Improvements in Feedwater-heaters for Steam Boilers.
Year: 1890

page_text: Date of Application, 28th Apr., 1890-Accepted, 31st May, 1890
COMPLETE SPECIFICATION.
Improvements in Feedwater-heaters for Steam Boilers.
A communication from abroad by HANS G. STUB, of Christiania, in the Kingdom
of Norway, Mechanical Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester, both in
the County of Lancaster and 323, High Holborn in the County of Middlesex, Civil
Engineer, do hereby declare the nature of this invention and in what manner the same
is to be performed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to feedwater-heaters for steam boilers and more especially to
that class which are adapted to be placed in the chimney or smoke-box and in which
the water is heated by the combustion gases.
In the use of this class of feed water-heaters difficulties have arisen for the reason
that the water sometimes evaporates in the heater pipes, whereby the air contained in
the water will collect at the highest points of the pipes and be an obstacle to the free
passage of the water. From this reason, as is well known, pipes frequently explode
in which the water was heated to evaporation or in which from some other reason air
had gathered in the elbows or bends of the heater pipes. Besides, the steam, that
may have been generated in the heater, sometimes presses the water out of the heater
into the boiler, so that the pipes become wholly or partially emptied, from which
reason the apparatus will be less efficient and is liable to be burnt.
The present invention provides means, whereby the said air and steam is led away
from the heater pipes, so that it does not collect therein and hinder the free passage
of the water to the boiler, and it consists essentially in connecting all points of the
heater pipes, where an accumulation of air and steam is liable to take place, (viz. the
highest points of the heater pipes or bends of the same) by means of relief pipes with
the boiler. In order to prevent the water in the heater from passing through the
relief pipes they are not carried directly to the boiler, but they are carried upwards,
sufficiently to prevent the water from passing up through them, and then downwards
to the steamspace of the boiler.
In the accompanying drawings is shown a marine boiler with a feedwater-heater
provided with relief pipes for steam and air according to this invention. Figure 1 is
longitudinal section through the heater and Figure 2 is a cross section through the
same. Figure 2 is an elevation of one of the headers hereinafter described.
The feedwater-heater as shown in the drawing consists of a series of pipes and a
number of headers Wand L, the pipes s running in a zig-zag line between the headers.
The uppermost header W is connected with the feedwater-pump, while the lowermost
header L is connected with the boiler by the pipe S¹. The water accordingly passes
through the heater in a zig-zag line and the steam and air will rise to the headers L.
From the upper corners of these headers L, (which, as will be seen from Figure 2ª
have a roof-shaped top,) the relief pipes for air and steam lead upwards, and are
then carried downwards, being united in a single pipe D which enters the steam-space
of the boiler.
The pipes must be carried upwards several feet in height, to prevent the feedwater
from running this way into the boiler, that is to say, the height of the pipes / must be
great enough to provide a hydrostatic pressure at the exits of the pipes from the
headers L, which shall exceed the frictional resistance the water has to overcome by
its passage through the heater pipes. The feed-valve at the boiler must be sufficiently
loaded to prevent the water in the heater from emptying itself into the boiler.
It is preferable to construct the heater in such a manner, that it will not take up
more than part-say one half-of the width of the chimney as shown in Figure 2.

page_text: A partition T divides the chimney in two channels and by means of the damper t, the
channel, in which the heater is placed, may be shut off, when the pump does not work,
or when steam is being raised,-to prevent the pipes from being burnt by reason of
steam generation in the heater.
By these means all steam and air will rise into the pipes and be conveyed to the
boiler without obstructing the water passages of the heater, so that heaters provided
with relief pipes according to this invention will not be liable to explode, as has
hitherto been the case with feedwater-heaters, heated by combustion gases.
.
The invention is not of course limited in its application to a heater of the con-
struction shown in the drawing, as it may be applied to any construction of heater.
The relief pipe or pipes may also be formed and arranged in different ways without.
departing from the invention.
Having now particularly described and ascertained the nature of the said invention
and in what manner the same is to be performed, as communicated to me by my
foreign correspondent, I declare that what I claim is:-
1. The combination with a feedwater-heater of a relief pipe or pipes leading from
the highest point or points of the heater to the steamspace of the boiler, being carried
to a sufficient height above the heater to prevent water from passing through the same,
said relief pipe or pipes serving as a means for conveying air and steam from the
heater to the boiler.
2. A feedwater-heater substantially as shown and described.