The Traveling Engineers Association | Page 5

too much cold air is drawn into the fire-box and through the tubes, retarding combustion and cooling the fire-box and tubes.
42. Q. If the injector is to be used after throttle is shut off, how should the fire be maintained?
A. A sufficient quantity of coal should be placed on the grates to maintain the maximum steam pressure and the blower used to keep the fire burning brightly.
43. Q. What would be the result of starting a heavy train or allowing drivers to slip with the fire too thin on the grates?
A. The fire would be pulled off the grates and into the tubes, leaving the fire bed full of holes and some of the fire remaining on the grates turned over. Large quantities of cold air would be drawn in, resulting in a rapid decrease of temperature and pressure. The tubes would possibly start leaking and the fire would be in such condition that it could not be built up properly in a long distance. Possibly the grates would become clogged up with green coal--an excellent opportunity for forming clinkers. In this condition, the engine would fail to make steam for the entire trip.
44. Q. Where should the coal, as a rule, be placed in the fire-box?
A. As a rule, more coal is burned along the sides and in the corners than in the middle of the grates; the fire should consequently be kept somewhat heavier along the sides and corners than in the middle.
45. Q. How is the fire affected by and what causes clinkers?
A. A clinker shuts off area of grate surface according to its size, and thereby shutting off that much of the air supply and interfering with proper combustion. Clinkers are caused by firing too heavy in spots, which prevents sufficient air passing up through these spots and allows the coal to run together, melting the ash, and sand; running a hoe or slash bar through the fire will bring the points of melted sand together, thereby causing a clinker.
46. Q. How can you best avoid their formation and dispose of them?
A. Light firing and occasionally moving the grates lightly is the best preventive. When once formed, they should be removed if possible by firing around and burning them out.
47. Q. How can you explain the slower burning of the coke and how understand the proper manner of supplying fresh coal?
A. The gases of coal are lighter than air and will pass away whether consumed or not. The slow burning of the coke is due to the fact that it burns from the outside only. When a fire reaches a white or incandescent heat it indicates that the gases are burned and a fresh supply of coal should be added; this is to be done as light as the service performed by the engine will permit.
48. Q. When and for what purpose is the use of a rake on the fire bed allowable?
A. The rake should be used on the fire very seldom, because raking the fire bed tends to form clinkers, especially when the rake is plunged down through the fire to the grate. It may be used when necessary to rake the fire lightly when on the road for the purpose of breaking the crust, which may be found as a consequence of too heavy firing.
49. Q. Within what limits may steam pressure be allowed to vary, and why?
A. Pressure should not be allowed to vary more than five pounds from the maximum for the reason that too much expansion and contraction will take place, which many times is the cause of flues leaking, cracked or broken side sheets and stay bolts.
50. Q. Has improper firing any tendency to cause the tubes to leak? How?
A. Yes; if the pressure is not regularly maintained, the fluctuations of temperature cause constant contraction and expansion to take place. If the fire is not carried level, but is carried heavy in some parts of the fire-box and light in others, holes will be worked in, cold air drawn through, lowering the temperature, chilling the tubes and causing leaks. Carrying the fire too heavy in some places, causes clinkers to form. If the door is open too long, too much cold air is drawn over the fire, causing the tubes to leak.
51. Q. What do you consider abuse of a boiler?
A. Careless or improperly supplying water to the boiler, improper firing or allowing steam to vary from high to low pressure, causing unnecessary expansion and contraction.
52. Q. Does the stopping up of flues affect the steaming capacity of the engine?
A. Yes; obstructed flues reduce the heating surface, reduce the steaming capacity of the engine, and, as a rule, result in causing the flues to leak. They also cause an increase of speed of the gases through the remaining flues