Double gated valve

There is disclosed a gate valve having a pair of side-by-side through conduit gates which are adapted to be reciprocated relatively to one another by a fail safe actuator of such construction as to move the upstream gate to closed position before the downstream gate and the downstream gate to open position before the upstream gate.

This invention relates to improvements in gate valves, and, in particular, 
to gate valves of the through conduit type. In one of its aspects, it 
relates to such gate valves which are also of the fail safe type. 
The greatest wear on both the gate and the valve body of a through conduit 
gate valve occurs at end of its closing movement and beginning of its 
opening movement. Thus, at this stage of the valve operation, line fluid 
is caused to flow at high velocity through a very small opening between 
the port in the gate and the end opening of the flowway in the valve body 
on the downstream side of the gate. 
Because of this problem, redundant gate valves are sometimes installed in 
the flow line being controlled, the upstream valve being "sacrificial" in 
the sense that it is adapted to be opened first and closed last so as to 
absorb substantially all of the wear. Even when the upstream valve first 
wears to the point it no longer seals, the downstream valve takes over the 
sealing function without significant wear, at least until wear on the 
upstream valve becomes so severe as to permit leakage of line fluid 
therepast at high rates. Consequently, the arrangement normally permits 
the useful life of the valves to be greater than would be expected of the 
combined lives of each individually. 
This redundant arrangement of gate valves is especially useful in remote 
locations where a single valve would be difficult to reach for replacement 
and/or repair. This is true, for example, in the case of valves installed 
on subsea wellheads a substantial distance below the water surface. As 
well known in the art, valves used at these installations are often fail 
safe--i.e., adapted to either open or close automatically in response to a 
given condition at a location remote from the wellhead. 
The use of redundant valve, each having its own valve body and actuator, is 
of course quite expensive. Also, they require considerable space in and 
around the flow line being controlled, which space may be at a premium. It 
is therefore a primary object of this invention to provide a through 
conduit type gate valve capable of performing the function of the 
redundant valves above described, but having only a single valve body and 
actuator. 
A more particular object is to provide such a valve in which a pair of 
through conduit gates mounted in side by side relation within the valve 
body are moved between opened and closed positions by an actuator which is 
so constructed and arranged as to automatically sequence their movement in 
such a manner that the upstream gate performs the function of an upstream 
or sacrificial valve. 
A further object is to provide such a valve in which the actuator causes 
the gates to move to one of their positions automatically in response to a 
failed condition. 
Yet another object is to provide such a valve in which the actuator is of 
compact construction. 
These and other objects are accomplished, in accordance with the 
illustrated embodiment of the invention, by a gate valve of the type 
described having first and second gates of the through conduit type 
mounted within the cavity of a single valve body for movement in side by 
side relation between opened and closed position, and an actuator for so 
moving the gates which includes means for moving the first gate from 
closed to open position only after the second gate has been so moved and 
for moving the second gate from open to closed position only after the 
first gate has been so moved. Thus, with the first gate on the upstream 
side of the valve body, the gates are automatically moved in such sequence 
as to duplicate the function of redundant valves connected in series in a 
flow line. 
In accordance with the preferred embodiment of the invention, the actuator 
comprises a cylinder and first and second pistons reciprocal within the 
cylinder and connected to the first and second gates, respectively, for 
moving each of them to one of its positions in response to the supply of 
fluid under pressure to the cylinder. More particularly, the actuator 
further includes first and second springs urging each of the first and 
second gates, respectively, to its other position, and means holding the 
first piston against movement in a direction to move the first gate from 
closed to open position until the second gate has been moved in a 
direction to move the second gate from closed to open position, and 
holding the second piston against movement in the direction to move the 
second gate from open to closed position until the first piston has been 
moved in a direction to move the first gate from open to closed position. 
Thus, as also described above, the valve is of the fail safe type in which 
both of the gates are caused to move to one of its positions, normally 
closed, in response to the loss of fluid pressure in the cylinder, which 
loss may occur in response to a predetermined condition remote from the 
valve itself. 
