GB1597711A

GB1597711A - Protectors for the ends of tubular elements

Info

Publication number: GB1597711A
Application number: GB52177A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-01-07
Filing date: 1977-01-07
Publication date: 1981-09-09

Description

(54) PROTECTORS FOR THE ENDS OF TUBULAR ELEMENTS (71) I ABDUL HAMEED QURAISHI, a British subject of 69 Roundhill Road, Kettering, Northamptonshire, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: Background of the Invention This invention relates to protectors for the ends of tubular elements (preferably tubular elements of annular cross-section), hereinafter referred to as "end protectors".

This invention is considered particularly, but not exclusively, applicable to end protectors for screw-threaded pipe ends.

In the past, commercially available end protectors for the screw-threaded ends of metal pipes have been constituted by a single homogeneous cap member of solid material e.g. either steel or a plastics or rubber material, the member being provided with a screw-thread for mating cooperation with the screw-threaded pipe ena.

With a single homogeneous cap member of solid plastics or rubber material, there is a danger that the end edge of the metal pipe will cut through the solid member when the latter is subjected to impact shock loads e.g.

from sharp objects such as stones on a rough ground during stacking operations. The insufficient puncture resistance of the solid member can, with some plastics materials, cause the member to shatter when strongly impacted, whilst other plastics materials have a poor tear strength or cut growth resistance, i.e. poor resistance to tear once a cut has been made. Such members are consequently limited to relatively light duty use.

For relatively heavy duty use, such as in the oil or gas exploration and/or extraction industry (e.g. off-shore drilling and mining), a steel end protector is commonly used.

Although this overcomes the above mentioned drawbacks of plastics or rubber materials, the steel member must undergo a costly process of being carefully and precisely machined with the requisite mating screwthread which, to avoid galling (i.e. metal-tometal welding or binding due to friction), must provide for a loose fit on the pipe end.

Even though the space between the steel end protector and metal pipe may be packed with an anti-corrosion agent such as a grease, ingress or corrosive elements can still occur during prolonged outdoor storage of the end protected pipes. Furthermore, assembling steel end protectors on to the screw-threaded ends of metal pipes requires considerable care and skill by the operatives to avoid over-tightening or cross-threading or an excessive interfacial stress at faces in metal-to-metal contact since any damage cannot be readily detected at the factory but only on the site or location of use when the end protectors are removed. Rejects or damage at this stage can have expensive consequences quite out of proportion to the intrinsic replacement cost of the components involved (a delay of one day in fulfilling a contract on a North Seal oil rig can involve a loss of several thousand pounds sterling). Moreover, there is a danger or likelihood that the steel end protector will transmit to the metal pipe end at least a substantial proportion of the shock, compression and bending stresses to which it is subjected.

Another form of end protector which has been proposed comprises an open ring of rubber having a metal band within it, the two ends of the open ring being forced towards one another by clamping means.

However, such an end protector leaves part of the metal pipe end open to corrosive elements through the gap between the ends of the open ring and also gives rise to problems in stacking the pipes provided with such incompletely encompassing end protectors.

Other proposals have been made for end protectors for the screw-threaded ends of metal pipes, e.g. in USA Patents Nos.

2212423, 2253729, 3000402, 4020873 and 4020874, in which the end protector comprises two separate components of which one is resilient and is sandwiched between the pipe thread and the other component which is a tubular metal formation having radially-directed flange-like portions overlying the pipe ends. In general it is necessary for the two components to be separated and sequentially applied in two assembly steps.

So far as the applicant is aware, none of these proposed two-component end protectors has been commercially manufactured or industrially adopted.

It is thought that this is due: (a) to the likely labour cost of the two-step assembly sequence, and/or (b) to the likely manufacturing cost of producing two separate components (of which said other component must be provided with its particular special formation), and/or (c) to the likely difficulty of inserting a mandrel for testing the pipe's straightness, and/or (d) to the likely difficulty of removing the end protector if the said other component is damaged and deformed (e.g. in the vicinity of the radially-directed flange-like portions).

Furthermore, none of the prior art end protectors for the screw-threaded ends of metal pipes provides a seal at each end of the protector that is transverse to the pipe axis.

Summary of the Invention It is thus clearly desirable to provide for tubular elements end protectors tht are capable of overcoming at least some of the disadvantages and drawbacks referred to above in connection with end protectors of the prior art.

