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Up Topic Welding Industry / General Welding Discussion / Cast Iron Boiler Problem
- - By swsweld (****) Date 11-27-2008 17:01
Wednesday afternoon I was contacted by a customer to try to "fix" a boiler in a government building. I asked the typical questions to try to prepare for the job. They were not sure where or why the boiler was leaking. Didn't know the material either. Oddly it was on the fourth floor penthouse in the middle of a complex instead of the basement or ground floor level. Set up was fun.
When we arrived I saw that it was a cast iron vertical sectional boiler (very common in commercial buildings) and was leaking out of the side section. I sent after some cast iron welding rods at the local supply. NLW9960 ENi-C1 (googled them and they are made in China)) is all the info I have on the rods. After excavation and preheat I tried the rods and could not get them to weld (WAF) worth a flip. Tried DCEN, DCEP, AC, hot, cold, medium, helicoil- ok I'm making stuff up now.

Anyhow they would not work. I've welded some cast iron before with good results and know a little about it though not an expert. That's the reason for this post. Any ideas on how to repair this crack? I welded it cold and hot, peen-ed and half bead temper. I brought 309 and it was only slightly better. 7018 would stick to the cast and actually welded OK but as you would expect it cracked at all fusion lines. I was prepared to use SMAW only due to no info and very limited time to try to repair the leak. No brazing, tig, mig attempts were made.

This is a link to a similar boiler. 
http://www.weil-mclain.com/downloads/literature/gasoil/808894lit.pdf
page 3 and 8 give a good idea of design.

The puddle would eat away the base metal, ball up and fall to the floor. Very humiliating :)

I left then with a nice looking  E7018 4" wide X 1" pad weld with a full crack on the top and bottom.
I told them up front that it was not likely that it could be repaired successfully by welding and no guarantee was made. They already have a replacement section an order but I don't think it will be here soon and if I can regroup I will try again. Like you, I don't like to fail.

Thanks in advance and hope you have a great Thanksgiving!
Parent - - By johnnyh (***) Date 11-27-2008 17:09
I think that they need to give you more information.  I cant believe that the welder would have to choose what rod to use.  Wouldnt that make you liable should the boiler fail again? 
Parent - By scrappywelds (***) Date 11-27-2008 17:47
the main problem I have found with welding cast steels or iron was the preheat needed or the post heat, mostly post heat. Anything that has to be water or pressurized was always a problem.
Parent - - By swsweld (****) Date 11-27-2008 22:52
They are just trying to fire it up a few more times until the replacement section arrives hopefully in a week or so.
I explained the liability to them up front. They just wanted me to try even though I told them it most likely wouldn't work. I have never heard of anyone trying to repair this type of boiler by welding.

Usually they will try to replace the entire boiler in the summer months.
Parent - - By Johnyutah (**) Date 11-28-2008 05:13
Tim sounds to me that you have a pre and post heat problem I have welded on several cast iron and steel boilers very frustrating. First I do a pre heat just for cleaning and to see where the cracks really are the clean and peen keeping the work hot at all times. On iron nickle 99 works great but you really have to work with it and then keep your post heat on or use some form of heat blankets to cool it work down slowly the faster you go the more times you have to start over. FYI in my neck of the woods some boiler work falls under an R stamp so watch yourself.
Parent - By vagabond (***) Date 11-29-2008 03:27
I'm pretty sure it falls under an R stamp everywhere.  Just food for thought. . .
Parent - - By tazmannusa (**) Date 12-01-2008 16:10
Actually johnnyh if you are a self employed welder and called in on a repair, you have to figure what procedures and rod or wire to use. Most customers dont have a clue or the time to mess with it, they just want it fixed.
Tom
Parent - By johnnyh (***) Date 12-01-2008 16:18
OK I see.  Y'all deserve a raise.
Parent - - By sbcmweb (****) Date 11-29-2008 05:11 Edited 11-29-2008 05:25
Cast sucks, no matter how you slice it. In the plant, (GM metal Fab) they would repair cracked press bases with hours of pre/post heat & braze them with good success. They were filthy, down in a pit. I couldn't speak for a boiler, but brazing seems to be the best fix for heavy cast. At least with what I have seen & been told. There used to be a LOT of heavy manufacturing & press metal & hot forging here in town & brazing seemed to be the mainstay for press repairs. All my welding instructors that worked on presses says it was anyways. Cast can be TIG welded with good results, but that's a LOT of welding for GTAW.