As illustrated, the pistons and springs are arranged concentrically of one 
another, and the pistons are connected to their respective gates by 
concentric rods which extend sealably from the cylinder into the valve 
body, thus, providing the actuator with a very compact construction. More 
particularly, the first piston is sealably slidable within the cylinder 
and the second piston is sealably slidable within the first piston, and 
the means for holding the pistons includes an expandable and contractible 
locking ring mounted in the cylinder to hold the first piston, as the 
second piston moves in a closing direction, and engageable by the second 
piston to release the first piston as the second piston reaches the end of 
its closing movement, and to hold the second piston as the first piston 
moves in an opening direction and engageable by the first piston to 
release the second piston as the first piston reaches the end of its 
opening movement. 
As illustrated, the valve further includes first and second seat rings 
which are sealably slidable in the valve body for engaging the outer sides 
of the first and second gates, respectively, and the gates are connected 
to their stems for relative movement with respect thereto in the direction 
of the flowway. More particularly, the end of the first seat ring and 
outer side of the first gate are yieldably urged against one another, so 
that upstream line fluid maintains the upstream seat in sealing engagement 
with the upstream gate. 
A means is mounted in the valve body for guiding the gates as they move 
between open and closed positions, including a guide frame having an inner 
wall extending between the gates and having a port therethrough adapted to 
be aligned with the ports in the gates, and an outer wall closely 
surrounding the second seat ring and bearing against the body cavity on 
the outer side of the second gate. Thus, the load on the first gate due to 
line pressure on the upstream side thereof is transmitted directly to the 
valve body so as to facilitate free movement of the gates which otherwise 
might bind due to force of line fluid. 
As illustrated, the gate guiding means also includes a guide plate which 
closely surrounds and is supported by the first seat ring and has flanges 
which extend along the side edges of the first gate. More particularly, 
the inner wall of the guide frame and the guide plate are arranged to 
cover the port in the first gate as it moves into and out of closed 
position and thus prevent the passage of debris into the valve body 
cavity. 
In the preferred embodiment, springs are compressed between the outer sides 
of the inner wall and the inner sides of the gates to urge the gates apart 
and thus force the front and second gates outwardly against the ends of 
their respective seat rings.

With reference now to the details of the drawings, the above described 
valve, which is indicated in its entirety by reference character 20, 
comprises a valve body 21 including a main portion 21A having a flowway 22 
therethrough adapted to be connected in a flow line and a cavity 23 
intersecting the flowway intermediate its ends. The valve body also 
includes a bonnet 26 bolted at 27 to the upper side of the main body with 
its open lower end forming an upward continuation of the upper end of the 
cavity and a top wall 26A at its upper end closing the upper body of the 
cavity 23. As shown in FIGS. 7 and 8, both the interior of the bonnet and 
cavity are of cylindrical shape. 
The valve further comprises a pair of gates 28A and 28B mounted in side by 
side relation within the valve body for relative reciprocation between 
positions opening and closing the flowway. As shown, gate 28A has a port 
25A therethrough and gate 28B has a port 29B therethrough, each of the 
ports being of the same size as the flowway and located above a solid 
portion of the gate. 
With flow through the valve in a direction from right to left, as shown in 
FIGS. 1 to 4, the gate 28A is the upstream gate and the gate 28B is the 
downstream gate. The valve is closed when the solid portion of one or more 
of the gates is over the flowway 23 as shown in FIGS. 1, 2 and 4. The 
valve is open when both of the ports are aligned with one another and the 
flowway, as shown in FIG. 3. 
The valve also includes an actuator 25 having a cylinder 27 connected to 
and extending upwardly from the top wall 26A of the bonnet, a piston 30A 
sealably slidable within the cylinder 27 and connected to the upstream 
gate 28A by means of a stem 31A extending sealably through the top wall 
26A of the bonnet of the valve body, and a piston 30B sealably slidable 
within the piston 30 and connected to the downstream gate 28B by means of 
a stem 31B which extends sealably through the stem 31A. More particularly, 
the lower end of stem 31A is releasably connected to the upper end of gate 
28A by means of a connector 32A, and the lower end of the stem 31B is 
releasably connected to the upper end of the downstream gate 28B by means 
of a connector 32B. 
As will be described in connection with the detailed construction of the 
actuator, the piston 30B may be moved downwardly from the position of FIG. 