According to a first aspect of this invention there is provided a composite, generally tubular end protector for the end of a tubular element, comprising first and second members of which the first is relatively resilient with respect to the second, wherein the relatively resilient member is dimensioned and arranged for in use inti mately contacting the end of the tubular element and engaging sealingly against the tubular element at at least two axially spaced sealing zones of which one is a radial end face of the tubular element, and wherein the relatively rigid member is in engage ment with said relatively resilient member and consists of a cylinder of both uniform and constant cross-section from end to end thereof, said relatively resilient member comprising an elastomeric material formed in a mold of which said relatively rigid member is a part such as to be bonded to said relatively rigid member and be integral therewith without deformation of the relatively rigid member and without a separate adhesive.

As used herein, the expression "a cylinder of both uniform and constant crosssection from end to end thereof" is not to be interpreted as excluding a cylinder which would have such a cross-section but for the prescence of one or more transverse holes through the wall thereof. With an end protector for the screw-threaded end of a tubular element, it is through such a hole or holes that a tommy-bar or like implement can be inserted for assisting the screwing on and/or off of the end protector.

Advantageously, the relatively rigid member has an elongation at break less than 30% and the relatively resilient member has an elongation at break equal to or greater than 30%.

The said two members may be each of the same material or, as is preferred, may be of different materials.

Where the said two members are of different materials, these two materials preferably have different values of Young's modulus of elasticity in compression.

Advantageously, the relatively rigid member has a value of Young's modulus of elasticity in compression that is at least approximately 10 times the corresponding value of the relatively resilient member, In accordance with vthe above criteria, the relatively resilient member and the relatively rigid member may be selected, for example, from the following: a rubber having a said modulus value in the range 1.2 x 102 psi to 1.5 x 103 psi, a cross-linked urethane having a said modulus value of the order of 9 x 104 psi, a polyethylene having a said modulus value in the range 1.5 x 104 psi to 1.5 x 105 psi, a p.t.f.e. material having a said modulus value in the range 3 x 104 psi to 4 x 104 psi, a polyamide having a said modulus value in the range 9 x 104 psi to 2 x 105 psi, a polycarbonate having a said modulus value in the range 2 x 105 to 2.5 x 105 psi, an acrylic resin having a said modulus value of the order of 3 x 105 psi, a rigid PVC having a said modulus value of the order of 3.5 x 105 psi, a fibre reinforced vulcanised rubber having a said modulus value in the range 4 x 10 psi to 9 x 105 psi, a glass fibre reinforced polyester having a said modulus value in the range 9 x 105 psi to 5 x 106 psi, an epoxy derived urethane rubber copolymer having a said modulus value in the range 1.5 x 104 psi to 8 x 104 psi, a metal or metal alloy having a said modulus value in the range 9 x 10 psi to 2 x 107 psi. Other combinations of materials for the relatively rigid and resilient members will be apparent to those skilled in the art.

Preferably, the relatively resilient member comprises a thermosetting elastomeric material (advantageously of cellular form) having a high cut-growth resistance, and the relatively rigid member comprises a metallic material.

In a preferred embodiment of this invention the relatively resilient member comprises a urethane rubber copolymer, e.g. epoxy derived, having a said modulus value in the range 102 psi to 8 x 104 psi (preferably 104 psi), and the relatively rigid member comprises a sleeve of steel, having a said modulus value in the range 1.2 x 107 psi to 2 x 107 psi. Alternatively, the relatively rigid member may comprise a sleeve of glass fibre, the elastomeric material impregnating or being bonded to this sleeve during the moulding or casting.

Advantageously, the relatively resilient member of elastomeric material is moulded or cast to the relatively rigid member at low pressure.

Preferably the plastics or rubber material comprises an organic polymer.

Advantageously the said material comprises an elastomer or a rubber having a Shore hardness in the range A20 to D85 on the durometer scale.

In a particularly preferred embodiment said material comprises a urethane polymer (advantageously an epoxy derived urethane copolymer) having a Shore hardness in the range A20 to D85 on the durometer scale and a Young's modulus of elasticity in compression in the range 102 psi to 8 x 104 psi, preferably of the order of 104 psi.

In one example the elastomeric material of the relatively resilient member is in cellular form, foamed form or expanded form, preferably having an average density equal to or greater than 1.5 Ibs/cu.ft.

