Valves and valve actuation – Fluid actuated or retarded – Fluid and non-fluid actuators
Reexamination Certificate
2001-12-26
2003-12-09
Kaufman, Joseph A. (Department: 3754)
Valves and valve actuation
Fluid actuated or retarded
Fluid and non-fluid actuators
C251S291000, C222S334000, C222S504000
Reexamination Certificate
active
06659419
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a modular hydraulic actuator for a valve.
BACKGROUND
Hydraulically actuated valve assemblies are often used in the oil industry, among other uses, to control the flow of oil. In a typical assembly
20
having a double-acting hydraulic actuator
22
for example, as shown in
FIGS. 1 and 2
, a piston
24
inside the actuator
22
is driven on either side by pressurized hydraulic fluid entering either of two hydraulic fluid ports
26
,
28
. Pressurized hydraulic fluid entering the cylinder
30
through the upper port
26
causes the piston
24
to move down (away from the upper port
26
). Because an operating stem
32
is coupled to the piston
24
, downward movement of the piston
24
causes downward movement of the operation stem
32
, which in turn causes downward movement of a gate
34
coupled to the other end of the operating stem
32
. Similarly, pressurized hydraulic fluid entering the cylinder
30
through the lower port
28
causes the piston
24
, as well as the operating stem
32
and gate
34
, to move upward.
Therefore, one end
36
of the operating stem is exposed to pressure within the cylinder
30
from the pressurized hydraulic fluid during actuation of the valve
34
, which may be as high as 3000 psi, for example. The other end
38
of the operating stem
38
is exposed to pressurized fluids flowing through the valve
34
, which can be as high as 30,000 psi. The operating stem is reciprocating up and down as valve opens and closes. The wear of the stem packing is directly proportional to the number of open/close cycles the valve experiences. The seals are non-metallic and therefore, experience quick wear. Thus, these seals
40
around the operating stem
32
need replacement quite often during the life of the assembly
20
.
FIG. 2
shows an exploded view of the assembly
20
of FIG.
1
. To access the seals
40
around the operating stem
32
at the lower portion of the actuator
22
shown in
FIGS. 1 and 2
(e.g., for replacing the seals
40
), at least the following steps are required (the order may vary). The six nuts
42
and corresponding studs
44
located about the hydraulic cylinder
30
are removed. Then the hydraulic cylinder
30
is removed and separated from the piston
24
, which remains attached to the operating stem
32
. A set screw
46
holding a centering pin
48
on the upper end
36
of the operating stem
32
is loosened or removed. The centering pin
48
is removed from the upper end
36
of the operating stem
32
. The piston lock nut
50
, which retains the piston
24
on the operating stem
32
, is removed. The piston
24
is unscrewed and removed from the upper end
36
of the operating stem
32
. Finally, the packing gland
52
, which holds the stem packing
54
and other seals
40
in place, is unscrewed. With the packing gland
52
unscrewed and/or removed, the stem packing
54
and the seals
40
held by the packing gland
52
can be accessed and replaced, if needed.
Note that to get to the step when the packing gland
52
is unscrewed, the piston
24
had to be separated from the cylinder
30
. Therefore, the piston rings or seals that provide a seal between one side of the piston
24
in the cylinder
30
and another become unseated when the piston
24
is separated from the cylinder
30
. Thus, upon reassembly of the actuator
22
, the piston rings and/or seals must be reseated or may even need replacement after being unseated. Reseating piston rings and seals when installing a piston
24
into a cylinder
30
is often a cumbersome procedure requiring special tools to ensure that the piston rings and seals seat properly and are not damaged in the process. Therefore, because accessing the packing gland
52
and its associated seals
40
in existing hydraulically actuated valve assemblies unnecessarily requires the piston
24
to be removed from the cylinder
30
, there is a need for a hydraulically actuated valve assembly that allows the packing gland
52
and its associated seals
40
to be accessed without requiring the actuator
22
to be disassembled or without requiring that the piston
24
be removed from the cylinder
30
.
Also, note that accessing the packing gland
52
and its associated seals
40
for replacement in the existing hydraulically actuated valve assembly
20
requires numerous steps and the removal of numerous parts. Typically, the packing gland
52
and its associated seals
40
are replaced in the field (e.g., on an oil rig platform). Because the environment in the field is not always conducive to the disassembly and reassembly of a complex device and parts can be easily lost, there is a need for a hydraulically actuated valve assembly that allows the packing gland
52
and its associated seals
40
to be accessed more easily, faster, and requiring fewer components of the actuator to be disassembled in the process.
Furthermore, in the field, often as many as a dozen or more hydraulically actuated valve assemblies may receive maintenance at one time. Thus, if numerous hydraulically actuated valve assemblies are disassembled and the parts for these get mixed together or mixed-up, the likelihood that a previously seated piston assembly will match or mate with a different cylinder may be low. A mismatch between a used piston assembly and a used cylinder can affect the performance of the actuator, and it may make reassembly difficult. Therefore, it would be better in most cases not to separate the piston assembly from its cylinder if it is not needed.
In addition, there are the economic considerations. The time that it takes to disassemble a hydraulically actuated valve assembly for maintenance requires production downtime, as well as labor time for skilled technicians in the field. Furthermore, there is cost involved with supplying special tools and training for these technicians to perform their tasks. Therefore, it is desirable to have a hydraulically actuated valve assembly where the packing gland and its associated seals can be more quickly and more easily accessed for maintenance, without the need to remove the piston from the cylinder.
BRIEF SUMMARY OF THE INVENTION
The problems and needs outlined above are addressed by the present invention. In accordance with one aspect of the present invention, a modular portion of a hydraulic valve actuator is provided. The modular actuator portion comprises a hollow cylinder portion, a piston, a cylinder head portion, and a piston retainer portion. The cylinder portion has a first end and a second end. The piston is located in the cylinder portion, and the piston is adapted to slidably fit in the cylinder portion. The piston has a slotted portion formed therein. For example, the slotted portion of the piston may have a generally T-shaped cross-section. The cylinder head portion closes the second end of the cylinder portion. The piston retainer portion is located at an interior surface of the cylinder portion and at the first end of the cylinder portion. Part of the piston retainer portion extends radially inward relative to the interior surface of the cylinder portion farther than a portion of the piston such that the piston cannot slide completely past the piston retainer portion. Thus, the piston retainer portion keeps the piston within the cylinder portion when the modular actuator portion is operably assembled.
In other embodiments, the modular actuator portion may further comprise a cylinder retainer portion and/or a locking screw. The cylinder retainer portion is located along an outside surface of the cylinder portion and at the first end of the cylinder portion. The cylinder retainer portion has a plurality of screw holes formed therein. The locking screw extends at least partially through the cylinder head portion and is threadedly coupled to the cylinder head portion. The locking screw is adapted to press against the piston with an end of the locking screw to displace the piston when needed.
In other embodiments, the modular actuator portion may further comprise a handle, one or more hydraulic flui
HP&T Products, Inc.
Kaufman Joseph A.
Slater & Matsil L.L.P.
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