Improvements in or relating to Safety Valves.
Year: 1899

page_text: Date of Application, 25th Nov., 1899
A
1000
PROVISIONAL SPECIFICATION.
Improvements in or relating to Safety Valves.
$
I, ERNEST FERNAND DECLERCQ, of 5, Rue Jean Roisin, Lille, in the Republic
of France, Engineer, do hereby declare the nature of this invention to be as
follows:-
In ordinary safety valves it is well-known that the rise of the valve is not
in proportion to the pressure of the steam which causes it to leave its seat, the
reason being that when the steam commences to escape the pressure of the body
of steam which is immediately below, the valve becomes reduced, immediately
the valve commences to leave its seat. It is also well-known that by comparing
the action of valves which are weighted for different pressures this loss of
pressure under the valve which is proportional to the difference of pressure
between that prevailing in the boiler and the outside atmospheric pressure, is
greater, the greater the pressure for which the valve is regulated to blow off,
so that to obtain the same amount of rise of the valve it is necessary that there
should occur an interior pressure which is considerably greater than the normal
pressure. It will thus be seen that there is considerable utility in employing
valves which are called progressive escapement valves, that is to say, valves in
which this aforesaid reduction of pressure at the moment they blow off is
either suppressed or compensated for by some arrangement. The different
arrangements which have been made up to the present for this purpose may be
classed in two distinct categories:-1. Valves where the lowering of pressure is
compensated for more or less truly by an increase of the surface of the valve
which is submitted to the action of the steam or by the use of the dynamic force
of the moving steam. 2. Valves in which the loss of pressure is suppressed or
equilibriated without increase of the surfaces submitted to the action of the
steam and without utilising the dynamic force of the latter. All the valves
in the first above mentioned category are found to fail in their object for the
following reasons: There is no proof, in fact, that the increase of the surfaces
or the action of the dynamic force of this steam will compensate exactly for
the lowering of the pressure; and, in fact the contrary effect can be deduced
in many cases. In all the valves in which the surface is increased, the action
of the steam on the increased surface, or the action of the dynamic force of
the steam will continue to act after the surplus of pressure in the boiler has
ceased, and the valve will only completely close again when the pressure of the
steam in the boiler has fallen below that of the normal pressure. The valves
with progressive escapement in the second category, have generally given better
results, but they have all certain inconveniences which are completely removed
by the present invention.
This invention consists essentially in providing a valve with helicoidal webs
which are prolonged into the boiler or a tubular extension of the valve casing,
so as to present a certain surface to the action of steam in a static state, whilst
the action of the steam in the dynamic state is exerted when the valve is raised
from its seat on the helicoidal surfaces of the helices, so as to produce equal

page_text: stresses in a direction contrary to one another, and thus reciprocally neutralise
one another.
As an example of such a valve the valve seat may be prolonged in the form
of a tube and to the underside of the valve there may be attached a rod pro-
jecting axially with the valve, such rod forming a spindle around which a suit-
able number of helicoidal plates project; the edges of these plates extend to
the inside of the tube aforesaid. These plates may be extended along
the axis for some distance beyond the internal end of the tube, and
may there end in a flat dise; above the valve and parallel to it is
a dise in one part with the valve and sliding when the valve is
raised in a short length of tube. When the steam pressure has increased in
the boiler to sufficient extent to lift the valve from its seat, the steam escapes
into a space above the valve and there acts not only to press the valve back upon
its seat but also to press the aforesaid disc in such a direction that the valve
is lifted from its 'seat. These two pressures counteract one another so that in
this form of valve there is no counter pressure on the back of the valve tending
to hold it closed against the pressure of the escaping steam. As the steam
begins to escape it will have to pass through the helicoidal passages formed
by the aforesaid helicoidal webs and the tubular extension of the seat of the
valve. In so passing along these helicoidal passages the pressure of the steam
will be gradually less and less as it approaches and issues around the valve, but
the upward pressure of the steam at the upper helicoidal web at any point of
any one of these helicoidal passages will be equal to its downward pressure on
the lower helicoidal web of such passage, and thus the pressure will be equalised
throughout the length of the helicoidal passages aforesaid, that is to say, the
whole pressure upward on the lower faces of the helicoidal webs will be met
and equalised by the total pressure downward on the upper faces of said webs.
