The present invention relates generally to machines for pushing and pulling rod strings through the ground and specifically to machines used to replace underground pipe and utilities.
The present invention is directed to an apparatus for pushing and pulling a rod string. The apparatus comprises a downhole tool, a stationary frame, a rod gripping assembly, and a cylinder assembly. The rod string is connected to the downhole tool at a first end and comprises a plurality of rod string sections connected together end-to-end. The stationary frame has an opening for the rod string to pass through the stationary frame. The rod gripping assembly comprises a slip bowl assembly, a pair of jaws disposed within the slip bowl assembly and around a rod string section disposed within the slip bowl assembly, a thrust member aligned with the slip bowl, and an actuator. The jaws are connected to the thrust member. The actuator moves the thrust member and the jaws relative to the slip bowl assembly to push the jaws into the slip bowl assembly to grip the rod string section disposed within the slip bowl assembly. The cylinder assembly pushes and pulls the rod gripping assembly relative to the stationary frame when the jaws are gripping the rod string and moves the gripping assembly relative to the rod string when the actuator has moved the yoke away from the slip bowl assembly to release the grip of the pair of jaws.
The present invention is directed to a rod gripping assembly. The assembly comprises a slip bowl assembly, a pair of jaws, a thrust member, and an actuator. The slip bowl assembly comprises a front flange, a rear flange, and a bowl supported between the front flange and the rear flange. The bowl has an opening with a greater diameter at an end proximate the rear flange and a lesser diameter at an end proximate the front flange. The jaws are disposed within the opening of the bowl and to surround a rod string section disposed within the opening. The thrust member is aligned with the opening of the bowl. The jaws are connected to the thrust member. The actuator moves the thrust member and jaws relative to the bowl to push the jaws into the bowl toward the end proximate the front flange to cause the jaws to grip the rod string section.
The present invention is likewise directed to a method for the replacement of an underground pipe. The method comprises connecting a rod string section to an end of a rod string and gripping the rod string section by moving a pair of jaws within a slip bowl assembly.
The rod string section is thrust toward the underground pipe while gripping the rod string section with the pair of jaws. The rod string section is released by partially withdrawing the pair of jaws from the slip bowl assembly and the pair of jaws are moved toward a proximate end of the rod string section. The rod string section or a new rod string section connected to the end of the rod string is gripped and thrust further into the underground pipe.
As the infrastructure of underground utilities has aged the need to replace these underground utilities has grown. However, home and business owners do not like to have their landscaping and streets dug up during the replacement of underground utilities. Thus, systems and methods for the replacement of underground utilities with minimal surface disruption have been developed. For example, horizontal directional drills are regularly used to install new and replace old utilities. Another technology widely used is pit launched rod pushing and pulling machines. These machines push a rod string, comprised of a series of rod string sections attached end-to-end, through the existing pipeline from the launch pit to an exit point remote from the machine. Sections of rod are added to the rod string as the rod string is pushed into the pipe.
One skilled in the art will appreciate that a downhole tool comprising a drill bit could be attached to the far end of the rod string to allow the rod string to be pushed through the ground or an existing pipe. Once the far end of the rod string reaches the target point a downhole tool may be attached to the far end of the rod string. The new pipe to be installed may be connected to the downhole tool so that the new pipe follows the downhole tool back through the ground or old pipe to the launch pit. The machine grips the rod string and, using hydraulic cylinders, pulls the rod string, downhole tool, and new pipe toward the launch pit. The downhole tool may comprise a pipe bursting head configured to either burst or slice the old pipe and push it into the surrounding soil.
Threaded pipe or rod strings are generally used in vertical and horizontal drilling and particularly in pipe bursting. The pipe sections range in length from a section of two feet to over fifteen feet in oil and gas operations. High tensile loads are applied to rod strings, whether they are hung vertically in a miles deep bore or deployed horizontally in a pipe burst.