Where the end protector is for the screwthreaded end of a tubular element, the resilient member is provided (e.g. by moulding) with a screw-threaded to correspond with the screw-threaded end of the tubular element.

Brief Description of the Drawings By way of example, embodiments of this invention will now be described with reference to the accompanying drawings of which: Figure 1 shows in longitudinal axial section an assembly of a pipe coupling and a hollow pipe of annular cross-section for use in an oil well; Figure 2 shows an axial section through a first pin end protector according to this invention for the "pin end" of the assembly of Figure 1; Figure 3 is a plan view of the end protector of Figure 2 in the direction of arrow III; Figure 4 shows in axial section a first box end protector according to this invention for the "box end" of the assembly of Figure 1; Figure 5 is a plan view of the box end protector of Figure 4 in the direction of arrow V: Figure 6 is a plan view of a second pin end protector according to this invention; Figure 7 shows in axial section a third pin end protector according to this invention; Figure 8 shows in axial section a second box end protector according to this invention; and Figures 9 and 10 show further embodiments of this invention.

Detailed Description of Embodiments The assembly illustrated in Figure 1 comprises a hollow tubular steel pipe 1 of annular cross-section provided at each end 2, 3 with a taper the angle of which is exaggerated in the drawings for clarity of illustration. Each tapered pipe end 2, 3 is provided with a screw-thread 4,5 respectively, the form of the taper and screw-thread being appropriate to that required for an oil well pipe. The assembly illustrated comprises a coupling 6 screwed on to the tapered pipe end 3 to provide a sealed connection, this coupling 6 serving for the connection of like assemblies in series. The assembly thus has a so-called "pin end" provided by the tapered threaded pipe end 2, and has a so-called "box end" provided by the matingly tapered and threaded coupling 6. Before the assembly can be despatched to a desired site for installation in an oil well, thread protectors for both the pin end and the box end must be fitted in accordance with API specification 5A, section 9.

Figures 2 and 3 illustrate a pin end protector 7 according to this invention, and Figures 4 and 5 illustrate a box end protector 27 according to this invention; The pin end protector 7 of Figures 2 and 3 is a composite body comprising an outer tubular steel member 8 that is bonded by its inner surface with the outer surface of an inner tubular resilient. member 9. Preferably, but not necessarily, the axial lengths of the two members 8, 9 are substantially equal to one another and to the pin end portion of the assembly of Figure 1. The inner surface of tubular resilient member 9 has a circular cross-section and is provided with an appropriate taper and screw-thread 10 to correspond to the taper and screw-thread 4 of the pin end of the assembly. The resilient member 9 is also provided internally adjacent its smaller diameter end with a transverse, e.g. radial, sealing surface 11 for resilient surfacial sealing contact with the annular end face 12 of the assembly's pin end (see Figure 1). The geometry of sealing surface 11 accords with that of the end of the pipe assembly, e.g. API, VAM, Hydril, BDS etc, (API = American Petroleum Institute, and VAM, Hydril & BDS are trade marks). The resilient member 9 is also provided internally at its opposite, larger diameter end with a cylindrical sealing surface 13 having a diameter fractionally less than the outside diameter of the pipe 1 so that this cylindrical sealing surface 13 can resiliently and sealingly contact the exterior surface portion 14 of the pipe 1 beyond the tapered thread 4.

The pin end protector 7 is screwed on to the pin end of the pipe assembly of Figure 1 until the sealing surfaces 11 and 13 both mate with the corresponding surfaces 12 and 14 respectively to provide resilient seals against the ingress of corrosion producing agents to the taper and thread 4 of said pin end, and simultaneously physically isolating the taper and thread 4 of said pin end from the exterior to protect it against damage due to direct impact and/or abrasion by an outside agency. The transverse end surface of member 9 adjacent sealing surface 13 may also sealingly engage a corresponding transverse surface of the pipe assembly adjacent surface portion 14. The geometry of this transverse end surface will, like that of the surface 11, accord with the particular geometry of the pipe assembly (e.g. BDS, VAM or Hydril).

A diametrically extending borehole 15 is provided through both members 8, 9 of the pin end protector 7 between the radial sealing surface 11 and the adjacent axial end of the pin end protector 7. This hole 15 serves as an eyelet for the insertion of a tommy-bar or other tool thay may assist screwing the pin end protector 7 on to or off from the pipe assembly's pin end 2.

