GB2131725A

GB2131725A - Improvements in or relating to a surface protected tubular member

Info

Publication number: GB2131725A
Application number: GB08332078A
Authority: GB
Inventors: William Robert Garrett
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-12-03
Filing date: 1983-12-01
Publication date: 1984-06-27
Also published as: GB8332078D0

Abstract

A tubular member 10 has a surface-protecting sleeve wherein the sleeve comprises at least two sections that meet together in at least one longitudinal slot 30. At the ends 26, 28 of the slot the mating edges are V- grooved, and the slot widens at the centre. A spacer 34, 36 is placed in the slot at either end of the sleeve and the sections of the sleeve are bridge welded together without penetrating the underlying tubular member. At the centre of the slot, the weld 38 does penetrate the surface. The longitudinal limits of the weld are within the thick area of the sleeve, not under a shoulder, and therefore any stress risers that occur because of the surface welding of the tubular member are not in a harmful location so that, the tubular member has the ability to flex or bend at either end of the sleeve since no weld is located in those places. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a surface protected tubular member The present invention relates to a tubular member protected against wear, such as a drill string member, by affixing a permanently-installed protective sleeve, to the tubular member without causing deleterious effects to the underlying tubular member.

A drill string operating in a well bore is in constant contact with the surface of the bore which leads to surface wear of the drill string members. If the drill string members are not suitably protected against such wear, the wall sections will weaken, through excess wear, causing the drill string members to fail. The prior art contains many methods of protecting a tubular member including, the addition of separate wear collars and the addition of wear elements to drill string members, or other tubular goods to provide the necessary protection against external surface wear. Also, many members are manufactured with sections of increased wall thickness strategically located to provide the required protection without an add-on structure.

Many of the specially designed and manufactured structures have proved to be satisfactory in operation; however, they are often expensive and unreliable in bore hole environments. Therefore, these special tubular members are generally only used where the expense is especially warranted and these tubular members are not employed in general service.

The use of separate wear collars has proved to be fairly satisfactory for short runs or for conditions of operation which are not too extreme.

However, separate collars are notorious for not maintaining their mechanical integrity under prolonged periods of service or under difficult, but routine, operating modes (e.g., during directional drilling operation). Finally, the methods that have previously been employed for attaching sleeves, or other structures, permanently to a standard drill string member have generally been unsatisfactory.

Many are unsatisfactory because attaching such collars to the tubular members has produced weakened zones within these tubular members.

These weakened zones are caused by a reduction in wall thickness of the tubular member or by the creation of stress risers or the like in the tubular member. Other methods are unsatisfactory due to inadequate attachment of the collar to the tubular member, leading to separation of the sleeve from the tubular member.

Two prior art methods of permanently attaching a collar to a tubular member are disclosed in the U.S. Patent Specification No.

3,193,918 and U.S. Patent Specification No.

3,360,846.

U.S. Patent Specification No. 3,193,918 discloses a method in which two sleeve halves are welded together without the weld penetrating the tubular member because the weld is made between the two sleeve halves on top of an asbestos rope. Random projections on the inside surface of the sleeve provide a frictional bond between the sleeve and the tubular member to maintain the sleeve in a desired position.

U.S. Patent Specification No. 3,360,846 also discloses a method of welding two sections of a sleeve together without the weld penetrating the underlying surface of the tubular member, with an epoxy resin used to cement the sleeve to the tubular member. In addition, one or more weld beads are made circumferentially around the sleeve and upon contraction, due to cooling, the weld beads hold the sleeve in place.

Both of the above patents avoid welding the sleeve into the surface of the underlying tubular member to avoid creating stress risers which promote material failure in the tubular members.

However, these techniques used to secure a sleeve to a tubular member without the addition of a weld that penetrates the surface of the tubular member have proved inferior in practice and, hence, the sleeves are unreliable under operating conditions, due to mechanical failure of the sleeve.

One of the reasons that a drill string member or other types of tubular member remain without protective collars or sleeves is due to the difference of opinion on the desirability of the prior art devices, all of which have drawbacks, as discussed above, for general use. A second reason is that a difference of opinions exists as to the exact location of collars and/or sleeves on the drill string or other tubular members (i.e., near the centre, near one or both of the joints, or in combination).