Thus the valve when lifted from its seat is raised by the superpressure of steam
which is always equal to the interior pressure prevailing in the boiler, and which
acts on the disc which terminates the helicoidal webs. Its rise will therefore
be more rapid and it will give passage to all the steam that passes to it imme-
diately the pressure exceeds the normal pressure, and it will close again
immediately the pressure has dropped again to the normal.
In another form of said valve the helicoidal webs do not extend below the
interior end of the aforesaid tube which surrounds them, and there is no disc
at the lower end of the said webs.
In this case the action of the steam in the static state is exercised on the
extreme face of the last spiral of the helicoidal webs in place of on the disc
which terminates these webs as in the former case.
Amongst the advantages of this improved form of valve are the following.
The escaping steam follows a continuous path without any abrupt bends, and in
its movement it therefore gives no abrupt changes of pressure on the walls or
plates of the boiler; also the diameter of the valve is limited to that of an
ordinary safety valve, whilst valves with progressive escapement, where the
reduction of pressure is reduced or suppressed by means of the introduction of
steam under the valve by means of lateral pipes, the diameter is increased and
in order to fix them on boilers it is necessary to make very large holes therein.
In the last mentioned valves, deposits due to the hardness of the water or other
causes which may be carried along with the steam are deposited in the interior
of the valve, by reason of the dead spaces which allow of such deposit; such
deposits often prevent completely the action of the valve, and in any case disturb
it's correct movement. Such disadvantages cannot take place with the valve
made according to the present invention.
Dated this 25th day of November 1800.
HERBERT HADDAN & Co.,
Agents to Applicant.

page_text: I, ERNEST FERNAND DECLERCQ, of 5, Rue Jean Roisin, Lille, in the Republic
of France, 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:-
In ordinary safety valves it is well known that the rise of the valve is not
in proportion to the pressure of the steam which causes it to leave its seat, the
reason being that when the steam commences to escape. the pressure of the body
of steam which is immediately below the valve becomes reduced, immediately
the valve commences to leave its seat. It is also well known that by comparing
the action of valves which are weighted for different pressures, this loss of
pressure under the valve, which is proportional to the difference of pressure
between that prevailing in the boiler and the outside atmospheric pressure, is
greater, the greater the pressure for which the valve is regulated to blow off,
so that to obtain the same amount of rise of the valve it is necessary that there
should occur an interior pressure which is considerably greater than the normal.
pressure. It will thus be seen that there is considerable utility in employing
valves which are called progressive escapement valves, that is to say valves in
which this aforesaid reduction of pressure at the moment they blow off is
either suppressed or compensated for by some arrangement. The different
arrangements which have been made up to the present for this purpose may be
classed in two distinct categories:
1. Valves where the lowering of pressure is
compensated for more or less truly by an increase of the surface of the valve
which is submitted to the action of the steam or by the use of the dynamic force
of the moving steam. 2. Valves in which the loss of pressure is suppressed or
equilibriated without increase of the surfaces submitted to the action of the
steam and without utilizing the dynamic force of the latter. All the valves
in the first above mentioned category are found to fail in their object for the
following reasons: There is no proof in fact, that the increase of the surfaces
or the action of the dynamic force of this steam will compensate exactly for
the lowering of the pressure and in fact the contrary effect can be deduced
in many cases. In all the valves in which the surface is increased the action
of the steam on the increased surface, or the action of the dynamic force of
the steam will continue to act after the surplus of pressure in the boiler has
ceased, and the valve will only completely close again when the pressure of the
steam in the boiler has fallen below that of the normal pressure. The valves
with progressive escapement in the second category have generally given better
results, but they have all certain inconveniences which are completely removed
by the present invention.
