Rope tensioning system for drilling rig

A hydraulic tensioning system is associated with a wire rope feed system of a drilling rig for applying tension to the hoist and pulldown ropes during hoist and pulldown operations. The hydraulic tensioning system includes a hydraulic tensioning circuit with a hoist hydraulic circuit directing hydraulic fluid to a hoist actuator applying tension to the hoist wire rope and a pulldown hydraulic circuit directing hydraulic fluid to a pulldown hydraulic actuator applying tension to a pulldown wire rope. A hydraulic control valve can selectively direct flow to the hoist and pulldown hydraulic circuits.

TECHNICAL FIELD

This patent disclosure relates generally to drilling rigs for drilling a hole into the earth and, more particularly, to a wire rope system that can move a rotary head with respect to a mast of the drilling rig.

BACKGROUND

Drilling rigs are integrated systems used to drill holes into the ground of the earth. Drilling rigs are commonly used in the petroleum and gas industry, but may also be used for developing water wells, mineral excavation, and other uses. Drilling rigs typically include a mast that can be positioned vertically with respect to the surface of the ground to be drilled and a rotary head that can be vertically moved along the mast. The rotary head includes a driver that can rotate with respect to the rotary head body. The driver may be coupled to a drill string that is an elongated column or drill pipe of multiple string segments that are attached at the distal end to a drill bit. When the driver is rotated, it transmits torque through the drill string to the drill bit that cuts into the surface and subsurface of the earth.

To vertically move the rotary head with respect to the mast, the drilling rig includes a wire rope feed system formed of wire ropes that may be hydraulically actuated to pull down (move vertically downward) and hoist (move vertically upwards) the rotary head. In operation, the rotary head is pulled down over the length of the mast, decoupled from the drill string, and hoisted back up the length of the mast. Once hoisted, another string segment is coupled between the rotary head and the rest of the drill string. The rotary head is then pulled down again thereby feeding the drill string into the ground.

The wire ropes of the wire rope feed system may stretch and elongate during pulldown and hoist operations due to the forces applied. The stretching and elongation may be dynamic and occur during a particular pulldown or hoist operation and recover thereafter or may be permanent such that the overall length of the wire ropes after a duration of use may be greater than when the wire ropes were originally installed on the drilling rig. Because the wire rope feed system coordinates movement of the rotary head, stretching and elongation of the wire ropes may adversely affect operation of the drilling rig. To compensate for the slack created by the stretching and elongation of the wire ropes, the drilling rig may be equipped with a tensioning system that applies tension to the wire ropes. The present application is directed to such a hydraulic actuated tensioning system for a drilling rig.

SUMMARY OF THE DISCLOSURE

The disclosure provides a rotary drilling rig for drilling a hole into the earth. The drilling rig includes a rig frame and a mast mounted to the rig frame. A rotary head is movably supported along the mast and operatively coupled to and adapted to rotate a drilling string with respect to the work surface. To vertically move the rotary head with respect to the mast, the drilling rig includes a wire rope feed actuator and a wire rope feed system operatively connecting the rotary head with the wire rope feed actuator. The wire rope feed system includes a hoist wire rope operatively associated with a hoist tensioning actuator and connected at a hoist rope end to the rotary head and a pulldown wire rope operatively associated with a pulldown tensioning actuator and connected at a pulldown rope end to the rotary head. To direct hydraulic fluid to the hoist and pulldown tensioning actuators, the drilling rig also includes a hydraulic tensioning circuit. The hydraulic tensioning circuit can include a hydraulic control valve in fluid communication with and configured to selectively direct hydraulic fluid to the hydraulic tensioning circuit and to the wire rope feed actuator.

DETAILED DESCRIPTION

Now referring to the figures, wherein whenever possible like reference numbers refer to like elements, there is illustrated a mobile drilling rig100that can form holes into the work surface102and the underlying subsurface of the earth for oil and gas extraction, mineral procurement, well formation, and other uses. In the illustrated embodiment the drilling rig100is mobile and can move with respect to the work surface102; however, the present disclosure is also applicable to fixed drilling rigs, offshore drilling rigs or platforms, and other configurations. The illustrated embodiment of the drilling rig100includes a rig frame104that is supported on a plurality of propulsion devices106that contact the work surface102. The propulsion devices106may be continuous tracks or crawler tracks that can translate with respect to the rig frame104thereby moving the drilling rig over the work surface102or the propulsion devices may be rotating pneumatic wheels or, as stated above, the drilling rig may be stationary and fixed in location. To power the propulsion devices106and other systems of the drilling rig100, a motor108is disposed on the rig frame104. The motor108may be an internal combustion engine or an electrical motor that receives electric power from a remote source.

The drilling rig100can include a mast110that is an erect structure that can be vertically positioned with respect to the work surface102. The mast110may extend between a top or crown112that is vertically elevated above the rig frame104and a base114that is located proximate to the work surface102. The mast110can be assembled as a truss made from a plurality of metal beams and bars interconnected together to form a rigid structure capable of standing upright in the vertically elevated position. In an embodiment, the mast110can be pivotally coupled to the rig frame104so that the mast110can be raised and lowered between the vertical and non-vertical positions via a lift cylinder116. When the mast110is in the raised position, the drilling rig100is configured for a drilling operation and when the mast is lowered, the drilling rig100is configured for a traveling operation.