As is apparent from Figure 3, the tubular steel member 8 is of uniform hexagpnal cross-section from end to end. The flats 16 provided by the hexagonal shape of member 8 enable the pipe assembly fitted with the pin end protector 7 to rest in states of stable equilibrium and thereby reduce the likelihood or tendency of rolling of the pin end protected pipe assembly. Furthermore, the flats 16 assist in stacking a plurality of like pin end protected pipe assemblies in a convenient and/or space-saving manner.

Similar advantages result from the use of a pin end protector 17 according to Figure 6 which is similar to the pin end protector of Figures 2 and 3 except that its tubular steel member 18 is of generally triangular crosssection. (It will be appreciated that the degree of rounding-off or radiusing of the corners of the triangle in Figure 6 can be greater or less than that shown). The tubular steel member or sleeve of a pin end protector according to this invention may have a cross-section of different shape providing one or more flats 16, e.g. other polygonal shapes or D-shaped, or providing cusp-shaped points to provide like states of stable equilibrium. Alternatively, the sleeve may be a right-cylinder of uniform annular cross-section from end to end. Advantageously such sleeves can be constituted by conventionally formed pieces of pipe section, e.g. scrap pipe ends to minimise expense, and, apart from the provision of transverse holes such as 15 or 35 (see below), thus require no further shapechanging, forming or machining such as to provide inwardly-directed flange-like portions.

The box end protector 27 of Figures 4 and 5 is a composite body comprising an inner tubular steel member 28 that is bonded by its outer surface with the inner surface of an outer tubular resilient member 29. Preferably, but not necessarily, the axial lengths of the two members 28, 29 are substantially equal to one another and to the box end portion of the pipe assembly of Figure 1.

The outer surface of tubular resilient member 29 has a tapered portion of circular cross-section that is provided with a screwthread 30 to correspond to the taper and screw-thread 5 of the box end of the pipe assembly. The resilient member 29 is also provided externally adjacent its larger diameter end with a transverse, e.g. radial, sealing surface 31 for resilient surfacial sealing contact with the annular end face 32 of the pipe assembly's box end 6 (see Figure 1). The resilient member 9 is also provided externally at its opposite smaller diameter end with a transverse, e.g. radial, sealing surface 33 for resilient surfacial sealing contact of the interior surface portion 34 of the coupling 6.

The box end protector 27 is screwed into the box end of the pipe assembly of Figure 1 until the transverse sealing surfaces 31 and 33 both mate with the corresponding transverse surfaces 32 and 34 respectively to provide resilient seals against the ingress of corrosion producing agents to the taper and thread 5 of said box end and its sealing faces 32, 34; and simultaneously physically isolating the taper and thread 5 and said faces 32, 34 from the exterior to protect against damage due to direct impact and/or abrasion by an outside agency. With so-called premium joints such as BDS, VAM and Hydril pipe assemblies, the surfaces sealingly engaged by end protector surfaces 31, 33 (i.e. corresponding to surfaces 32, 34 of the illustrated pipe assembly) are spaced from the screw-thread and are inclined at an angle to the slope line of the threads 5.

A diametrically extending borehole 35 is provided through both members 28, 29 of the box end protector 27 between the radial sealing surface 31 and the adjacent axial end of the box end protector 27. This hole 35 serves as an eyelet for the insertion of a tommy-bar or other tool that may be used to assist the screwing of box end protector 27 into or out from the box end 6.

As is apparent frorn Figure 5, the tubular steel member 28 is a right-cylinder of uniform and constant annular cross-section from end to end and requires no further shape-changing forming or machining, e.g.

to provide outwardly-directed flange-like portions. The member 28 may be constituted by a conventionally formed piece of piPe section, e.g. a scrap pipe end. The tubular resilient member 29 has the portion of its outer surface between its sealing surface 31 and adjacent axial end formed with a hexagonal cross-section providing flats 36. These flats 36 enable the pipe assembly fitted with the box end protector 27 to rest in states of stable equilibrium, thereby reducing the likelihood or tendency of rolling of the box end protected pipe assembly, and assist in stacking a plurality of like box end protected pipe assemblies in a convenient and/or space-saving manner.

Similar advantages can arise by forming said resilient member portion with a different cross-sectional shape providing one or more flats 36, e.g. other polygonal shapes or Shaped, or with cusp-shaped points to provide like states of stable equilibrium.

