Part 8 (1/2)
Q. Steel?
A. 2532 degrees.
Q. What cla.s.s of boilers are generally used in a thres.h.i.+ng engine?
A. The flue boiler and the tubular boiler.
Q. About what amount of heating and grate surface is required per horse power in a flue boiler.
A. About 15 square feet of heating surface and 3/4 square feet of grate surface.
Q. What would you consider a fair evaporation in a flue boiler?
A. Six pounds of water to I pound of coal.
Q. How do these dimensions compare in a tubular boiler.
A. A tubular boiler will require I/4 less grate surface, and will evaporate about 8 pounds of water to I pound of coal.
Q. Which do you consider the most available?
A. The tubular boiler.
Q. Why?
A. It is more economical and is less liable to ”collapse?”
Q. What do you mean by ”collapse?”
A. It is a crus.h.i.+ng in of a flue by external pressure.
Q. Is a tube of a large diameter more liable to collapse than one of small diameter?
A. Yes.
Q. Why?
A. Because its power of resistance is much less than a tube of small diameter.
Q. Is the pressure on the sh.e.l.l of a boiler the same as on the tubes?
A. No.
Q. What is the difference?
A. The sh.e.l.l of boiler has a tearing or internal pressure while the tubes have a crus.h.i.+ng or external pressure.
Q. What causes an explosion?
A. An explosion occurs generally from low water, allowing the iron to become overheated and thereby weakened and unable to withstand the pressure.
Q. What is a ”burst?”
A. It is that which occurs when through any defect the water and steam are allowed to escape freely without further injury to boiler.
Q. What is the best way to prevent an explosion or burst?
A. (I) Never go beyond a safe working pressure. (2) Keep the boiler clean and in good repair. (3) Keep the safety valves in good shape and the water at its proper height.
Q. What is the first thing to do on going to your engine in the morning?
A. See that the water is at its proper level.
Q. What is the proper level?
A. Up to the second gauge.