To accommodate one or more human operators for conducting drilling operations, an onboard operator station118may be accommodated on the rig frame104. Located within the operator station118can be various operator control devices119such as levers, pedals, wheels, displays, and the like. In the illustrated embodiment, the operator station118can be an enclosed space but, in other embodiments, the operator station118may be located exteriorly. Furthermore, in possible embodiments, the drilling rig100can be configured for remote operation with the operator station118and the operator control devices119located off board of and remote from the drilling rig100.

Referring toFIG.2, there is illustrated an embodiment of the drilling system120of the drilling rig100. The drilling system120may include a rotary head122that is guided by and vertically movable along the mast110with respect to the work surface102. The rotary head122can be operatively coupled to an elongated drill string124at the distal end of which may be a drill bit126for boring into the work surface102and the subsurface underneath. The drill string124can be assembled from a plurality of string sections128that can be coupled together to adjust the length of the drill string124. To rotate the drill string124, the rotary head122can include one or more hydraulic motors130that can be operatively associated with a hydraulic system of the drilling rig. The hydraulic motors130can receive pressurized hydraulic fluid from the hydraulic system and can convert the fluid pressure into mechanical rotational motion or torque to rotate a driver132disposed in the body134of the rotary head122and coupled to the drill string124, thereby rotating the drill string124with respect to both the rotary head122and the work surface102.

To move the rotary head122with respect to the mast110, the drilling system120includes a wire rope feed actuator150that includes a disc-shaped feed actuator piston152disposed within a tubular feed actuator cylinder154. The feed actuator piston152can separate the feed actuator cylinder154into an upper chamber156and a lower chamber158. The wire rope feed actuator150can be fluidly coupled to the hydraulic system of the drilling rig100to receive pressurized hydraulic fluid to either the upper chamber156or the lower chamber158of the feed actuator cylinder154. The feed actuator piston152can be fixedly connected with the mast110so that when hydraulic fluid is introduced, for example, into the upper chamber156, the feed actuator cylinder154is forcibly moved upwards with respect to the mast110. Similarly, when hydraulic fluid is introduced into the lower chamber158, the feed actuator cylinder154is forcibly move downwards with respect to the mast110.

In the illustrated embodiment, to fix the feed actuator piston152to the mast110and enable vertical motion of the feed actuator cylinder154, the wire rope feed actuator150can include a first feed actuator piston rod160joined to the feed actuator piston152that extends axially upwards through the upper chamber156of the hollow feed actuator cylinder154and can be fixedly connected proximate to the crown112of the mast110. Likewise, a second feed actuator piston rod162joined to the feed actuator piston152can extend axially downwards through the lower chamber158of the hollow feed actuator cylinder154and can be fixedly connected proximate to the base114of the mast110. Accordingly, the relative vertical position of the feed actuator piston152with respect to the mast110is rigidly fixed. The feed actuator cylinder154therefore acts as a free body such that introduction of hydraulic fluid into either the upper chamber156or the lower chamber158of the wire rope feed actuator150results in vertical movement of the feed actuator cylinder154generally between the mast crown112and the mast base114. In another embodiment, the feed actuator cylinder154may be fixed with respect to the mast110and the feed actuator piston152and the first and second feed actuator piston rods160,162may move with respect to the mast.

To translate vertical movement of the wire rope feed actuator150with respect to the mast110to relative movement of the rotary head122, the drilling system120can include or be operatively associated with a wire rope feed system170including a plurality of wire ropes that can operatively connect the wire rope feed actuator150to the body134of the rotary head122. The wire ropes can be formed as steel wire ropes assembled from many individual strands of thinner metal wires wound or braided together to form a flexible, elongated, and larger diameter wire rope. The flexible steel wire rope can be used as the running rigging of the wire rope feed system170and are adapted to bend around and extend about sheaves and pulleys. Depending on the drilling operation, the wire rope feed system170can be further differentiated into a hoist rope system172responsible for hoisting the rotary head122and a pulldown rope system174responsible for pulling down the rotary head122with respect to the work surface102. It should be appreciated however that the hoist rope system172and the pulldown rope system174operate in cooperation to perform their respective operations.

The hoist rope system172can encompass the upper components of the wire rope feed system170and can include a feed actuator hoist pulley180that may fixedly mounted to and movable with the feed actuator cylinder154such that the feed actuator hoist pulley180can vertically move in unison with the feed actuator cylinder154. The hoist rope system172can also include a mast hoist pulley182fixedly mounted to the crown112of the mast110and is thus suspended vertically high above the work surface102. Directed around and operatively linking the feed actuator hoist pulley180and the mast hoist pulley182can be a fixed length of flexible hoist wire rope184. The hoist wire rope184can extend between a first hoist rope end186proximately connected with the crown112of the mast110and a second hoist rope end188fixedly connected to the exterior upper end of the body134of the rotary head122. To enable the hoist wire rope184to run between and extend around the feed actuator hoist pulley180and the mast hoist pulley182, those components can each include a rotating sheave supported by a pulley frame and which is formed as a grooved wheel that contains and guides the hoist wire rope.

