Mast safety system

A spool may include a drum rotatably supported on an axle shaft and flanges integrally formed with opposite ends of the drum. The drum has a continuous groove on the outer surface of the drum to guide the movement of the safety wireline. Both of the flanges may include an opening, internal threads circumscribing the opening, and a plurality of mechanical brakes. Each of the mechanical brakes may include a rotor rotatably supported on the axle shaft of the spool and a pawl arranged within the opening. The pawl is pivotally linked to the rotor such that when the rotation of the axle shaft is in a direction and at a rotation speed that exceeds a threshold then the pawl is moved by centrifugal force and engages with the internal threads circumscribing the opening and does not permit the spool to rotate.

FIELD

The disclosure relates to a safety system and a method for using a mast system.

BACKGROUND

A mast is a structural tower comprised of one or more sections that are assembled on the ground in a horizontal position. A mast is generally raised to an operating position by using a hoisting system and wires coupling the mast to the hoisting system. Such masts are rectangular or trapezoidal in shape and used to hold drilling equipment in a desired location. Once a mast is raised to the operating position, the mast stays erect while the drilling equipment carries out its mission. If the drilling equipment needs to be moved, wires may be used to couple the drilling equipment to the hoisting system where the wires pass through the mast such a way that the location of the drilling equipment may be controlled by the hoisting system.

SUMMARY

In accordance with one or more embodiments, a spool may include an axle shaft rotatably supporting the drum and flanges integrally formed with opposite ends of the drum. Both of the flanges of the spool may include an opening, internal threads circumscribing the opening, and a plurality of mechanical brakes. Each of the mechanical brakes may include a rotor rotatably supported on the axle shaft and a pawl where both the rotor and the pawl are arranged within the opening. The pawl is pivotally linked to the rotor such that when the rotation of the axle shaft is in a rotation direction and at a rotation speed that exceeds a threshold then the pawl is moved by centrifugal force and engages with the internal threads circumscribing the opening and does not permit the spool to rotate. The spool may further include an S-shaped plate with an aperture at the center to guide the rotation of the axle shaft and a torsion spring configured to attenuate vibration and to maintain positions of the rotor and the S-shaped plate. The spool may further include a flapper leg with a compression spring configured to limit motion of the S-shape plate and to retain the pawl from locking in normal speed.

A system in accordance with one or more embodiments may include a spool and a safety wireline coupling between the spool and a mast. The safety wireline may include a first end and a second end, where the first end is anchored to a drum of the spool and the second end is configured to be coupled to the mast. A three-point connector may be used to couple the mast with the spool by coupling a first point of the three-point connector to the second end of the safety wireline and coupling each of the second and third points to a separate sling wire, where each sling wire is configured to be coupled to the mast at different points. The coupling of the safety wireline to the mast is such that each sling wire, the three-point connector and the safety wireline do not contact a drilling line from the drawworks. The system may further include a shock absorber jack coupled to each of the sling wires to attenuate vibrations. An external drive may be used to rotate the spool such that the safety wireline coupled to the mast is retrieved when the spool is engaged with the external drive.

In accordance with one or more embodiments, a method of using a system begins with coupling a safety wireline to a mast by using a three-point connector, a plurality of sling wires, and a plurality of shock absorber jacks, where a first end of the safety wireline is coupled to a wall of a drum in a spool. A drawworks may be used to move the mast, and the spool may be rotated in coordination with the drawworks such that the position of a pawl in a mechanical brake on the spool is maintained in a first position. The first position of the pawl in the mechanical brake of the spool permits the spool to rotate, and a second position of the pawl in the mechanical brake engages the pawl with internal threads of the spool and does not permit the spool to rotate. The pawl is pivotally linked in the spool such that when a rotation occurs and a rotation speed exceeds a threshold then the pawl is moved from the first position to the second position by centrifugal force.

DETAILED DESCRIPTION

In the following detailed description, certain specific details are set forth in order to provide a thorough understanding of various disclosed implementations and embodiments. However, one skilled in the relevant art will recognize that implementations and embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, and so forth. In other instances, well known features or processes associated with the safety system has not been shown or described in detail to avoid unnecessarily obscuring descriptions of the implementations and embodiments.

