Method and apparatus for multi-slip gripping of pipe and tubular goods

Abstract

A slip assembly for gripping against the external surface of a section of pipe or other tubular goods and supporting axial loading has multiple sets of cooperating wedge-like slip members movably mounted within a slip bowl. A first set of slip members having a smaller taper angle (that is, having a greater vertical component) exerts a predetermined and limited radial gripping force on the pipe or other tubular good. Thereafter, a second set of slip members having a larger taper angle (that is, having a lesser vertical component) takes over and exerts additional radial gripping force on the pipe or other tubular good.

Claims

1. A slip assembly for gripping pipe and other tubulars comprising: a) a slip bowl member having a central bore defining a tapered inner bowl surface; b) a first slip member having first tapered inner slip surface, a first tapered outer slip surface, and at least one substantially upwardly facing shoulder on said first tapered inner slip surface, wherein said first tapered outer slip surface is slidably disposed on said inner bowl surface; c) a second slip member having a second inner slip surface, a second tapered outer slip surface and at least one substantially downwardly facing shoulder on said second tapered outer slip surface, wherein said second tapered outer slip surface of said second slip member is slidably disposed on said first tapered inner slip surface of said first slip member; d) at least one insert die member disposed on said second inner slip surface of said second slip member; and e) a bias spring disposed between said first and second slip members wherein said bias spring is adapted to create a gap between said upwardly and downwardly facing shoulders, and wherein said upwardly and downwardly facing shoulders contact each when gripping force exerted by said second slip member on a pipe section exceeds a predetermined amount.

2. The slip assembly of claim 1, wherein said tapered inner bowl surface and first tapered outer slip surface of said first slip member define a first acute angle from a longitudinal axis of said pipe section, said first inner slip surface of said first slip member and said second tapered outer slip surface of said second slip member define a second acute angle from the longitudinal axis of said pipe section, and said first acute angle is larger than said second acute angle.

3. The slip assembly of claim 1, wherein the size of said gap between said upwardly and downwardly facing shoulders is adjustable.

4. A slip assembly for gripping pipe and other tubulars comprising: a) a slip bowl member having a central bore defining a first tapered inner bowl surface; b) a first plurality of slip members, each having an inner surface, an outer surface, and at least one substantially upwardly facing shoulder on said inner surface, wherein said outer surfaces are slidably disposed on said tapered inner bowl surface and said inner surfaces cooperate to define a second tapered bowl surface; c) a second plurality of slip members, each having an inner surface, an outer surface and at least one substantially downwardly facing shoulder on said outer surface, wherein said outer surfaces of said second plurality of slip members are slidably disposed on said second tapered bowl surface defined by said inner surfaces of said first plurality slip members; d) a plurality of insert die members disposed on said inner surfaces of said second plurality of slip members; and e) a bias spring disposed between said first plurality and second plurality of slip members wherein said bias spring is adapted to create a gap between said upwardly and downwardly facing shoulders, and wherein said upwardly and downwardly facing shoulders close said gap and contact each other when gripping force exerted by said second plurality of slip members on a pipe section exceeds a predetermined amount.

5. The slip assembly of claim 4, wherein said outer surfaces of said first plurality of slip members define a first acute angle from a longitudinal axis of said pipe section, said inner surfaces of said first plurality of slip members and outer surfaces of said second plurality of slip members define a second acute angle from the longitudinal axis of said pipe section, and said first acute angle is larger than said second acute angle.

6. The slip assembly of claim 4, wherein the size of said gap between said upwardly and downwardly facing shoulders is adjustable.