The pulldown rope system174can encompass the lower components of the wire rope feed system170and can include a feed actuator pulldown pulley190that may be fixedly mounted to and moveable with the feed actuator cylinder154such that the feed actuator pulldown pulley190can vertically move in unison with the feed actuator cylinder154. The pulldown rope system174can also include a mast pulldown pulley192fixedly mounted to the base114of the mast110and is thus generally located proximate to the work surface102. Directed around and operatively linking the feed actuator pulldown pulley190and the mast pulldown pulley192can be a fixed length of flexible pulldown wire rope194. The pulldown wire rope194can extend between a first pulldown rope end196proximately connected with the base114of the mast110and a second pulldown rope end198fixedly connected to the exterior lower end of the body134of the rotary head122. To enable the pulldown wire rope194to run between and extend around the feed actuator pulldown pulley190and the mast pulldown pulley192, those components can each include a rotating sheave supported by a pulley frame and which is formed as a grooved wheel that contains and guides the pulldown wire rope.

The pulleys and wire rope of the hoist rope system172and the pulleys and wire rope of the pulldown rope system174form block and tackle systems for vertically hoisting and pulling down the rotary head122. For example, during a hoist operation, pressurized hydraulic fluid is directed into the lower chamber158of the wire rope feed actuator150, causing the feed actuator cylinder154acting as a free body to move vertically downwards with respect to the mast110. This may be referred to as fluidly actuating the lower chamber158of the wire rope feed actuator150because the hydraulic fluid directed thereto displaces the feed actuator cylinder154downwards. The feed actuator hoist pulley180likewise moves vertically downwards with the feed actuator cylinder154and thus moves vertically apart from the mast hoist pulley182. To accommodate the increasing vertical distance between the feed actuator hoist pulley180and mast hoist pulley182, and likewise the increasing vertical distance between the feed actuator hoist pulley180and the crown112of the mast110, the length of the hoist wire rope184between those elements must be increased. Because the hoist wire rope184has a fixed length between the first hoist rope end186connected to the mast crown112and the second hoist rope end188connected to the body134of the rotary head122, the increase in the length of the hoist wire rope184between the feed actuator hoist pulley180and mast hoist pulley182is accompanied by a corresponding decrease in length of the hoist wire rope184between the mast hoist pulley182and the rotary head122. The result is that the rotary head122is pulled vertically upwards with respect to the mast110and towards the crown112. It will be appreciated that pulldown rope system174must function in an opposite manner to increase the length of the pulldown wire rope194extending between the mast pulldown pulley192and the body134of the rotary head122to allow the rotary head to vertically rise with respect to the mast110.

Correspondingly, during a pulldown operation, pressurized hydraulic fluid is directed into the upper chamber156of the wire rope feed actuator150, causing the feed actuator cylinder154acting as free body to move vertically upwards with respect to the mast110. This may be referred to as fluidly actuating the upper chamber156of the wire rope feed actuator150because the hydraulic fluid directed thereto vertically moves the feed actuator cylinder154vertically upwards. The feed actuator pulldown pulley190likewise moves vertically upwards with the feed actuator cylinder154and thus moves vertically apart from the mast pulldown pulley192. To accommodate the increasing vertical distance between the feed actuator pulldown pulley190and mast pulldown pulley192, and likewise the increasing vertical distance between the feed actuator pulldown pulley190and base114of the mast110, the length of the pulldown wire rope194between those elements must be increased. Because of the fixed length of the pulldown wire rope194, the increase in the length of the pulldown wire rope194between the feed actuator pulldown pulley190and mast pulldown pulley192is accompanied by a corresponding decrease in length of the pulldown wire rope between the mast pulldown pulley192and the rotary head122. This results in the rotary head122being pulled downwards with respect to the mast110and towards the base114. Downward movement of the rotary head122drives the drill string124and drill bit126into the work surface102. It will be appreciated that the hoist rope system172must cooperatively function in an opposite manner to increase the length of the hoist wire rope184extending between the mast hoist pulley182and the body134of the rotary head122to allow the rotary head to move vertically downwards.

The hoist wire rope184and the pulldown wire rope194are placed under significant stress and tension during the respective hoist and pulldown operations. The tension can stretch and cause elongation of the hoist wire rope184and pulldown wire rope194and, because of the substantial lengths of the hoist and pulldown wire ropes, elongation of the wire ropes may be approximately several millimeters or inches. Maintaining the hoist wire rope184and the pulldown wire rope194in tension may compensate for elongation of the wire rope. However, if tension on the hoist wire rope184or the pulldown wire rope194is suddenly released, for example, when switching between hoist and pulldown operations or if the drilling system120were to encounter a hard rock formation during a pulldown operation, the wire ropes may become slack as result of the previous stretching and elongation. Slack in the hoist wire rope184and the pulldown wire rope194may allow the wire ropes to dislodge or come off of the pulleys and the freed wire ropes may swing about and cause damage to the surrounding components of the drilling system120. Moreover, because the fixed lengths of the hoist and pulldown wire ropes coordinate much of the operation of the drilling system120including vertical movement of the rotary head122with respect to the mast110, slack and elongation may adversely affect operation of the drilling rig.

