The Traveling Engineers Association | Page 4

the gases from the coal and they are
ignited by the hot flame as they pass over the bright fire; the coke
which is left burns where it is.
28. Q. In what condition should the fire be to consume these gases?
A. A bright white coke fire, almost incandescent.
29. Q. What is the temperature of the fire when in this condition?
A. It must not be less than 1,800 degrees Fahrenheit to consume the
gases liberated from the coal, and it only requires from 750 to 900
degrees Fahrenheit to burn the coke that remains on the grate; as coke
burns from the outside, less heat is required to consume it.
30. Q. How can the fire be maintained in this condition?
A. By adding coal to the fire in small quantities, spreading it over the
grate surface and no faster than it is burned.
31. Q. What is black smoke? Is it combustible?
A. Black smoke consists of small particles of carbon suspended in the
gases of combustion and indicates incomplete combustion. Black
smoke is not combustible, it is like lampblack and cannot be burned
after having been produced. The production of it can be prevented by
suitable arrangements and manipulation.
32. Q. Should the gas not burn in the fire-box, will it burn after it enters
the flues? Why?

A. Gas will not burn only a short distance in the flues of a boiler, as the
water absorbs the heat so quickly that the temperature of gas is lowered
below the igniting point.
33. Q. What is the effect on the flow of air through the fire from
opening the door? What on the burning of the gases? What on the flues
and sheets of the fire-box?
A. When the furnace door is opened, the flow of air through the grate is
stopped in proportion to the amount that passes through the door. The
vacuum will be filled from the quickest source and the door is closer
than some parts of the grate. The gases mix with the air from the door
and pass out through the flues; no combustion takes place, as the air is
not hot enough to unite with the gas. The flues and sheets of the box
will be caused to leak on account of the rapid contraction.
34. Q. Can the firing be done more effectively if the water level is
observed closely?
A. Yes, in order to know how much water there is in the boiler and
whether it is necessary to hurry the fire; if the boiler is full, it is
possible to prevent the pops opening by delaying the fire.
35. Q. How should the fire and water be handled in starting from a
terminal or other station?
A. The steam pressure should be near the maximum and there should
be sufficient water in the boiler to last until such time as the fire is
burning well so that the pressure will not be reduced when water is put
into the boiler. There should be a moderately heavy bed of fire well
burned and distributed evenly over the grates. After the fire is burning
well, the injector should be started lightly; the feed being gradually
increased so as not to cause any decrease of steam pressure.
36. Q. What is the purpose of a safety valve on a locomotive boiler?
Why are more than one used?
A. A safety valve is used to limit the maximum pressure in the boiler

by opening and allowing steam to escape. More than one safety valve
are used as additional protection against excessive pressure; one is set
at the maximum pressure and the others are set at two or three pounds
above the maximum pressure.
37. Q. What is usually the reason for steam being wasted from the
safety valve? What can be done to prevent this waste?
A. Careless firing, careless running. Both engineer and fireman work in
harmony to obtain the best results.
38. Q. What is the estimated waste of coal for each minute the safety
valve is open?
A. About fifteen pounds. The estimated waste of steam when an engine
pops equals every second all the heat obtained from a quarter pound of
coal. Safety valves usually remain open about half a minute, resulting
in the loss of about eight pounds of coal.
39. Q. What should be the condition of the fire on arriving at a station
where a stop is to be made?
A. On approaching the station where a stop is to be made, firing should
be stopped far enough back to allow the carbon gases to be consumed
before the throttle is closed, so there will be little or no black smoke
from the stack and yet have sufficient fire that it will not be necessary