Manual override for hydraulic gate valve actuators

A double acting manual override mechanism for the hydraulic actuator of a subsea gate valve, and a visual indicator device for indicating the gate position. The gate is normally held open by hydraulic pressure and is moved by a spring to a fail closed position in the event of a malfunction. The override includes a drive nut threaded onto the valve stem and a drive sleeve which is telescoped on the drive nut and connected therewith by a series of splines. Spaced apart abutment surfaces are provided on the sleeve to limit axial movement of the drive nut on the valve stem in both directions. Rotation of the sleeve by means of an adapter is translated into rotation of the drive nut which contacts one of the abutment surfaces and thereafter effects axial movement of the valve stem to open or close the gate. The indicator device includes a watertight, transparent housing within which an indicator disc moves in response to movement of the gate.

BACKGROUND OF THE INVENTION 
This invention relates generally to valve actuators and deals more 
specifically with a manual override mechanism for a gate valve actuator, 
especially the hydraulic actuator of a subsea gate valve. The invention is 
directed additionally to a visual indicator device that provides a visual 
indication of the position of the gate. 
Subsea gate valves are normally equipped with hydraulic actuators which 
control the position of the gate remotely from the surface. Typically, the 
gate is maintained in an open position by hydraulic fluid directed against 
a piston of the actuator. If an emergency occurs so as to cause a loss of 
fluid pressure in the actuator, the combined force of a spring and thrust 
of the valve stem moves the gate to a fail closed position. Conversely, 
some gates are held in a normally closed position by the fluid pressure 
and are moved to a fail open position in the event of a loss of hydraulic 
pressure. As still another alternative, the valve may be a 
fail-in-position type which is maintained in the position it occupies at 
the time of failure. With each type of valve, it is usually necessary or 
desirable to provide a manual override mechanism which permits the gate to 
be manually opened and closed. 
In the past, a telescoping type override has been employed in order to 
minimize the size of the unit because space limitations take on primary 
importance in connection with subsea valves. This telescoping override 
arrangement is the closest known prior art to the present invention and 
includes a sleeve telescoped over a drive nut which is threaded onto the 
valve stem. A splined connection between the sleeve and drive nut 
translates rotation of the sleeve into rotation of the drive nut and 
consequent threaded advancement of the valve stem to open or close the 
gate. Rotation of the sleeve is facilitated by an adapter which is 
connected with the sleeve and which is formed to conveniently receive a 
wrench or handwheel or another type of tool. To provide for subsequent 
movement of the gate in an opposite direction in the event of a spring 
failure, a handwheel located on the opposite end of the valve may be 
turned to engage a secondary override mechanism. The secondary override 
acts directly against the gate to push it in a direction opposite the 
direction it is moved by the primary override. 
Although this telescoping type of override mechanism has been generally 
satisfactory for subsea use, it has not been wholly without problems. The 
second override necessarily adds to the overall length of the valve, which 
is a significant drawback with subsea valves and with any other valve used 
in an environment where size is an important factor. Also, since the two 
override mechanisms are located on opposite ends of the valve body, the 
diver or other worker operating the override must have access to both ends 
of the valve and must know which handwheel to operate in a particular 
situation. The latter problem has been compounded because of the lack of 
any type of indicator to provide the diver with an indication of the gate 
position. The second override has the further disadvantage of requiring 
additional bearings, packing, seals, and other components which increase 
the cost and complexity of the valve. 
SUMMARY OF THE INVENTION 
The present invention is an improvement over the telescoping type manual 
override which has been used in the past, and its primary goal is to 
substantially eliminate the problems associated with existing manual 
overrides for hydraulically actuated gate valves. Another important object 
of the invention is to provide a visual indicator which is watertight and 
which is readily visible to a diver in order to give him an indication of 
the gate position. 