Alternatively said portion of the resilient member 29 may have a cylindrical outer surface.

The end protectors of Figures 2 to 6 have their axial ends open, the opening being circlar and of diameter "d". This diameter "d" is arranged to provide the diametric clearance necessary to enable a pipe assembly fitted with these pin end and box end protectors to pass over a pipe-straightness testing-mandrel according to the relevant API specification (for oil well use) without requirung that the end protectors be first unscrewed and removed from the pipe assembly. Thus the end protectors can be unscrewed and removed after the end protected pipe assembly has been mounted on the mandrel and immediately before the pipe assembly is fed down the oil well.

However, the present invention also contemplates the provision of end protectors with closed ends. Preferred examples of such end protectors are shown in Figures 7 and 8.

The pin end protector 37 of Figure 7 is similar to that described above with reference to Figures 2 and 3 and/or to Figure 6, and is a composite body comprising an outer tubular steel member 38 integral with, and bonded by its inner surface to, the outer surface of an inner hollow resilient member 39. However, the pin end protector 37 is provided with a closure disc 40 integral with the resilient member 39 at the smaller diameter end of the resilient member 39 whereby the latter has an axial crosssectional shape of generally U-form.

The box end protector 47 of Figure 8 is similar to that described above with reference to Figures 4 and 5 and is a composite body comprising an inner tubular steel member 48 that is bonded by its outer surface to the inner surface of an outer hollow resilient member 49 s as to be integral therewith. However, the box end protector 47 is provided with a cup-shaped extension 50 integral with the resilient member 49 at the smaller diameter end of the latter whereby the latter has an axial crosssectional shape of generally U-form. Alternatively, the limbs of the cup-shaped extension 50 may be of zero extent so that its disc-like radial bight wall 51 extends across the opening in contact with the adjacent end of member 48. The radial discwlike wall 51 may even be disposed slightly inwardly of member 48 so as to enable the adjacent end of the protector 47 to seal resiliently against a transverse surface such as 34 of the pipe assembly of Figure 1.

When the pin end and box end protectors 37 and are fitted to a pipe assembly such as that of Figure 1, they seal off the whole of the inner surface of the pipe assembly against corrosive elements and thus enable the end protected pipe assembly to be stored outdoors for long periods of time without internal degradation. Furthermore, due to the resiliency of the material, the disc 40 and the radial disc-like wall 51 can serve as flexible diaphragms to accommodate pressure changes in the air trapped within the sealed pipe assembly as the temperature varies. The box end protector 47 also allows a lifting hook to be inserted into the box end without damaging the coupling or pipe interior, particularly the threads and sealing faces.

The integral closure disc 40 of pin end protector 37 and the cup-shaped extension 50 (or at least wall 51) of box end protector 47 may each be attached in a tear-away fashion to its associated resilient member 39, 49 for easy removal by or prior to insertion of the aforesaid pipe-straightness testing mandrel, leaving the remainder of resilient member 39, 49 in position on the ends of the pipe assembly. Alternatively, the closure disc 40 and the cup-shaped extension 50 may each be formed as a separate component attached (preferably in a readily removable manner) to the resilient member 39, 49.

In the above-described embodiments of this invention, the relatively rigid member 8, 18, 28, 38 and 48 was steel, preferably mild steel. Other compositions may however be employed for the rigid member.

Examples include glass fibre compositions and metal compositions such as bronze, copper, brass, aluminium and like metals and/or metal alloys.

The relatively resilient member 9, 29, 39 or 49 is moulded or cast of a mouldable or castable elastomeric material, advantageously so as to have a cellular or foam construction, in a mould that is partially formed by the relatively rigid member 8, 28, 38 or 48 respectively so that the two members are bonded to one another in the manner of a laminate. Preferably the moulding or casting operation is by the pouring or low-pressure injection of the material into the mould. This casting or low-pressure injection moulding technique renders it unnecessary for the relatively rigid member to be accurately dimensioned since, in the absence of high pressure, there is only a minimal sealing requirement between the mould parts - one of which is constituted by the relatively rigid member itself. The taper and threads of the resilient member are formed by the mould as the mouldable material is being cast or moulded to form the resilient member and bond it to the rigid member. This mouldable material may be a natural rubber or a synthetic polymer e.g. a styrene butadiene rubber or a polyurethane elastomer. Other examples of suitable mouldable materials are organic polymers of the nature of thermoplastics (e.g. polyethylene, polypropylene and polystyrene) or of a thermosetting nature (e.g. a polyester, urethane or epoxy). Two especially suitable mouldable thermosetting elastomeric materials are a urethane polymer and an epoxy derived urethane rubber copolymer such as those manufactured by Wright & Sumner Limited (of 55 Argyll Street, Kettering, Northants, England) respectively under the names CUE 02036 (cellular or non-cellular) and CUE 02038; each is moulded to have a Young's modulus of elasticity in compression in the range 102 psi to 8 x 104 psi, preferably of approximately 104 psi.

