Improvements in or connected with Steam-boiler Safety Valves.
Year: 1891

page_text: Date of Application, 7th Nov., 1891
Complete Specification Left, 8th Aug., 1892-Accepted, 22nd Oct., 1892
PROVISIONAL SPECIFICATION.
Improvements in or connected with Steam-boiler Safety Valves.
I, ROBERT BRUCE SMITH, of 44, Seymour Street, Higher Tranmere, in
Cheshire, Engineer, do hereby declare the nature of this invention to be as follows,
that is to say :-
My said invention has for its object, by improved safety valve apparatus, to save
the steam or water ordinarily wasted by blowing off.
In carrying out my invention I arrange a safety valve in a box or casing which
is made to communicate by a pipe with a main, or auxiliary, or any condenser, or
with a low pressure receiver or with an evaporator. The valve may be loaded with
a spring or other appliance arranged within the box; or the valve spindle may be
continued through the top of the box and be loaded externally, due allowance
being made for the vacuum or low pressure within the box. I however prefer to
arrange a piston or diaphragm or disk or upper valve fixed or applied to the valve
spindle, and arranged to work in connection with the top of the box in a manner
to be subjected externally to atmospheric pressure and internally to the vacuum
or low pressure in the box, in which arrangement the load applied to the valve
spindle may be the same as for an ordinary, safety valve. Or a loaded piston or
diaphragm may be arranged to be acted on directly by the boiler steam, and
have connected to it an equilibrium valve or other suitable valve for opening
and closing the communication with the pipe for leading the steam to a condenser
or low pressure receiver or evaporator.
Provision is made for indicating when the safety valve is allowing the steam
to blow off as for example by the movement of the loaded valve or spindle
making a contact in an electric circuit arranged to ring a bell in the engine room
or other place. Or when the main valve opens a small valve moving with it
may allow a small visible escape of steam, or may allow the steam access to a
whistle or sounder.
Dated this Sixth day of November 1891.
EDMUND HUNT,
Applicant's Agent.
COMPLETE SPECIFICATION.
Improvements in or connected with Steam-boiler Safety Valves.
I, ROBERT BRUCE SMITH, of 44 Seymour Street, Higher Tranmere, in Cheshire,
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 :-
My said invention has for its object, by improved safety valve apparatus, to
save the steam or water ordinarily wasted by blowing off.
In carrying out my invention I arrange a safety valve in a box or casing
which is made to communicate by a pipe with a main, or auxiliary, or any
condenser, or with a low pressure receiver or with an evaporator. The valve
may be loaded with a spring or other appliance arranged within the box; or the
valve spindle may be continued through the top of the box and be loaded
externally, due allowance being made for the vacuum or low pressure within the
box. I however prefer to arrange a piston or diaphragm or disc or upper valve
fixed or applied to the valve spindle, and arranged to work in connection with
the top of the box in a manner to be subjected externally to atmospheric pressure
Pin1

page_text: and internally to the vacuum or low pressure in the box, in which arrangement
the load applied to the valve spindle may be the same as for an ordinary safety
valve.
In the accompanying drawings which illustrate my invention Fig. I is an
elevation in diametral vertical section showing the arrangement adopted when
the steam which passes the safety valve is to be led to a receiver containing low-
pressure steam, such for example as one of the intermediate or low-pressure
receivers of a compound engine. Fig. II is an enlarged view of a portion of
Fig. 1. Throughout the drawings the same parts are indicated by the same
reference figures.
1 is the safety valve box fitted with valve seat 2 and safety valve 3, all of
ordinary construction; the valve is loaded in the usual manner by the spring +
contained within the casing 5.
The outlet branch 6 of the valve box communicates with the receiver into which
the steam is to be delivered, by the pipe 7. As the pressure in this receiver may
be considerable, it is necessary to take into account its pressure on the upper
surface of the safety valve; if the said pressure were definite and constant this
might be done by making a corresponding deduction in the load to which the valve
is subjected by the spring 4; as this pressure is usually not constant, however, I
neutralise its effect upon the valve by the device shown to an enlarged scale in
Fig. II which will be referred to hereinafter, so that the load applied by the spring
may be the same as for an ordinary safety valve.
In order to prevent any undue accumulation of pressure in the receiver to which
the pipe 7 leads, which might occur if the safety valve were passing a large
quantity of steam, I provide a secondary safety valve 8 which may be of ordinary
construction and is loaded to the pressure permissible in the receiver; as the steam.
passing the safety valve 3 expands on account of the fall of pressure, the area of
the valve 8 should be made correspondingly greater than that of the valve 3.
The waste steam from the valve 8 may be led directly to the atmosphere as this
valve will not lift under normal circumstances, or if preferred, it may be led to the
main or other condenser; in this case, an unloaded non-return valve of sufficient
area must be fitted on the pipe leading to the condenser, so as to deliver the
steam to the atmosphere if the volume passing the valve 8 should exceed the
condensing capacity of the condenser.
The arrangement for neutralising the pressure of the steam within the box 1
on the top of the valve 3 is shown in Fig. II. 9 is a cylindrical liner fitted into
the cover 10 of the valve box 1; from 11 to 12 it is of the same diameter as the
bore of the valve seat 2 or approximately so and is accurately bored. 13, 14, 15
and the elastic packing rings 16 form a steam-tight piston working freely in the
liner; the portions 13 and 15 are held firmly in position on the valve spindle by
the pressure transmitted from the spring 4; 14 is pressed upwards by the spring 17,-
the object of this will be subsequently described.
It will be seen that any stearn pressure that there may be in the valve box 1 will
act in an upward direction on the piston and in a downward direction on the valve
and as the areas are equal there will be no resultant force on the valve. The
object of the spring 17 is to provide against the contingency of the packing rings 16
sticking in the liner;-in such a case, the yielding of 17 will permit the valve to
lift. The rings 16 may be of metal, ebonite, vulcanite or lignum vitæ.
18 is a thin smooth diaphragm of elastic metal also held in position on the
spindle by the downward pressure of the spring 4 and resting at its periphery on
the top edge of the cylindrical liner 9, which is accurately faced; the space 19
enclosed by the diaphragm communicates with a condenser or condensing tank by
a small passage 20 and a pipe; the object of the said diaphragm and passage is to
prevent any steam which may leak past the piston from entering the spring casing 5
as any such leakage will flow away through 20.
It has already been pointed out that by the action of the neutralising piston,
the load on the valve is unaffected by the pressure within the box 1, so that