In accordance with the invention, a sleeve is telescoped over a drive nut 
which is threaded onto the stem of a gate valve at a location beyond the 
hydraulic actuator which normally operates the gate. A splined connection 
between the sleeve and the drive nut permits the valve stem and drive nut 
to move axially in normal hydraulic operation without moving the sleeve 
axially. However, when the override is engaged and the sleeve is turned by 
means of a hexagonal adapter secured to it, the drive nut is turned and 
eventually engages one of a pair of abutment surfaces which limit movement 
of the drive nut axially on the stem in both directions. Continued 
rotation of the adapter after the drive nut has contacted one of the 
abutments results in longitudinal advancement of the valve stem in 
threaded fashion to open or close the valve, depending upon the direction 
of rotation of the adapter. The override mechanism is double acting in 
that it is able to both open and close the valve. At the same time, the 
override is compact by virtue of the telescopic arrangement of its 
components. 
The invention further provides a visual indicator which includes a 
transparent, watertight cylinder that closely receives an indicator disc 
carried on a rod forming an axial extension of the valve stem. A metal 
outer housing which surrounds the transparent cylinder is provided with 
cutouts or windows so that the disc is readily visible to provide the 
diver with a visual indication of the position of the gate. A variable 
volume bellows prevents the pressure in the transparent cylinder from 
fluctuating appreciably due to extension and retraction of the indicator 
rod into and out of the cylinder.

Referring now to the drawings in more detail and initially fo FIG. 1, 
numeral 10 generally designates a gate valve constructed in accordance 
with a preferred embodiment of the present invention. Valve 10 is intended 
primarily to be used in a subsea environment, although it is suited for 
use in various other environments, particularly those in which compactness 
is important. The valve 10 includes a valve body 12 having an inlet 
passage 14 and an outlet passage 16 which cooperate to present a flow 
passage extending through the valve body. A valve chamber 18 is formed 
between the inlet and outlet passages 14 and 16. A plate 20 is secured to 
the bottom of valve body 12 by threaded studs 22 and nuts 24. A seal ring 
element 26 provides a tight seal between valve body 12 and cover plate 20. 
A slab type gate 28 is mounted in valve chamber 18 for movement between an 
open position and a closed position relative to the flow passage presented 
by passages 14 and 16. In the closed position shown in FIG. 1, gate 28 
blocks flow between passages 14 and 16. The gate has a port 30 which 
aligns with passages 14 and 16 when the gate is moved downwardly to its 
open position wherein fluid is able to pass through the flow passage. A 
pair of annular valve seats 32 are mounted in seat pockets formed adjacent 
to the valve chamber 18 to provide seats for gate 28. A short stem 34 
extends upwardly from gate 28 into a bonnet 36 which is secured to the top 
of the valve body by screws 38. A seal ring 40 provides a seal between 
body 12 and the bonnet 36. 
With continued reference to FIG. 1, an elongate valve stem 42 forms an 
upward axial extension of stem 34. Stem 42 is internally threaded and is 
screwed onto mating external threads formed on the lower stem 34. A 
transverse pin 44 secures the connection between stems 34 and 42. Packing 
46 is disposed between stem 42 and the central bore through bonnet 36 
which receives the stem. Packing 46 includes a plurality of packing rings 
which are held in place by a packing retainer 48 which is secured to 
bonnet 36 by screws 50. 
Valve stem 42 extends upwardly into a cylinder 52 which forms part of the 
hydraulic actuator that normally controls the operation of gate 28. 
Cylinder 52 is supported on top of bonnet 36 and is covered at the top by 
a cylinder cap 54. The cylinder cap 54 is secured on top of cylinder 52 by 
tie rods 56 which extend between the cylinder cap and valve bonnet. The 
lower end of each rod 56 is threaded into bonnet 36, and the tie rods 
receive nut 58 at their top ends to hold cap 54 in place. A cylindrical 
metal shroud 60 surrounds cylinder 52 a spaced distance outwardly thereof. 
A plurality of screws 62 mount shroud 60 to bonnet 36 and to cylinder cap 
54. Screws 62 also serve to secure a flexible bladder 64 in place between 
cylinder 52 and shroud 60. Bladder 64 serves to compensate for the effects 
of the ambient pressure when the valve is used at a subsea location. 