This invention consists essentially in providing a valve with helicoidal webs
which are prolonged into the boiler or a tubular extension of the valve casing,
so as to present a certain surface to the action of steam in a static state whilst
the action of steam in the dynamic state is exerted when the valve is raised
from its seat on the helicoidal surfaces of the helices, so as to produce equal
stresses in a direction contrary to one another and thus reciprocally neutralize
one another.
As an example of such a valve the valve scat may be prolonged in the form
of a tube and to the underside of the valve there may be attached a rod pro-
jecting axially with the valve, such rod forming a spindle around which a suit-
able number of helicoidal plates project; the edges of these plates extend, to

page_text: the inside of the tube aforesaid. These plates may be extended along
the axis for some distance beyond the internal end of the tube and
may there end in a flat dise; above the valve and parallel to it is
a disc in one part with the valve and sliding when the valve is
raised in a short length of tube. When the steam pressure has increased in
the boiler to a sufficient extent to lift the valve from its seat, the steam escapes
into a space above the valve and there acts not only to press the valve back upon
its seat but also to press the aforesaid disc in such a direction that the valve
is lifted from its seat. These two pressures counteract one another so that in
this form of valve there is no counter pressure on the back of the valve tending
to hold it closed against the pressure of the escaping steam. As the steam
begins to escape it will have to pass through the helicoidal passages formed
by the aforesaid helicoidal webs and the tubular extension of the seat of the
valve. In so passing along these helicoidal passages the pressure of the steam
will be gradually less and less as it approaches and issues around the valve but
the upward pressure of the steam on the upper helicoidal web at any point of
any one of these helicoidal passages will be equal to its downward pressure on
the lower helicoidal web of such passage, and thus the pressure will be equalised
throughout the length of the helicoidal passages aforesaid, that is to say, the
whole pressure upward on the lower faces of the helicoidal webs will be met
and equalized by the total pressure downward on the upper faces of said webs.
Thus the valve when lifted from its seat is raised by the super pressure of steam
which is always equal to the interior pressure prevailing in the boiler and which
acts on the disc which terminates the helicoidal webs. Its rise will therefore
be more rapid and it will give passage to all the steam that passes to it imme-
diately the pressure exceeds the normal pressure and it will close again
immediately the pressure has dropped again to the normal.
In another form of said valve the helicoidal webs do not extend below the
interior end of the aforesaid tube which surrounds them, and there is no disc
at the lower end of the said webs.
In this case the action of the steam in the static state is exercised on the
extreme face of the last spiral of the helicoidal webs in place of on the disc
which terminates these webs as in the former case.
The annexed drawings show two forms of construction of this invention.
The safety valve represented in Fig. 1 is provided with progressive escapement
and disengagement by lateral tubes, m.
a
The valve consists of a principal body a preferably of cast iron carrying
seating preferably of bronze on which the clack valve rests guided in the
lower parts by the helicoidal webs h terminated at the bottom by a disc g and
at the upper part by the disc d in the sleeve or tube e. An upper plate r of
cast iron serves at the same time as a cover and support for the lever and
counterweight which act on the clack valve by means of the central spindle s.
When the valve e rests on its seat and the steam is in a static state, that is
to say, in a resting state in all parts below the closed valve all the surfaces of
the webs and lower disc g will everywhere be exposed to the same pressure and
all these forces remain balanced: only the lower surface of the clack valve will
be exposed to the steam pressure without compensation exactly as in an ordinary
valve. The clack valve will therefore commence to leave its seat when this pres-
sure has surpassed the normal pressure which is balanced by the weight of the
counterweight and lever on the valve.
As soon as the steam finds a passage it will escape and a gradual depression
will be produced between the initial point of its movement (that is to say at
it's entrance into the spirals formed by the helicoidal webs h) and the point
where it escapes, that is to say at the opening ring of the raised clack valve.
