welding on speciall casted grates

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I was asked the big question today if we could build up the burned grates for inside out Bio-mass boiler. I took some pictures and will post them when I get home. These grates are cast HH 20 Cr - 10 Ni . This stands for high heat, 20% Chromium and 10% Nickle. I have added a link to the company site that makes these. As you will see in the pictures when I post them that the ends get cracked and burned off due to the high temps during operation. We normally run 1500 - 2000 Degrees F in the combustor. We would like to build up the ends again so they can be reused. These grates run in price from 900.00 to 1300.00 each so if we could manage to get a little more running on them it would save some big dollars.http://amscocast.com/amscocast_016.htmI hope we have some members with some ideas on this.  :canada:Last edited by jamlit; 03-18-2010 at 09:08 PM.Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:Ummm, call Amsco or Lincoln or McKay or Stoody and ask -them- what to use to weld and build-up the grates?  The best laid schemes ... Gang oft agley ...
Reply:Here are the pic's The first couple pic's are of the new and used grates we haveThe last two pic's are of the grate end we want to repair. We just want to grind them down and build them back up.Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:What style grates are those? I've worked recip grates (Martin) in the past, and recently with a non moving grate very similar to the "tile" shown on the top of your link. I've seen grate bars break due to wear and misalignment, but the "burning" of the tiles/bars seems like an airflow issue (or lack of). The 1500-2000 degree temps are in your upper furnace and that is flue gas temp, correct? The grate bars shouldn't be anywhere near that hot. Ours run about 250-400 degrees F depending on the zone. We have had magnesium shavings from a machine shop come through our  units and melt bars clean through, but that wear / burning is odd. Oh, and a far as what to use to weld em up  Sorry for responding without helping, but I LOVE BOILERS. Seeing pics, talking "shop" gets me blood pumpin!Just another clown trying to be cool
Reply:I will try to get you a pic of the boile. It is a Bio-mass boiler which we burn sawdust and hog from the sawmill. I am not sure what the grate temps are but I know they are above 400 F. When the fans are off the grates are subject to the full cell temp. This doesn't happen very often but it sometimes can't be helped. The boiler has three fans on it. one we call the under fire fan which blows air under the grates and comes up through the holes you see in the grates. Then we have a over fire fan which is used to control cell temp while ensuring complete combustion. Then we have an induced for to keep a negative draft in the cell. The under and over fire fan are controlled to meet out steam demand and to trim the cell for proper combustion. The combustor has a moving floor. every second grate is a moving one. Its a very good design and works awesome. Here is a link to the manufacturer http://www.kmwenergy.com/solutions/how-it-works/Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:I know exactly what you're talking about - My units run basically the same - We have 1 large forced draft fan for overfire / underfire air, and an ID fan. We also run a flue gas recirc fan, sort of an EGR valve for a boiler. I work in waste to energy - a bio unit sounds like a dream. No pallet jacks, engine blocks, jersey barriers, refridgerators, not to mention the "good" fuel - all the nastyness everyone throws in the can! Your unit is pretty much like a Martin. They do work really well.Just another clown trying to be cool
Reply:Thats sound cool. My chief engineer did a construct and start up of a very large waste burning boiler unit in Bermuda. Worked there for 4 years supervising the place. Where I work now we use the steam for drying lumber in four large kilns. We have about one million board feet of lumber drying at one time. Monitoring and quality are top priority. The boiler itself isn't huge, We run 100 - 120 PSI steam @ 30,000 lbs per hour. We also have a Clever Brooks boiler just a little smaller but we haven't had it running for a couple years due to the economy. Bunker C coast way to damn much,  I wish someone had some ideas on if and how we might be able to repair these grates. I have others working on the idea but thought I might learn something here.Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:Jamlit,The fact that the grates are cast presents a whole different degree of difficulty in repairing/building up.Probably not what you want to hear, but has anyone discussed with the manufacturer (of the grates) a different design whereas the high stress/wear points could be unbolted/detached and replaced with a new casting.  It would appear from your photos that only a relatively small portion of the overall grate is being subjected to this extreme wear.The manufacturer may not be very supportive of the idea since they probably make more by casting the entire grate (even thought only a small portion is wearing out).I'll be the first to say I don't know a lot about boilers and their operation so my idea may really come from left field, however sometimes "out of the box" thinking is necessary.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Those repair areas are sorely degraded.To affect a lasting repair one would need to air/plasmacut out the expanded, distorted, spalled, gross cracking,clean up grind and then build up; then grind back.I have no idea as to rod to use, possibly A_DAB_will_dohttp://weldingweb.com/member.php?u=21484might be able to suggest.Blackbird
Reply:Originally Posted by SundownIIIJamlit,The fact that the grates are cast presents a whole different degree of difficulty in repairing/building up.Probably not what you want to hear, but has anyone discussed with the manufacturer (of the grates) a different design whereas the high stress/wear points could be unbolted/detached and replaced with a new casting.  It would appear from your photos that only a relatively small portion of the overall grate is being subjected to this extreme wear.The manufacturer may not be very supportive of the idea since they probably make more by casting the entire grate (even thought only a small portion is wearing out).I'll be the first to say I don't know a lot about boilers and their operation so my idea may really come from left field, however sometimes "out of the box" thinking is necessary.
Reply:Now that I can see the pictures, I think with that amount of degradation you kind of have to replace the entire grate/tile.Because by the time you remove all of the cracked/worn/melted/degraded material until you get all the way back to solid and sound cast metal, you will have removed a pretty good amount of metal from those grates/tiles.  Add in the labor costs to do the metal removal/clean-up, then add in the cost of the (special) filler material to build-up those castings back to (or close to) the original dimensions and the labor cost to do the build-up, and I think you would be close (or a significant fraction there-of) to your replacement cost for a whole new grate/tile.  That wear doesn't look like mechanical wear (obviously  ) but rather thermal and/or chemical and/or 'jet' erosion.  Maybe get Amsco or the boiler maker (not the drink!  )  or both to review the worn out grates/tiles and come up with a solution.  It might be a different material is needed, or a different grate/tile design, or a different operating procedure for the boiler, or all of the above might be needed.  The best laid schemes ... Gang oft agley ...
Reply:Thanks for the replies and they company as far as I know had the idea but hasn't  done anything yet. The ends are worn for the heat and  jet type erosion as moonrise put it. I was talking to my LWS and they actually have a arc rod for this and made with the same material. Not sure if we are going to do this but we are still looking at the idea. We are also looking at other processes as I was thinking tig was the way to go. I think we are going to need a proper procedure to. My LWS is getting back to me the first of next week with some more info. I will post the findings for those interested.Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:Dont know too much about grates, nut I have worked with hog fuel furnaces. Are these grates cast? What kind of material exactly is it other than CrNi? The ends look like they are pretty rough, dont know how suitable they are for build up. To me the best way to build it up looks like it would be a thermal spray weld, other than that I would try using 317L. What is the carbon content?
Reply:I am still waiting for the complete make up of the grate material. The grates are a type of casting.Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:If you can't get help from the manufacturer, cut (with a bandsaw or other cold cutting tool) a corner from an area that isn't too badly damaged.  A piece that is a 1" cube would be plenty.  A grating you were going to throw away anyway is good for this.  It should cost you about $75 USD to get an accurate chemical analysis from a metallurgical lab in your area.  Takes about 1 day for turnaround on the work, but for extra $$$ most labs could turn it in 30 minutes.If you post the chemistry of the grating material, somebody here should be able to recommend a matching electrode.  Then it's up to you to decide which grates are salvagable.  As several have mentioned, the photos you posted show a lot of areas that will have to be plasma gouged or ground down reach clean metal.  Your company will have to figure out where the break point is between paying your time to prep and build-up vs buying new grates.... Originally Posted by jamlitI am still waiting for the complete make up of the grate material. The grates are a type of casting.