The valve actuator includes a piston 66 which is carried on valve stem 42 
at a location within cylinder 52 and which is sealed against the internal 
wall of the cylinder by seal rings 67. Piston 66 is held in place on the 
valve stem by a nut 68 and a lock nut 70 which are threaded onto the stem 
and which receive screws 72. An O-ring 74 effects a seal between piston 66 
and stem 42. A piston stop 76 is sleeved onto valve stem 42 and held 
against the underside of piston 66. The piston stop 76 engages the top 
surface of the packing retainer 48 in order to limit downward movement of 
the piston to a position wherein port 30 of gate 28 aligns with passages 
14 and 16. 
A pair of compression springs 78 and 80 are nested one within the other 
within cylinder 52 and act upwardly on piston 66 to bias the piston 
upwardly toward the position shown in FIG. 1, wherein gate 28 is in its 
closed position. A pressure chamber 82 is formed within the top portion of 
cylinder 52 above piston 66 to receive hydraulic fluid under pressure 
through a passage 84 which is formed through cylinder cap 54. The 
hydraulic fluid is supplied by a suitable source controlled from the 
surface. If the fluid pressure in chamber 82 is sufficiently high, it 
overcomes the force of springs 78 and 80 and forces piston 66 downwardly 
until gate 28 is in its open position. It should be apparent that the 
valve is of the fail closed type because springs 78 and 80 close gate 28 
in the event of a loss of fluid pressure in chamber 82, as may be caused 
by a malfunction. 
In accordance with the present invention, a double acting manual override 
mechanism is provided to permit manual opening and closing of gate 28. 
Referring to FIG. 2 in particular, the cylinder cap 54 is provided with a 
central vertical bore 86 of generally cylindrical shape through which the 
top portion of valve stem 42 extends. The portion of the valve stem 
extending through bore 86 is threaded as indicated at 42a. An elongate 
drive nut 88 of generally cylindrical shape has internal threads which 
mate with the external threads 42a of stem 42. Drive nut 88 is thus 
threaded onto valve stem 42 such that rotation of the drive nut effects 
relative longitudinal movement between it and the valve stem 42. Drive nut 
88 receives a generally cylindrical drive sleeve 90 which is fit on the 
drive nut in a telescopic or sleeved relationship thereto. Sleeve 90 has 
at its lower end an outwardly projecting flange 90a which is received in a 
counterbore 86a at the bottom of bore 86. A bearing 91 is mounted in 
counterbore 86a above flange 90a to permit the sleeve to be easily rotated 
with respect to cylinder cap 54. A plurality of packing rings 93 are 
disposed between the outside surface of sleeve 90 and the wall of bore 86. 
As best shown in FIG. 4, drive nut 88 has a plurality of splines 88a formed 
integrally on its outside surface. Splines 88a extend axially of the drive 
nut along its entire length and are closely received in mating grooves 90b 
formed in the inside surface of sleeve 90. Grooves 90b extend 
longitudinally of sleeve 90 along the majority of its length. Sleeve 90 is 
considerably longer than drive nut 88, and the grooves 90b are somewhat 
longer than the splines 88a. It should be apparent that the splined 
connection between drive nut 88 and drive sleeve 90 translates any 
rotation of sleeve 90 into corresponding rotation of nut 88. However, the 
axial movement of nut 88 that occurs during normal operation of the valve 
takes place withing sleeve 90 and without imparting any axial movement to 
sleeve 90. 
A plate 92 is secured to the bottom of sleeve 90 by screws 94 which are 
threaded through the plate and into the flange 90a of the drive sleeve. 
Plate 92 has a central opening to permit passage of valve stem 42 
therethrough. The upper surface of plate 92 forms a flat shoulder 92a 
which serves as a lower abutment surface to limit downward movement of 
drive nut 88 on valve stem 42. When the limiting position is reached, the 
bottom end 88b of drive nut 88 contacts shoulder 92a to prevent further 
downward movement of the drive nut. Upward movement of nut 88 on stem 42 
is limited by an upper abutment surface 96 formed on the bottom of a solid 
top end portion 98 of sleeve 90. The flat upper abutment surface 96 faces 
downwardly, while shoulder 92a faces upwardly and is spaced well below 
surface 96. The top end 88c of drive nut 88 engages surface 96 to prevent 
further upward movement of nut 88 after its limiting position is reached. 