1 to the position of FIG. 2 to lower the gate 28B and thus move its port 
into substantial alignment with the downstream end of the flowway. 
However, at this stage, the piston 31A and gate 28A are still in their 
upper positions so that the solid portion of the gate is aligned with the 
flowway to maintain the valve closed. 
As shown in FIG. 3, the piston 30B has been lowered still further to move 
the gate 28B to its lowermost position fully aligned with the downstream 
end of the flowway, and the piston 31B has been lowered to in turn lower 
gate 28A to its lowermost position in which its port is aligned with the 
upstream end of flowway 23 and the port in gate 28B, whereby the valve 
itself is open. 
During the closing phase of the valve, piston 30A is first raised to in 
turn raise the gate 28A toward its uppermost position of FIG. 2 in which 
its solid portion covers the port in gate 28B. Upon further upward 
movement of piston 30A to its uppermost position, as shown in FIG. 1, 
piston 30B is released in order to raise gate 28B to a position in which 
its port is aligned with the port in gate 28A and the flowway, whereby the 
valve itself is closed. 
A pair of seat rings 33A and 33B are mounted within recesses 34A and 34B, 
respectively, in the flowway of the valve body at its intersection with 
the cavity 23 on the upstream and downstream sides thereof. More 
particularly, and as best shown in FIGS. 6 and 8, the seat ring 33A 
carries a seal ring 35A about its outer diameter which is sealably 
slidable within the recess 34A and another seal ring 36A on its inner end 
which is engageable with the upstream side of the gate 28A. Thus, with the 
inner end of the seat ring 33A and outer side of the upstream gate 
yieldably urged into engagement with one another, as will be described to 
follow, upstream line pressure in the valve is effective to maintain the 
seat sealably engaged with the upstream gate. 
The downstream seat ring 33B, on the other hand, has flexible lips 35B 
formed thereabout for sealably engaging the recess 34B in metal-to-metal 
sealing relation. Also, a seal ring 36B is carried within its inner end so 
as to seal against gate 28B when the seat ring and the inner end of the 
seat are yieldably urged against one another. The lips 35A face inwardly 
so as to seal against flow from within the cavity into the flowway of the 
downstream side of the downstream gate. 
The downstream gate 28B is guidably movable within the valve body by means 
of a D-shaped guide frame having an inner wall 37 which is disposed 
between the inner sides of the gates and an outer curved wall 38 which is 
received closely within the cavity 23 of the main valve body portion on 
the downstream side of the downstream gate and which has an opening 39 
therein closely surrounding the downstream seat ring 33B. The lower end of 
the guide frame is supported on a ledge 40 in the body cavity and, due to 
its semi-circular shape, is prevented from moving out of the left-hand 
side of the body cavity, as shown in FIG. 8. 
The inner wall 37 of the guide frame has a port 40A therethrough aligned 
with the port in gate 28B, and a flange 41 on its opposite side edges 
which provides a guide surface 42 in which the side edges of the 
downstream gate are slidable, as best shown in FIG. 8. Thus, gate 28B is 
guided during its reciprocation between open and closed positions by means 
of the inner end of the downstream seat ring 33B as well as the inner wall 
37 of the guide frame. 
The upstream gate 28A, on the other hand, is guidably reciprocable between 
the opposite side of the inner wall 37 of the guide frame and a guide 
plate 43 which closely surrounds and is supported by the inner end of the 
seat ring 33A on the upstream side of the upstream gate. Thus, as best 
shown in FIG. 6, the guide plate 43 has an opening 44 therein which fits 
closely within a notch about the inner end of the upstream seat ring and 
flanges 45 on its opposite sides which are close to the opposite side 
edges of the upstream gate so as to guide it against lateral movement 
within the cavity, as best shown in FIG. 8. 
In addition to guiding the gates during their reciprocation between open 
and closed positions, the guide frame and guide plate serve to prevent 
debris in the line fluid from entering the cavity as the upstream gate 
moves between opened and closed positions. Thus, as will be understood 
from FIGS. 1-4, the port through upstream gate 28A is disposed between the 
inner wall of the guide frame and the guide plate as it moves between its 
opened and closed position. At the same time, the downstream end of the 
port in the downstream gate 28B is covered by the opposite side of the 
inner wall of the guide frame as the downstream gate moves between open 
and closed positions, and, in any event, the port in the downstream gate 
moves across the flowway only when the upstream gate is in closed 
position. 
