IMPROVEMENTS IN APPARATUS FOR HEATING WATER INTENDED FOR THE SUPPLY OF STEAM BOILERS
Year: 1861

page_text: PROVISIONAL SPECIFICATION left by Zerah Colburn at the Office of the
Commissioners of Patents, with his Petition, on the 17th August
1861.
I, ZERAH COLBURN, of No. 15, Tavistock Street, Bedford Square, in the
County of Middlesex, Mechanical Engineer, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN APPARATUS FOR HEATING WATER
INTENDED FOR THE SUPPLY OF STEAM BOILERS," to be as follows:-
This Invention consists of apparatus for heating the water intended for the
supply of steam boilers to a temperature not only above that at which water
boils in the open air, but up to or above the temperature at which the water is
maintained in the boilers when in regular working. The heat for thus heating
the feed water for one or more boilers is not to be derived from any waste heat
escaping from the furnaces or flues of the boilers themselves, nor (as it would
indeed be impracticable to do so) from the exhaust steam from the engine or
engines worked by steam generated in such boilers; but the heat required to
heat the feed water up to a temperature equal to or greater than that at which
the water in the boiler or boilers has to be maintained in ordinary working is
to be derived from the steam escaping from a supplementary engine worked by
steam of a pressure considerably higher than that maintained in the boiler or
boilers, the feed water for which is to be heated. This supplementary steam
engine will necessarily require a boiler of its own, this boiler being adapted to
the safe generation of steam of the high pressure required for working such

page_text: supplementary steam engine. The power exerted by the supplementary
steam engine may be applied to any purpose preferred, either in conjunction
with the power of the engine or engines supplied with steam from the boiler
or boilers, the feed water for which is to be heated according to this Invention,
or the power of the supplementary engine may be applied independently of the
power of such engine or engines.
The supplementary engine is not intended to, and indeed must not, work up
or utilise the whole pressure of the steam by which it is impelled, inasmuch
as the exhaust steam on escaping from the supplementary engine, should have
a pressure equal to or greater than that maintained in the boiler or boilers,
the feed water for which is to be heated according to this Invention. This
result is attained by permitting the exhaust steam from the supplementary
engine to escape into a vessel in which the steam is partially condensed, that
is to say, a vessel into which is forcibly injected, by a pump or other means, a
regulated quantity-of condensing-water, sufficient_only to reduce the pressure
and temperature of the steam entering the condensing vessel to a limit not
below if as low as the pressure and temperature of the steam in the boiler
This condensing
or boilers, the feed water for which is to be heated.
water, together with the steam condensed in it, will then be supplied as
feed water to the boiler or boilers, the feed water for which it was
desired to heat, and if the pressure-maintained in the condensing vessel
exceed, as it should, that in the boiler or boilers to be fed, the liquid
contents of the condensing vessel will be forced thence into the boiler or
boilers under the pressure of the steam remaining in the condensing vessel,
and therefore, without the aid of pumps, which, as applied for forcing water
into the boiler or boilers, may thus be dispensed with. If the boiler or boilers,
the feed water for which it is desired to heat, work at a pressure of 40 pounds
per square inch above the atmosphere, the steam from the supplementary
engine should never be condensed much, if any, below a pressure of 50 pounds
per square inch in the condensing vessel, so that sufficient pressure should
always exist in the condensing vessel to force its heated liquid contents into
the boiler or boilers. There would thus be what is technically known as a
"back pressure" of 50 pounds per square inch above the atmosphere upon
the piston of the supplementary engine, and in order to reduce this loss of
pressure to a proportion relatively moderate to the maximum pressure in the
cylinder of the supplementary engine, the maximum pressure might be as high
as or higher than 200 pounds per square inch. By partially condensing the
exhaust steam from the supplementary engine so as to retain a pressure o

page_text: 52 pounds per square inch, the temperature in the condensing vessel would be
300 degrees Fahrenheit, and about 3 pounds of water at 60 deg. would
be required to condense one pound of steam of any pressure above 52 lb.
down to the said temperature of 300 deg. And as the whole of this condensing
water, and the steam condensed in it, would be devoted to feeding the boiler
or boilers, the water supply for which it was desired to heat the supplementary
engine should in this case be so proportioned to the boilers to be fed that the
former should discharge one pound by weight of steam for every four and
three-fourths (43) pounds of water required to be supplied to the latter.