Sounds like this was out of position too?? Ni 99 might butter it, (I take it you already tried it) with a LO HI cap, but would probably still crack, regardless of what you did to it. Not like you have an induction heater handy either for post heat. I did a cast iron tail base on a lathe with a Ni 99 butter & LO HI fill. I only got a recrack in one place. I drilled them out & ground the crack completely out. It was pretty FUBARed, so it was better than nothing. Cracks in 5 different places. I don't really have the stuff to do heavy brazing like that. I put charcoal over it for a ghetto post heat & it came out OK.

Again, I know you're doing a boiler, press & machine base repair is a bit different. Still, brazing worked very well for that in the plant anyways. :-)

Good luck on it. I sure would of had them sign a waiver of responsibility before I touched it!

S.W.
Parent - - By Joseph P. Kane (****) Date 11-30-2008 16:05 Edited 11-30-2008 23:55
Everyone here has got  it wrong!!!!

Welding cast iron boilers, engine block water jackets, and marine exhaust manifolds is different than welding cast iron bases and tools.

When welding cast iron boiler sections "in place", you do not use preheat, except maybe to dry the weld area off.  I often used a highly oxidizing flame to flare off remaining graphite or carbon flecks on the surface of the prepared weld groove face, but not as a preheating operation.  Short passes are used (3/4 inch.)  The passes are staggered along the length of the crack, to allow the previous weld to cool to ambient, prior to starting the adjacent and contiguous pass, or another layer.  Cascade sequence should be used..  The lowest amperage possible is used.

Great patience is required!

The complex geometry of cast iron boiler sections is so restrained, and so fragile, that the differential expansion from a preheating operation or a high amperage welding operation can and probably will cause more cracking.

Brazing is only used when the section can be disassembled and uniformly preheated to very high preheat temperature, and cooled gradually to reduce stresses. This is done in a oven.  If you are going to use this method, you might as well go ahead and weld it with a cast iron type oxy-gas welding rod.  (This will make the repair a "cast iron on cast iron" permanent repair.)

Many cast boiler sections will not be completely weldable with electrical welding.  While most are good gray castings, there are often tramp areas in the piece that will continue to crack because you are welding and adding stresses.  For these areas, you need to use something like Atlas Boiler Mender, which is melted on with a low heat torch, and seals up the small cracks, after welding, to make the boiler waterproof.

For the best results get a Eutectic electrode designed for vertical and overhead welding. Even though they sell for several bucks each for a 3/32 inch electrode, they offer the best chance of success. Otherwise use NI-Rod 99.  Never use E-7018 or E6010.  Use 3/32 for the first pass, and preferably for all passes.  In any case no larger than 1/8 electrodes.  Never use Stainless Steel electrodes.

After using a grinding wheel to establish your groove, use a rotary file (Carbide Burr) to remove any "Smear" left by the grinding operation.  chip the slag by light tapping with the smooth back of a small ball-pein hammer, as this will also help stress relieve the 3/4 inch long pass.  Use a Stainless Eteel brush for further cleaning.  Do not dent the weld face too much!  Stop drill the ends of all transverse branch cracks first, or as soon as you see them. (You will probably need Magnetic Particle Testing to see the true ends of the cracks)  Weld the branch cracks last.

These nickel electrode type repairs are only temporary, and stop-gap until a new boiler section can be installed.

Joe Kane
Parent - - By sbcmweb (****) Date 11-30-2008 17:26 Edited 11-30-2008 18:00
Good to know there's an expert like you to keep all us weevels in line.

You should have told him this earlier & saved us all a lot of typing.

It would have been a good idea to respond directly to his post, instead of mine. Now, the only way he's going to get this information is if he scrolls down & reads ALL the posts.

Had any good pizza lately?? :-)

S.W.
Parent - - By Joseph P. Kane (****) Date 11-30-2008 21:28
Steve, since I have arrived home in August, I have not had a single edible slice of pizza here on Long Island.  It is really disheartening.
Parent - By sbcmweb (****) Date 11-30-2008 23:30
I am sorry to hear that!

