GB2117851A

GB2117851A - Improvements in or relating to lined pipes

Info

Publication number: GB2117851A
Application number: GB08201516A
Authority: GB
Inventors: James Aiden Hawe
Original assignee: C AND J ENGINEERING
Current assignee: C AND J ENGINEERING
Priority date: 1982-01-20
Filing date: 1982-01-20
Publication date: 1983-10-19

Abstract

A pipe comprises pipe lengths (12, 13) having cement-mortar linings (14, 15) with the pipe lengths butt welded (24) together. The linings are provided with annular recesses (19) adjacent the marginal end portions of the inner surfaces (21) of the pipe lengths. The lining ends are sealed together with a resin (23). The weld material can penetrate radially inwardly of the inner surfaces (21) and overly the marginal end portions of the pipe lengths. The weld applies compression to the resin seal. The recesses (19) can be formed by using a removable former during centrifugal casting of the linings on the inner surfaces (21). <IMAGE>

Description

SPECIFICATION Lined pipes Cement-mortar lining is known for pipes; it is low in cost and applicable to new or used pipes.

Typically, a cement-mortar lining for a steel pipe is a concentric sheet of cement, between 0.3 cm and 0.6 cm (1/8 inch to 1/4 inch) in thickness depending on the inside diameter of the steel pipe. The lining is centrifugally cast against the internal wall of the pipe by high speed rotation of the pipe. The material of the lining can be a mixture of natural pozzolans and portiand cement, blended to give uniform consistency and high density, mixed with sand and water.

After curing, a strong mechanical bond is present between the lining and the steel pipe because of prestressing of the lining against the pipe wall during spinning.

Such pipes find use in the petroleum industry for coolant water flow. They can be used for sea water flow where corrosion potential is high.

The present invention is concerned with joining two lengths of lined pipe.

The known procedure for joining cement lined steel pipes is by use of an auxiliary sleeve into which the two ends of the pipes to be joined are located. Welds are then made between sleeve ends and pipes. A resin joint is made between the ends of the cement linings. This is somewhat cumbersome jointing procedure; the resultant joint has a rather limited ability to withstand internal pressures without leaking, and to retain its seal at the ends of the cement linings when the jointed pipe is being lowered into a trench with a measure of bending. The external surface of the pipe is not smooth at its joints.

The present invention aims to reduce or avoid the shortcomings of the known joints referred to above and provides a metal pipe length having a non-metallic protective lining in which the metal pipe is end-prepared for butt welding and the lining has annular recesses at the peripheries of its exposed ends.

In a jointed pipe made from two such pipe lengths, a seal at the joint is derived from two elements. The first element is a butt weld at the metal pipe ends with some of the weld metal extending into the cavity defined by two facing ends of the linings and the second element is a resin seal between the facing ends of the linings.

The invention also provides a method of making a metal pipe length having a non-metallic protective lining comprising an annular former adjacent the marginal end region of the inner surface of the pipe, centrifugally casting the lining on said inner surface and removing the former.

The former may, for example, be a resilient circular cross-section ring. The former is removed after casting to leave an annular recess in the lining adjacent said marginal end portion.

The invention may be formed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a section through a joint between two lengths of pipe according to the invention; and Fig. 2 is a section on an enlarged scale of an end of a length of pipe.

Fig. 1 shows the ends 1 0, 11 of two lengths of tubular steel pipe 1 2, 13 having cement-mortar linings 14, 1 5 respectively. The pipe ends are prepared (faces 1 6, 1 7) for butt welding. Prior to welding the pipes are clamped so as to leave a gap 18.

Quadrant-shaped, annular recesses 9 are provided in the linings 14, 1 5 at the junction between the end faces 20 of the linings and the inner walls 21 of the pipes. Similar recesses 19 are provided at the other (not shown) ends of the pipes 14, 1 5. The end faces 20 of the linings are in the same radial planes as the end faces of the pipes. The recess 1 9 extends inwardly from the pipe surface 21 by less than half of the radial thickness of the lining. Conveniently the annular recess 19 is formed during centrifugal casting of the lining by placing a removable former against the marginal end portion of the pipe wall 21. Such a former could, for example, be a circular crosssection rubber ring as indicated dotted at 22. The ring is removably held in place during casting, for example by a releasable clip.

After casting and lining, the two pipes are clamped to leave the space 18, and a suitable resin jointing compound 23 is then applied between the linings 14, 1 5 to fill the space between opposed end faces 20.

The pipes 12, 1 3 are then butt welded together at a weld 24, the weld material filling the space between surfaces 16, 17 and space 18 and flowing into recesses 19. The weld overlies a part of the adjacent marginal end portions 21 a of pipe inner surfaces 21 to provide a full penetration weld without damage to the linings whilst maintaining the desired lining thickness.

In forming and cooling the weld a small degree of shrinkage takes place at the gap 18 and this acts to compress and improve the seal provided by the resin 23.

A suitable jointing resin 23 is that available from Ault & iborg Paints Limited of Birmingham, England, under the name "Peridite".

The former 22 and recess 19 could have other shapes.

Whilst the invention is basically concerned with concrete-lined steel pipes it potentially has advantages generally for other metal pipes having other non-metallic linings such as may be required for example for heat insulated pipes.

A pipe line made of pipe lengths according to the invention can be trench laid so long as an allowable bending threshold is not exceeded. This may typically be 50 metres for a 7 cm pipe and 180 metres for a 27 cm pipe.

