Note: Descriptions are shown in the official language in which they were submitted.
2182825
SEPARATELY POWERED TUBE ~ ~T~G
MECHANISM FO~ A GATE VALVE
By
David X. Green
Field of the Invention
The present invention provides a mechanism separate from that
responslble for opening and closing the gate in a gate valve for
shearing off colled or rigid tubing held in the flow passage of the
gate valve.
Ba~o~.d of the Invention
Oil and gas wells are completed with a wellhead having an
arrangement of valves, including those comprising the wellheA~ for
blowout control. In the normal operating position, rigid or coil
tubing extends through the wellhead valves so that the tubing can
be located at the proper depth in the well. Wellhe~ valves
typically are gate valves with a full bore opening onto a flow
passage when the hole in the gate is aligned with the bore through
the valve.
Typically, wellhe~d valves have hydraulic or alr operated
actuators ana assorted mechAn1sms, such as springs, to make sure
that the gate closes, and seals off the wellbore in the event of a
failure. In such gate valves, a spring or similar structure
provides the force nececsary to open and close the valve.
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Before tubing ls extended through the flow passage, nothing
obstructs the gate from closing off the flow passage, and the force
of the spring or similar mechanism of the actuator ls sufficient to
close the gate. After tubing is extended through the flow passage,
the tubing obstructs the flow passage and interferes with gate
closure. The spring return actuator may not be powerful enough to
shear off the tubing and leave an unobstructed area for closing the
gate valve.
Various means to obtain the force required to shear off the
tubing have been employed in the past. These approaches primarily
have involved increasing the size or power of the actuator or the
working pressure of the hydraulic or pneumatic fluid responsible
for actuating the actuator. Unfortunately, increAs~ ng the
operating fluid pressure increases the cost of the actuator h~c~l~æe
the actuator components must safely withstand the higher operating
pressures. In addition, the springs that are required to close the
valve may be larger and heavier than desirable. This can be a
problem, especially in offshore applications, where space is a
primary conc~-rn. A very bulky spring also is difficult to handle
and may present maint~n~nr-~ problems.
An alternate, less cumbersome apparatus ls ne~ed to shear off
tubing extending through the flow passage of a gate valve to permit
closure of the gate valve.
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Summary of the Inventlon
The present invention provides a system for shearing tubing
disposed in the flow passage of a gate valve. The system lncludes
a gulllotlne that is reciprocally movable transverse to the flow
passage. A pressure source communicates with an actuating surface
of the guillotine, and a separate actuator signal~ the pressure
source to exert sufficient pressure upon the actuating surface to
reciprocate the guillotine, forcing an opposed shearing surface of
the guillotine to flow into the flow passage and shear the tubing.
In a preferred embodiment, the pressure source is an explosive
charge.
Brief Description of the Drawings
Fig. 1 illustrates in section a gate valve with the guillotine
of the present invention in the open position and the gate in the
closed position.
Fig. 2 illustrates in section a gate valve with the guillotine
and the gate in the closed position.
Fig. 3 illustrates in section a gate valve with the guillotine
in the closed position and the gate in the open position.
Fig. 4 is a plan view of the guillotine and gate valve of the
present invention.
Detailed DescriPtion of the Invention
The present invention provides a separate mechAn~sm in a gate
valve for shearing off tubing held in the flow passage of the gate
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valve. Preferably, the shearing mechanism is an explosive powered
guillotine.
Fig. 1 shows a spring return actuated gate valve 10 having a
flow passage 12. Mounted ad~acent to and in alignment with the
wall 13 of the flow passage 12 is a guillotine 14 with a shearing
surface 16 substantlally opposed to an actuating surface 18.
Opposite the guillotine 14 is the gate 20 in a closed position.
The flow passage 12 is sealed from the remainder of the gate valve
10 by seals 32. The guillotine 14 is reciprocally and sealingly
mounted within a bore 25 (see Fig. 3) in a complimentary sleeve 26.
The guillotine 14 is sealed using conventional means, for example,
using o-rings 28. Coiled tubing 30 extends through the flow
passage 12.
AdJacent to the actuating surface 18 of the guillotine 14 is
a power source 22 in communication with an actuator 24. In a
preferred embodiment, the power source 22 is an explosive charge,
and the actuator 24 is an igniter. The explosive charge may be any
stAn~Ard explosive charge. The igniter may be any stAn~Ard
lubricator/bleeder with electrical co~nections.
In Fig. 2, the gate 20 is shown, again, in the closed
position. The actuator 24 has ignited the power source 22, forcing
the guillotine 14 against the gate 20, thereby shearing the coiled
tubing 30. Both o-rings 28 continue to maintain the seal between
the guillotine 14 and the sleeve 26, and the seals 32 continue to
2 ~ 82~25
maintaln the seal between the flow passage 12 and the rema~nd~r of
the gate valve 10.
Fig. 3 illustrates the operation of the guillotine 14 when the
gate 20 is in the open position. When the gate 20 is open, the
force exerted on the guillotine 14 by the power source 22 pushes
the guillotine 14 onto the coil tubing 30 and cuts it cleanly.
This allows the coil tubing 30 to drop into the wellbore and
permits the spring to move the whole gate 20 to the "closed"
position, thereby permitting the gate 20 and seals 32 to mate and
seal the wellbore.
Referring to Fig. 4, the guillotine 14 is seen in plan view
ad~acent to the flow passage 12. 0-rings 28 maintain the seal
between the guillotine 14 and the sleeve 26. A vent 34 may be
provided between the last o-ring 28 and the pressure source 22 as
a safety valve to release excesc pressure that may result from
actuatlng the power source. Of course, the vent 34 should release
only excess pressure, and care should be taken to retain sufficient
pressure within the bore 25 behind the actuating surface 18 of the
guillotine 14 to ensure that the guillotine 14 shears any tubing in
the flow passage 12.
The connection between the actuator 24 and the power source 22
is seen in more detail in Fig. 4. In a preferred embodiment, the
connection 36 ls an electrical connection that is integral with a
plug 38 that may be inserted into the end of the bore 25 and
sealingly engaged in the sleeve 26. In a preferred embodiment,
2 1 82825
.
shown ln Flg. 4, the plug 38 and the bore 25 are provided wlth
complimentary threads for threaded engagement between the plug 38
and the bore 25.
The guillotine 14 may be installed in a suitable gate valve 10
by m~ch~ n~ ng lnto the gate valve 10 a bore 25 slzed to form a
compllméntary sleeve 26 for the guillotlne. The gulllotine 14,
surrounded by the neces-sAry seals 28, then may be inserted into the
bore 25, and the plug 38 should be engaged in the bore 25, e.g., by
thr~ n~.
The explosive charge or other power source 22 should be
capable of exerting sufficient force on the actuatlng surface 18 of
the guillotine 14 to propel the guillotine 14 through any tubing
extending through the flow passage 12 untll the shearlng surface 16
of the guillotine 14 impacts the gate 20. Other power sources 22
also may be used as long as they are capable of exerting sufficient
force on the actuating surface 18 of the guillotine 14 to shear the
tubing. An alternate power source 22 would be chemical reactants
that react with one another to result in sufficient thermal
PYp~nslon of the alr ad~acent to the actuatlng surface 18 to propel
the gulllotine 14 through the tubing in the flow passage 12.
Persons of skill in the art will appreciate that many
modifications may be made to the embod~ents described herein
wlthout departing from the spirit of the present invention.
Accordingly, the embodiments described herein are illustrative only
and are not int~nd~ to limit the scope of the present invention.