The abutment surfaces 92a and 96 are spaced apart a distance considerably 
greater than the distance gate 28 moves between its open and closed 
positions so that drive nut 88 does not contact the abutment surfaces 
during normal operation of the gate effected by the hydraulic actuator. 
A hexagonal adapter 100 is secured to the outside of sleeve 90 by a pair of 
keys 102 which are fitted in grooves of adapter 100 and sleeve 90. The 
adapter 100 is mounted on top of cylinder cap 54 and is received at its 
bottom end on a thrust washer 104 mounted in a counterbore in the upper 
portion of bore 86. An O-ring 106 provides a seal between adapter 100 and 
cylinder cap 54, while another O-ring 108 seals between the adapter and 
sleeve portion 98. As shown in FIG. 3, adapter 100 is hexagonal in section 
in order to conveniently receive a wrench or power operated tool (not 
shown). Alternatively, a handwheel (also not shown) may be attached to 
adapter 100 and turned to rotate the adapter 100 and sleeve 90 through the 
connection provided by keys 102. 
The present invention is also directed to a visual indicator device which 
provides a visual indication of the position of gate 28. A rigid metal 
outer housing 110 of the visual indicator is generally cylindrical in 
shape and has internal threads on its bottom portion which are screwed 
onto mating male threads formed on the top of sleeve portion 98. Outer 
housing 110 and sleeve portion 98 are sealed by O-rings 112 and 114, while 
a set screw 116 secures the threaded connection between housing 110 and 
sleeve 90. The metal outer housing 110 closely surrounds an inner 
indicator housing which is in the form of a transparent cylinder 118. The 
cylinder 118 is a watertight structure and is sealed to outer housing 110 
by an O-ring 120. The top portion of outer housing 110 is internally 
threaded in order to receive an externally threaded cylinder cap 122 which 
is screwed down onto outer housing 110 and against the top of cylinder 
118. A set screw 124 is threaded into housing 110 and against cap 122, and 
an O-ring 126 provides a seal between the cylinder and cylinder cap. The 
cylinder cap 122 has a central vertical passage 128 which provides 
communication between the watertight chamber or compartment defined within 
cylinder 118 and a bellows 130 which is mounted on top of cap 122. The 
bellows 130 has an expansible and contractable internal chamber which 
connects with passage 128 and which serves to compensate for volume 
changes in cylinder 118, as will be explained in more detail. Bellows 130 
is braised to cap 122 as indicated at 132. A rigid metal cover 134 is 
fitted closely around the bellows and is secured to cap 122 by a set screw 
136. 
The visual indicator device includes a rod 138 which is secured to the top 
end of valve stem 42 in a manner to form an upward axial extension 
thereof. The lower end of rod 138 fits in an opening in the top end of 
valve stem 42 and is secured therein by a transverse pin 140. Rod 138 
projects upwardly from stem 42 through a central passage formed in sleeve 
portion 98 and through an opening in the bottom of housing 110. A 
plurality of GT rings 142 seal the rod with sleeve portion 98 while 
permitting it to reciprocate back and forth with respect thereto. The 
upper end of rod 138 is located within cylinder 118 and carries a disc 144 
which serves as an indicator element to indicate the position of gate 28. 
Disc 144 is received on the top end of rod 138 and is secured thereon by a 
shoulder screw 146. Disc 144 has approximately the same diameter as the 
inside of cylinder 118 and has a groove on its periphery which carries a 
wiper ring 148 that firmly contacts the internal wall of cylinder 118. 
Disc 144 has a plurality of openings 150 passing through it to provide 
fluid communication between its upper and lower surfaces. 
As best shown in FIG. 6, the outer housing 110 of the indicator has a pair 
of cutouts of windows 152 formed through it so that the transparent 
cylinder 118 and indicator disc 144 are readily visible from the exterior 
of the valve. Windows 152 are diametrically opposed on housing 110, and 
each window extends through an arc of approximately 90.degree.. 
Accordingly, a diver is provided with visual access to disc 144 from 
either side of the indicator device. 