The relatively resilient member 9, 29, 39 or 49 preferably has a value of Young's modulus of elasticity at least 10 times less than that of the relatively rigid member 8, 28, 38 or 48 respectively, and preferably also has a value of Shore hardness in the range A20 to D85 on the durometer scale. The Shore hardness D scale is an expanded scale of the upper end of the Shore hardness A scale (D45 is approximately equal to A92) which ranges from a minimum value of 0 to a maximum value of 100. Values of Shore hardness on the A scale correspond numerically with close approximation to the values of hardness on the International Rubber Hardness Scale which likewise ranges from a minimum value of 0 to a maximum value of 100. The American Society for Testing Materials provides a method (D1415/62T) whereby a correlation can be obtained between the IRH value and the value of Young's modulus of elasticity in compression.

The properties of the two materials of the members 8, 9; 28, 29; 38, 39 or 48, 49 are such that they each have a value of Young's modulus of elasticity in compression equal to or greater than 102 psi, the relatively ngid member having an elongation at break less than 30% and the relatively resilient member having an elongation at break equal to or greater than 30%.

Advantageously, the relatively resilient member 9, 29, 39 or 49 comprises an expanded polymer. The use of a foamed rubber or elastomer provides for increased resiliency and shock-absorbing properties, lightness of weight, economy and ease of manufacture. Each of the aforesaid urethane polymer CUE 02036 and the epoxy derived urethane copolymer CUE 02038 provides good results when expanded of the order of 10% of its original volume as well as when expanded up to 30 times its original volume. Expanded polymers having an average density of between approximately 1.5 Ibs/cu.ft. to 60 Ibs/cu.ft. (i.e. a void to solid ratio between about 98:2% and 2:98%) are considered suitable for the application of this invention. Methods of polymer expansion into foams of appropriate density and cell structure (e.g. open cells, closed cells, mixed open/closed cells, foams with non-cellular skins, foams with non-skinning surface(s), foam laminates, etc.) are all well documented in the literature and will be apparent to one skilled in the art without further elaboration here. It is considered that syntactic foams (including preformed hollow sphere

The exemplary composite bodies described above with reference to the drawings are each in the form of a laminate having two layers or plies integral with one another. Additional plies or layers may be provided of suitable material within the scope of the invention.

It will also be appreciated that the two members forming plies or layers of the composite body constituting an end protector according to this invention need not be of dissimilar materials but can be of the same material. This is exemplified by the end protectors 57 and 67 of Figures 9 and 10 according to this invention wherein the relatively rigid members 58 and 68 are each in the form of an imperforate skin or layer of plastics or rubber mouldable or castable material upon the surface of the relatively resilient member 59 or 69 which is a cellular or foamed form of the same plastics or rubber material. The relatively rigid member 58, 68 has an extension at break less than 30% whereas the relatively resilient member 59, 69 has an extension at break equal to or greater than 30%. Advantageously the mouldable or castable material is a thermosetting elastomer, e.g. a urethane polymer, or a foamed thermoplastic, e.g. polyethylene or PVC.

It will be noted that each of the abovedescribed end protectors according to this invention is of generally cylindrical form whereby when a pin end protector it encompasses all round the exterior surface of the pin end of a pipe assembly and when a box end protector it encompasses all round the interior surface of the box end of a pipe assembly (i.e. is encompassed all round by the box end of the pipe assembly). Although the resilient member of respectively the pin end and box end protectors extends axially over at least the majority of the pipe assembly's threads, the resilient member's threads need not extend over the entire length of the resilient member itself. This facilitates screwing on and off the protector, especially where the pipe assembly threads gradually run out, i.e. decrease in depth along the taper.