As shown in FIG. 9, the inner faces of the upstream and downstream gates 
are provided with slots 47A and 47B, respectively, on opposite sides of 
the ports therethrough and near their opposite side edges. More 
particularly, slots 47A are adapted to receive wavy springs 48A of such 
configuration as to protrude from the slot, when unstressed, so as to 
engage the opposite sides of the inner wall 37 of the guide frame, thus 
maintaining the end of the upstream seat ring and upstream gate engaged 
with one another, as previously described. Similar wavy springs 48B 
received in the slots 47B are of such configuration as to protrude 
therefrom and thus urge the downstream gate against the inner end of the 
downstream seat ring and thus the outer end of the seat ring against the 
outer end of its recess. 
The piston 30A connected to the upstream gate carries a seal ring 50 
thereabout sealably slidable within the cylinder of the actuator, whereby 
it is urged downwardly in response to the supply of fluid under pressure 
to the cylinder above it, as will be described. Piston 30A is urged 
upwardly to in turn raise the upstream gate by means of a coil spring 51A 
compressed between the lower side of piston 30A and the top wall 26A of 
the bonnet. The piston 30B connected to the downstream gate carries a seal 
ring 50B thereabout for sealably sliding within the upper end of the 
piston 30A whereby it is also urged downwardly by fluid pressure 
thereabove, as will be described. Piston 30B is urged upwardly to move the 
downstream gate upwardly by means of a coil spring 51B compressed between 
the wall 26A of the valve body and a ring 52 disposed between the upper 
end of the coil spring and rods 53 which connect to the piston 30B. More 
particularly, the coil spring 51A is disposed concentrically within the 
coil spring 51B, and the rods 53 extend downwardly through the lower end 
of the piston 30A. 
The cylinder 27 has a head 55b across its upper end with a port 55a through 
which fluid under pressure may be supplied to or exhausted from the 
chamber 55 formed between the head and the upper ends of the pistons 30A 
and 30B. More particularly, the lower end of the chamber is closed by 
means of the seal rings 50A and 50B carried by the pistons, whereby, as 
previously described, fluid pressure within the chamber 55 is effective to 
urge each of the pistons downwardly to move the gates to which they are 
connected toward open positions. 
The rod 31A connecting piston 30A to the upstream gate 28A is sealably 
slidable within a seal ring 56 about an opening through the upper wall 26A 
of the bonnet to which the cylinder is connected. More particularly, the 
rod 31A is hollow so as to closely receive the rod 31B therethrough for 
sealed reciprocation with respect to one another during opening and 
closing movement of the gates. 
As shown in FIG. 9, the connector 32A for connecting the lower end of the 
rod 31A to the upstream gate 28A comprises a body having a cylindrical 
upper end 54 which is interiorly threaded for connection to the lower end 
of the rod 31A and a substantially semi-cylindrical lower end 56 having a 
tee 57 at its lower end for releasably fitting within a T-slot 58 in the 
upper end of gate 28A. The lower semi-cylindrical end 56 of the connector 
32A has an inner cylindrical surface 59 to receive the upper cylindrical 
end 60 of the connector 32B, as shown in FIGS. 1-4. The inner face of the 
lower end 56 of the connector is flat to permit it to move past the inner 
flat face of the lower end 62 of the connector 32B. 
The upper cylindrical end 60 of connector 32B is interiorly threaded for 
connection to the lower threaded end of the rod 31B and is adapted to fit 
within the inner diameter of the upper end 54 of the connector 32A. The 
lower end 62 of the connector 32B has a substantially semi-cylindrical 
shape whose outer arcuate surface is generally aligned with the 
cylindrical surface of the upper end 54 of the connector 32A. Thus, both 
connectors move freely within the cylindrical interior of the bonnet, and, 
as above noted, the inner face of the lower end 62 of connector 32B is 
flat to permit its movement past the oppositely facing flat face of the 
connector 32A during relative reciprocation between them. A tee 63 at the 
lower end of the connector 32B is adapted to fit removably within a T-slot 
64 in the upper end of the gate 28B. 