Therefore, to maintain tension on the hoist wire rope184and the pulldown wire rope194, the drilling system120may be associated with a hydraulic tensioning system200including a hoist tensioning actuator202and pulldown tensioning actuator204. The hoist and pulldown tensioning actuators202,204may be embodied as double acting cylinders or, in an embodiment, as spring-loaded, single acting cylinders responsive to the receipt and discharge of hydraulic fluid therein. The hoist and pulldown tensioning actuators202,204may include a hollow, tubular hydraulic cylinder body210with a disc-like hydraulic piston212disposed therein. The hydraulic piston212can separate the hydraulic cylinder body210into a first hydraulic chamber, referred to as the rod end chamber214, and a second hydraulic chamber, referred to as the piston end chamber216. The hoist and pulldown tensioning actuators202,204can include a hydraulic piston rod218that is connected to the hydraulic piston212and extends through the rod end chamber214to protrude from the hydraulic cylinder body210. Moving the hydraulic piston212toward the rod end chamber214extends the hydraulic piston rod218from the hydraulic cylinder body210and moving the hydraulic piston212toward the piston end chamber216retracts the hydraulic piston rod218into the hydraulic cylinder body210.

In the illustrated embodiment, the hoist and pulldown tensioning actuators202,204can be fixedly mounted to and movable with the feed actuator cylinder154of the wire rope feed actuator150. For example, the hoist tensioning actuator202may be associated in location with the upper chamber156of the feed actuator cylinder154and oriented so that the hydraulic piston rod218is directed vertically upwards toward the crown112of the mast110. Likewise, the pulldown tensioning actuator204may be associated in location with the lower chamber158of the feed actuator cylinder154and oriented so that the hydraulic piston rod218is directed vertically downwards toward the base114of the mast110. In other embodiments, the hoist and pulldown tensioning actuators202,204may be disposed in other locations and with different orientations, for example, the hoist tensioning actuator202may be fixedly disposed on the crown112and the pulldown tensioning actuator204may be fixedly disposed on the base114.

To interact with and apply tension to the hoist wire rope184, the distal end of the hydraulic piston rod218of the hoist tensioning actuator202can be connected to the feed actuator hoist pulley180thereby connecting the feed actuator hoist pulley180with the feed actuator cylinder154. The feed actuator hoist pulley180, which the hoist wire rope184extends about, can extend and retract with the hydraulic piston rod218of the hoist tensioning actuator202. Likewise, the distal end of the hydraulic piston rod218of the pulldown tensioning actuator204can be connected to the feed actuator pulldown pulley190thereby connecting the feed actuator hoist pulley180with the feed actuator cylinder154. The feed actuator pulldown pulley190, which the pulldown wire rope194extends about, can thus extend and retract with the hydraulic piston rod218of the pulldown tensioning actuator204.

To selectively direct hydraulic fluid to and from the hoist tensioning actuator202and the pulldown tensioning actuator204and thereby actuate movement of the feed actuator hoist pulley180and feed actuator pulldown pulley190, the wire rope feed system170can be operatively associated with a hydraulic tensioning circuit220. The hydraulic tensioning circuit220can be separated into a hoist tensioning circuit222operatively associated with the hoist tensioning actuator202and a pulldown tensioning circuit224operatively associated with the pulldown tensioning actuator204. To accommodate and channel hydraulic fluid for the hoist and pulldown tensioning circuits222,224, the hydraulic tensioning circuit220can be in fluid communication with a hydraulic reservoir226or tank and with a hydraulic pump228that can pressurize and direct the hydraulic fluid through various fluid conduits that may be, for example, flexible hoses or rigid tubular pipes. In an embodiment, the hydraulic reservoir226and the hydraulic pump228may also be responsible for directing hydraulic fluid to the wire rope feed actuator150causing the feed actuator cylinder154to move vertically with respect to the mast110during hoist or pulldown operations.

To selectively establish fluid communication between the hydraulic reservoir226and hydraulic pump228and the hoist and pulldown tensioning actuators202,204associated with the hydraulic tensioning circuit220, a hydraulic control valve230can be disposed in the circuit. To fluidly communicate with the hoist and pulldown tensioning actuators202,204, the hydraulic control valve230can be fluidly coupled to a tensioning actuator supply conduit232arranged to direct hydraulic fluid from the hydraulic pump228to the tensioning actuators. Likewise, in an embodiment, the hydraulic control valve230can be fluidly coupled to a tensioning actuator return conduit234arranged to direct hydraulic fluid from the tensioning actuators to the hydraulic reservoir226. In addition, in an embodiment, the hydraulic control valve230can be operatively associated with and in fluid communication with the wire rope feed actuator150via an upper chamber conduit236fluidly connected with the upper chamber156of the feed actuator cylinder154and via a lower chamber conduit238fluidly connected to the lower chamber158of the feed actuator cylinder154. The hydraulic control valve230can regulate and direct hydraulic fluid flow to and from the hoist and pulldown tensioning actuators202,204in response to the pulldown and hoist operations of the wire rope feed actuator150by responding to flow of pressurized hydraulic fluid in the upper chamber conduit236and the lower chamber conduit238.

In an embodiment, the hydraulic control valve230can be configured as a three-position, four-way valve with a plurality of positions that selectively direct fluid flow through the valve. The different positions, which may be defined by internal valve passages fluidly coupled to fluid conduits connected to the hydraulic control valve230, can be selectively shifted into and out of active operation. The hydraulic control valve230can be actuated mechanically, electrically, or hydraulically.

In an embodiment, the hydraulic control valve230can include a closed center position240that prevents fluid flow between the hydraulic tensioning circuit220and the hydraulic reservoir226and hydraulic pump228. When in the closed center position240, the hydraulic control valve230operatively deactivates the hydraulic tensioning circuit220and the hydraulic fluid cannot flow to or from the hoist and pulldown tensioning actuators202,204. The hydraulic control valve230can also include a first position242and a second position244. When in the first or second positions, the hydraulic control valve230can selectively direct hydraulic fluid to the hoist tensioning circuit222and the pulldown tensioning circuit224, and thus onto the hoist tensioning actuator202and the pulldown tensioning actuator circuit204respectively associated therewith.