Oil rigs use gravity assisted slips to hold the drill string off the bottom of the bore, such as when tripping out to change the drilling tooling, or to provide torsional restraint when adding or removing the top pipe from the string. Gravity assisted slips have a heavy walled outer slip bowl, slips, and jaws. The slip bowl is generally mounted on a structure that passes reaction forces to the ground, The slip bowl is ring shaped and has a conical inside surface running for its functional length, both ends of the bowl are open. The pipe or rod string is disposed at cylindrical centerline of the slip bowl. The angle of the conical side relative to the centerline is on the order of five (5) to fifteen (15) degrees with a preferred angle of ten (10) degrees per side. Without the slips engaged with the rod string, the rod string is free to move in either direction along the axial centerline, Slips are generally thin walled segments having a conical surface on a first side and a cylindrical surface on a second side. The conical surface of the slip is configured to slide with low friction against the conical inner surface of the slip bowl. The cylindrical inner surface of the slip is intended to produce a high coefficient of friction against the matching cylindrical surface of the rod and may have a hardened and serrated finish intended to bite into the mating rod surface. The inner surface is the jaw and may be a replaceable component within the slip. There are generally a minimum of two slips and often there are more, up to a dozen.
Gravity causes the slips to drop into the tapered annular space between slip bowl and the rod. This causes friction between the rod and the slips. As the rod string moves down under the force of gravity the slip moves with it deeper toward the small diameter end of the slip bowl. Movement continues until at least two opposing slips apply normal forces to the slip bowl cone and the rod string. At this point the rod will be centered in the bowl and both the normal forces and the friction forces of the engaged components rise quickly with slight distances of rod string travel.
The rod string and slips move deeper into the slip bowl until the friction forces on the rod string are equal in magnitude and opposite in direction to the weight (or other) forces pulling the rod string and causing movement. The rod will stop when the normal force around the bowl has caused the bowl to grow slightly within its elastic nature allowed by the geometry of all the components involved adjacent to and including the slip bowl. The present invention provides a system to induce slip movement toward the small end of the slip bowl without requiring the force of gravity. Such a system helps lead to successful clamping of the rod string in either the vertical or horizontal orientation. The system of the present invention also allows the rod string to be clamped when it is being pushed in a direction that would typically cause the slips and jaws to release their grip. Additionally, the system allows the rod string to be clamped for resisting torsional loads when no tensile or compressive load exists on the rod string to cause the jaws to grip the rod string. The powered gripping system of the present invention also provides a residual force on the rod string in the event the rod string is suddenly unloaded. The powered grip maintains the clamp load on the rod string and will cause the mass of the machine to absorb at least some of the stored energy to reduce the likelihood of the rod string traveling backwards through the machine unimpeded.
Turning now to the figures,
Turning now to
The rod gripping assembly 24 travels toward and away from the stationary frame 32 as the thrust frame 22 moves along the rails 20. The cylinders 26 are connected on a first end to the thrust frame 22 and on a second end to the stationary frame 32. Each cylinder 26 comprises a cylinder rod 36. The cylinder rods 36 are movable between a retracted and extended position in response to flow of hydraulic fluid to and from the cylinders 26. As shown, cylinder rods 36 of the cylinders 26 are in the extended position. The cylinders 26 expand and retract to increase or decrease the distance between the stationary frame 32 and the thrust frame 22, causing the rod string to either push into the ground or be pulled out of the ground. As shown, the cylinders 26 are diagonally disposed about the thrust frame 22 and therefore the rod string 12.
With continued reference to
The rod spinner 30 threads on or off sections of the rod string 12 to make up or break out the rod string during pushing or pulling operations. The rod spinner 30 may alternatively connect sections of the rod string without threading, if unthreaded sections are utilized. A rod support frame 40 travels with the thrust frame 22 and maintains alignment between a rod section about to be added or a newly removed rod section.
The stationary frame 32 is a reaction plate that is positioned to ground the machine 10 and allow the extension of the cylinders 26 to cause the thrust frame 22 to pull or push the rod string. The stationary frame 32 comprises a central aperture 42 and jacks 44. The rod string 12 travels through the central aperture 42 and through the rod gripping assembly 24. Jacks 44 stabilize the stationary frame 32 to the ground such that the operation of the thrust unit 10 does not cause excessive movement in the stationary frame.