According to one aspect of the invention there is provided a surface-protected tubular member, comprising a tubular member, a sleeve having at least one slot extending longitudinally the length of said sleeve, and a longitudinal weld securing said sleeve to said tubular member.

Preferably, said weld comprises; portions bridging said slot at either end of said sleeve without penetrating the surface of the tubular member, and a penetrating portion securing the slot edges of said sleeve to said tubular member intermediate said bridging portions.

Desirably said sleeve includes a second slot extending longitudinally the length of said sleeve and also includes a second weld comprising portions bridging said second slot at either end of said sleeve without penetrating the surface of the tubular member, and a penetrating portion securing the edges of said second slot of said sleeve to said tubular member intermediate said bridging portions.

Conveniently said sleeve is tapered to a small dimension at both ends thereof, and said penetrating portion of the or each weld is located within the thick non-tapered part of the said sleeve.

Additionally said slot may be wider in the middle than at the ends for permitting the weld to penetrate freely therethrough to said tubular member.

In a preferred embodiment the two longitudinal limits of the bonding weld are within the thick area of the sleeve, not under a shoulder, and the tubular member has the ability to flex or bend at either end of the sleeve since no weld is located in these positions. Therefore any stress risers that occur because of the surface welding are not in a harmful location.

Preferably spacers are included at the ends of the or each said slot to prevent said bridging portions of said weld from penetrating to the surface of said tubular member.

Conveniently said sleeve is made of low carbon steel weldable without preheating.

According to another aspect of the invention there is provided a tubular sleeve for protecting the surface of a tubular member, comprising at least one slot extending longitudinally the length of said sleeve, the edges of said slot being V-shaped for welding convenience and said edges being closely spaced apart at their ends compared to their centres to permit weld flow-through between said centres for penetratingly welding to an underlying tubular member.

According to a further aspect of the invention there is provided a method of adding a surface protecting sleeve to a tubular member having end tool joints, which comprises the steps of forming a sleeve including at least one slot having longitudinal mating edges of the sections closely contiguous at the ends of said sleeve and leaving a centre opening therebetween, snugly pressing said sleeve about a location of said tubular member, bridge welding the edges of said slot of the sleeve together at its ends without penetrating to the surface of the tubular member and welding the edges of the centre of the slot together with the weld penetrating to said tubular member through said centre opening.

Additionally, after the step of snugly pressing said sleeve about said tubular member, a preferred method includes the step of inserting spacers between said mating edges of said slot at the ends thereof to prevent said bridge welding from penetrating said tubular member.

Conveniently said sleeve has tapered ends, said sleeve being welded to said tubular member whereby the weld is limited to a thick portion of said sleeve.

In order that the invention may be more readily understood and so that further features thereof may be appreciated, the invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a tubular member with a protective collar in accordance with a preferred embodiment of the invention; Figure 2 is a cross-sectional view of a sleeve on a tubular member in accordance with the preferred embodiment of the invention with parts of the view taken at different axial locations to show one region of the upper weld and another region of the lower weld, the view being taken on line 2-2 of Figure 4; Figure 3 is a top view of the mating edges of two sleeve sections of the embodiment of the present invention shown in Figure 2 prior to welding; and Figure 4 is a part longitudinal cross-sectional and part elevational view to the embodiment of the present invention shown in Figure 2.

Referring to the drawings Figure 1 shows a section of a tubular member in the form of drill pipe 10 having a protective sleeve or collar 12 affixed thereto in accordance with the invention at a desired location with respect to the pipe. The drill pipe is conventionally made from medium carbon content steel, and has a pin end 14 and a box end 1 6 and a length of approximately 30 feet (9.15 metres). Although there is a great variation in sizes, typically a drill pipe is available in two common sizes with outside diameters of about 4 inches (11.43 cms) and 5 inches (12.70 cms) respectively. The sleeve which is attached to the tubular member cannot be slipped over one of the ends since the pin and box joints are both of larger dimension than the outside diameter of the main body portion of the drill string member.Therefore, the sleeve 12 comprises two complementary sections 18 and 20 permitting the sleeve to be placed around the body of a tubular member at the desired location in two sections. As shown in Figure 2, each of the sections circumscribes aproximately one-half of the surface of tubular member 10 at the time of securement. The sleeve or collar 12 is typically approximately 6 to 24 inches (15 to 60 cms) in length and is tapered to form a shoulder at either ends 22 and 24.

