Figure 2-7. - Side-cutting chisel.
After removing the main part of the tube from the boiler, use a safety ripping chisel of the type shown in figure 2-8 to make a cut on the inside of the remaining portion of the tube. The safety ripping chisel is designed so it cannot cut entirely through the tube; therefore, it cannot score the tube sheet.
After cutting the tube approximately three fourths of the way along the tube sheet, crimp the edges of the tube and drive out the stub with a blunt chisel. If the tube is a large one, you may have to make two cuts with the safety ripping chisel instead of one; the cuts should be about an inch apart.
If a safety ripping chisel is not available, you can remove the tube by the following method:
1. Split the ends of the tube with a flat chisel, from the end of the tube to the drum or header, at two places about three fourths of an inch apart.
2. Force the 3/4-inch piece upward with a bar until it has been raised off its seat and has curled into the tube.
3. Split the tube to a point beyond the other side of the tube seat with a tool ground to conform to the tube hole. Be careful not to damage the tube hole.
4. Break in the ends of the tube with a crimping tool, and then drive out the stub.
Arc welding equipment can be used as an aid to the tube removal on some boilers. This procedure requires running two beads, three fourths of an inch apart, through the entire tube sheet, quenching with water, and then using a backing-out tool. Do NOT use this method of tube removal if the drums or headers are made of 4-6 chromium steel.
Replacement tubes must be thoroughly cleaned to remove all scale, dirt, and preservatives. One way of cleaning a tube is to push a kerosene-soaked rag through it and wipe the outside of the tube with a similar rag. Diesel oil may also be used. If a large enough tank is available, boiler tubes may be cleaned by immersing them in an approved cleaning solution, such as a saturated solution of boiler compound in hot water, to which a small amount of kerosene has been added. Boiler tubes may also be cleaned with steam jets.
Figure 2-8. - Safety ripping chisel.Continue Reading