page_text: if the diaphragm 18 were removed and the atmosphere allowed to act on top of
the said piston (which is equal in diameter to the bore of the valve seat), the
valve might simply be regarded as exposed above to the atmosphere, as in the
case of an ordinary valve, and loaded by the spring 4 accordingly. As the pressure
within the space 19 when the diaphragm is in place is normally below atmospheric
pressure, the effect is to reduce the pressure on top of the neutralising piston ;
at the same time the atmospheric pressure on top of the annular area of the
diaphragm covering the space 19 produces a downward load which falls partly
on the top edge of the liner 9 and partly on the top of the collar 13' attached
to the valve spindle, and the bore of the liner from A to B must be made such.
that the load so transmitted to the valve spindle from the diaphragm shall be
equivalent to the diminution in the load on top of the neutralising piston
in virtue of the partial vacuum within the space 19. In other words, the
diameter from A to B must be such that the proportion of the total atmospheric
load on the annular area of the diaphragm covering the space 19 which would
fall on the valve spindle shall be equal to that which the atmosphere would exert
on the annular area of the neutralising piston beyond the collar 13 if the
diaphragm were removed. The required diameter can be readily calculated if the
rigidity of the diaphragm be neglected; the simplest supposition to make is that
the space 19 is a perfect vacuum and it will be seen that the result is unaffected
by any partial vacuum there may be in this space,-any pressure therein will act
upwards on the diaphragm and partially relieve the load on it and will also act
downwards upon the neutralising piston, the two effects counterbalancing and
producing no resultant on the valve spindle, so that, as before, in loading the valve
by the spring 4, it may be regarded as an ordinary valve exposed above to
atmospheric pressure.
When the valve lifts, the diaphragm leaves its seating and air enters the space 19
and flows to the condenser by the passage 20; in order to minimise this as far as
possible, the passage is made small,-only large enough to carry away any leakage
of steam from the box 1 past the neutralising piston.
becomes an
When the pipe 7 is led to a condenser, the secondary safety valve
unloaded non-return valve delivering to the atmosphere and the passage 20 may be
dispensed with, the diaphragm 18 being in this case serviceable as an additional
means to the piston to prevent air leakage into the box 1 and thence to the
condenser. Under these circumstances, the piston might be dispensed with as the
flow of steam when the safety valve lifts will tend to prevent the entry of air to
the condenser past the diaphragm when lifted from its seat.
My invention may also be fitted to the main steam pipe of an engine and
arranged to deliver to the condenser, so as to act as an automatic silent blow-off
when the engines are stopped or slowed.
Provision may be made for indicating when the safety valve is allowing steam
to blow off, as for example, by the movement of the loaded valve or spindle making
a contact in an electric circuit arranged to ring a bell in the engine room or other
place. Or when the main valve opens, a small valve moving with it may allow
a small visible escape of steam, or may allow the steam access to a whistle or
sounder.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is ;-
(1). The combination of a safety valve and a box which contains the said valve
and communicates beyond the valve with a condenser, low-pressure receiver or
evaporator, whereby the loss of steam passing the safety valve is prevented,
substantially as described.
(2). In combination with a safety valve and box, as claimed in Claim 1, a piston
connected to the valve spindle and adapted to neutralise the effect of the pressure

page_text: within the box upon the top of the safety valve, substantially as described and
illustrated.
(3). In combination with a safety valve and box, as claimed in Claim 1, an
elastic diaphragm connected to the valve spindle and resting at its periphery upon
a fixed seating, substantially as described and illustrated.
(4). In combination with a safety valve, a box and a neutralising piston, as
claimed in Claim 2, an elastic diaphragm connected to the valve spindle and resting
at its periphery upon a fixed seating, substantially as and for the purpose described
and illustrated.
(5). In combination with a safety valve and box, as claimed in Claim 1, a
secondary safety valve placed on the delivery side of the main safety valve,
substantially as and for the purpose described.
(6). In safety valves of the kind herein described, the use of a spring interposed
as 17 between the valve and the packing ring of its neutralising piston, whereby
relative movement between the valve and the piston ring is permitted, substantially
as and for the purpose described and illustrated.
(7). The improved safety valve, substantially as described and illustrated in the
drawings.
Dated this Sixth day of August 1892.
SLOAN & LLOYD BARNES,
Castle Street, Liverpool, Agents for the Applicant.