welds were determined to have been hydrogen embrittled; 15 welds no determination as to how the embrittlement occured. Welds were in service for 4 months.
3. tubes in a power boiler/superheats - combination problem, overpressure with original weld IP 17 welds. X ray film interpreter was determined to not have read the film right. (those of you who read film can understand the significance of that)
4. tubes in a power boiler/waterwall - deliberate wrong filler material. 38 welds

I don't know if that helps you, but it's my 2 cents worth. Based on what you've stated, I'm leaning towards the metallurgy.

By Sourdough (****)

Date 01-03-2007 14:09

Could be, I don't know for sure. I'll tell you one thing though, I wont relish the next boiler job I get. You never know, maybe next time I'll turn it down unless I can work on it in the shop.

By makeithot (***)

Date 01-17-2007 16:32

It's hard to build character though when your working in a nice warm shop.

By Sourdough (****)

Date 01-21-2007 20:59

I've got enough character. -36* north of I-80 last week. Fabbed over 900ft of production, dump, sales, and tracer lines and got em backfilled. Got frostbitten again on my face. Screw character!

By genotag Date 06-05-2007 01:15

I know you said that the old welds were cracking but, a lot of boiler tubes are rolled. Also many tubes are made of some % Cr. A speciality boiler may have tubes made of inconel or other materials. You don't mention what your preheat temp was or if you used PWHT. GTAW probably worked better so you could control your heat better. Sounds to me you got the tube sheet too hot.
Gene

By Sourdough (****)

Date 06-05-2007 15:38

I was standing on my head in -15 on a dirty old boiler!

By J-GROVE JER Date 08-12-2007 14:49

Nice try at repairing a powerboiler,my first question is do you have a boiler repair procedure and if so did you follow that procedure? When working on a high pressure steamboiler anything over 15 psig the boilers branch must be informed of the work been done, a boiler failure can be catostrofic causing extreme damage and loss of life.I know we have a job to do but we have to do it within the law and I could not sleep if my actions lead to death of a nother person.Sorry for being so tough but steamboilers are nothing to play with.