Determine what the operating conditions and method of firing should be
to conform to the object in view, and see that they prevail throughout
the trial, as nearly as possible.
Where uniformity in the rate of evaporation is required,
arrangement can be usually made to dispose of the steam so that
this result can be attained. In a single boiler it may be
accomplished by discharging steam through a waste pipe and
regulating the amount by means of a valve. In a battery of
boilers, in which only one is tested, the draft may be regulated
on the remaining boilers to meet the varying demands for steam,
leaving the test boiler to work under a steady rate of
evaporation.