7. A method of gripping pipe and other tubulars comprising: a) inserting a section of pipe in a slip assembly, said slip assembly comprising: i) a slip bowl member having a central bore defining a first tapered inner bowl surface; ii) a first plurality of slip members, each having an inner surface, an outer surface, and at least one substantially upwardly facing shoulder on said inner surface, wherein said outer surfaces of said first plurality of slip members are slidably disposed on said first tapered inner bowl surface, and said inner surfaces of said first plurality of slip members cooperate to define a second tapered bowl surface; iii) a second plurality of slip members, each having an inner surface, an outer surface and at least one substantially downwardly facing shoulder on said outer surface, wherein said outer surfaces of said second plurality of slip members are slidably disposed on said second tapered bowl surface defined by said first plurality of slip members; iv) at least one insert die member disposed on said inner surfaces of said second slip members; v) at least one bias spring disposed between said first plurality and second plurality of slip members, wherein said at least one bias spring is adapted to create a gap between said upwardly and downwardly facing shoulders; b) engaging said second plurality of slip members against said pipe section and said second tapered bowl defined by said inner surfaces of said first plurality of slip members; c) closing said gap between said upwardly and downwardly facing shoulders, wherein said shoulders contact each other, when pipe gripping force exerted by said second plurality of slip members exceeds a predetermined amount; and d engaging said first plurality of slip members against said first tapered inner bowl surface of said slip bowl.

8. The method of claim 7, wherein said outer surfaces of said first plurality of slip members define a first acute angle from a longitudinal axis of said section of pipe, said inner surfaces of said first plurality of slip members and outer surfaces of said second plurality of slip members define a second acute angle from the longitudinal axis of said pipe section, and said first acute angle is larger than said second acute angle.

9. The method of claim 7, wherein the size of said gap between said upwardly and downwardly facing shoulders is adjustable.

Description

BRIEF DESCRIPTION OF DRAWINGS/FIGURES

(1) The foregoing summary, as well as any detailed description of the preferred embodiments, is better understood when read in conjunction with the drawings and figures contained herein. For the purpose of illustrating the invention, the drawings and figures show certain preferred embodiments. It is understood, however, that the invention is not limited to the specific methods and devices disclosed in such drawings or figures.

(2) FIG. 1 depicts a side sectional view of a section of pipe being gripped by the slip assembly of the present invention.

(3) FIG. 2 depicts an exploded perspective view of slip members and insert dies of the present invention.

(4) FIG. 3 depicts a top view of assembled slip members and insert dies of the present invention.

(5) FIG. 4 depicts a side view of assembled slip members and insert dies of the present invention.

(6) FIG. 5 depicts a side sectional view of assembled slip members and insert dies of the present invention along line 5-5 in FIG. 3.

(7) FIG. 6 depicts a detailed view of the highlighted area depicted in FIG. 4.

(8) FIG. 7 depicts an alternative detailed view of the components in FIG. 6.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

(9) FIG. 1 depicts a side sectional view of a pipe section 200 being gripped by slip assembly 100 of the present invention. As depicted in FIG. 1 and as described herein, slip assembly 100 comprises a set of “lower slips” or “spider slips” that are generally disposed surrounding an opening in a rig floor that is substantially aligned with the upper opening of a well. Notwithstanding the foregoing, it is to be observed that the slip assembly of the present invention can be utilized in connection with other pipe gripping uses or applications (other than lower spider slips) without departing from the scope of the present invention. Generally, slip assembly 100 of the present invention comprises a plurality of slip members, as more fully described herein, that cooperate to selectively grip against the outer surface of pipe section 200.

(10) Slip assembly 100 of the present invention comprises a slip bowl member 10 having a body member 11 with a central bore 12 extending therethrough for receiving a section of pipe or other tubular (such as pipe section 200), and defining a generally arcuate inner surface 13. Said inner surface 13 is generally disposed at an acute angle relative to the central longitudinal axis of bore 12 (and pipe section 200). Accordingly, the diameter of bore 12 is greater at its upper end than at its lower end. Although not depicted in FIG. 1, a plurality of elongate keyway slots extend along at least a portion of said bore 12.

