NZ569341A - Repair free welded joint and method - Google Patents

Abstract

A leak inhibition system for a welded joint is disclosed. The system comprises a first pipe end 102, a second pipe end 104, both having an annular recess 132 along their interior surfaces. An inner sleeve 100, having a first end 108 and a second end 110 which has an outer diameter less than the inner diameter of the first and second pipes. The inner sleeve has a length greater than twice the distance from the annular recess to the end of one of the first and second pipes.

Description

569341 NEW ZEALAND Patents Act 1953 Patent Form No 5 COMPLETE SPECIFICATION Title: REPAIR FREE WELDED JOINT AND METHOD We, Orrcon Operations Pty Ltd, 121 Evans Road, Salisbury, Qld 4107, Australia (Australian), do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement.

P:\ComrrtonWord97\25501 -260Q0\25800QRR\20GBG&23JPONZ - cap ftfing.doc received IPONZ 02/09/2008 569341 REPAIR FREE WELDED JOINT AND METHOD Field of the Invention The present invention relates to a system and method for providing a substantially repair free welded pipe joint.

Background of the Invention A joint allows pipe portions to be joined together during installation of a pipeline by a metal welding process. The steel pipe is internally lined with various corrosion protective materials. These lining materials wil! have thermal properties that make them sensitive to large temperature gradients and the high temperatures typically observed during welding processes. Accordingly it is 15 desirable to contain the heat from the welding process in such a way so that the weld region will remain free of corrosion during use. This has the benefit of eliminating the need for any interna! repair of the lining to be made.

Summary The present invention in one preferred aspect provides for a joint design including of a length of pipe which has both ends expanded and an internal sleeve to couple the two lengths of pipe. The pipes and the sleeve are coated externally and lined internally with a corrosion protective film. The region in the immediate 25 vicinity of the girth welding process is not coated to avoid fumes during welding.

The expanded ends are formed in such a way as to contain a gasket one of the purposes of which is to create a fully sealed and self contained area; called the weld chamber. The gaskets stops fluid, slurry or gas from entering the weld 30 chamber and results in negligible ongoing corrosion. During operation, as the pipeline conveys a fluid or slurry, oxygen becomes depleted inside the weld chamber and reduces the corrosion rate to a negligible amount. Furthermore the 2 received IPONZ 02/09/2008 569341 coupling sleeve with the gaskets acts in such a way as to contain the pressure of the pipeline outside of the weld chamber. The girth weld if it were to corrode will not leak as long as the pipeline pressure does not exceed the capacity of the gasket. in the centre of the sleeve a heat resistant material may be applied to reduce the amount of radiant heat onto the sleeve from the welding process and to stop any weld spatter from damaging the sleeve. The two ends of the sleeve have a slight taper to reduce the force required to assemble the joint. The length of the sleeve 10 is designed to cause minimum disruption to the fluid flow through the pipe, but avoid physical contact with the internal surface of the expanded pipe ends.

The internal sleeve is spaced sufficiently far away from the girth weld so that radiant heat and subsequent conduction of that heat does not damage the 15 internal lining of the sleeve. Attached to the sleeve may be wedges that act to restrain lateral movement of the sieeve inside the joint during joint assembly and operation of the pipeline. The wedge material is made of a material that has thermal properties such that it resists and insulates the sleeve from the weld heat that dissipates along the expanded pipe ends during the girth welding operation.

Brief Description of the Figure Fig. 1 is a partial cross-sectional side view of a system for inhibiting leaks in a welded joint in accordance with a preferred embodiment of the present invention.

Detailed Description of the Drawings Alternative embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed 30 herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the claims which follow. 3 received IPONZ 02/09/2008 569341 Fig. 1 shows a preferred embodiment of a welded joint system 10 including an inner sleeve 100, a first pipe 102 and a second pipe 104. The preferred elements of the system and their interrelationship are described below.

Referring to Fig. 1, inner sleeve 100 includes a body 106 having a first end 108, a second end 110, a mid-longitudinal axis MLA through the ends, an exterior surface 112, and an interior surface 114 that forms a passage 116, preferably with a coating 118 of corrosion protection material. Exterior surface 112 preferably includes a securing means such as annular wedges 120 and a layer 10 122 of thermal resistant material. Examples of appropriate thermal resistant material include, but are not limited to thin silica refractory braid tape or aluminium reflective tape. Layer 122 preferably circumferentially surrounds body 106 in a central portion of the body. Layer 122 preferably has a width of approximately 25 mm. Wedges 120 are preferably a weld bead. It will be appreciated that inner 15 sleeve 100 may be assembled with the pipes by friction fit without the use of wedges 120.