During hoist and pulldown operations, pressurized hydraulic fluid to be directed to one of the upper chamber156or lower chamber158of the feed actuator cylinder154while the other of the upper chamber156or lower chamber158may be exposed to low pressure, for example, by established fluid communication between the upper or lower chamber156,158and the tensioning actuator return conduit234that communicates with the hydraulic reservoir226. The wire rope feed actuator150can be configured in a hoist or pulldown operation depending upon which of the upper chamber156or lower chamber158receives the pressurized hydraulic fluid and which of the upper chamber156and the lower chamber158is fluidly connected with the tensioning actuator return conduit234.

Because the pressure of hydraulic fluid directed to the hydraulic tensioning circuit220may be in excess or higher than the pressure which the hoist and pulldown tensioning actuators202,204are intended to operate at, the hydraulic tensioning circuit220can include a pressure reducing valve250disposed downstream of the hydraulic control valve230to control or reduce the pressure of the inflowing fluid. The pressure reducing valve250can be a spring biased valve that is normally opened but can throttle or reduce flow there through to lower the pressure of the hydraulic fluid from the hydraulic pump228. In various embodiments, the pressure reducing valve250may be actuated mechanically, electrically or hydraulically. The hydraulic pressure established by the pressure reducing valve250can be referred to as the tensioning pressure of the hydraulic tensioning circuit220.

To direct inflowing pressurized hydraulic fluid at the tensioning pressure onto the hoist tensioning actuator202or the pulldown tensioning actuator204, the tensioning actuator supply conduit232can be differentiated downstream of the pressure reducing valve250into a hoist actuator supply conduit252associated with the hoist tensioning circuit222and a pulldown actuator supply conduit254associated with the pulldown tensioning circuit224. The hoist actuator supply conduit252can be fluidly connected to the rod end chamber214of the hoist tensioning actuator202fixedly mounted to the feed actuator cylinder154of the wire rope feed actuator150. When pressurized hydraulic fluid is introduced to the rod end chamber214, the fluid will displace the hydraulic piston212to the piston end chamber216thereby retracting the hydraulic piston rod218into the hydraulic cylinder body210. Retracting the hydraulic piston rod218further retracts the feed actuator hoist pulley180connected thereto and applies tension to the hoist wire rope184and reduces any slack that may occur in the hoist wire rope184. Similarly, the pulldown actuator supply conduit254can be fluidly connected to the rod end chamber214of the pulldown tensioning actuator204. Flow of pressurized hydraulic fluid to the rod end chamber214displaces the hydraulic piston212toward the piston end chamber216retracting the hydraulic piston rod218and the feed actuator pulldown pulley190connected thereto with respect to the hydraulic cylinder body210. The pulldown tensioning actuator204therefore applies tension to the pulldown wire rope194removing slack therein.

In an embodiment, to facilitate retraction of the hydraulic piston rod218into the hydraulic cylinder body210of the hoist and pulldown tensioning actuators202,204, the piston end chamber216can be in fluid communication with a hoist actuator return conduit256and a pulldown actuator return conduit258respectively. In this embodiment, the hoist actuator return conduit256and the pulldown actuator return conduit258can be fluidly coupled to the hydraulic reservoir226to discharge hydraulic fluid thereto. In other embodiments, the piston end chambers216may not receive or accommodate hydraulic fluid and the hoist and pulldown tensioning actuators202,204may be spring-loaded, single acting cylinders.

During a pulldown operation, the feed actuator cylinder154and the pulldown tensioning actuator204attached thereto are moved vertically upwards while the rotary head122is correspondingly moved downwards thereby forcing the drill string124into the work surface102. Due to forcibly driving the rotary head122toward work surface102, significant stresses and forces are applied to the pulldown wire rope194that may cause the pulldown wire rope194to stretch and elongate. However, in an opposite reaction, slack may develop in the hoist wire rope184that is fed through the block and tackle system configured by the feed actuator hoist pulley180and mast hoist pulley182to follow the vertically downward movement of the rotary head122. Because the rod end chamber214of the hoist tensioning actuator202is in direct fluid communication with the pressure reducing valve250, it receives hydraulic fluid at and is maintained at the tensioning pressure established by the pressure reducing valve250. Accordingly, during a pulldown operation with the hoist tensioning actuator202maintained at the tensioning pressure, thereby retracting the hydraulic piston rod218and the feed actuator hoist pulley180connected thereto, a corresponding tensioning force is applied to the hoist wire rope184and slack that may otherwise occur is reduced.

If the drilling system120is switched between to a pulldown operation and a hoist operation, however, the forces applied to the hoist and pulldown wire ropes184,194may change significantly. For example, the hydraulic pressure in the rod end chamber214of the hoist tensioning actuator202, and thus the stresses therefore applied to the hoist wire rope184, may increase beyond the stresses associated with the tensioning pressure established by the pressure reducing valve250. Maintaining significant or excess stress on the hoist wire rope184can adversely impact the life of the wire rope and require premature replacement.