(11) Still referring to FIG. 1, a plurality of central slip members 20 are slidably disposed within bore 12 of slip bowl assembly 10. Said central slip members 20 have a substantially tapered contour profile, wherein each of said central slip members 20 is wider at its top 27 than at its bottom 28. Each of said central slip members 20 further defines an inwardly-facing inner surface 21 and an outwardly-facing outer surface 25 that is generally shaped to conform to inner surface 13 of bore 12 of slip bowl member 10. Outer surface 25 of each central slip member 20 is slidably disposed on cooperating inner surface 13 of slip bowl 10. Said inner surface 21 of each central slip member 20 defines an angled surface having at least one upwardly facing shoulder member 22.

(12) A supplementary slip member 30 is moveably disposed on inner surface 21 of each central slip member 20. Said supplementary slip members 30 each have a substantially wedge-shaped or tapered contour profile; each of said supplementary slip members is wider at its top 37 than at its bottom 38. Said supplementary slip members each define an inwardly-facing inner surface 31, as well as outwardly-facing outer surface 35 having at least one downwardly facing shoulder member 36. Insert die assemblies 40 having a plurality of teeth-like projections are disposed along the inner surfaces 31 of said supplemental slip members 30. Said insert die assemblies 40 have generally arcuate inner surfaces which beneficially have similar curvature to the outer surface of pipe section 200. Alternatively, said insert die assemblies 40 can optionally have substantially flat faces with little or no arcuate curvature, which may be more effective when used with certain types or sizes of pipe.

(13) FIG. 2 depicts an exploded perspective view of a central slip member 20, supplemental slip member 30 and an insert die assembly 40 of the present invention. Said central slip member 20 has a substantially tapered contour profile defining an inwardly-facing inner surface 21 and an outwardly-facing outer surface 25. At least one alignment key member 26 extends from said outer surface 25. As depicted in FIG. 1, outer surface 25 of each central slip member 20 is slidably disposed on cooperating inner surface 13 of slip bowl 10; although not shown in FIG. 1, said alignment key 26 can be slidably received within a keyway slot extending along said inner surface 13 of bore 12 of slip bowl 10 to secure said central slip members 25 against lateral movement within said bore 12.

(14) Inner surface 21 of central slip member 20 defines an angled surface having upwardly facing shoulder members 22, as well as a recess or void 23 extending into the body of said central slip member 20. Threaded bore 24 extends from the upper surface of said central slip member 20 into recess 23. Adjustment bolt 60 and bias spring 70 are received within said threaded bore 24 as described in more detail below.

(15) As noted above, supplementary slip member 30 is moveably disposed on inner surface 21 of central slip member 20. Supplementary slip member 30 has a substantially wedge-shaped or tapered contour profile defining inner surface 31 and outer surface 35 having downwardly facing shoulder members 36. Biasing member 39 extends from said outer surface 35 of supplementary slip member 30 and is generally aligned with recess 23 in inner surface 21 of central slip member 20. Although not visible in FIG. 2, said biasing member 29 has a bore extending through said biasing member.

(16) In a preferred embodiment, inner surface 31 has a plurality of beneficially arranged die carrier projections 32 and a central elongate slot 33 for mounting insert die assemblies 40. Insert die assemblies 40 comprise die carriers 43 having rear wedge projections 44. Said rear wedge projections 44 are beneficially arranged to engage in mating relationship between die carrier projections 32 of supplemental slip member 30. Locking rod 52 can be received within central elongate slot 33 and secured in place to prevent lateral movement of said die carriers 43 relative to supplemental slip member 30. In a preferred embodiment, said locking rod 52 can be secured in place using locking plate 50 having bores 53 extending there through; locking plate 50 is removably anchored to supplemental slip member 30 using locking bolts 51 that extend through bores 53 and are secured in threaded bores 34.

(17) Insert die assemblies 40 each further comprise die members 41 having a plurality of inwardly facing teeth-like projections 42. Said insert die members 41 are disposed along the inner surfaces of said die carriers 43 and can have generally arcuate inner surfaces which beneficially have similar curvature to the outer surface of a pipe or tubular to be gripped by slip assembly 100 of the present invention (such as, for example, pipe section 200 depicted in FIG. 1). Alternatively, said insert dies can optionally have substantially flat faces with little or no arcuate curvature, which may be more effective when used with certain types or sizes of pipe.

