GB2531026A

GB2531026A - Apparatus and method for heating a section of a pipeline

Info

Publication number: GB2531026A
Application number: GB1417740.6A
Authority: GB
Inventors: Brindley David; Lord Lee
Original assignee: Pipeline Induction Heat Ltd
Current assignee: Pipeline Induction Heat Ltd
Priority date: 2014-10-07
Filing date: 2014-10-07
Publication date: 2016-04-13
Anticipated expiration: 2034-10-07
Also published as: GB2531026B; GB201417740D0

Abstract

An apparatus 10 for heating uncoated pipeline between coatings of a section of pipeline comprises at least two pivotally connected frame sections. The frame sections are rotatable between an open state in which the frame sections may be placed over or removed from a pipeline and a closed state in which the frame sections may surround a pipeline. It further comprises electrical conductors 60 mounted on the frame sections and arranged to form an induction heating coil having a central axis X-X when the frame sections are in the closed state. The apparatus also comprises support members 54, 56 disposed at each end of the induction heating coil 60 for supporting the apparatus upon coatings of a section of pipeline. The support members are disposed further from the central axis than the internal diameter of the induction heating coil 60. The support members can comprise support rollers, which are adjustable with respect to the central axis. It can optionally comprise means for aligning the induction coil with the uncoated section of pipeline.

Description

I

APPARATUS AND METHOD FOR HEATING A SECTION OF A PIPELINE

The present invention relates to an apparatus for heating uncoated pipeline between coatings of a section of pipeline and a method of heating uncoated pipeline between coatings of a section of pipeline.

The use of induction heating to heat bare steel sections of pipelines in preparation for field joint coating is well know and well documented. Many induction heating coils use electrical cables or other flexible elements as electrical conductors mounted in a substantially hollow cylindrical frame which may surround a section of pipeline. The frame may be hinged along one side for opening and closing to facilitate removal and replacement of the induction heating coil around the section of pipeline. The position of the induction heating coil needs to be closely controlled to maintain a uniform heat profile along the uncoated section of pipeline. For mechanical reasons, the centre line of electrical cable forming an induction heating coil passes through, very near to, the axis of the hinge to prevent the electrical cables from being stretched when the frame and its induction heating coil are moved between the open and close states.

A hollow cylindrical hinged frame is a well known construction which reduces weight and complexity and which reliably supports the induction heating coil during use. An induction heating process often directly follows a blasting and cleaning process. Preferably the induction coil frame does not come into contact with what is a freshly prepared bare surface of pipeline. To avoid this, known induction coil frames usually support themselves directly upon the factory coatings on either side of a bare uncoated section of pipeline to be heated. This may present a problem for field joints with thick factory coatings on either side of the uncoated section of pipeline. When the section of pipeline has a thick factory coating on each side of the field joint, the frame and the induction heating coil must have internal diameters that are greater than the factory coating diameter.

According to a first aspect of the invention, there is provided an apparatus for heating uncoated pipeline between coatings of a section of pipeline, the apparatus comprising: at least two pivotally connected frame sections rotatable between an open state in which the frame sections may be placed over or removed from a pipeline and a closed state in which the frame sections may surround a pipeline; electrical conductors mounted on the frame sections and arranged to form an induction heating coil having a central axis when the frame sections are in the closed state; support members disposed at each end of the induction heating coil for supporting the apparatus upon coatings of a section of pipeline, wherein the support members are disposed further from the central axis than the internal diameter of the S induction heating coil.

With induction heating, it is beneficial to have the electrical conductors, which may be flexible electrical cables, as close to the bare section of pipeline as possible.

As mentioned above, this presents a problem for pipelines with thick coatings, often used for improved insulation and mechanical protection, because the induction heating process usually directly follows blasting and cleaning of the uncoated section of pipeline. It is preferable that the induction coil frame does not contact the newly prepared surface. The invention allows the support members to be mounted upon, and supported by, the coatings of a pipeline section, regardless of the coatings thickness, whilst at the same time allowing the electrical conductors to be close to the bare pipeline which may be well below the outer circumference of the coatings. The invention effectively suspends the induction heater coil in the correct place at a chosen proximity to the uncoated pipeline. Advantageously, the pivot axis of the frame sections may be just as close to the uncoated pipeline as the electrical conductors. This avoids stretching the electrical conductors when the frame sections rotated between the open and close states. Advantageously, the induction heating coil may gain access to tight spaces between coatings or 90 degree cutbacks in coatings.

Preferably, the support members facilitate movement of the apparatus along the central axis. This may allow fine adjustment of frame sections in relation to the uncoated pipeline without need to spend time on raising the apparatus repetitively.