For convenience of welding, the mating or contiguous edges of the two sections are slightly outwardly milled or slotted at edges 26 and 28 to form a V shape, as best shown in Figure 2. In addition, the dimension of the sleeve vis-a-vis the dimension of the drill pipe is such that there is a slight gap 30 at either end of sleeve 12 when the sections are placed around the pipe. The dimension of gap 30 is nominally one-eighth inch (0.31 cms). The gap 30 which exists between the edges of the two mating sections, has a wide central opening 32 approximately one half inch (1.27 cms) wide. The central opening 32 has, at each end, rounded shoulders having a radius of curvature of approximately one quarter inch (0.63 cms) located between the central opening 32 and the end regions of the gap 30. In the end regions of the gap 30 the edges of the sleeve sections are very close together. When the sleeve is assembled, as will now be described, spacer members 34,36 are located in the regions of the gap 30.

Figure 4 shows the final configuration of the sleeve after it has been applied to the drill pipe 10.

Welds connect the two sections of the sleeve together without penetrating the surface of the tubular member at the position of the spacer members 34 and 36. Thus the mating edges in the regions of the gap 30 are effectively welded to the spacer members 34, 36. However, the weld 38 in the central opening 32 between the spacer locations not only connects the two sections together but also penetrates the surface of the tubular member, as best shown in Figure 2.

When securing the sleeve 12 to the drill pipe 10 the desired location for attaching the sleeve is prepared, by cleaning the surface of the pipe. The bore of the sleeve 12 is then machined so that the sleeve 12 fits tightly or snugly on the pipe. This tight or snug fit is achieved by making the internal circumference of the sleeve section slightly smaller than the external circumference of the prepared area of the drill pipe to which the sleeve is to be attached.

One-half of the sleeve is then clamped in position to the drill pipe at the desired location resulting in slight expansion of the sleeve section, and spacer members 34 and 36 of one-eighth inch (0.03 cms) key stock of low carbon steel are placed in the desired positions adjacent the edges of the sleeve section that will be at the ends of the gap 30 that will be on either side of the sleeve section. Tack welds are then applied to connect the sleeve section to the spacer members.

The second section of the sleeve is then clamped in position, in alignment with the first section again resulting in a slight expansion of the sleeve section. Tack welds are again applied to hold the section to the spacer members 34 and 36. Care is taken so that the welds do not penetrate the surface of the drill pipe.

Complete welds are then made within the gap 30 at the ends of the sleeve welding the two sleeve sections completely together and to the key stock. As before deep welding is avoided so that the weld does not penetrate the surface of the drill pipe at these end locations. The welding of these end locations pre-heats the underlying drill pipe in preparation for the subsequent welding step.

The mounting of the sleeve sections of the drill pipe is completed by beading a weld into the central opening 32, joining the two sections of the sleeve together and also penetrating into the surface of the drill pipe which lies beneath the central opening 32. Pre-heating of the tubular member to at least 4000 is required to ensure a satisfactory welding of the tubular member, and this is achieved during the welding of the sleeve sections to the spacers and thus usually no additional pre-heating is required.

It will be understood that by following the welding procedure detailed above the regions of the drill pipe underlying the end sections of the sleeve 12 are not welded directly to the sleeve and the drill pipe is only welded directly to the sleeve in the region of the central opening 32. As a result there is no bending which occurs in use of the pipe which is in a harmful stress riser location, even though the weld does shrink slightly when it cools and provides a stiffer area than the area of the sleeve at the ends where there is no penetrating weld.

In addition to attaching a protective sleeve in the manner described above, it may be desirable to affix one or more additional hard metal rings of about 3/32 of an inch (0.23 cms) in thickness for enhancing the wear protection property of the sleeve. Typically, such a ring comprises tungsten carbide in a steel binder. The tungsten carbide does not melt when the ring is applied and provides no tensile strength to the ring or to the underlying member. However, the tungsten carbide does provide a very hard first contact surface to resist wear of the string pipe against the bore hole in operation.

The description which has just been given assumes a single sleeve 12 on drill pipe 10, located substantially mid-way between the pin end 14 and the box end 16. In another embodiment, sleeve 12 may be located near either the box or the pin end, as desired, or, multiple sleeves 12 may be located along the drill pipe, again as desired. The outside diameter of the sleeve may be of any dimension but it is preferably approximately the same as the external diameter of the pin end and the box end of the drill pipe.