To prevent the hydraulic pressure in the hoist tensioning actuator202and thus the tensioning forces applied to the hoist wire rope184from becoming excessive, the hoist tensioning circuit222can include a pressure relief valve260. The pressure relief valve260can be in fluid communication with the rod end chamber214of the hoist tensioning actuator202and may be located in bypass conduit262that is fluidly coupled to and extends between the hoist actuator supply conduit252and the hoist actuator return conduit256. The pressure relief valve260can be in a normally closed state thereby closing the bypass conduit262so that hydraulic fluid entering the hoist tensioning circuit222from the pressure reducing valve250is directed to the rod end chamber214of the hoist tensioning actuator202.

In the event the hydraulic pressure in the rod end chamber214exceeds a predetermined hydraulic pressure, referred to herein as the relief pressure threshold, the pressure relief valve260can partially open allowing a portion of the hydraulic fluid in the hoist tensioning circuit222to flow directly to the hoist actuator return conduit256and onto the hydraulic reservoir226thereby bypassing the hoist tensioning actuator202. The pressure relief valve260thus maintains or limits the rod end chamber214of the hoist tensioning actuator202at the relief pressure threshold and the tension applied to the hoist wire rope184is maintained in accordance with the relief pressure threshold. In an embodiment, the relief pressure threshold at which the pressure relief valve260opens may be factor or multiple of the tensioning pressure set by the pressure reducing valve250which is located fluidly upstream of the pressure relief valve260and the bypass conduit262. For example, if the tensioning pressure established by the pressure reducing valve250is 10 bars, the relief pressure threshold can be a factor of between 3 and 6 times of the tensioning pressure.

To ensure that hydraulic fluid is directed to the pressure relief valve260in the event the hydraulic pressure in the hoist tensioning actuator202exceeds the tensioning pressure established by the pressure reducing valve250, in an embodiment, a hoist circuit check valve264can be located in the hoist actuator supply conduit252. The hoist circuit check valve264can be a one-way flow control valve that allows inflowing hydraulic fluid to flow into the hoist tensioning actuator202but prevents hydraulic fluid from flowing back upstream towards the pressure reducing valve250. The hoist circuit check valve264maintains or limits hydraulic pressure downstream in the hoist actuator supply conduit252and in the hoist tensioning actuator202at the relief pressure threshold. If the hydraulic pressure in the hoist tensioning actuator202exceeds the inflowing pressure, for example, the tensioning pressure established by the pressure reducing valve250, the hydraulic fluid is trapped in the hoist tensioning circuit222by the hoist circuit check valve264until the relief pressure threshold is exceeded and the pressure relief valve260in the bypass conduit262opens diverting fluid flow to the hydraulic reservoir226.

The pulldown actuator supply conduit254of the pulldown tensioning circuit224can be fluidly connected with the hoist actuator supply conduit252downstream of the pressure reducing valve250and can be fluidly connected to the rod end chamber214of the pulldown tensioning actuator204. The pulldown actuator supply conduit254thereby directs hydraulic fluid at the tensioning pressure from the pressure reducing valve250to the rod end chamber214of the pulldown tensioning actuator204establishing at least the tensioning pressure therein. The tensioning pressure will tend to retract the hydraulic piston rod218and the feed actuator pulldown pulley190connected thereto with respect to the hydraulic cylinder body210. Accordingly, during a hoisting operation, for example, the pulldown tensioning actuator204can maintain the pulldown wire rope194under tension in accordance with the tensioning pressure set by the pressure reducing valve250.

In an embodiment, the pulldown tensioning circuit224can include a pressure isolation feature that is configured to isolate the hydraulic pressure established in the pulldown tensioning actuator204. More specifically, the pressure isolation feature may function to isolate or trap hydraulic fluid in the rod end chamber214of the pulldown tensioning actuator204and thus maintains the hydraulic pressure established therein, even if above the tensioning pressure established by the pressure reducing valve250. In an embodiment, the pressure isolation feature may be a pulldown circuit check valve270disposed in the pulldown actuator supply conduit254and located between the fluid connection to the hoist actuator supply conduit252and the pulldown tensioning actuator204. The pulldown circuit check valve270can be a one-way flow valve that allows inflowing hydraulic fluid to flow into the pulldown tensioning actuator204but prevents hydraulic fluid from flowing back upstream toward the pressure reducing valve250.

The pulldown circuit check valve270ensures the pulldown tensioning actuator204is maintained at least at the predetermined pressure set by the pressure reducing valve250, for example, the tensioning pressure. For example, if the rod end chamber214of the pulldown tensioning actuator204were to fall below the tensioning pressure, the pulldown circuit check valve270would open to direct inflowing hydraulic fluid to the rod end chamber214and return the hydraulic pressure therein to the tensioning pressure. If the hydraulic pressure in the rod end chamber214were to exceed the tensioning pressure established by the inflowing hydraulic fluid, the pulldown circuit check valve270would prevent hydraulic fluid flowing back upstream towards the hoist actuator supply conduit252and pressure reducing valve250and maintains the rod end chamber214of the pulldown tensioning actuator204at the elevated hydraulic pressure.