Preferably, the support members comprise support rollers. This may allow low friction fine adjustment. Preferably, the support rollers are adjustable with respect to the central axis. This may allow additional fine adjustment of frame sections in relation to the uncoated pipeline and/or allow for tolerances in the coating thicknesses.

Preferably, the frame sections comprise means for aligning the induction heating coil with uncoated pipeline. This may allow adjustment of frame sections in relation to the uncoated pipeline substantially without intervention of an operator.

Preferably, the support members are connected to the frame sections via at least one pivot having a pivot axis. This may allow movement of the frame sections between the open and close states independently of the state of the support members.

Preferably, the support members are connected to each other. This may provide additional stability to the apparatus as a whole.

S Preferably, the frame sections depend from the support members when in normal use. This may allow movement of the frame sections between the open and close states while the support members are supported upon coatings of a section of pipeline.

Preferably, the frame sections each comprise a handle. This may allow manual fine adjustment of frame sections in relation to the uncoated pipeline.

In a second aspect of the invention, there is provided a method of heating uncoated pipeline between coatings of a section of pipeline, the method comprising the steps of: (a) providing an apparatus of the first aspect of the invention; (b) disposing the at least two pivotally connected frame sections in an open state; (c) disposing the frame sections adjacent uncoated pipeline; (d) disposing the support members upon coatings of the section of pipeline; (e) disposing the frame sections in the closed state thereby surrounding the pipeline and forming the induction heating coil around the uncoated pipeline; and (U supplying the induction heating coil with alternating electrical current. The second aspect of the invention provides the advantages of the first aspect of the invention.

Preferably, the method comprises the steps of: ( g) ceasing supply of alternating electrical current to the induction heating coil; (h) disposing the frame sections in the open state thereby facilitating removal of the electrical conductors from around the pipeline; and (i) removing the support members from the coatings.

This may allow the apparatus to be raised and moved to another field joint further down the pipeline for heating more uncoated sections of pipeline.

Preferably, the method comprises the step of: locking the frame sections in the closed state between steps (e) and (fl; and optionally automatic unlocking of the frame sections from the closed state upon completion of step (g). This may prevent the frame sections from being inadvertently opened while alternating electrical current is flowing through the induction heating coil.

In order that the invention may be more clearly understood embodiments thereof will now be described, by way of example, with reference to the accompanying drawings of which: Figure 1 is a front perspective view of an apparatus for heating a field joint of a pipeline, with the apparatus in a closed state; Figure 2 is a side elevational view of the apparatus of Figure 1 with the apparatus in the closed state; S Figure 3 is a plan view of the apparatus of Figure 1, with the apparatus in the closed state; Figure 4 is an end view of the apparatus of Figure 1, with the apparatus in the closed state; Figure 5 is a side elevational view of the apparatus of Figure 1, in a closed state and supported by coatings of a section of pipeline; Figure 6 is an end view of the apparatus of Figure 1, with the apparatus in the closed state and supported by coatings of a section of pipeline; Figure 7 is a front perspective view of the apparatus of Figure 1, with the apparatus (without induction coil) in an open state and supported by coatings of a section of pipeline; and Figure 8 is an end view of the apparatus of Figure 1, with the apparatus in the open state and supported by a yoke.

Referring to Figures 1 to 8, there is shown an apparatus 10 for induction heating the bare steel of a field joint 12 between two factory coatings 14a, 14b of a section of a pipeline 16. The apparatus 10 comprises a generally hollow cylindrical frame 20 intended to be supported, in use, by the factory coatings 14a, 14b so that the frame 20 may be substantially fixed in relation to a longitudinal central axis X-X of the pipeline 16. The apparatus 10 may be adapted for heating field joints 12 between two factory coatings 14a, 14b of a section of a pipeline 16 having any diameter from about 100mm. As such, the dimensions of the apparatus 10 are project dependent and may change according to thickness of factory coatings 14a, 14b, length of field joint 12 and/or diameter the pipeline 16.

For clarity in the following description, arrow A in Figure 1 indicates what is considered to be the front and rear of the apparatus 10 in relation to the central axis X-X and, when viewed from the front of the apparatus 10, what is considered to be the left and right sides of the apparatus 10.

The frame 20 is formed from two generally semi-circular (in cross-section) frame sections 30, 40 which face each other to define a generally hollow cylinder.

