GB2029917A - Improvements in pipe swivels - Google Patents

Abstract

The invention describes a pipe swivel intended to be used at low temperatures, for example pipes carrying liquefied gas in the North Sea. The pipe swivel comprises an inner annular member 14 secured to one pipe section 10 and an outer annular member 18 secured to the other pipe section 12. The annular members 14 and 18 are formed of separable parts and retain inner and outer races 30 and 32 made of a different material. In this way, the material used for the annular members 14 and 18 is suitable for welding whilst the material used for the races is one chosen to be suitable for such use at low temperature. <IMAGE>

Description

SPECIFICATION Improvements in pipe swivels This invention relates to pipe swivels. The invention is particularly intended for use to enable relative rotation of sections of a pipe carrying a liquefied gas under low temperature for use in fluid transfer systems in the North Sea.

A pipe swivel is normally comprised of a pair of annular bearing races spaced by rolling bearing elements and each connected to a respective one of the two pipe sections which are to be permitted to rotate relative to each other. A seal is provided between the inner and outer races to prevent leakage. Hitherto, it has not been possible to produce a fully satisfactory pipe swivel for use at low temperatures as it has been difficult to adopt a material which, whilst operating satisfactorily has a bearing, at low temperatures can reliably be welded to the pipe sections.

According to the present invention, there is provided a pipe swivel comprising an inner annular member adapted to be welded to a first pipe section and formed of a material suitable for welding, a second annular member surrounding the first annular member and connected to a flange arranged to be welded to the second section of the pipe, the inner and outer annular members being assembled from separable parts which retain respective inner and outer race members formed of a material which is suitable for low temperature bearings.

Preferably, the material used for the bearing races is titanium orthe alloy Nimonic 90 as marketed by the firm INCO (Europe) limited.

Preferably, the separable halves of the inner annular member are arranged to be secured to each other by means of bolts which lie at an angle to the swivel axis of the pipe swivel. The latter construction enables the swivel to have a smaller outer dimension.

Conveniently, seals are provided between the inner annular member and the said flange to prevent fluid leakage.

The invention will now be described further, by way of example, with reference to the accompanying drawing, which is a partial section through a pipe fitted with a swivel in accordance with the invention.

In the accompanying drawing, two pipes 10 and 12 are connected to each other by means of a swivel generally designated 22 which allows the pipes 10 and 12 rotate relative to each other. The swivel 22 is formed on an inner annular member 14 welded at 16 to the pipe 10 and an outer annular member 18 welded at 20 to the pipe 12. The inner annular member 14 is formed of separable parts 14a and 14b which are secured to one another by means of bolts 24 which extend at an angle to the axis of the pipes 10 and 12. The outer annular member 18 is formed of a flange 18a welded to the tube 12 and two cylindrical rings 18b and 18c which are held together by means of bolts 26. The parts 14a and 18a are formed of a material which may readily be welded to the tubes 10 and 12. Such a material is not normally suitable for use as a race in a low temperature bearing.For this reason, balls 28 provided as the rolling bearing elements of the swivel do not roll directly on the inner and outer members 14 and 18 but instead roll on races 30 and 32 which are held in place by the inner and outer annular members. The inner race 30 is held axially between a shoulder of the part 14a and the part 14b whilst the outer race 32 is formed of two parts 32a and 32b which are held between shoulders on the parts 18b and 18e of the outer annular member. The inner and outer annular members are formed in separable parts in order to allow assembly of the races 30 and 32 and the outer race 32 is formed in parts in order to allow the introduction of the balls 28. It is, of course, alternatively possible for the inner race to be formed of separable parts.

Two seals 40 and 42 are arranged between the flange 18a and the part 14a, each seal being generally U-shaped in section and having opposite limbs in contact with the respective parts 14a and 18a. Metal rings separated by an annular corrugated spring are assisted by the pressure in the pipes 10 and 12 to urge the sides of the U-section ring against the parts 14a and 14b. A further seal 44 is provided to prevent ingress of dirt into the rolling bearing.

A passage 41 is formed in the flange 18a and terminates in the annular gap between the seals 48, 42. The passage 41 enables the pressure between the two seals to be monitored so that in the event of failure of the seal 40 this failure can be detected before any leakage past the second seal 42.

1. A pipe swivel comprising an inner annular member adapted to be welded to a first pipe section and formed of a material suitable for welding, a second annular member surrounding the first annular member and connected to a flange arranged to be welded to the second section of the pipe, the inner and outer annular members being assembled from separable parts which retain respective inner and outer race members formed of a material which is suitable for low temperature bearings.

2. A pipe swivel as claimed in Claim 1 in which the bearing races are formed of titanium.

3. A pipe swivel as claimed in Claim 1, in which the bearing races are formed of Nimonic 90 alloy.

4. A pipe swivel as claimed in any preceding Claim, in which the separable halves of the inner annular members are arranged to be secured to each other by means of bolts which lie at an angle to the swivel axis of the pipe swivel.

