Cutting Cast Iron

[DDelle338]

  I lately I have had the need to cut cast iron boiler sections open for inspection to determine the cause of failures. I have been using a band saw set at it's slowest speed but it still "eats" the blades up real fast. This is getting very expensive. Is there a special steel blade or technique to get more life out of the blades?

[Rex in OTZ]

I would recomend useing a abrasive blade chop saw, or use carbide embeded demolition blades in a saw-z-all, you could score the sections most the way through useing 3" air powerd cut off tool chucked in the diegrinder, or electric 4 or 7 inch disc grinder use abrasive blades score most the way through and whack useing a cold chisel. You are going to use allot of blades so get extras!!

I had boiler sections cracked (on a 400K btu) due to cooling shock, some boilers are more prone to cracking,  twice in the past 7 years (Weil Mclain 76) due to casting imperfections one by the top threaded pipe boss, second on the side of the inlet section mid way up

[DDelle338]

  I tried the chop saw idea. That didn't work out so well. I had cut all the way across the a section about 4" up from the bottom and ruined the blade. It took about 30 minutes to go the last 3". So, to cut this lower part in half to measure the thickness of the calcium build-up, I thought the chop saw would work great. WRONG,, it took me about ten minutes to cut less than 1/2" into this iron. I think that when the boiler is fired with all the crud in it for a long time it hardens the iron because the crud acts as an insulator and won't pass the heat along to the water. I alsotried the Carbide sawzall, same results as the band saw, when I get near the part of the section that is closest to the heat, they just die. I guess I had better just buy ALOT of band saw blades.
  I have verified that hard water causes serious problems in boilers. And have found quite a bit of steel from piping systems in these boilers also.
  Treat your water and install a strainer. That may save the cost of replacing a boiler.

[SHOOTALL]

use a grinder with a cut off wheel .

[Rex in OTZ]

Sounds like a bummer, I suppose you could use a cutting torch, if you dont have one take it down to the welding shop and have them cut it open for you,
Is this a commercial boiler or a residential one?
Steel/rust coating the boiler, you are getting electrallissis the oxygen in the fresh water is creating problems in conjunction with the mineral deposits in the water used, they do make Die-electric unions that reduce this proble if eliminate it completely.
 I live in a area where our city water is snow melt water collected in a lake and pumped throughout the year, the lake is surrounded by tundra so we have allot of tannins and peat particles in our water the city treats the water so it is pottable, Ive seen bathtub water look like tea it was so dark from the tannins, I stockpile distilled water recomended by boiler manufacturers, we have a water distiller on site, I use a glycol resivoure/ injection pump system to maintain any make up glycol that is needed.
Hard water scale is a booger because you have a fresh water service valve you are getting those hard water contaminants in the boiler, as I remember tec's in our area flushed out boiler systems with a nasty corrosive solution to remove buildup, Today we buy pre-mix 60/40% or you can get your own water and stockpile like me.
Had a accointance who used a domestic water service valve supplying his boiler, he had leaks that sugar'd and steamed off the old mix of glycol/water which was made up with the straight water from the service valve which he dident know what he had in the system, he was gone for a few days during the winter, heat went off in that building tand froze everything, not only the fresh water lines but the heating lines as well, split finn tube, broken boiler, split supply lines in walls and celings a real mess!
I'd rather deal with a low water cut out than deal with busted pipes, I use sensea phones for remote monitoring of building heat during the winter here in Arctic North West Alaska.

[SHOOTALL]

you don't "cut" cast iron with a torch . You can cut it very expensive on a large scale , use a grinder with a cutoff wheel or break it either controlled with a snap cutter or uncontroled with a hammer . When replacing a boiler , bath tub or such and there is no worry of damage to the remaining area then the hammer is the most enomical . If damage is a concern and cutting the bolts on a sectional boiler is not render the boiler in small enough pices to remove ( in all cases but a very few as a new boiler has to be built back in place ) then we cut it with a grinder . There is an abrasive saw blade for cutting CI pipe but it cost alot and does not work well as the vibration creats more leaks as often as it dosen't .
Failure can be caused by many things , CI boilers are far more forgiving than steel with regard to water . They also can take draining and leaving dry for the warm mos. whers a steel boiler often has problems when drained and left dry. Most failures we see is either a poor casting job or the boiler was fired dry . Of course some do fail for other reasons such as neglect . CI once it is in service builds up a coating between the water and itself . This coating protects it from alot of water damage , this is not the case with a steel boiler .
Good luck cutting , often you can score deep with a hand grinder and tap the area with a hammer and it will snap out .

[mechanic]

You basically have two options, abrasive wheel, or carbon arc setup in a stick welder.  They also make a gouging rod that I have cut small sections of cast with.  I've never found a saw, even a diamond saw that would hold up.  The carbon arc is noisy, nasty and takes a very wide kerf. 

[hunt-m-up]

I suppose plasma torch is a no go too?

[SHOOTALL]

i didn't mention carbon arc rods because he was cutting to inspect for a cause of the failure and carbon arc cutting could cover or destory evidence he might need to see . High pressure water cutting and plasma might work but cost would be high if it could be done .

[DDelle338]

  Thanks for all the input.
  The plasma cutter has been "on the fritz" and I haven't been able to try that. I'm going to send it out for repair and try to get my hands on a longer tip for it so that I might be able to reach down between the pins on the castings. I'll give it a try on the next boiler I have to inspect. I have never used the plasma cutter on iron, I am assuming that it cuts about the same as steel.
  Thanks for the ideas.
         

[oldandslow]

Have you tried an Arc Aire cutter?

[DDelle338]

I don't have access to air arc. Right now I'll wait for the plasma cutter to be repaired. I don't have any more sections that need inspected at this time so I'll see how the plasma cutter works on the next one that comes in.