It will be appreciated that end protectors according to this invention may be unthreaded and/or untapered and smoothly cylindrical at their faces adapted and/or intended to contact the tubular element. It will also be aPpreciated that this invention is not restricted to end protectors for the ends of pipe assemblies as illustrated in Figure 1, but that end protectors for other tubular elements can be formed in accordance with this invention. Such tubular elements may be provided on or constituted by distillation columns, boilers, heat exchangers, riser pipes, pipe lines, drill bits, oil-well production strings, casings and drill pipes, and couplings. End protectors according to this invention can be arranged to protect the ends of such tubular elements against damage during manufacturing, stacking, storage, loading and/or unloading, shipment, transportation and installation operations.

There is no metal-to-metal contact between the above-described and illustrated end protectors and the tubular element so that galling and over-tightening of threads and sealing faces cannot occur, there is no danger of a burr accidentally spoiling the pipe thread, inter-metallic galvanic corrosion cannot arise, the end protectors can be removed and refitted by screwing on or off without demaging the thread, and crossthreading damage cannot occur.

WHAT I CLAIM IS: 1. A composite, generally tubular end protector for the end of a tubular element, comprising first and second members of which the first is relatively resilient with respect to the second, wherein the relatively resilient member is dimensioned and arranged for in use intimately contacting the end of the tubular element and engaging sealingly against the tubular element at at least two axially spaced sealing zones of which one is a radial end face of the tubular element, and wherein the relatively rigid member is in engagement with said relatively resilient member and consists of a cylinder of both uniform and constant crosssection from end to end thereof, said relatively resilient member comprising an elastomeric material formed in a mold of which said relatively rigid member is a part such as to be bonded to said relatively rigid member and be integral therewith without deformation of the relatively rigid member and without a separate adhesive.

2. An end protector according to clairn 1, wherein the relatively rigid member has an elongation at break less than 30% and the relatively resilient member has an elongation at break equal to or greater than 30%.

3. An end protector according to claim 1 or claim 2, wherein said two members each have a Young's modulus of elasticity in compression of at least 102 psi, and the relatively rigid member has a value of said modulus at least 10 times the value of said modulus for the relatively resilient member.

4. An end protector according to any one of the preceding claims, characterised in that the relatively resilient member comprises an organic polymer.

5. An end protector according to any one of the preceding claims, characterised in that the relatively resilient member comprises a thermoplastic or a thermosetting organic polymer.

6. An end protector according to any one of the preceding claims, characterised in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The exemplary composite bodies described above with reference to the drawings are each in the form of a laminate having two layers or plies integral with one another. Additional plies or layers may be provided of suitable material within the scope of the invention. It will also be appreciated that the two members forming plies or layers of the composite body constituting an end protector according to this invention need not be of dissimilar materials but can be of the same material. This is exemplified by the end protectors 57 and 67 of Figures 9 and 10 according to this invention wherein the relatively rigid members 58 and 68 are each in the form of an imperforate skin or layer of plastics or rubber mouldable or castable material upon the surface of the relatively resilient member 59 or 69 which is a cellular or foamed form of the same plastics or rubber material. The relatively rigid member 58, 68 has an extension at break less than 30% whereas the relatively resilient member 59, 69 has an extension at break equal to or greater than 30%. Advantageously the mouldable or castable material is a thermosetting elastomer, e.g. a urethane polymer, or a foamed thermoplastic, e.g. polyethylene or PVC. It will be noted that each of the abovedescribed end protectors according to this invention is of generally cylindrical form whereby when a pin end protector it encompasses all round the exterior surface of the pin end of a pipe assembly and when a box end protector it encompasses all round the interior surface of the box end of a pipe assembly (i.e. is encompassed all round by the box end of the pipe assembly). Although the resilient member of respectively the pin end and box end protectors extends axially over at least the majority of the pipe assembly's threads, the resilient member's threads need not extend over the entire length of the resilient member itself. This facilitates screwing on and off the protector, especially where the pipe assembly threads gradually run out, i.e. decrease in depth along the taper. It will be appreciated that end protectors according to this invention may be unthreaded and/or untapered and smoothly cylindrical at their faces adapted and/or intended to contact the tubular element. It will also be aPpreciated that this invention is not restricted to end protectors for the ends of pipe assemblies as illustrated in Figure 1, but that end protectors for other tubular elements can be formed in accordance with this invention. Such tubular elements may be provided on or constituted by distillation columns, boilers, heat exchangers, riser pipes, pipe lines, drill bits, oil-well production strings, casings and drill pipes, and couplings. End protectors according to this invention can be arranged to protect the ends of such tubular elements against damage during manufacturing, stacking, storage, loading and/or unloading, shipment, transportation and installation operations. There is no metal-to-metal contact between the above-described and illustrated end protectors and the tubular element so that galling and over-tightening of threads and sealing faces cannot occur, there is no danger of a burr accidentally spoiling the pipe thread, inter-metallic galvanic corrosion cannot arise, the end protectors can be removed and refitted by screwing on or off without demaging the thread, and crossthreading damage cannot occur. WHAT I CLAIM IS:

