stuck and rusty 3/4 inch diameter bolts
I have a 400 horse Cleaver Brooks boiler with 12 rusty stud bolts. I cannot drill completely thru as it would compromise the pressure vessel. I have done the welded on nut thing before. The drill out until the last of the treads thing. What does waxing due? What chemically can be done to desolve the rust ? Another ideas would be most appreciated.
Knowing little if anything about boilers but having spent a lot of years with heavy equipment repair my solution for rusty bolts is as follows.
Wire brush off any dirt you can. Then heat just the bolt red hot. When the bolt has cooled hit it with a hammer and turn it out. I do not know if the heat is allowed with a boiler. I do know the heat and hammer trick works on the roller bolts of a crawler tractor.
I have been using Kroil prior to heating and it works even better.
This may not help in your case.
Just recently I broke a head bolt on a 12hp Kohler engine. Right beside the exhaust port and rusted really solid. Even after drilling out to the root of the bolt threads there was no shifting the remains. Grade 8 bolt and I figured a tap would just ream out the cast iron.
Built a modelling clay dam around the hole, nail for a sacrificial electrode (2 narrow strips of electrical tape for insulation), washing soda solution, nail connected to positive of battery charger.
Left overnight and part of next day, cleaning nail and changing electrode a few times.
Eventually a small cold chisel to start, and needle nose pliers removed the remains of the bolt with no damage to the threads in the iron cylinder.
Turns out the bolts were welded in . A boiler repair is in order; thanks for the help guys !