A. The exhaust steam escaping through the stack tends to empty the
smoke-box of gases and produces a partial vacuum there, atmospheric
pressure then forces air through the grates and tubes to refill the
smoke-box, and in this way the draft through the fire is established and
maintained.
43. Q. Explain what adjustments can be made and the effect of each
adjustment on the fire.
A. Larger or smaller nozzle tips cause less or greater draft on the
fire; raising or lowering the draft pipes and diaphragm causes the
engine to burn the fire more at the rear or front end of the fire-box;
the size and position of the draft pipes increase the draft through the
top or bottom flues; the latter adjustments should always be attempted
before reducing the nozzle.
44. Q. What does it indicate when the exhaust issues strongest from one
side of the stack?
A. The stack, exhaust pipe or petticoat pipe are out of plumb.
45. Q. What is the effect of leaky steam pipe joints inside the
smoke-box?
A. The engine will not steam freely.