We have been urging you to keep your boiler clean. Now, to get the best
results from your fuel, it will also be necessary to keep your flues
clean; as soot and ashes are non-conductors of heat, you will find it
very difficult to get up steam with a coating of soot in your tubes.
Most factories furnish with each engine a flue cleaner and rod. This
cleaner should be made to fit the tubes snug, and should be forced
through each separate tube every morning before building a fire. Some
engineers never touch their flues with a cleaner, but when they choke
the exhaust sufficiently to create such a draught as to clean the flues,
they are working the engine at a great disadvantage, besides being much
more liable to pull the fire out at the top of smokestack. If it were
not necessary to create draught by reducing your exhaust nozzle, your
engine would run much nicer and be much more powerful if your nozzle was
not reduced at all. However, you must reduce it sufficiently to give
draught, but don't impair the power by making the engine clean its own
flues. I think ninety per cent of the fires started by. traction
engines can be traced to the engineer having his engine choked at the
exhaust nozzle. This is dangerous for the reason that the excessive
draught created throws fire out at the stack. It cuts the power of the
engine by creating back pressure. We will illustrate this: Suppose you
close the exhaust entirely, and the engine would not turn itself. If
this is true, you can readily understand that partly closing it will
weaken it to a certain extent. So, remember that the nozzle has
something to do with the power of the engine, and you can see why the
fellow that makes his engine clean its own flues is not the brightest
engineer in the world.
While it is not my intention to encourage the foolish habit of pulling
engines, to see which is the best puller, should you get into this kind
of a test, you will show the other fellow a trick by dropping the
exhaust nozzle off entirely, and no one need know it. Your engine will
not appear to be making any effort, either, in making the pull. Many a
test has been won more through the shrewdness of the operator than the
superiority of the engine.
The knowing of this little trick may also help you out of a bad hole
some time when you want a little extra power. And this brings us to the
point to which I want you to pay special attention. The majority of
engineers, when they want a little extra power, give the safety valve a
twist.
Now, I have already told you to carry a good head of steam, anywhere
from 100 to 120 pounds of steam is good pressure and is plenty, and if
you have your valve set to blow off at 115, let it be there; and don't
screw it down every time you want more power, for if you do you will
soon have it up to I25, and should you want more steam at some other
time you will find yourself screwing it down again, and what was really
intended for a safety valve loses all its virtue as a safety, as far as
you and those around you are concerned. If you know you have a good
boiler you are safe in setting it at I25 pounds, provided you are
determined to not set it up to any higher pressure. But my advice to
you is that if your engine won't do the work required of it at 115
pounds, you had best do what you can with it until you can get a larger
one.
A safety valve is exactly what its name implies, and there should be a
heavy penalty for anyone taking that power away from it.
If you refuse to set your safety down at any time, it does not imply
that you are afraid of your boiler, but rather you understand your
business and realize your responsibility.
I stated before what you should do with the safety valve in starting a
new engine. You should also attend to this part of it every few days.
See that it does not become slow to work. You should note the pressure
every time it blows off; you know where it ought to blow off, so don't
allow it to stick or hold the steam beyond this pressure. If you are
careful about this, there is no danger about it sticking some time when
you don't happen to be watching the gauge. The steam gauge will tell
you when the pop ought to blow off, and you want to see that it does it.