However, the actual diameter of the sleeve is a matter of choice.

Although only a single embodiment of the invention has been shown and described, it will be understood that the invention is not limited thereto, since many modifications may be made and will become apparent to those skilled in the art. For example, although the sleeve which has been described is shown in two sections, it is possible to construct the sleeve from one section or from multiple sections. Also, the shape of the centre slot 32 is shown with a fairly uniform dimension longitudinally parallel to the axis of the tubular member and terminating in rounded radii in the vicinity of gap 30. This is to provide a convenient guide for welding. However, in a particular structure, gap 32 may take a different form so long as it provides the basic functional opening for the weld to connect the sections of the sleeve together as well as to penetrate to the underlying tubular member.

From the foregoing it will be understood that the preferred embodiment of the invention provides an improved method of protecting the surface of a tubular member wherein a sleeve can be attached to the tubular member by using surface-penetrating welds without creating harmful material stress risers. Also it will be understood that this embodiment provides an improved protective sleeve for attachment to the surface of an existing drill string member using surface penetrating welds which do not cause harmful stress risers in the material.

Claims

1. A surface-protected tubular member, comprising a tubular member, a sleeve having at least one slot extending longitudinally the length of said sleeve, and a longitudinal weld securing said sleeve to said tubular member.

2. A surface-protected tubular member according to claim 1, wherein said weld comprises portions bridging said slot at either end of said sleeve without penetrating the surface of said tubular member, and a penetrating portion securing the slot edges of said sleeve to said tubular member intermediate said bridging portions.

3. A surface-protected tubular member according to claims 1 or 2, wherein said sleeve includes a second slot extending longitudinally the length of said sleeve and including a second weld comprising portions bridging said second slot at either end of said sleeve without penetrating the surface of said tubular member, and a penetrating portion securing the edges of said second slot to said sleeve to said tubular member intermediate said bridging portions.

4. A surface-protected tubular member according to any one of the preceding claims, wherein said sleeve is tapered to a small dimension at both ends thereof, and wherein said penetrating portion of the or each said weld is located within the thick non-tapered body of said sleeve.

5. A surface-protected tubular member according to any one of the preceding claims, wherein the or each said slot is wider in the middle than at the ends for permitting the weld portion to penetrate freely therethrough to said tubular member.

6. A surface-protected tubular member according to any one of the preceding claims, and including spacers at the ends of the or each said slot to prevent said bridging portions of said weld from penetrating to the surface of said tubular member.

7. A surface-protected tubular member according to any one of the preceding claims, wherein said sleeve is made of low carbon steel weldable without preheating.

8. A tubular sleeve for protecting the surface of a tubular member, comprising at least one slot extending longitudinally the length of said sleeve, the edges of said slot being V-shaped for welding convenience and said edges being closely spaced apart at their ends compared to their centres to permit weld flow-through between said centres for penetratingly welding to an underlying tubular member.

9. A method of adding a surface-protecting sleeve to a tubular member having end tool joints, which comprises the steps of forming a sleeve including at least one slot having longitudinal mating edges of the sections closely contiguous at the ends of said sleeve and leaving a centre opening therebetween, snugly pressing said sleeve about a location of said tubular member, bridge welding the edges of said slot of the sleeve together at its ends without penetrating to the surface of the tubular member, and welding the edges of the centre of the slot together with the weld penetrating to said tubular member through said centre opening.

10. A method according to claim 9, and including, after the step of snugly pressing said sleeve about said tubular member, the step of inserting spacers between said mating edges of said slot at the ends thereof to prevent said bridge welding from penetrating said tubular member.

11. A surface-protected tubular member, comprising a tubular member, a sleeve with tapered ends, said sleeve welded to said tubular member whereby the weld to said tubular member is limited to a thick portion of said sleeve.

12. A surface-protected tubular member substantially as herein described with reference to and as shown in the accompanying drawings.

13. A tubular sleeve substantially as herein described with reference to and as shown in the accompanying drawings.

14. A method of adding a surface-protecting sleeve to a tubular member substantially as herein described with reference to the accompanying drawings.

15. Any novel feature or combination of features disclosed herein.