The left frame section 30 comprises generally semi-circular front 32a and rear 32b inner face plates fastened together in an axially spaced-apart arrangement by inner tie bars 50. Likewise, the right frame section 40 comprises generally semi-circular front 42a and rear 42b inner face plates fastened together in an axially spaced-apart arrangement by inner tie bars 50. The left and right frame sections 30, 40 are pivotally connected together by a pair of pivot points 22, 24 at the top of the left 30 and right 40 frame sections. The front pivot point 22 connects the front inner face plates 32a, 42a and the rear pivot point 24 connects the rear inner face plates 32b, 42b to enable the frame 20 to be opened, so that it may be mounted onto the factory coatings 14a, 14b, and closed, so that it may fully encircle the section of the pipeline 16. The bottom sides of the front inner face plates 32a, 42a and the rear inner face plates 32b, 42b are substantially flat so that when the left 30 and right 40 frame sections are in the closed state, the apparatus 10 may be stood on a flat surface S without necessarily rolling over, as is shown in Figure 4.

A plurality of insulated electrical conductors 60 are arranged side by side along the axial length of each frame section 22, 24 between the front 32a, 42a and rear 32b, 42b inner face plates. The electrical conductors 60 are flexible electrical cables with external insulation, like, for example, copper cable wrapped in a rubber sheath. Each of the electrical conductors 60 extends in a circle (with a small break) from a free end at the bottom of the left frame section 30 to a free end at the bottom of the right frame section 40. At the bottom free end of each frame section 30, 40, the conductors 60 terminate in sliding electrical contacts 62, 64. The male electrical contacts 62 on the left frame section 30 are arranged to contact the female electrical contacts 64 of the right frame section 40 when the frame 20 is in the closed state so that the conductors 60 complete an electrical induction heating coil through which an alternating electrical current can flow from an external power supply. The electrical contacts 62, 64 comprise brass contacts. Unless otherwise mentioned, the components of the frame 20 are made of aluminium, stainless steel or another substantially non-magnetic rigid material.

The left frame section 30 comprises curved front 34a and rear 34b outer face plates each fastened to a respective front 32a and rear 32b inner face plate by outer tie bars 52. The right frame section 40 comprises curved front 44a and rear 44b face plates each fastened to a respective front 42a and rear 42b inner face plate by outer tie bars 52. The inner face plates 32a, 32b, 42a, 42b are located in the space between the front outer face plates 34a, 44a, at the front of the apparatus 10, and the rear outer face plates 34b, 44b, at the rear of the apparatus 10.

The apparatus 10 comprises a front pivot extension plate 26 extending upward from the front pivot point 22 and a rear pivot extension plate 28 extending S upward from the front pivot point 24. The tops of the extension plates 26, 28 are fastened together in an axially spaced-apart arrangement by an inner tie bar 50.

The apparatus 10 comprises front 54 and rear 56 support plates each fastened to a respective front 26 and rear 28 pivot extension plates by outer tie bars 52. The front support plate 54 is parallel to, and slightly outside, a plane occupied by the front outer face plates 34a, 44a. The rear support plate 56 is parallel to, and slightly outside, a plane occupied by the rear outer face plates 34b, 44b. The front 54 and rear 56 support plates have a generally triangular shape each with a lower curved side which, in use, faces the factory coatings 14a, 14b of the field joint 12.

The axial length of inner tie bars 50, and thus the induction heating coil of the electrical conductors 60, is about two and half times longer than the axial length of the outer tie bars 52, although this may be varied from project to project according to the dimensions of the field joint 12, the factory coatings 14a, 14b andlorthe pipeline 16.

As is shown in Figures 5 and 6, the semi-circular shapes of the inner face plates 32a, 32b, 42a, 42b define a circle having a diameter slightly greater than the diameter of the uncoated field joint 12 of the section of pipeline 16 when in the closed state. The curved shapes of the outer face plates 34a, 34b, 44a, 44b and the curved sides of the support plates 54, 56 define a circle having a diameter slightly greater than the factory coatings 14a, 14b of the section of pipeline 16.

The front 54 and rear 56 support plates each comprise a pair of support rollers 58 arranged to support the apparatus 10 on the factory coatings 14a, 14b of the section of pipeline 14. The support rollers 58 are adjustable so that their axes of rotation may be arranged tangential to the factory coatings 14a, 14b upon which the support rollers 58 are supported. Support from the support rollers 58 is transmitted to the left 30 and right 40 frame sections via the outer tie bars 52 connected to the front 26 and rear 28 pivot extension plates which, in turn, are connected to the front 22 and rear 24 pivot points. The support rollers 58 facilitate rolling movement of the apparatus 10 in either direction along the central axis X-X. This is to facilitate adjustment and correct alignment of the apparatus 10 with respect to the uncoated field joint 12 and factory coatings 14a, 14b of the section of pipeline 16.