1. A composite, generally tubular end protector for the end of a tubular element, comprising first and second members of which the first is relatively resilient with respect to the second, wherein the relatively resilient member is dimensioned and arranged for in use intimately contacting the end of the tubular element and engaging sealingly against the tubular element at at least two axially spaced sealing zones of which one is a radial end face of the tubular element, and wherein the relatively rigid member is in engagement with said relatively resilient member and consists of a cylinder of both uniform and constant crosssection from end to end thereof, said relatively resilient member comprising an elastomeric material formed in a mold of which said relatively rigid member is a part such as to be bonded to said relatively rigid member and be integral therewith without deformation of the relatively rigid member and without a separate adhesive.

that the relatively resilient member comprises an elastomer or a rubber having a Shore hardness in the range A20 to D85 on the durometer scale.

7. An end protector according to any one of the preceding claims, characterised in that the elastomeric material of the relatively resilient member comprises a urethane polymer having a Shore hardness in the range A20 to D85 on the durometer scale.

8. An end protector according to any one of the preceding claims, characterised in that the elastomeric material comprises an epoxy derived urethane copolymer.

9. An end protector according to any one of the preceding claims, characterised in that the elastomeric material of the relatively resilient member is in cellular, foamed or expanded form having an average density equal to or greater than 1.5 lbs/cu.ft.

10. An end protector according to any one of claims 1 to 9, characterised in that said relatively rigid member is of metal, preferably mild steel.

11. An end protector according to any one of claims 1 to 10, and for the screwthreaded end of a tubular element, characterised in that the relatively resilient member is moulded or cast with a screw threaded surface enabling the end protector to be screw-threaded on to the said screwthreaded end of the tubular element.

12. An end protector according to any one of claims 1 to 11 and to encompass the so-called "pin" end of a tubular element, characterised in that the relatively rigid member is shaped to provide one or more states of stable equilibrium for the tubular element fitted with said end protector.

13. An end protector according to any one of claims 1 to 11 and to be encompassed by the so-called "box" end of a tubular element, characterised in that the relatively resilient member has a portion to extend outwardly of the tubular member, which portion is shaped to provide one or more states of stable equilibrium for the tubular element fitted with said end protector.

14. An end protector according to claim 12 or 13, characterised in that said shape is polygonal, D-shaped or provided with pointed cusps.

15. An end protector according to any preceding claim and for the screw-threaded end of a tubular element, wherein the resilient member has threads to engage the threads of said tubular element when in use and also has two axially spaced surfaces, other than threads, constituting said sealing zones and extending in planes transverse to the axis of the end protector for engaging sealingly against corresponding surfaces of the tubular element when in use, the threads of said resilient member being disposed between said two surfaces.

16. An end protector according to any preceding claim, characterised in that the resilient member has a Young's modulus of elasticity in compression in the range 102 psi to 8 x 104 psi.

17. An end protector according to any preceding claim and for the screw-threaded end of a tubular element, characterised by the provision of one or more transverse holes through a generally cylindrical wall thereof whereby a tommy-bar or like implement can be inserted for assisting the screwing on and/or off of the end protector.

18. An end protector for the end of a tubular element, substantially as herein described with reference to and/or as illustrated in Figures 2 to 9 of the accompanying drawings.

19. An end protector according to any preceding claim fitted on the end of a tubular element.

20. An end protector according to claim 19, wherein the tubular element is a pipe assembly substantially as herein described with reference to and/or as illustrated in Figure 1 of the accompanying drawings.