In normal operation of the valve, pressurized hydraulic fluid is forced 
into chamber 82 through passage 84 in order to move piston 66 downwardly 
such that gate 28 is held in its open position. In the event of a 
malfunction cutting off fluid pressure, chamber 82 is relieved and springs 
78 and 80 push piston 66 upwardly, thereby moving gate 28 to the fail 
closed position shown in FIG. 1. It should be noted that during such 
normal operation of the valve, drive nut 88 is able to move upwardly and 
downwardly within and relative to sleeve 90 without contacting the 
abutment surfaces 92a or 96. 
In order to override springs 78 and 80 and move gate 28 manually to its 
open position, adapter 100 can be turned by a diver in the appropriate 
direction, such as with a wrench, a power tool, or a handwheel mounted on 
the adapter. Rotation of adapter 100 is translated by keys 102 into 
rotation of drive sleeve 90, which in turn rotates drive nut 88 due to the 
splined connection between the sleeve and the drive nut. Such rotation of 
drive nut 88 initially causes it to move upwardly in threaded fashion on 
valve stem 42 until the top end 88c of the drive nut contacts the upper 
abutment surface 96 (see FIG. 2), whereupon further upward movement of nut 
88 is precluded. Continued rotation of nut 88 after its limiting position 
is reached causes valve stem 42 to move downwardly in threaded fashion 
against the force applied to piston 66 by springs 78 and 80. Consequently, 
valve stem 42 is moved downwardly to effect movement of gate 28 downwardly 
and eventually to its open position. 
Ordinarily, springs 78 and 80 return gate 28 to the closed position if the 
override mechanism is subsequently backed off by turning adapter 100 in an 
opposite direction so as to permit stem 42 to move upwardly with respect 
to drive nut 88. However, if springs 78 and 80 should break or otherwise 
fail, the gate will remain open when the override is initially backed off. 
To close the gate in this situation, adapter 100 is turned in the 
appropriate direction a sufficient number of times to thread drive nut 88 
downwardly on valve stem 42 until the bottom end 88b of the drive nut is 
moved into contact with the lower abutment surface or shoulder 92a, 
whereupon further downward movement of the drive nut is precluded. 
Continued rotation of adapter 100 causes valve stem 42 to move upwardly 
due to its threaded relationship with drive nut 88. Such upward movement 
of the valve stem eventually moves gate 28 to its fully closed position. 
It should be noted that the sleeved or telescopic relationship among 
adapter 100, sleeve 90, and drive nut 88 results in a compact arrangement 
of the components of the override mechanism. In addition, normal hydraulic 
actuation of the valve can take place without interference from the 
override mechanism and without movement of sleeve 90 or the other parts of 
the override except nut 88, which moves freely up and down within sleeve 
90. Accordingly, the override is particularly well suited for use with 
subsea gate valves, although it is equally well suited for use with any 
type of valve employed in a situation involving space limitations. 
As gate 28 is moved between the opened and closed positions, either by 
means of the hydraulic actuator or the manual override, indicator disc 144 
moves up and down in direct proportion to the gate movement, by reason of 
its rigid connection with the valve stem. Therefore, when disc 144 is near 
the upper end of cylinder 118 as shown in FIG. 2, it provides a visual 
indication that the gate is closed. Conversely, when disc 144 is near the 
bottom of cylinder 118 as shown in FIG. 5, an indication is given that the 
gate is in its open position. The diver or other worker operating the 
override can thus simply sight through one of the windows 152 and notice 
the position of disc 144 to determine whether the gate is open or closed. 
It is contemplated that cylinder 118 may be provided with calibration 
marks labeled to indicate whether the gate is fully open, fully closed, or 
at any of a variety of intermediate positions between opened and closed. 
Cylinder 118 is watertight in order to prevent the ambient pressure from 
affecting operation of the indicator device. The openings 150 through disc 
144 permit the air within cylinder 118 to pass between opposite sides of 
the disc without being compressed as the disc moves upwardly and 
downwardly within the cylinder. During operation of the device, rod 138 is 
extended into and retracted out of the fluid tight cylinder 118, thereby 
varying the open volume within the cylinder. As this occurs, the variable 
volume chamber within bellows 130 expands and contracts in order to 
compensate for the volume change while avoiding an undue buildup of 
pressure within the indicator device which could adversely affect its 
operation.