PRIME MOVERS AND POWER PLANT' MACHINERY.
LOCATION OF FEED-WATER PIPE AND CHECK VALVE.
The feed water should enter the boiler at the coldest part or at
that part where the sediment will do the least harm, as mud or scale
is most likely to be deposited where the feed water first reaches the
temperature of the boiler. If the boiler has a mud drum, the feed
water can enter there.
The feed for portable locomotive-type boilers should be through the
shell and as far from the fire box and crown sheet as is convenient.
Should the feed-water pipe be extended some distance into the boiler,
as sometimes occurs, care must be taken to keep it clean, since with
some feed waters the pipe will become filled with scale.
A straight-way valve or angle-globe valve should be placed in the
feed-water pipe between the boiler and the check valve to permit re-
pairs if the check valve gets out of order. Both valves should be as
near the boiler as possible so that in winter the water lines may drain
and not freeze when the boiler is shut down for the night.
METHODS FOR INTRODUCING FEED WATER TO THE BOILER.
Water may be forced into the boiler by a pump, or an injector, or
fed in by gravity. Any pump, plunger or centrifugal, that can
force water into the boiler can be used as a feed-water pump. Steam,
electric, or air-driven pumps are used, some geared and others belt-
driven. Belt-driven pumps are more economical of power than steam
pumps. The cost of fuel and the size and type of plant influence
In many plants an injector would not be economical because the
water fed by it must be cold, which would make impossible the use
of a feed-water heater. If, however, the feed water is cold enough
an injector is more economical than a pump because an injector re-
turns to the boiler almost all of the heat in the steam used. An
injector is cheaper than a steam pump of the same capacity, is dura-
ble and easy to repair, and it delivers to the boiler water that is hot
when it enters, which increases efficiency and reduces the expansion
and contraction stresses of the boiler.
When the source of water supply is higher than the top of the
boiler, gravity feed can be readily used. The simplest device for
gravity feed is a closed vessel, usually a steel tank, the bottom about
6 feet above the water line of the boiler, which at the top is con-
nected to the boiler by the steam pipe and at the bottom by the feed
pipe. A pipe connects the top of the closed vessel to the source of
water supply. The vessel is nearly filled with water by gravity.
Steam from the boiler is then admitted at the top, after the valve
in the water supply pipe has been closed and the valve regulating
George, H. C. Surface Machinery and Methods for Oil-Well Pumping. Washington D.C.. UNT Digital Library. http://digital.library.unt.edu/ark:/67531/metadc12407/. Accessed August 27, 2014.