Improved Method and Arrangement of Apparatus for Feeding High Pressure Boilers.
Year: 1897

page_text: Date of Application, 17th July, 1897-Accepted, 11th Sept., 1897
COMPLETE SPECIFICATION.
Improved Method and Arrangement of Apparatus for Feeding High
Pressure Boilers.
We, JOHN BROKENSHIRE FURNEAUX and ALEXANDER HORNE, both of Victoria
Works, Gateshead, in the County of Durham, Engineers, 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:-
Since the introduction of high pressures in marine boilers of the water tube
type, great difficulty has been experienced with the main feed pumps arising
chiefly from the use in the steam cylinders of the pumps of steam taken direct
from the boilers at pressures of from about 250 to 300 lbs. per square inch and
consequently of such high temperature as to injuriously affect the rubbing surfaces
of the slide valves, pistons and glands and also the steam joints of the steam
cylinders. The severe tensile strain to which all the parts are subjected, when
working at the above pressures, and the high percentage of slip, which takes place
in the water chamber, due to the high pressure that is on one side of the pump
plunger whilst there is only atmospheric pressure on the other, are also sources
of trouble.
Now this invention has for object to overcome the foregoing difficulties for
which purpose instead of pumping the feed water direct from the hot well into
the boiler in the usual manner the water is pumped in stages as hereinafter described
whereby it is rendered possible to use steam in the motor cylinders of the pumps
at a pressure much below that in the boiler and thus to avoid the inconveniences
hereinbefore referred to.
The accompanying illustrative drawing shows partly in front elevation and
partly in vertical section an arrangement of feeding apparatus for high pressure
boiler feeding in stages according to this invention. The apparatus comprises
two pump cylinders 1 and 2 of the same capacity, the cylinder 1 drawing water
from the hot well or tank 3 through a pipe 4, and discharging through the pipe 5
into the suction of the pump cylinder 2. 1, 1b are the suction valves for
admitting water to the respective ends of the pump cylinder 1, and 1°, 1d are
the delivery valves for the water discharged from the respective ends of the said
cylinder into the pipe 5. 2ª, 2b, 2°, 2d are the corresponding valves for the pump
cylinder 2. 6 and 7 are the steam or motor cylinders the pistons of which operate
the pistons in the pump cylinders 1 and 2 respectively; they are each supplied
with steam at a reduced pressure, say about half that in the boiler with which
the water feeding apparatus is to be used. The steam may be obtained from the
said boiler through a reducing valve, or from either of the steam receivers of
the main engines that are supplied with steam from the said boiler. The
steam cylinder 6 is supplied with steam at the reduced pressure through a pipe 8,
stop valve 9 and a pipe 10 which is connected to the steam chest 6ª of the cylinder,
whence the steam is caused to pass to and from the respective ends of the
said cylinder by any known or suitable arrangement of motive fluid distributing

page_text: apparatus, as well understood. This supply of steam is automatically controlled
by a throttle valve 11 that is connected to automatic float apparatus governed
by the level of the water in the tank 3 so that the speed of the pump 1 shall vary
with the level of the water in the' said tank.
In the example shown, the automatic float apparatus comprises a rod 12 con-
nected to a float in the tank 3 and to a lever 12" which is fixed on the throttle
valve spindle 11" and is provided with a balance weight 12b, the arrangement
being such that the throttle valve will close more or less as the level of the water
in the said tank falls, and will open more or less as the level of the water rises.
12 is an air pipe connected to the top of the tank and through which the rod 12
extends.
The steam cylinder 7 receives its supply of steam, at reduced pressure, through
a branch pipe 13, stop valve 14, pipe 15 and steam chest 7 without the inter-
vention of a regulating throttle valve. 16 is the water inlet to the tank 3.
17 is the water outlet from the pump 2 to which the main feed pipe is connected.
The working of the apparatus is as follows:-
As soon as the feed water rises sufficiently in the tank 3 to open the throttle
valve 11 through the action of the float controlling gear, the first pump com-
prising the pump proper 1 and motor 6 starts pumping water from the tank 3
and discharging it through the pipe 5 into the suction side of the cylinder 2 of
the second pump. When the first pump has filled the entire water end of the
pump cylinder 2 and the main feed pipe up to the main check valve (not shown)
on the boiler, and raised the pressure in such cylinder and feed pipe sufficiently
to suit the ratio between the areas of the steam and pump cylinders of the second
pump when using steam at a reduced pressure of say half the boiler pressure,
the second pump will start to work at the same speed as the first pump and feed
the boiler direct against a pressure therein of say 300 lbs. per square inch, the
rate of feeding varying with the height of the water in the tank 3.
In feeding boilers according to this invention, the action of the suction and
delivery valves of the second pump is greatly improved, as the pump piston on
leaving the end of its stroke, has already a pressure equal to half the boiler
pressure on its suction side instead of only atmospheric pressure as is usual when
feeding boilers according to the ordinary method of drawing from an open tank
and discharging direct into the boiler. Furthermore the impact given to the
suction and delivery valves of both pumps never exceeds that given to these
valves when working with and against 150 lbs. pressure, so that the wear and
tear of these parts are considerably reduced. The percentage of slip past the
plungers is also materially reduced owing to the high pressure on the suction
side of the pump cylinder 2. Moreover as all the glands and rubbing surfaces
are exposed to only half the boiler pressure, and therefore to a comparatively
low temperature, friction on those parts is reduced and the use of metallic packing
in the steam glands becomes unnecessary.
The valve chests of the two pump cylinders, and also those of the steam
'cylinders, may, if desired, be combined instead of being separate and connected
together by pipes. Water may be pumped according to this invention against
practically any pressure, the ratio of the steam and pump cylinders to one another
being varied to suit given pressures.
When feeding boilers against excessive pressures, the pumping may be effected
in three or more stages instead of in two stages only as in the foregoing example.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that what
we claim is:-
1. The herein described improved method of feeding high pressure boilers
according to which the feeding is effected in stages by two or more steam pumps,
the delivery from each pump excepting the last, being discharged into the suction
of the succeeding pump and the steam cylinders of the several pumps being

page_text: supplied with steam at a pressure below that of the boiler that is being fed, as
set forth.
2. Apparatus for feeding high pressure boilers comprising two or more steam
pumps having the delivery side of the first pump connected with the suction
side of the next and so on, and means for supplying the steam cylinders with
steam at a lower pressure than that within the boiler being fed, substantially as
described.
3. For feeding high pressure boilers, apparatus constructed and operating sub-
stantially as hereinabove described with reference
in
and shown
the
accompanying drawings.
to
For the Applicants,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.