Turning now to
Turning now to
A bracket 70 is attached to the rear flange 64 to support the actuator 50 in alignment with the slip bowl assembly 56. The bracket 70 may be fastened to the rear flange 64 with bolts 72. The actuator 50 is supported by the bracket 70 and comprises a hydraulic cylinder having an opening 74 which allows the rod string to pass through the actuator,
The rod gripping assembly 24 has a pair of shafts 76 to support the front flange 62, a bowl 92 (
Turning now to
The bracket 70 is supported on a side of the rear flange 64 opposite the bowl ring 88. The bracket 70 supports the actuator 50 in-line with the centerline axis 93 of the rod gripping assembly 24. The yoke 80 is connected to the actuator 50 and supports the actuator on the shafts 76.
Referring now to
The pair of slips 96 support jaws 58 disposed within the slip bowl assembly and around a rod string section 12 (
Thrust member 98 is connected to bracket 70, which is connected to actuator 50. The actuator 50 is a dual-action device that can move the thrust member 98, slips 96, and the jaws 58 relative to the slip bowl 92 to push the jaws into the slip bowl to grip the rod string section (
Turning now to
Actuators 116 are secured between flanges 108 and 110 with a rod 120 of each actuator extending through a hole in flanges 108 and 110. A spacer 122 facilitates actuator 118 and 116 assembly into the flanges 108 and 110 and mounts to the thrust member 124 via fasteners 126. In the embodiment of
Slips 134 are bolted in the tension/compression directions to the thrust member/yoke 124 by fasteners 136. Jaws 138 may be affixed to the slips 134. Jaws 138 are susceptible to wear and are therefore designed to be replaced easily, reusing slips 134. Slips 134, jaws 138 and fastener 136 make up an assembly that moves as a unit. While fastener 136 extends through yoke 124, the shouldering configuration causes the slips 134 to be loose in the obround holes 140 through which the bolts 136 extend.
The conical inner profile 114 of the bowl 112 causes a reduction in the distance between jaws 138 when slips 134 are thrust deeper into bowl 112. This reduction in distance causes jaws 138 to squeeze down and clamp on the rod string (
In operation, the push/pull machine 10 is positioned at a desired location such as a launch pit and a rod string is placed within the machine and started into the bore 14. Rod string sections are added to the uphole end of the rod string 12 using the spinner 30. Once a new rod string section has been connected to the uphole end of the rod string, the actuator 50 is operated to move the pair of jaws 58 or 138 within the slip bowl assembly 92 or 112 to grip the rod section. After the rod string has been gripped, the rod string section is thrust toward the underground pipe using the cylinders 26 while maintaining the grip to push the rod string into the pipe. Gripping the rod string section may be accomplished by activating the actuators 50 or 118 and 116 to move the jaws 58 or 138 to a gripping position. At the end of the cylinders' 26 push stroke the rod string section is released by partially withdrawing the pair of jaws from the slip bowl assembly. The rod gripping assembly 2 is moved toward the proximate end of the rod string section and the rod section is gripped again. The rod string is repeatedly gripped and released with the pair of jaws in coordination with operation of the cylinders 26 to thrust the distal end of the rod string to the target location.
The rod string is pushed into the ground or underground pipe until a distal end of the rod string reaches a target point. A downhole tool and a new pipe may then be connected to the distal end of the rod string. The downhole tool and new pipe are then pulled through the ground toward the machine 10 by repeatedly gripping and releasing the rod string to pull the rod string until it is removed from the ground and the new pipe has been pulled into its desired location.
Various modifications can be made in the design and operation of the present invention without departing from the spirit thereof. Thus, while the principle preferred construction and modes of operation of the invention have been explained in what is now considered to represent its best embodiments, which have been illustrated and described, it should be understood that the invention may be practiced otherwise than as specifically illustrated and described.
This application claims the benefit of provisional patent application Ser. No. 61/807,004, filed on Apr. 1, 2013, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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61807004 | Apr 2013 | US |