5. A pipe swivel as claimed in any preceding Claim, in which seals are provided between the inner annular member and the said flange to prevent fluid leakage.

6. A pipe swivel constructed substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawing.

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in pipe swivels This invention relates to pipe swivels. The invention is particularly intended for use to enable relative rotation of sections of a pipe carrying a liquefied gas under low temperature for use in fluid transfer systems in the North Sea. A pipe swivel is normally comprised of a pair of annular bearing races spaced by rolling bearing elements and each connected to a respective one of the two pipe sections which are to be permitted to rotate relative to each other. A seal is provided between the inner and outer races to prevent leakage. Hitherto, it has not been possible to produce a fully satisfactory pipe swivel for use at low temperatures as it has been difficult to adopt a material which, whilst operating satisfactorily has a bearing, at low temperatures can reliably be welded to the pipe sections. According to the present invention, there is provided a pipe swivel comprising an inner annular member adapted to be welded to a first pipe section and formed of a material suitable for welding, a second annular member surrounding the first annular member and connected to a flange arranged to be welded to the second section of the pipe, the inner and outer annular members being assembled from separable parts which retain respective inner and outer race members formed of a material which is suitable for low temperature bearings. Preferably, the material used for the bearing races is titanium orthe alloy Nimonic 90 as marketed by the firm INCO (Europe) limited. Preferably, the separable halves of the inner annular member are arranged to be secured to each other by means of bolts which lie at an angle to the swivel axis of the pipe swivel. The latter construction enables the swivel to have a smaller outer dimension. Conveniently, seals are provided between the inner annular member and the said flange to prevent fluid leakage. The invention will now be described further, by way of example, with reference to the accompanying drawing, which is a partial section through a pipe fitted with a swivel in accordance with the invention. In the accompanying drawing, two pipes 10 and 12 are connected to each other by means of a swivel generally designated 22 which allows the pipes 10 and 12 rotate relative to each other. The swivel 22 is formed on an inner annular member 14 welded at 16 to the pipe 10 and an outer annular member 18 welded at 20 to the pipe 12. The inner annular member 14 is formed of separable parts 14a and 14b which are secured to one another by means of bolts 24 which extend at an angle to the axis of the pipes 10 and 12. The outer annular member 18 is formed of a flange 18a welded to the tube 12 and two cylindrical rings 18b and 18c which are held together by means of bolts 26. The parts 14a and 18a are formed of a material which may readily be welded to the tubes 10 and 12. Such a material is not normally suitable for use as a race in a low temperature bearing.For this reason, balls 28 provided as the rolling bearing elements of the swivel do not roll directly on the inner and outer members 14 and 18 but instead roll on races 30 and 32 which are held in place by the inner and outer annular members. The inner race 30 is held axially between a shoulder of the part 14a and the part 14b whilst the outer race 32 is formed of two parts 32a and 32b which are held between shoulders on the parts 18b and 18e of the outer annular member. The inner and outer annular members are formed in separable parts in order to allow assembly of the races 30 and 32 and the outer race 32 is formed in parts in order to allow the introduction of the balls 28. It is, of course, alternatively possible for the inner race to be formed of separable parts. Two seals 40 and 42 are arranged between the flange 18a and the part 14a, each seal being generally U-shaped in section and having opposite limbs in contact with the respective parts 14a and 18a. Metal rings separated by an annular corrugated spring are assisted by the pressure in the pipes 10 and 12 to urge the sides of the U-section ring against the parts 14a and 14b. A further seal 44 is provided to prevent ingress of dirt into the rolling bearing. A passage 41 is formed in the flange 18a and terminates in the annular gap between the seals 48, 42. The passage 41 enables the pressure between the two seals to be monitored so that in the event of failure of the seal 40 this failure can be detected before any leakage past the second seal 42. CLAIMS

1. A pipe swivel comprising an inner annular member adapted to be welded to a first pipe section and formed of a material suitable for welding, a second annular member surrounding the first annular member and connected to a flange arranged to be welded to the second section of the pipe, the inner and outer annular members being assembled from separable parts which retain respective inner and outer race members formed of a material which is suitable for low temperature bearings.

2. A pipe swivel as claimed in Claim 1 in which the bearing races are formed of titanium.

3. A pipe swivel as claimed in Claim 1, in which the bearing races are formed of Nimonic 90 alloy.

4. A pipe swivel as claimed in any preceding Claim, in which the separable halves of the inner annular members are arranged to be secured to each other by means of bolts which lie at an angle to the swivel axis of the pipe swivel.

5. A pipe swivel as claimed in any preceding Claim, in which seals are provided between the inner annular member and the said flange to prevent fluid leakage.

6. A pipe swivel constructed substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawing.