Boiler Tube Overlay

[OldSparks]

Alright I have a job interview at an industrial Contractor August 4th... Problem is i have no idea what boiler tube overlay is (The job calls for boiler tube overlay welder) and really am worried, but im not sure if the welding test that proceeds me is boiler tube overlay or if its a another type of test... but in the mean time im just focused on wanting to know what Boiler Tube Overlay is and what the task at hand will be

Youngwelder856
We do a lot of field overlay here on the west coast where the companies are just patching rather then replacing. Alot of the time there will be known wear points which are ndt'd every time the boiler is down and at a certain point you overlay, i.e. bends and areas near soot blowers. These can be short one to two foot areas and are usually just done by downhand stick or downhand tig. The areas would be marked off by testing people and you run a bead down either side working towards the middle. Work on two or three tubes at a time to keep them cool and so you can power brush a batch between passes. Each pass overlaps the previous by at least 50% because as you come to the front the tube will be getting thinner (more worn). Final inspection will be a dye pen test.
There are various designs of automatic wire feeders in use and usually the company gives training to their procedure and then tests you. Simplest set-up was downhand with a pulse-wire suitcase. On bigger projects, there is a system where a track can be attached to a boiler wall and an automatic head runs up and down while you turn knobs and watch. Tough part is that as a newby you may be required to do prep work, sandblasting and grinding/buffing. Heard some of these companies like to run 4-6 hours between breaks to keep machines running. With multiple machines running there is usually ventilation problems and hopefully you get supplied fresh air.