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.
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