A safety system in accordance with one or more embodiments may provide a safety measure to a mast system by introducing a separately independent spool and coupling a mast to the spool with wires and other components. This spool may provide a safety measure to the mast even if a failure occurs in the hoisting system or in its operation, such as a failure in power supply, a fatigue failure in one of internal components of the hoisting system, or human error. The spool in accordance with one or more embodiments may include an axle shaft, a drum rotatably supported by the axle shaft, and a mechanical brake. The safety system may be activated upon a sudden increase in centrifugal force on the spool generated by falling of the mast. The mechanical brake then stops and locks further rotation of the axle shaft, which locks the spool, and prevents the mast from falling any further due to the coupling between the mast and the spool.

FIG.1shows a side view of a mast system50including a mast1, a traveling block56, a crown block54, a drawworks10disposed under a support53, a drilling line51in part wound around the drawworks10. The drilling line51passes through a location2at a crown block54and extends further to the traveling block56where the traveling block56couples the drilling line51and raising lines58in the middle of the mast1. The raising lines58are anchored at the mast1at one end while the other end is coupled to the traveling block56. The raising lines58are in part wound around the raising sheaves46that are disposed at the sides of the support53whereas the drilling line51is in part wound around a drilling sheave48that is disposed in the middle of the support53. Side sheaves49may be disposed on sides of the mast1to guide the movement of the raising lines48. This provides additional structural integrity during raising operation where the drawworks10is pulling the drilling line51that is coupled to the raising line58at the traveling block56.

In more details,FIG.2shows a side view of the mast system50inFIG.1where the mast1is being raised to an operating position. The drilling line51is anchored at the drawworks10at one end while the other end is coupled to the raising lines58at the traveling block56after passing through the location2at the crown block54on the mast1. During such raising operations, the movement of the drilling line51is guided by the drilling sheave48and the movement of the raising lines is guided by the raising sheaves46on the sides of the support53and the side sheaves49on the mast1.

FIG.3shows a side view of a safety system100in accordance with one or more embodiments in combination with the mast system50as shown previously inFIG.1. The safety system100includes an A-frame9and a separately independent spool8disposed next to a support53. The A-frame9includes a sheave7that has a groove on its outer surface that comes in surface contact with a safety wireline6. This ensures that the sheave7guides the movement of the safety wireline6to avoid any undesired whipping or vibrations of the safety wireline6. The spool8is configured to brake and lock the rotation of the axle shaft upon a sudden increase in centrifugal force in order to halt the mast1from falling further. The safety wireline6has one end coupled to the spool8and the other end coupled to a three-point connector5that is further connected to the mast1by other components. One skilled in the art would appreciate how the mast system50may be arrested from continuing to fall even if the drawworks10fails because the mast1is concurrently coupled to the safety system100that works separately from the drawworks10. The spool can prevent the mast1from falling due to the coupling between the spool8and the mast1with the safety wireline6and the other components, which will be explained in the following description in more details.

FIG.4illustrates an application of a safety system100to a mast system50in accordance with one or more embodiments where a mast1is being raised to an operating position. The mast1is coupled to an A-frame9that is holding the mast1at a different level than that of a support53, which is better described inFIG.5showing a rear view ofFIG.4. A drilling line51bears the weight of the mast1while the mast1is being raised to the operating position by a drawworks10. The mast1must fall uncontrollably for a short respond time to generate the centrifugal force to activate the safety system100. The respond time in accordance with one or more embodiments may be between 1 and 1.5 seconds.

FIG.5shows a rear view of an application of a safety system100to a mast system50in accordance with one or more embodiments where a spool8is disposed under an A-frame9that guides a safety wireline6at a level57whereas a support53guides a drilling line at a level55. This is to guide the safety wireline6at a different height from that of the drilling line in order to avoid any undesired contacts between the drilling line and the safety wireline6. Further, the safety wireline6is not contacted with a traveling block56that couples the drilling line and raising lines58. This further provides different points of contact and angles with respect to the mast1for improved structural integrity while the mast1is being raised to an operating position.

FIG.6illustrates a spool8in accordance with one or more embodiments.FIGS.6A,6B, and6Ccorrespond to plane views of AA′, BB′, and CC′, respectively, ofFIG.6. The spool8typically would have at least some of the safety wireline coiled around it; however, for simplicity of the drawing and discussion the safety wireline has been omitted fromFIG.6. A drum11of the spool8rotates on an axle shaft when lowering the mast and its rotation is aligned with the pulling of a drawworks. The outer surface of the drum11has grooves38on it that guides the safety wireline as it winds around the drum11so that the safety wireline wraps evenly and continuously. The safety wireline is affixed to the wall37of the drum11. One skilled in the art would appreciate how even and continuous wrapping would keep the drum11balanced and prevents the safety wireline from whipping back and forth in the air between the longitudinal ends of the drum8.