(18) Referring to FIG. 1, inner surface 21 and outer surface 25 of each central slip member 20 are disposed at acute angles relative to the central longitudinal axis of slip bowl bore 12 and pipe section 200; in most operational installations, including the configuration of slip assembly 100 depicted in FIG. 1, the central longitudinal axis of slip bowl bore 12 and pipe section 200 are both oriented in a substantially vertical direction. In a preferred embodiment, the angle formed by said inner surface 21 and said vertical axis is less than the angle formed by outer surface 25 and said vertical axis.

(19) Similarly, outer surface 35 of each supplemental slip member 30 is also disposed at an acute angle relative to the central longitudinal axis of slip bowl bore 12 and pipe section 200 (vertical axis depicted in FIG. 1); such acute angle is substantially the same as the acute angle formed by said vertical axis and inner surface 21 of central slip member 20. By contrast, surface 31 of each supplemental slip member 30 is oriented substantially parallel to the central longitudinal axis of slip bowl bore 12 and pipe section 200 (vertical axis depicted in FIG. 1).

(20) FIG. 3 depicts a top view of an assembled central slip member 20, supplemental slip member 30 and insert die assembly 40 of the present invention. As discussed above, said central slip member 20 has a substantially tapered contour profile defining outwardly-facing outer surface 25 having at least one alignment key member 26 extending from said outer surface 25. Outer surface 35 of supplementary slip member 30 is moveably mounted against inner surface 21 of central slip member 20. Insert die assembly 40, comprising die member 41 having a plurality of inwardly facing teeth-like projections 42, is attached to supplemental slip member 30 and secured in place using locking plate 50 and locking bolts 51.

(21) FIG. 4 depicts a side view of an assembled central slip member 20, supplemental slip member 30 and insert die assemblies 40 of the present invention. Central slip member 20 has a substantially tapered contour profile defining outwardly-facing outer surface 25 and inner surface 21, as well as protruding alignment key member 26 extending from said outer surface 25. Outer surface 35 of supplementary slip member 30 is moveably mounted on inner surface 21 of central slip member 20.

(22) Inner surface 31 of supplemental slip member 30 has a plurality of beneficially arranged die carrier projections 32. Rear wedge projections 44 of die carriers 43 are beneficially arranged to engage in mating relationship between said die carrier projections 32 of supplemental slip member 30. Locking plate 50 is anchored to supplemental slip member 30 (using locking bolts 51 not visible in FIG. 4). Insert die members 41, each having a plurality of inwardly facing teeth-like projections 42, are disposed along the inner surfaces of die carriers 43.

(23) FIG. 5 depicts a side sectional view of assembled slip members and insert die assemblies of the present invention along line 5-5 in FIG. 3. Central slip member 20 has a substantially tapered contour profile defining outwardly-facing outer surface 25 having protruding alignment key member 26 extending from said outer surface 25. Outer surface 35 of supplementary slip member 30 is moveably mounted against inner surface 21 of central slip member 20.

(24) Biasing member 39 extends from said outer surface 35 of supplementary slip member 30 and is received within recess 23 in inner surface 21 of central slip member 20. Bias spring 70 is disposed below said biasing member 39 within said threaded bore 24, while bolt 60 having external threads 61 is received within said threaded bore 24 and extends through bore 39a in said biasing member 39, as well as bias spring 70. Insert die assemblies 40 are disposed on inner surface 31 of supplemental slip member 30. Locking rod 52 is received between supplemental slip member 30 and insert die members 40 and is secured in place using locking plate 50 which is anchored to supplemental slip member 30 using locking bolts 51 in threaded bores 34.

(25) Referring to FIG. 1, when slip assembly 100 of the present invention is used to grip against the external surface of pipe section 200, supplemental slip members 30 will first engage against said pipe section 200. As noted above, said supplemental slip members 30 are oriented at a smaller slip angle (that is, a slip angle having a larger vertical component) than central slip members 20. Said supplemental slip members 30 cooperate to exert sufficient radial force on said pipe section 200 so that said pipe section 200 will not slip or fall in an axial direction, even at lower string weights.

