g to end.

If questions of fulfillment of contract are involved, there should be a
clear understanding between all the parties, preferably in writing, as
to the operating conditions which should obtain during the trial, and as
to the methods of testing to be followed, unless these are already
expressed in the contract itself.

Among the many objects of performance tests, the following may be noted:

Determination of capacity and efficiency, and how these compare
with standard or guaranteed results.

Comparison of different conditions or methods of operation.

Determination of the cause of either inferior or superior
results.

Comparison of different kinds of fuel.

Determination of the effect of changes of design or proportion
upon capacity or efficiency, etc.

2. PREPARATIONS

_(A) Dimensions:_

Measure the dimensions of the principal parts of the apparatus to be
tested, so far as they bear on the objects in view, or determine these
from correct working drawings. Notice the general features of the same,
both exterior and interior, and make sketches, if needed, to show
unusual points of design.

The dimensions of the heating surfaces of boilers and
superheaters to be found are those of surfaces in contact with
the fire or hot gases. The submerged surfaces in boilers at the
mean water level should be considered as water-heating surfaces,
and other surfaces which are exposed to the gases as
superheating surfaces.

_(B) Examination of Plant:_

Make a thorough examination of the physical condition of all parts of
the plant or apparatus which concern the object in view, and record the
conditions found, together with any points in the matter of operation
which bear thereon.

In boilers, examine for leakage of tubes and riveted or other
metal joints. Note the condition of brick furnaces, grates and
baffles. Examine brick walls and cleaning doors for air leaks,
either by shutting the damper and observing the escaping smoke
or by candle-flame test. Determine the condition of heating
surfaces with reference to exterior deposits of soot and
interior deposits of mud or scale.

See that the steam main is so arranged that condensed and
entrained water cannot flow back into the boiler.

If the object of the test is to determine the highest efficiency or
capacity obtainable, any physical defects, or defects of opera