nce impact against elbows, valves or other obstructions, is
the equivalent of a heavy hammer blow that may result in the fracture of
the pipe. If there is not sufficient water in the system to produce this
result, it will certainly cause knocking and vibration in the pipe,
resulting eventually in leaky joints. Where the water reaches the prime
mover, its effect will vary from disagreeable knocking to disruption.
Too frequently when there are disastrous results from such a cause the
boilers are blamed for delivering wet steam when, as a matter of fact,
the evil is purely a result of poor piping design, the most common cause
of such an action being the pocketing of the water in certain parts of
the piping from whence it is carried along in slugs by the steam. The
action is particularly severe if steam is admitted to a cold pipe
containing water, as the water may then form a partial vacuum by
condensing the steam and be projected at a very high velocity through
the pipes producing a characteristic sharp metallic knock which often
causes bursting of the pipe or fittings. The amount of water present
through condensation may be appreciated when it is considered that
uncovered 6-inch pipe 150 feet long carrying 3600 pounds of high
pressure steam per hour will condense approximately 6 per cent of the
total steam carried through radiation. It follows that efficient means
of removing condensation water are absolutely imperative and the
following suggestions as to such means may be of service:

The pitch of all pipe should be in the direction of the flow of steam.
Wherever a rise is necessary, a drain should be installed. All main
headers and important branches should end in a drop leg and each such
drop leg and any low points in the system should be connected to the
drainage pump. A similar connection should be made to every fitting
where there is danger of a water pocket.

Branch lines should never be taken from the bottom of a main header but
where possible should be taken from the top. Each engine supply pipe
should have its own separator placed as near the throttle as possible.
Such separators should be drained to the drainage system.

Check valves are frequently placed in drain pipes to prevent steam from
entering any portion of the system that may be shut off.

Valves should be so located that they cannot form water pockets when
either open or closed. Globe valves will form a water pocket in the
piping to which they are