Inner sleeve 100 preferably has a length of approximately 150 mm. First and second ends 108, 110 are each preferably angled toward the mid-longitudinal 20 axis approximately 2.5 degrees. It will be appreciated that these dimensions and orientations are representative only and may be varied as appropriate.

The structure of second pipe 104 is similar to that of first pipe 102, so unless otherwise stated, the description of first pipe 102 will be understood to apply to 25 second pipe 104 as appropriate. First pipe 102 preferably includes a neck region 123, an end region 124 having an end 126, an exterior surface 128 and an interior surface 130 having an annular recess 132. First pipe 102 preferably has a mid-longitudinal axis that is coaxial with the mid-longitudinal axis of inner sleeve 100. Neck region 123 has a first diameter that is preferably substantially uniform over a 30 majority of the length of the pipe. End region 124 is preferably an enlarged region with a diameter preferably greater than that of neck region 123. End region 124 preferably has a length in the range of approximately 50 to 80 mm. Annular 4 received IPONZ 02/09/2008 569341 recess 132 is preferably configured to receive at least a portion of a sealing means, such as gasket 134. Pipes 102, 104 are preferably made from steel. It will be appreciated that the pipes may be made from other materials such as iron, copper and alloys thereof. Inner sleeve 100 is preferably made of the same 5 material as the pipes, but may be made of a different material than the pipes if appropriate or if desired.

Exterior surface 128 and interior surface 130 each preferably include a coating 136 of corrosion protection material. Coating 136 preferably terminates before 10 reaching end 126 to form a bare region 138. Terminating the coating before the end reduces the possibility that the heat from the weld could affect the coating and release noxious fumes into the environment. Coating 136 is preferably an epoxy material. An example of a coating suitable for use with the joint is Copon Hycote. It will be appreciated that other materials may be used such as, but not 15 limited to polyethylenes and ploy urea.

Preferably inner sleeve 100, first pipe 102, second pipe 104 and gaskets 134 are assembled together to form a sealed weld chamber 140 below the region where a weld 142 is to be applied. Weld chamber 140 preferably includes a gap 144 with 20 a depth or vertical height between the interior surfaces 130 of the pipes and the exterior surface 112 of the inner sleeve in the range of approximately 2 to 7 mm, more preferably 4 to 6 mm, and most preferably approximately 5 mm. It will be appreciated that the ranges described above may include a subset of ranges therein without departing from the scope of the present invention. The precise 25 gap required depends on the wall thickness of the pipe and the welding specification. For example, a thicker wall requiring a number of weld passes may require an increase in the dimension of the gap.

When assembled, the inner diameter of inner sleeve 100 preferably substantially matches the diameter of the neck region of the adjoining pipes to reduce the turbulence of the flow through the pipes and inner sleeve. It will be appreciated that the wall thickness of the inner sleeve may vary as desired. For example, the received IPONZ 02/09/2008 569341 wall thickness of the inner sleeve may be the same, greater than or less than the wall thickness of one of the pipes.

Having described the preferred components of the welded joint system, a 5 preferred method of use will now be described with reference to Fig. 1. First pipe 102 is positioned as appropriate in the field. Gasket 134 is inserted into annular recess 132. First end 108 of inner sleeve 100 is inserted into the end region of pipe 102, preferably to a depth in the range of approximately 80 to 200 mm, more preferably 120 to 160 mm. Another gasket 134 is inserted into second pipe 104. 10 Second end 110 of inner sleeve 100 is inserted into the enlarged portion of second pipe 104. Preferably, the inner sleeve is inserted relative to the interior surfaces of the first and second pipes so that a weid chamber having a gap is formed between the exterior of the inner sleeve and the interior surfaces of the first and second pipes below the region which is to be welded. First and second 15 pipes 102, 104 are positioned relative to one another so that their ends contact. A first pass weld is performed to weld the first and second pipes to one another. Subsequent weld passes are preferably performed 2 to 6 minutes, more preferably 5 minutes after the previous weld pass. Additional weld passes are performed as required. If desired, in some circumstances, subsequent weld 20 passes may be performed immediately after the previous weid pass.

It will be appreciated that the steps described above may be performed in a different order, varied, or omitted entirely without departing from the scope of the present invention. For example, the gaskets may be inserted simultaneously with 25 the inner sleeve with the inner sleeve including annular recesses configured to receive gaskets instead of or in addition to annular recess 132 of the interior of the pipes.

The foregoing description is by way of example only, and may be varied considerably without departing from the scope of the present invention. For example oniy, the outer diameter of the inner sleeve may be less than the minimum diameter of the pipes. The inner sleeve may be attached to the pipes 6 received IPONZ 02/09/2008 569341 using other means such as other shaped surface projections as appropriate. Other sealing means may be used to seal the weld chamber, for example, use of an appropriate sealing material that is applied as a liquid or coating. The inner sleeve may omit the thermal resistant material as desired. One or both of the 5 pipes may be configured so that a weld chamber is formed without the need for an inner sleeve. For example only, the ends of each pipe may include an interlocking and/or partially overlapping inner extension that when assembled, forms a weld chamber below the region where the weld will be applied.

