_a._ Set safety-valves at 115 lbs., shut all water outlets, admit steam
enough to give 100 pounds water pressure, then pump will move very
slowly under the influence of the leakage past plungers. About one
revolution of pump per minute shows a proper accuracy of fit. Anywhere
from 1/3 to 2 revolutions per minute is satisfactory.
_Too tight a fit is bad_, as if not exceedingly uniform it induces
scoring or cutting of the metals. Moreover, should the pump happen
to be run dry for a few minutes before catching its suction a slight
warming and expansion of the plunger may cause it to stick and cut.