The cylinder of the actuator has a groove 70 formed thereabout near its 
upper end to receive an expandable and contractible split locking ring 71 
which, when relaxed, occupies the inner position best shown in FIG. 10 
with its outer side is spaced from the inner side of the recess 70 and 
lips 72 and 73 at its upper and lower ends projecting into the cylinder. 
The upper end of the piston 30A has a tapered surface adapted to slide 
over the lower tapered end of the lip 73 of the ring 71 in order to permit 
a groove 74 thereabout to fit over the lip of piston 30A as it moves 
upwardly. On the other hand, the enlarged upper diameter of piston 30B has 
a tapered surface for sliding over the tapered upper end of the lip 72 so 
as to permit it to move past and beneath the lip 72 as piston 30B moves 
downwardly. 
In the closed position of the valve shown in FIG. 1, fluid pressure in the 
chamber 55 above the pistons has, of course, been exhausted to permit both 
of the coil springs 51A and 51B to expand to raise the pistons to their 
uppermost positions. At this time, a shoulder 75 about the rod 31A is 
engaged with a back seat 76 about the lower end of the opening in the top 
wall of the bonnet so as to locate the upstream gate in its closed 
position in which the solid lower end thereof is disposed across the port 
in the downstream seat ring. At this time, the downstream gate is also 
located in its closed position, as shown in FIG. 1, by engagement of the 
upper end 77 of the connector 32B with a seat 78 on the lower end of the 
outer rod 31A. At this stage, the lower lip 73 of the locking ring is 
disposed within the groove 74 about piston 30B to hold it against downward 
movement. 
As fluid pressure is supplied to the chamber 55, the piston 30B is 
initially moved downwardly, while the piston 30A is held against downward 
movement, to compress the coil spring 51B and move the downstream gate 28B 
downwardly toward its open position. As shown in FIG. 2, as the piston 30B 
nears its lowermost position, its upper end engages the upper lip 72 of 
the locking ring to move it outwardly to its expanded position, so that, 
as best shown in FIG. 11, the lower lip 73 of the locking ring is removed 
from the groove 74 to release the piston 30A for movement downwardly to 
compress spring 51A in order to move the upstream gate 28A toward its open 
position, as shown in FIG. 3. Thus, as will be understood from a 
comparison of FIGS. 11 and 3, the piston 30B continues to move downwardly 
to move the downstream gate 28B to its fully open position in which it 
engages the lower end of the cavity, and the piston 30A continues to be 
moved downwardly until the lower end of upstream gate 28A engages the 
lower end of the cavity, thus bringing the port in the gate 28A into 
alignment with the port in the gate 28B as well as the flowway 23 on 
opposite sides of the body cavity to open the valve itself. 
The valve is automatically caused to "fail-safe close" or move back toward 
closed position upon the loss of fluid pressure from the chamber 55. Thus, 
as can be seen from a comparison of FIGS. 3 and 4, the loss of such fluid 
permits the outer coil spring 51A to expand and thus move the piston 30A 
upwardly in order to raise the gate 28A to its upper position wherein the 
solid portion of the gate is disposed across the inner end of the port in 
the upstream seat ring to close it. As the upstream gate approaches its 
uppermost position, in which the surface 75 engages the seat 76, the upper 
tapered end of the piston 30A engages the lower lip 73 to expand the 
locking ring, so that, upon continued upward movement of the piston, the 
locking ring releases the piston 30B so that it may be raised by expansion 
of coil spring 51B. At this time, of course, the piston 30A has moved 
upwardly to a position in which the lower lip 73 of the locking ring 
springs inwardly into groove 74 to hold the piston 30A and thus the 
upstream gate against downward movement until the valve is returned to its 
open position by the supply of pressure fluid to chamber 55. 
From the foregoing it will be seen that this invention is one well adapted 
to attain all of the ends and objects hereinabove set forth, together with 
other advantages which are obvious and which are inherent to the apparatus 
and structure. 
It will be understood that certain features and subcombinations are of 
utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of the 
claims. 
Because many possible embodiments may be made of the invention without 
departing from the scope thereof, it is to be understood that all matter 
herein set forth or shown in the accompanying drawings is to be 
interpreted as illustrative and not in a limiting sense.