The pipes may include one or more tapped and threaded plugs in the wall which allow access to the weld cavity or gap after the weld has been completed. The plugs may be used to inject a filler material and/or anticorrosive material into the cavity or gap to provide additional anti-corrosion protection and structural stability. The plug also allows access to test the integrity of the weld via pressurising each 15 individual joint, independent of pressurising an entire pipeline.

The present invention in a preferred form provides many advantages. Examples of some of the advantages of the present invention include, but are not limited to providing a rigid restraint joint at pressures and in pipe sizes that are not viable 20 via mechanical couplings; a reduction in the preparation required for the joint prior to welding compared to conventional systems; reduction of the risk of damage to pipe lining (eg, either epoxy or cement mortar lining) and hence the need for internal repair after jointing; permits for higher pressure pipelines in high strength pipe to be considered for chemical and slurry applications simply by selecting an 25 appropriate liner based on the considerations of the properties such as wear and abrasion resistance; and is cost effective compared to thick wall PVC, cast iron or stainless steel pipes in demanding fluid transport applications. Another advantage of the present invention in a preferred form is that the configuration of the inner sleeve allows it to straddle the joint without projections or other 30 indicating means between the two pipes, thereby permitting at least a portion of the pipe ends to be in direct contact with each other for the weld process. Such a configuration also eliminates a step in the assembly of the joint (e.g., centring the received IPONZ 02/09/2008 569341 sleeve relative to the pipes) and contributes to the over all efficiency of the joint assembly method.

It will of course be realised that the above has been given only by way of 5 illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth. 8 received IPONZ 02/09/2008

Claims (13)

569341 The claims defining the invention are as follows:

1. A leak inhibition system for a welded joint, said system including: a first pipe having a length, an interior surface and an end region, said end 5 region including an end, an inner diameter and an annular recess along the interior surface; a second pipe having a length, an interior surface and an end region, said end region of said second pipe including an end, an inner diameter and an annular recess along the interior surface; and 10 an inner sleeve having first end, a second end, a mid-longitudinal axis through said first and second ends, a passage having an interior surface oriented toward the mid-longitudinal axis and an exterior surface oriented away from the mid-longitudinal axis, said first and second ends of said inner sleeve each having an outer diameter less than the inner diameter of said end region of each of said first and second pipes, 15 said inner sleeve having a length greater than twice the distance from said annular recess to said end of one of said first and second pipes.

2. The system of claim 1, wherein a portion of the interior surface of one of said first and second pipes and a portion of the exterior surface of said inner sleeve 20 forming a gap in a plane perpendicular to the mid-longitudinal axis and passing through the exterior surface of said inner sleeve and the interior surface of said one of said first and second pipes.

3. The system of claim 2, wherein the gap extends between a portion of the 25 interior surface of both of said first and second pipes and a portion of the exterior surface of said inner sleeve.

4. The system of either claim 2 or 3, wherein the gap has a vertical height between the interior surface of each of said first and second pipes and the exterior 30 surface of said inner sleeve, the vertical height being in the range of 2 to 6 mm.

5. The system of claim 4, wherein the vertical height of the gap is approximately 5mm' ',NTELo^V^7l 2 5 AUS 2008 E C E I V F Di 569341

6. The system of any one of the preceding claims, wherein said inner sleeve includes a coating of corrosive resistant material along a portion of the interior surface of said sleeve. 5

7. The system of any one of the preceding claims, wherein at least one of said first and second pipes has a first inner diameter along a majority of the length of said pipe, said end of said pipe having a second inner diameter greater than the first inner diameter, said inner sleeve having an inner diameter generally equal to the first inner diameter of said pipe. 10

8. . The system of any one of the preceding claims, further including a means for sealing said inner sleeve with at least one of said first and second pipes.

9. The system of claim 8, wherein said sealing means includes a gasket 15 configured to fit at least partially within said annular recess of one of said pipes.

10. The system of claim 1, wherein each of said first and second pipes has an inner diameter along a majority of the length of each pipe that is less than the inner diameter of said end region of each of said first and second pipes. 20

11. The system of claim 10, wherein said inner sleeve has a thickness from said exterior surface to said interior surface that is approximately the same as the difference between the inner diameter of said end region of one of said pipes and the inner diameter along the majority of one of said pipes. 25

12. The system of any one of the preceding claims, wherein the end region of each pipe has a length in the range of 50 to 80 mm.

13. A system substantially as hereinbefore described with reference to any one of 30 the drawings.