Because the pulldown circuit check valve270is capable of isolating and trapping pressurized hydraulic fluid in the rod end chamber214of the pulldown tensioning actuator204, the pulldown tensioning circuit224can include a feature to limit and prevent the hydraulic pressure in the pulldown tensioning actuator from becoming excessive. For example, during a hoisting operation, substantial tensioning pressures may be applied to the hoist wire rope184due to the vertically downward motion of the feed actuator cylinder154that result in stretching or elongation of the hoist wire rope184. The pulldown wire rope194may undergo an opposite action and begin to slacken. Accordingly, the pulldown tensioning circuit224will direct hydraulic fluid at the tensioning pressure from the pressure reducing valve250through the pulldown circuit check valve270in the pulldown actuator supply conduit254to the rod end chamber214of the pulldown tensioning actuator204to maintain the pulldown wire rope194in tension and reduce any slack therein.

However, when the hoisting operation ceases, there may be an excess amount of hydraulic fluid in the pulldown tensioning actuator204that may cause excessive pressures in the pulldown tensioning actuator when the pulldown wire rope194is placed under significant tension stresses again, for example, by initiating and undergoing an pulldown operation. To limit flow of hydraulic fluid to the pulldown tensioning actuator204during such circumstances, the pulldown tensioning circuit224can include a pulldown control valve272disposed in the pulldown actuator supply conduit254. The pulldown control valve272may be configured as a two-position, two way valve including an opened position274establishing fluid communication between the rod end chamber214of the pulldown tensioning actuator204and the pulldown actuator supply conduit252and the closed position276preventing the flow of hydraulic fluid to the rod end chamber214of the pulldown tensioning actuator204.

The pulldown control valve272may configure itself in the closed position276if the hydraulic pressure in the wire rope feed actuator150exceeds a predetermined hoisting pressure limit. The hoisting pressure limit associated with the wire rope feed actuator150may be set to prevent the flow of hydraulic fluid to the pulldown tensioning actuator204based on the hydraulic pressure in the wire rope feed actuator150during hoisting operations. Because the hydraulic pressure in the pulldown tensioning actuator204is limited under these circumstances, the pulldown tensioning actuator204will not apply or result in an excessive pulldown rope tension when the hoisting operation ceases.

Referring toFIG.3, there is illustrated another embodiment of the hydraulic tensioning circuit220configured to selectively regulate the flow of hydraulic fluid between the hoist tensioning circuit222, the pulldown tensioning circuit224, and the wire rope feed actuator150. The components and arrangement of the drilling system120, wire rope feed system170, the hoist tensioning circuit222, and the pulldown tensioning circuit224are substantially the same as shown and described inFIG.2.

The hydraulic control valve230however may include a first valve246and a second valve248. The first valve246may be fluidly associated with the tensioning actuator supply conduit232and configured to direct hydraulic fluid to the hoist and pulldown tensioning actuators202,204. The second valve248may be fluidly associated with the tensioning actuator return conduit234and configured to direct hydraulic fluid from the hoist and pulldown tensioning actuators202,204to a hydraulic reservoir226. The first and second valves246,248may also be in fluid communication with the wire rope feed actuator150. For example, the first and second valves can selectively establish fluid communication between either the upper chamber156and the lower chamber158of the wire rope feed actuator150and the tensioning actuator return conduit234to place the upper or lower chamber at a relatively low hydraulic fluid pressure during hoist or pulldown operations. The first and second valves246,248of the hydraulic control valve230can facilitate operation of the wire rope feed actuator150and the wire rope feed system170associated there with. In an embodiment, the first and second valve246,248can be configured as three-position, two way valves and can be actuated mechanically, hydraulically, or electrically.

Referring toFIG.4, there is illustrated yet another embodiment of the hydraulic tensioning circuit220used to selectively regulate hydraulic flow to the hoist tensioning circuit222, the pulldown tensioning circuit, and the wire rope feed actuator150that is operatively associated with the drilling system120and rotary head122. The illustrated embodiment includes additional components to improve the overall functionality of the drilling system120.

For example, the hydraulic tensioning circuit120may include an additional hydraulic logic valve280that is in fluid communication with the hydraulic control valve230that regulates the direction of hydraulic fluid flow to and from the wire rope feed actuator150. One of the upper chamber156or lower chamber158of the wire rope feed actuator150may retain pressurized hydraulic fluid therein, due, for example to the weight of the rotary head122that is trying to move the feed actuator piston with respect to the feed actuator cylinder154and thereby compress the hydraulic fluid therein. Because the wire rope feed actuator150is fluidly connected with the hydraulic control valve230, the fluid pressure in the wire rope feed actuator150may tend to cause the hydraulic control valve230to shift between the closed center position240and the first and/or second positions242,244at unintended times. Providing the hydraulic logic valve280that can be operatively associated with the pilot system that actuates the hydraulic control valve230. The logic control valve280may be a 2-position, four-way valve the selectively blocks hydraulic pressure to the pilot mechanism of the hydraulic control preventing unintended shifts.

The hydraulic tensioning circuit230may also include a thermal relief valve282operatively associated with the hoist and pulldown tensioning actuator202,204of the hydraulic tensioning system200. Hydraulic fluid may be retained in the rod end chamber214and/or piston end chamber216of the hoist and pulldown tensioning actuators202,204and may thermally expand and contract due to changes in ambient temperature even if the drilling system120is idle or inoperative. The thermal relief valve282is fluidly disposed in communication with the tensioning actuator return conduit234and can be set to open at an elevated pressure resulting from the thermal expansion of the fluid in the hoist pulldown tensioning actuators202,204. The thermal relief valve282may discharge hydraulic fluid to the hydraulic reservoir226and thereby relieve hydraulic pressure in the hydraulic tensioning actuators.

