Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~95VZ
This invention relates to an emergency two-way shut-off
valve.
According to the invention there is provided an emergency
two-way shut-off valve comprising a housing and two valve members
each one of which is movable apart from and towards the other
valve member, and spring-urged apart towards respective stops
within the housing, the valve members having openings therethrough
which, when the valve members are spaced apart, permit flow of
fluid through the valve but, when the valve members are pressed
together, are blocked off by imperforate por$ions of the valve
members.
Thus, in the event of a pipeline failure downstream of
the installed valve, the loss of back pressure on the downstream
of the installed valve, the loss of back pressure on the down-
stream side of the upstream valve member causes a sufficient pres-
sure differential to be set up across the upstream valve member
to result in the upstream valve member moving in a downstream
direction off its stop against the spring bias into contact with
the downstream valve member and thus block-off fluid forward flow
through the valve. Conversely in the event of a pipeline failure
upstream of the installed valve, the loss of forward pressure on
the upstream side of the downstream valve member causes a suffi-
cient pressure differential to be set up across the downstream
valve member to result in the downstream valve member moving in
an upstream direction off its stop against the spring bias into
contact with the upstream valve member and thus block-off fluid
back flow through the valve.
An embodiment of the invention will now be described, by
way of example, with reference to the accompanying drawings, in
which:
Fig. 1 is an axial section through an emergency two-way
shut-off valve;
~1~950Z
Fig. 2 is a view from line II-II in Fig. l;
Fig. 3 is an axial section through two modified valve
plates which may replace the valve plates in Figs. 1 and 2.
Referring to Figs. 1 and 2, an emergency two-way shut-
off valve comprises a housing formed in two portions 1 and 2
each having at one end an annular flange 3, 4 from which a neck
5, 6 reduces in its internal diameter from about double the in-
ternal diameter of the pipeline to the internal diameter of the
pipeline at the other end 7, 8 where it can be connected to a pipe
end.
Housing portion 1 has a hard steel ring 9 removably fit-
ted about the opening in the face of the flange 3 while the neck
6 of the housing portion 2 has a cylindrical inner surface 10
extending from the face of the flange 4 to a hard steel ring 11
removably fitted within the neck 6.
When the two flanges 3, 4 are bolted or otherwise secured
together, the two rings 9, 11 constitute stops for respective
valve plates 12, 13 within the housing. Each valve plate 12, 13
is circular with a diameter such as to have a sliding fit within
the surface 10. Each valve plate 12, 13 has three bored openings
14 of equal diameter and equally spaced apart. The total area of
the three openings 14 in each valve plate 12, 13 is preferably
slightly in excess of the cross-sectional area of the pipeline
but the area of each opening 14 is less than the area between
adjacent openings 14 in each valve plate 12, 13. Also in each
valve plate 12, 13 there is provided a central blind hole 15 pro-
viding a seat for each end of a compression spring 16 which urges
the plates 12, 13 apart against their respective stop rings 9, 11.
Means (not shown) may also be provided to stabilise the spring 16,
such means may be telescoping sleeves or pins locating the ends
of the spring 16 within the blind holes 15. It is necessary that
when the valve plates are pressed together each opening 14 in
-- 2 --
1~19502
each valve plate is blocked of~ by the area between adjacent open-
ings 14 in the other valve plate. In order to provide this angular
relationship between the valve plates 12, 13 two rib formations are
disposed diametrically opposite each other on the circumferential
surface of each valve plate 12, 13. These rib formations are
shown in the form of an axially elongate protruding insert 17
slidable within correspondingly diametrically opposed axially
elongate grooves 18. The actual disposition of the inserts 17
on the valve plate 12 is shown in Fig. 2, the showing in Fig. 1
being merely for ease of illustration. Three large diameter 0-
rings 19 are set in annular grooves in the valve plates 12, 13
the valve plate 12 having one ring 19 on each side, one to seal
against stop ring 9 and the other to seal against the valve plate
13, and the valve plate 13 having one ring 19 to seal against
stop ring 11. Furthermore, three small diameter 0-rings 20 cir-
cumscribe each opening 14 in the valve plate 12 at one side there-
of to seal against the valve plate 13 in the areas between ad-
jacent openings 14. A restricted bleed line for fluid across the
valve is provided by means of mating channels 21 and 22 in the
flanges 3 and 4 respectively. An adjustable restriction is pro-
vided in the form of a manually adjustable needle valve member 23
accessible through an opening in the flange 4 threadedly receiving
a blanking screw 24.
Under normal operating conditions the spring 16 keeps
the valve plates 12, 13 apart so that fluid can flow through the
valve, via the openings 14 in the upstream valve plate, the space
between the valve plates 12, 13 and the openings 14 in the down-
stream valve plate. Turbulence in the space between the valve
plates 12, 13 also tends to keep the valve plates 12, 13 apart.
In the event of a pipe failure downstream of the valve, the back
pressure downstream of the valve will fall and this fall in back
pressure will be felt in the space between the valve plates 12,
13 so that pressure differential across the upstream valve plate
. 3
~9s~z
will rise sufficiently to move the upstream valve plate in a
downstream direction against the spring 15 to contact with the
downstream valve plate and thus block-off fluid forward flow
through the valveO In the event of a pipe failure upstream of
the valve, the forward pressure upstream of the valve will fall
and this fall in forward pressure will be felt in the space be-
tween the valve plates 12, 13 so that the pressure differential
across the downstream valve plate will rise sufficiently to move
the downstream valve plate in an upstream direction against the
spring 15 into contact with the upstream valve plate and thus
block-off fluid back flow through the valve. The restricted
bleed 21, 22, 23 across the valve tends to equalise the pressures
on both sides of the valve so that ultimately the spring 15 urges
one valve plate away from the other so that fluid flow through
the valve can begin again.
The valve described and illustrated is designed primarily
for use with air, other gas or steam at high or medium pressure.
For use with liquids it is desirable to minimise turbulence in
the space between the valve plates 12, 13 during normal operation.
In such case the grooves 18 may be helical into which slidingly
fit formations projecting from the circumference of both valve
plates 12, 13. When the valve plates 12, 13 are fully apart the
openings 14 in both valve plates are substantially in alignment
with one another so that under normal operating conditions tur-
bulence between the valve plates is minimised. However, due to
the helical grooves, when one valve plate moves towards the other
the moving valve plate also turns so that when contact is made
between the valve plates 12, 13 the openings 14 in each valve
plate are blocked off by the areas between adjacent openings 14
in the other valve plate. Preferably, the formations projecting
from the circumference of both or one of the valve plates are
helical ribs.
- 4 -
,
, .
11~95~Z
The valve described and illustrated may be modified by
replacing the valve plates 12 and 13 with the valve plates 25 and
26 shown in Fig. 3. A central opening 27 is provided in the valve
plate 25 and a ring of smaller openings 28 is provided in the
valve plate 26. 0-rings 19 are provided as before but the 0-rings
20 are replaced by a single 0-ring 29 either on the valve plate
26 (as shown) or on the valve plate 25. A spring 16 may be pro-
vided between the valve plates with its ends seated in the blind
hole 15 in the valve plate 26 and in an annular recess 30 in the
valve plate 25 surrounding the opening 27.
.~.
.,~, , .
.