Claims

1. A metal pipe length (12) having a non metallic protective lining (14) in which the pipe

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Lined pipes Cement-mortar lining is known for pipes; it is low in cost and applicable to new or used pipes. Typically, a cement-mortar lining for a steel pipe is a concentric sheet of cement, between 0.3 cm and 0.6 cm (1/8 inch to 1/4 inch) in thickness depending on the inside diameter of the steel pipe. The lining is centrifugally cast against the internal wall of the pipe by high speed rotation of the pipe. The material of the lining can be a mixture of natural pozzolans and portiand cement, blended to give uniform consistency and high density, mixed with sand and water. After curing, a strong mechanical bond is present between the lining and the steel pipe because of prestressing of the lining against the pipe wall during spinning. Such pipes find use in the petroleum industry for coolant water flow. They can be used for sea water flow where corrosion potential is high. The present invention is concerned with joining two lengths of lined pipe. The known procedure for joining cement lined steel pipes is by use of an auxiliary sleeve into which the two ends of the pipes to be joined are located. Welds are then made between sleeve ends and pipes. A resin joint is made between the ends of the cement linings. This is somewhat cumbersome jointing procedure; the resultant joint has a rather limited ability to withstand internal pressures without leaking, and to retain its seal at the ends of the cement linings when the jointed pipe is being lowered into a trench with a measure of bending. The external surface of the pipe is not smooth at its joints. The present invention aims to reduce or avoid the shortcomings of the known joints referred to above and provides a metal pipe length having a non-metallic protective lining in which the metal pipe is end-prepared for butt welding and the lining has annular recesses at the peripheries of its exposed ends. In a jointed pipe made from two such pipe lengths, a seal at the joint is derived from two elements. The first element is a butt weld at the metal pipe ends with some of the weld metal extending into the cavity defined by two facing ends of the linings and the second element is a resin seal between the facing ends of the linings. The invention also provides a method of making a metal pipe length having a non-metallic protective lining comprising an annular former adjacent the marginal end region of the inner surface of the pipe, centrifugally casting the lining on said inner surface and removing the former. The former may, for example, be a resilient circular cross-section ring. The former is removed after casting to leave an annular recess in the lining adjacent said marginal end portion. The invention may be formed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a section through a joint between two lengths of pipe according to the invention; and Fig. 2 is a section on an enlarged scale of an end of a length of pipe. Fig. 1 shows the ends 1 0, 11 of two lengths of tubular steel pipe 1 2, 13 having cement-mortar linings 14, 1 5 respectively. The pipe ends are prepared (faces 1 6, 1 7) for butt welding. Prior to welding the pipes are clamped so as to leave a gap 18. Quadrant-shaped, annular recesses 9 are provided in the linings 14, 1 5 at the junction between the end faces 20 of the linings and the inner walls 21 of the pipes. Similar recesses 19 are provided at the other (not shown) ends of the pipes 14, 1 5. The end faces 20 of the linings are in the same radial planes as the end faces of the pipes. The recess 1 9 extends inwardly from the pipe surface 21 by less than half of the radial thickness of the lining. Conveniently the annular recess 19 is formed during centrifugal casting of the lining by placing a removable former against the marginal end portion of the pipe wall 21. Such a former could, for example, be a circular crosssection rubber ring as indicated dotted at 22. The ring is removably held in place during casting, for example by a releasable clip. After casting and lining, the two pipes are clamped to leave the space 18, and a suitable resin jointing compound 23 is then applied between the linings 14, 1 5 to fill the space between opposed end faces 20. The pipes 12, 1 3 are then butt welded together at a weld 24, the weld material filling the space between surfaces 16, 17 and space 18 and flowing into recesses 19. The weld overlies a part of the adjacent marginal end portions 21 a of pipe inner surfaces 21 to provide a full penetration weld without damage to the linings whilst maintaining the desired lining thickness. In forming and cooling the weld a small degree of shrinkage takes place at the gap 18 and this acts to compress and improve the seal provided by the resin 23. A suitable jointing resin 23 is that available from Ault & iborg Paints Limited of Birmingham, England, under the name "Peridite". The former 22 and recess 19 could have other shapes. Whilst the invention is basically concerned with concrete-lined steel pipes it potentially has advantages generally for other metal pipes having other non-metallic linings such as may be required for example for heat insulated pipes. A pipe line made of pipe lengths according to the invention can be trench laid so long as an allowable bending threshold is not exceeded. This may typically be 50 metres for a 7 cm pipe and 180 metres for a 27 cm pipe. Claims

1. A metal pipe length (12) having a non metallic protective lining (14) in which the pipe length is end-prepared (16, 18) for butt welding and the lining (14) has annular recesses (19) at the peripheries of its exposed ends.

2. A pipe comprising two pipe lengths as claimed in claim 1 in which the metal pipes are butt welded together with weld material (24) extending radial inwardly to occupy parts of the recesses (19) and the linings sealed by a resin (23) taken into compression between the ends of the linings.

3. A metal pipe length according to claim 1 substantially as hereinbefore described with reference to Fig. 2 of the drawings.

4. A pipe comprising two pipe lengths substantially as hereinbefore described with reference to Fig. 1 of the drawings.

5. A method of making a pipe lined with cement-mortar comprising providing an annular former adjacent the marginal end region of the inner surface of the pipe, centrifugally casting the lining on said inner surface, and removing the former.

6. A method as claimed in claim 5 in which the former is a resilient circular cross-section ring.

7. A method of making a pipe substantially as hereinbefore described.