The hydraulic tensioning circuit220may also include a pressure trapping valve284fluidly disposed in the tensioning actuator return conduit234to selectively trap hydraulic fluid pressure in the pulldown tensioning actuator204. For example, the pressure trapping valve284may be a two-position valve configurable between fluidly opened and fluidly closed positions that is manually opened but can automatically close. The pressure trapping valve284can selectively control fluid flow within the tensioning actuator return conduit234from the pulldown tensioning actuator204to relieve or trap hydraulic pressure therein.

INDUSTRIAL APPLICABILITY

Referring now toFIG.5, with continued reference to the proceeding figures, there is illustrated the possible actions undertaken by the hydraulic tensioning circuit220to maintain the hoist wire rope184and/or the pulldown wire rope under tension and reduce the formation of slack therein during pulldown and hoist operations of the wire rope feed system170. To provide pressurized hydraulic fluid for operation of the wire rope feed system170and the hydraulic tensioning circuit220, in a pressurize fluid supply step300, the hydraulic pump228can pressurize hydraulic fluid from the hydraulic reservoir226and direct the pressurized hydraulic fluid to both the wire rope feed actuator150and to the hydraulic control valve230of the hydraulic tensioning system220.

In a pulldown operation step302, the pressurized hydraulic fluid is directed particularly to the upper chamber156of the wire rope feed actuator150causing the feed actuator cylinder154to move vertically upwards with respect to the mast110thereby lowering the rotary head122toward the work surface102. To maintain the hoist wire rope184under tension during the pulldown operation and reduce slack formation, in a hoist tensioning actuator fluid pressurization step304, the hydraulic control valve230of the hydraulic tensioning circuit220can be configured to direct pressurized hydraulic fluid to the rod end chamber214of the hoist tensioning actuator202. This retracts the hydraulic piston rod218and the feed actuator hoist pulley180connected thereto into the hydraulic cylinder body210of the hoist tensioning actuator202. The hoist wire rope184is therefore maintained taut.

To facilitate operation of the hoist tensioning actuator202, in a hoist tensioning actuator pressure release step306, the hydraulic control valve230may simultaneously established fluid communication between the piston end chamber216of the hoist tensioning actuator202and the lower chamber158of the wire rope feed actuator150. For example, the hydraulic control valve230can fluidly connect the hoist actuator return conduit256with the lower chamber conduit238connected to the lower chamber158of the wire rope feed actuator150that is maintaining the lower chamber158at a relatively low hydraulic pressure during the pulldown operation. In an further embodiment, both the lower chamber conduit238and the hoist actuator return conduit256may fluidly communicate with the hydraulic reservoir226. Hence, the hydraulic pressure in the piston end chamber216of the hoist tensioning actuator202is released or reduce to facilitate retraction of the hydraulic piston rod218and the feed actuator hoist pulley180connected thereto and which the hoist wire rope184is wrapped about.

In a hoist operation step312, the pressurized hydraulic fluid is directed to the lower chamber158of the wire rope feed actuator150causing the feed actuator cylinder154to move vertically downwards with respect to the mast110and thereby raise the rotary head122away from the work surface102. To maintain the pulldown wire rope194under tension during the hoist operation and reduce slack formation therein, in a pulldown tensioning actuator fluid pressurization step314, the hydraulic control valve230can be configured to direct pressurized hydraulic fluid to the rod end chamber214of the pulldown tensioning actuator204. This retracts the hydraulic piston rod218and the feed actuator pulldown pulley190connected thereto into the hydraulic cylinder body210of the pulldown tensioning actuator204. The pulldown wire rope194is therefore maintained taut.

To facilitate operation of the pulldown tensioning actuator204, in a pulldown tensioning actuator pressure release step316, the hydraulic control valve230may simultaneously established fluid communication between the piston end chamber216of the pulldown tensioning actuator204and the upper chamber156of the wire rope feed actuator150. For example, the hydraulic control valve230can fluidly connect the pulldown actuator return conduit258with the upper chamber conduit236connected to the upper chamber156of the wire rope feed actuator150that is maintaining the upper chamber156at a relatively low hydraulic pressure during the hoist operation. In a further embodiment, both the upper chamber conduit236and the pulldown actuator return conduit258may fluidly communicate with the hydraulic reservoir226. Hence, the hydraulic pressure in the piston end chamber216of the pulldown tensioning actuator204is released or reduce facilitating retraction of the hydraulic piston rod218and the feed actuator pulldown pulley190connected thereto and which the pulldown wire rope194is wrapped about.

An advantage of the foregoing is that disclosed tensioning hydraulic circuit can reduce or eliminate the slackening of the hoist and/or pulldown wire ropes wire rope feed system by utilizing and manipulating the hydraulic pressure in the hoist and pulldown tensioning actuators to reduce the tension applied, or avoid prolonged application of tension, to the hoist and pulldown wire ropes. Operating the hoist and pulldown wire ropes at lower tension prolongs the operational life of the wire rope feed system and reduces operating cost of the drilling rig. A related advantage is that the hydraulic control valve associated with the hydraulic tensioning circuit can regulate the operation of the tensioning hydraulic circuit in cooperation interaction with the wire rope feed circuit to further regulate the tension stress applied to the hoist and pulldown wire ropes. These and other advantages and features of the disclosure should be apparent from the foregoing description and accompanying drawings.