If the pressure in the boiler or at the entrance of the steam into the spirals
is designated "P" and the pressure of the same steam reduced arrived at the
point of escapement under the clack valve designated as "p". there will result

page_text: at the various points of the spirals pressures p¹p² p³ p* &c. and the total pressure
will be equal to the amount of pressure acting on the lower surfaces minus the
amount of pressure acting on the upper surfaces, that is to say as each surface
of the discs in vertical projection is equal to the surface "S" of the clack
valve, Sp+ Sp' + Sp² + Sp² + Sp. . . Sp" + SP− (Sp + Sp¹ + Sp² + Sp³ + Sp*
Sp") SP.
=
It is evident that through the arrangement of the helical webs the clack valve
even when it has left its seat leaving a passage for the steam which slackens and
produces a depression, is exposed to a pressure equal to that in the interior of
the boiler, it will therefore rise much faster and leave a passage for all steam
produced as soon as the pressure has surpassed the normal pressure and close
again as soon as it has fallen again to the same pressure.
The following takes place above the clack valve when it leaves its seat and
the steam escapes.
If the escapement took place in the open air there would only be the atmo-
spheric pressure on the external surface of the clack valve during the escapement
as well as during inoperation but with the addition of the disengagement chamber
with lateral tube m which is placed above the seat, there would be produced in
this chamber at the moment of the rise a pressure greater than the atmospheric
pressure which would counterbalance the interior pressure and reduce the rising
if this counterpressure itself was not balanced by the addition of the disc d which
has the same diameter as the upper surface of the clack valve and sustains the
action of the pressure equal and in the contrary direction to that acting on
the said clack valve.
in the example represented in Fig. 2 the helicoidal webs of the clack valve
are not prolonged onto the interior of the boiler and the lower disc g is dis-
pensed with so that the entrance of the steam into the spiral's takes place through
the space between the consecutive spirals.
It is evident that the desired result in this form of construction is obtained
in the same manner as in the example shown in Fig. 1.. In the case of 4 webs
as shown in Fig. 2 the steam acts constantly at the pressure of the boiler on
the first quarter turn of each of the webs and in proportion as it slackens
between the consecutive spirals exercises equal pressures in the contrary sense
on the different surfaces of the webs as indicated by the arrows in Fig. 2.
Amongst the advantages of this improved form of valve are the following.
The escaping steam follows a continuous path without any abrupt bends and in
its movement it therefore gives no abrupt changes of pressure on the walls or
plates of the boiler: also the diameter of the valve is limited to that of an
ordinary safety valve, whilst with valves with progressive escapement where the
reduction of pressure is reduced or suppressed by means of the introduction of
steam under the valve by mean's of lateral pipes, the diameter is increased, and
in order to fix them on boilers it is necessary to make very large holes therein.
In the last mentioned valves deposits due to the hardness of the water or other
causes which may be carried along with the steam are deposited in the interior
of the valve by reason of the dead spaces which allow of such deposit: such
deposits often prevent completely the action of the valve and in any case disturb
it's correct movement. Such disadvantages cannot take place with the valve
made according to the present invention.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what
I claim is:
1. A safety valve with progressive escapement in which the clack-valve is
provided with hencoidal webs which extend into the body of the boiler, the
object of which is to allow, at the moment of rising of the valve, of the expansion
of the steam in the spirals formed by the webs by keeping a determined surface
exposed to the action of the steam in a static state.

page_text: 2. A form of construction of the valve described in Claim 1, in which the
webs only extend into the escapement tube of the valve and are open at their
lower part in order to allow of the steam entering into the spirals of said webs
and to constitute the surface exposed to the action of the steam in static state.
3. In the valve as described in Claims 1 and 2 the combination of the clack-
valve with a compensating disc for counter-balancing the action of the escaped
steam acting on the upper surface of the valve.
Dated this 20th day of August 1900.
HERBERT HADDAN & Co.,
Agents to Applicant, 18, Buckingham Street, Strand, W.C., London.