If we go to NY again, you'll have to tell me where I can get something descent. I promise I won't bother any mobsters!!! :-) :-)

Bye Joe. :-) S.W.
Parent - By Fredspoppy (**) Date 11-30-2008 19:57
Good reply Joe!  I would add that welding a mild steel (7018, etc) over a nickel based electrode should never be an option.  If you can get a couple beads to work with the Ni types, just keep on with them.  Some have proposed using steel over Ni based fillers (625) for ID clad piping, but this technique is NOT universally accepted in the welding industry.
Parent - - By Johnyutah (**) Date 12-01-2008 04:00
All hail the GOLDEN ARM of Joe Kane who new we were so dumb all the other repairs must be repaired as soon as possible according to the above strict standards. I'm just kidding Joe I just thought the "Everyone here has it wrong !!!!"  was funny. I never new you didn't pre heat boiler parts I always have with good success and then cooled them slowly. Something new every day on this forum what about the R stamp would this be code work in all states. Also that is very true about using a bur for cleaning an abrasive wheel just seems to fold the material over.
Parent - By Joseph P. Kane (****) Date 12-01-2008 13:21
Johnny Utah

Sorry, I did not read your post first.   You did not have it all wrong.  Preheat can be helpful, but if you add additional stress to the internal tenons and bolsters, you can cause them to crack,  If the part is in place, and the weld has to be done in position, I have always had greater success without preheat.

In my State, (NY), emergency repairs are not subject to ASME/National Board "R" stamping.  In fact, there is a company in Farmingdale NY, called Superweld, which specializes in cast iron repair.  They also do "Metal  locking".  They take cast iron sections and build an oven around the part with firebrick.  Then they gradually preheat it and then weld it right in the flame, (Either weld or braze using Oxy-Acetylene)    They also weld old Locomotive Steam Engine powerblocks and cylinders, which are sometimes very thick in some sections and relatively this in other sections.  In any case, they do not have any kind of stamp.
Parent - By swsweld (****) Date 12-02-2008 04:33
Thanks for the replies everyone. I had a lengthy post earlier today but had to go before I was complete and when I returned, the job site Internet was lost and so was he post. Hate it when that happens.

I did some research last weekend and learned a few things as I did from the replies here.
All my cast iron welding in the past was with pre and PWHT and usually was successful. I have never tried repairing a CA boiler or any pressure or water containing CA piece. I do think I would try the cold method as Joe described next time if there is a next time. I couldn't obtain the desired preheat for fear of damaging the rope gasket. Fixing the metal but melting the gasket would have been equally bad. I/they didnt know what temperature the rope would withstand. So that and the sorry cheap rods (1lb/$38.00) and the tramp area that would not take any metal resulted in failure to repair the boiler.

When I got the call they were not sure if it was the boiler or a pipe in the boiler room. I suspected it was the boiler but didn't have time to do any research on CA boiler repair.
The NI rods did poorly on some CS pipe laying in the boiler room. It did poorly but did weld. Same rods on the CA boiler would not take.

I tried 309 because I remembered a post on here about 309 on CA if in a pinch.
They did only slightly better. Although I used 309 on a CA vice a couple of weeks ago and it did very well.
The 7018s were just to show the county guys that I could make metal stick to the boiler and not just the floor :) 
We did a chiller (2) changeout a few weeks ago for the same county guys and they thought our welds were made by a machine. So they know we CAN do good work. OK the welds he was referring to were my nephews that I trained not mine.
I knew it was a bust early after trying the NI rods. I thought it was a large silicon deposit or possibly chemicals from the water treatment boiling out of the pores/crack where the leak was. I've made lots of welds where the existing pipe gave me a fit (you know, it flows like butter on the new pipe and you have to fight it in on the old pipe) when making a tie in but this was very different from that.
As tasmannusa said they didn't have a clue as to what rods and how to repair it. They did have one former welder and he knew what I was doing was typical for CA but not for a CA boiler.
Also I didn't know about the rotary file.
I don't have access to MT but what about PT? I forgot to bring a PT kit (not that it would have mattered) but would that work on CA if that's all you had?

The boiler was out of service when I got there and they will replace the bad section as soon as it arrives. It's 20 years old. I don't think that is too old. I wonder why it failed.
I know many factors can contribute; poor water treatment, water level, adding water too frequent( oxygen in water contributes to rust inside) adding cold water could shock the walls, too much air in the system, etc. I didn't notice an air separator in the room. This boiler replaced a much larger and different style boiler (according to the maint. men)
I wonder if this type boiler being in the penthouse instead of ground level or the basement was a factor.
A lesson learned at the school of hard knocks. Not the first and probably not the last one.

Thanks to all for the valuable replies.
Parent - By Joseph P. Kane (****) Date 11-30-2008 23:56
SWS Weld

PLEASE SEE MY REPLY FURTHER DOWN.

Joe Kane
Up Topic Welding Industry / General Welding Discussion / Cast Iron Boiler Problem

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