The drum11has flanges22at both sides that have an opening with internal threads12, as shown inFIG.6A. A pawl14and a rotor13are arranged within the opening with internal threads12and stop the rotation of the drum11once the pawl14is moved outwardly. The pawl14is received into the internal threads12upon a sudden increase in centrifugal force. For example, when a mast falls, a safety wireline coupling the mast and the spool rapidly accelerates the rotation rate of the drum11, which results in an increase in centrifugal force on the drum11. The increase in centrifugal force pushes the pawl14outward from the center to the internal threads12. Once forced outwardly and received into the internal threads12, the pawl14locks. This locking halts the rotation of the drum11, which in turn, stops the fall of the mast1. The pawl14has a pivot link15with the rotor13that allows the pawl14to rotate with the rotor13. This pivot link15also allows the outward movement of the pawl14due to centrifugal force. The rotor13has a cut-out that spans approximately a quarter of the opening, the cut-out representing the area occupied by the pawl14.

Both flanges22of the drum11have rotors13and pawls14extended by an integral knob18from the middle of rotors13to connect the axle shaft with other components, as shown inFIG.6B. The integral knob18extends from one end to the other end of the drum11. At one end of integral knob18is a handle16. The integral knob18may be shaped as illustrated inFIG.6Bsuch that the integral knob18can be fitted into a corresponding slot within the axle shaft, which rotationally couples the axle shaft and the integral knob18. A torsion spring17inFIG.6Ais used to provide a space between the rotor13and an S-shape plate20inFIG.6B. Torsion spring17prevents both the rotor13and the S-shape plate20from sticking together. More specifically, the torsion spring17provides frequent spring motion for the S-shape plate20that attenuates vibration during normal operation, such as hoisting the mast1. Furthermore, the torsion spring17retains the pawl14from locking and braking if the rotation speed is less than a certain threshold value. The threshold value may depend on the specification of a mast system such as weight of a mast and power of a drawworks. For example, a spool8in accordance with one or more embodiments may activate if the rotation speed exceeds 10% of the falling speed of the mast1. If the falling speed of the mast1in this embodiment corresponds to 60 revolutions per minute (RPM) according to the size of the pawl14and the rotor13, then the threshold may be set at 10% of the 60 RPM of the falling speed of the mast1. The computed threshold value, 6 RPM in this embodiment, may ensure that the pawl14is not moved and received into the internal threads12when the rotation speed is less than 6 RPM. The value of the threshold may also change according to the size of the mast1and the spool8in accordance with other embodiments.

The S-shape plate20has a wide aperture in the middle to guide and smoothen the rotation of the axle shaft. The S-shape plate20also has two guided pins19,23, one from the pawl14and the other from the cover. The pin19coming from the cover fits into a cavity21formed in the rotor13. The cover has a flapper leg attached with a compression spring limiting the movement of the S-shape plate20to retain the pawl14from locking and braking in normal speed (speed less than a threshold) and also to keep the S-shape plate20in right balanced position. The cover has an aperture at the center of the integral knob18which extends from the axle shaft to the outside of the drum11. At the end of this integral knob18a handle16is installed to let an operator unlock the drum if locked due to a falling of the mast1.FIG.6shows a handle16disposed on a cover on a first flange22to manually rotate an axle shaft if the axle shaft is locked due to an activation of a mechanical brake in the spool8. As seen inFIG.6C, the first flange22further includes an opening with internal threads12where the shape of the internal threads12can be chosen from either one or combination of sharp, ACME, knuckle, square, and other conventionally known shapes of threads. This is to avoid any slipping between the internal threads12and a pawl14once the safety system100is activated. All of the components are enclosed in the cover for protection where the cover is attached with bolts, washers, locks, or any conventionally known attachment methods. At the top of both of the flanges of the spool8, there are rollers27to protect the drum11from being damaged due to friction between the safety wireline6with the drum11.

FIG.7shows a spool8being engaged with an external hoisting system such as an electrical motor28in accordance with one or more embodiments. Again, spool8is shown without the safety wireline coiled around it in part for the ease of viewing and discussion. The electrical motor28is used to retrieve the safety wireline to the drum11or to help unlock the pawl if the pawl is locked. A key slot29connects a side of the axle shaft to a jaw clutch30,31.FIG.7Ashows a lever32used to disengage the spool8with the electrical motor28at the jaw clutch30,31. The engagement of the jaw clutch30enables the spool8to retrieve the safety wireline after the mast is fully lowered. During the disengagement, the lever32squeezes the spring33and makes a space between the clutch jaw31closed to the drum11and the other jaw30connected to the electrical motor28. During the engagement, the lever32is in vertical position and the spring33is in its normal position, as shown inFIG.7.