(26) Although the more aggressive vertical slip angle of supplemental slip members 30 could ordinarily crush or otherwise damage pipe section 200, said supplemental slip members 30 have a limited axial travel distance. Specially, as depicted in FIG. 7, as outer surface 31 of a supplemental slip member 30 slidably moves along the inner surface 21 of central slip member 20, downwardly-facing shoulder(s) 36 of said supplemental slip member 30 moves toward upwardly-facing shoulder(s) 22 of central slip member 20. As depicted in FIG. 6, eventually said downwardly-facing shoulder(s) 36 of said supplemental slip member 30 bottom out against upwardly-facing shoulder(s) 22 of central slip member 20.

(27) Referring to FIG. 5, threaded bolt 60 can be adjusted within threaded bore 24. When said threaded bolt 60 is unscrewed relative to said threaded bore 24, bias spring 70 acts to direct supplemental slip member 30 upward relative to central slip member 20. As such, downwardly-facing shoulder(s) 36 of said supplemental slip member 30 separate or form a gap relative to opposing upwardly-facing shoulder(s) 22 of central slip member 20 (see FIG. 7). In this manner, the travel distance between said opposing shoulders can be adjusted, thereby accommodating pipe having different sizes and/or specifications.

(28) Because downward movement of supplemental slip members 30 is limited, inward radial movement of insert die assemblies 40 is likewise limited. As a result, teeth 42 of insert die assemblies 40 are permitted to penetrate the outer surface of pipe section 200 only a predetermined amount. In a preferred embodiment, said teeth 42 generate a sufficient friction factor (typically over 1) against pipe section 200, even when debris or foreign material (for example, mill scale, pipe dope or drilling mud) is on the outer surface of such pipe, in order to securely grip said pipe section 200.

(29) After downwardly-facing shoulder(s) 36 of said supplemental slip member 30 bottom out against upwardly-facing shoulder(s) 22 of central slip member 20, the less aggressive slip angle (that is, a slip angle having a larger horizontal component) of said central slip members 20 acting against inner surface 13 of slip bowl assembly 10 take over. As a result, this less aggressive angle ensures that radial loading will not increase as quickly as pipe weight or other axial loading increases, thereby minimizing the crushing effect of such combined slip members on pipe section 200.

(30) Slip assembly 100 of the present invention automatically transfers from the more aggressive (more vertical) slip angle of the supplemental slip members 30 to the less aggressive (more horizontal) slip angle of the central slip members 20. Thus, no interaction from an operator is required, thereby reducing the risk associated with human error. Slip assembly 100 of the present invention has a large gripping range so multiple pipe diameters can be accommodated without significant changing of parts or other equipment in the field.

(31) Additionally, angled outer surface 25 of central slip member is substantially flat. Conventional slip and bowl assemblies typically include a cone member machined into a bowl and a matching cone member machined onto a corresponding slip member segment. Such a design is adequate when only a single pipe size is gripped with each slip configuration because the taper of the slip and the bowl match exactly when it contacts the pipe keeping the die contact on the pipe vertical, and distributing the load into the pipe evenly.

(32) Slip assemblies exist that can grip multiple pipe diameters without changing slip inserts. However, such assemblies are generally not compatible with such conventional cone designs. If slip members do not sit in a bowl at a machined position, the back of each slip member segment will only be supported in the center not on the sides—or, alternatively, only on the outside edges and not in the center.

(33) By contrast, the slip assembly of the present invention comprises a substantially flat back side along with a mating substantially flat surface on the inner surface of slip bowl assembly, thereby permitting a uniformly distributed load on the back of each slip member throughout the gripping range of the slip member, insuring a more uniform contact on pipe and minimizing any pinching or stress concentration areas.

(34) The above-described invention has a number of particular features that should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While the preferred embodiment of the present invention is shown and described herein, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention.