Please contact an organization which posseses an ASME R stamp and also try the NBIC. TEMA will be able to help you also.
I have used 625 overlay on boiler tubes in the steel industry. We used the overlay on the waste heat boilers that sit over the BOP vessel. The tubes in this area take a real beating. On average, we were repairing tubes every six months on the hood (about 4000 heats). This was due to a combination of erosion and corrosion. Wear rates were extremely high. The ultimate goal was to reach 10000 heats before any work had to be done. Shortly after we overlaid the tubes I left the steel industry but have been in close contact with some friends there. I have been informed that after 5000 heats the tubes look like they were just overlaid. You can still see the weld ripples. If memory serves me correctly the company we hired to do the job overlaid approximately 700-800 sq. feet in 6 or 7 days. They use automated GMAW welding. The process is synergic pulse GMAW but they have taken it to the next level. If you would like contact information for the company please call me at 814-897-7177.
Good luck
Mark
What was the cost? Is this a procedure that might be practical and cost effective on 30 - 35 year old scotch marine boilers used for heating?
You could try Zuescorp - I don't know if they do the overlaying, or just provide the equipment, but there was an article in the Welding Journal 10 or so years ago about it.
This web page shows some overlay compared to the pulse technology of the day - don't know how valid the comparison is today - any one with experience who can comment?
http://www.zuescorp.com/rapidarc/rapid14.htm
The comparison that was on this web site is not accurate. The technology that was used at the steel mill was not stringer beads but a weave bead. Every thing was done in the vertical down position. This helps with distortion because the heat input is lower than vertical up.
The cost was on the high side but I can not remember the exact amount. I guess you will have to evaluate the number of repairs and/or replacements you make and the cost associated with the repairs vs. the cost of the overlay. If I’m not mistaken, I believe the process can be used on any type of boiler. Maybe in your case you might look at replacing tubes with new tubes that have been overlaid using the spiral technique using GTAW as the welding process. The company we used was Riggs Distler the sales rep is Mr. Bob Brazier. You can call me for the phone number. I don’t know if they have a web site.
What is the advantage of the overlay process as opposed to thicker tubes? ( If the job is not done in place )
I found the answer, it's to deposit stainless on the tubes. Unfortunately much too expensive for my application at about $50 per foot for two inch tubes.
Overlaying with corrosion/erosion resistant material is different than weld build up of wasted areas. If you have a thinning problem in which the minimum wall thickness has been reduce below the allowable then buildup with a dissimilar metal may get into design criteria. Originall tube MWT's are based on the material used during fabrication/erection of the tubes. The overlay material if different than the tube material may not have the allowable stress values at the operating tempuratures.
Buildup of wasted tubes using material compatable with the base metal is addresses by the NBIC. Corrosian Resistant overlay is addressed by ASME. These are two seperate issues. There is a company called "Welding Services" in the metro Atlanta area (Or they used to be)
Anyway thats my 1-1/2 cents worth
Gerald Austin
Iuka Mississippi
http://www.geocities.com/pipewelder_1999/
Welding services was who I contacted, very helpful and professional outfit.
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