A safety wireline in accordance with one or more embodiments is a multi-threaded and twisted wire rope that is threaded or reeved. The safety wireline is made of strands wound around a steel core. For example,FIG.12illustrates an example of a structure of strands wound around a steel core used for a safety system. Each strand contains a number of small wires wound around a central core. This size for this safety wireline should be greater than or equal to that of a drilling line to ensure a safe condition in working load. The safety wireline has three parts, namely a core, strands and wires.

FIG.8shows an enlarged portion of a sheave7guiding a safety wireline6inFIG.5. The sheave7is made of high strength steel configured to bear the load due to the tension in the safety wireline6when the mast1descends in an uncontrolled manner. A sheave7in accordance with other embodiments may be made of other material that is capable of carrying the weight of mast weight. The groove on the sheave7is manufactured by undergoing middle-frequency quenching in order to strengthen the groove and to extend its operating life. A sheave7in one or more embodiments is assembled on an A-frame9with double-conical bearing where each bearing has its individual lubricating channel.

FIG.9shows an enlarged portion of a three-point connector5in accordance with one or more embodiments. The three-point connector includes three holes for the safety wire pins42to distribute the load in one safety wireline6into two sling lines43. A socket41is used to fasten the sling wires43and safety wireline6to the three-point connector. Specifically, the two separate sling wires43are connected to the three-point connector5at two holes, and the three-point connector5is connected to the safety wireline6at the other hole. This way of connection further avoids unwanted contact between the drilling line and the safety wireline6. This way of coupling also ensures that each sling wire43, the three-point connector5and the safety wireline6do not contact each other.

FIG.10shows shock absorber jacks44including springs59to reduce and attenuate the vibrations on the mast1and the safety wireline6. The frequency of vibrations emanating from the safety wireline6is approximately ten times higher than the vibrations of the mast1. The shock absorber jacks44are the means to dampen such undesired vibrations or shocks.

FIG.11shows a pad eye45used to couple the sling wires47to the mast1using a socket with lock pins to facilitate lifting of the mast1with sling wires47. The pad eye45may vary in size and shape based on the required safe working load. Specifically, the actual diameter of the hole, plate thickness, and other dimensions of the pad eye45varies according to the chosen safe working load which considers a load of the mast1, gravity force, bearing stress, shear stress, tensile stress and combined bending and tensile stress—Von-Mises stress. In particular, the pad eye45is mounted on desired locations2on the mast1, and connected to two separate wires47(sling wires) followed by shock absorber jacks44and another set of sling wires47.

A method associated with using a safety system in accordance with one or more embodiments may include coupling one end of the safety wireline6to a mast1by using a three-point connector5, a plurality of sling wires3, and a plurality of shock absorber jacks44, as shown inFIG.10. The other end of the safety wireline6remains anchored to a wall37of a drum11in a spool8, as shown inFIG.6. Once the mast1is raised to an operating position, such as shown inFIG.1, a safety system100may be applied to a mast system50such as shown inFIG.3. The spool8is rotated in coordination with the drawworks10such that the pawl14is maintained in a position that allows the rotation of the spool8. The spool8is rotated until the safety wireline6is in tension in order to avoid any accidental fall of the mast1due to sagged safety wireline6. One skilled in the art would appreciate how the method immediately detects the falling of the mast1once the falling accident occurs without any delays because the safety wireline6is maintained in tension.

Positions of components of a mechanical brake in the spool8, mainly a pawl14, is maintained while the rotation speed is less than or equal to a threshold (that is, 6 RPM), as shown inFIG.6Awhere pawl14stays with the rotor13without being received to the internal threads12. When the rotation speed exceeds the threshold, the pawl14moves to a different position to engage with the internal threads12of the spool8due to an increase in centrifugal force, which locks further rotation of the drum11. One skilled in the art would appreciate how the safety system100would mitigate the complete collapse of the mast1even when a failure occurs in the drawworks itself, because the safety system100is a separately working system that activates upon centrifugal force. The safety system100in accordance with one or more embodiments does not rely on power supply such as electricity. This further gives a benefit of the safety system100over other currently available safety systems that may fail if a failure occurs in the power supply because of their reliance on electricity.

While the disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate that other embodiments can be devised that do not depart from the scope of the disclosure as described. Accordingly, the scope of the disclosure should be limited only by the accompanying claims.