The apparatus 10 may be lifted by lifting gear attached to the support plates 54, 56 or the inner 50 and outer 52 tie bars between the support plates 54, 56 and S the pivot extension plates 26, 28. For this purpose, the inner 50 and outer 52 tie bars connected to the front 26 and rear 28 pivot extension plates are made of 1 inch diameter bars. The rest of the inner 50 and outer 52 tie bars are made of five eighths inch diameter bars. Preferably, a generally rectangular (when viewed from above) yoke 70 may be attached, via lifting lines 72 depending from each corner, to lifting points 33a, 33b, 43a, 43b on each of the front 32a, 42a and rear 32b, 42b inner face plates of the left 30 and right 40 frame sections, as is shown in Figure 8.

When the yoke 70 is raised above a section of pipeline 16 the centre of gravity of the apparatus 10, which is located near the central axis X-X, drops downwardly under the force of gravity. This causes the left 30 and right 40 frame sections to pivot about the pivot points 22, 24 away from each other. In this position, the bottom free ends of the left 30 and right 40 frame sections are spread far enough apart to receive the uncoated field joint 12 of a section of pipeline 16 between the inner face plates 32a, 32b, 42a, 42b and receive the factory coatings 14a, 14b between the outer face plates 34a, 34b, 44a, 44b.

When the yoke 70 is lowered upon the section of pipeline 14, the centre of gravity of the apparatus 10 is supported by the support rollers 58. As the yoke 70 continues to lower, the weight of the left 30 and right 40 frame sections tends to cause them, under the force of gravity, to pivot about the pivot points 22, 24 towards each other until the lifting lines 72 become slack.

The left frame section 30 comprises a left coil handle 36 and the right frame section 40 comprises a right coil handle 46. The coil handles 36, 46 are arranged parallel to the inner tie bars 50 and are manually operable to move the left and right frame sections 30, 40. The coil handles 36, 46 may be used to push the bottom free ends of the frame sections 30, 40 towards each other to make a good contact between the sliding electrical contacts 62, 64 and transform the conductors 60 into a complete electrical induction heating coil. Guide blocks 38, 48 attached to the bottom free ends of the front 32a, 42a and rear 32b, 42b inner face plates help guide contact between the sliding electrical contacts 62, 64.

The position of the electrical induction heating coil formed by electrical conducts 60 with respect to the uncoated field joint 12 of the section of pipeline 16 needs to be closely controlled to maintain a uniform heating profile. For mechanical reasons, the pivot axis Y-Y of the front 22 and rear 24 pivots points passes through S the electrical induction heating coil formed by the electrical conducts 60, as is shown in Figures 2 and 5. This prevents the electrical conductors 60 from stretching when the induction heating coil opens and closes (i.e. when the frame 20 moved between open and closed states).

With the present arrangement 10, the electrical conductors 60 are as close to the bare steel of the uncoated field joint 12 of the pipeline section 16 as is possible.

Resilient non-conductive stops 39a, 39b, 49a, 49b attached to the inside of the front 32a, 42a and rear 32b, 42b inner face plates abut the bare steel to assist in correctly positioning the electrical conductors 60 between the factory coatings 14a, 14b when the frame 20 closes. As a result, the induction heating coil formed by the electrical conducts 60 is coaxial with the central axis X-X. A manual locking clamp (not shown) is mounted at the free end of the left frame section 30 and is operable to fasten the two free ends of the left 30 and right 40 frame sections together when the frame 20 is closed. The manual locking clamp assists in overcoming frictional resistance between the electrical contacts 62, 64 as they are brought together. The frame 20 is prevented from closing if any of the stops 39a, 39b, 49a, 49b abuts the thick factory coatings 14a, 14b. If this occurs, or is likely to occur, the coil handles 36,46 may be used manually reposition the electrical conductors 60 correctly between the factory coatings 14a, 14b. This may be done without necessarily raising the apparatus 10 with the yoke 70.

Operation of the apparatus 10 is controlled by a human machine interface (HMI) (not shown). The HMI may be mounted on, or separately to, the apparatus 10.

The HMI controls the supply of alternating electrical current to the induction heating coil formed by the electrical conductors 60 when the frame 20 is closed around the uncoated field joint 12 of a section of pipeline 16. The HMI allows manual control of the apparatus 10 but it may also be configured to allow for a degree of automatic control. The HMI may include a number of safety interlocks. For example, the HMI's safety interlocks may prevent the locking clamp on the left frame section 30 from being released, and hence the frame 20 from being opened, unless the electrical current has ceased to flow through the induction heating coil.

The apparatus 10 is normally used after the bare steel of the uncoated field joint 12 has been blasted and cleaned and shortly before is to be coated with a protective coating, typically a liquid or powder coating. The coating process may be enhanced when the bare steel is heated prior to the application of the coating.

S In use, the apparatus 10 is suspended from a hoist or other suitable lifting apparatus by way of the yoke 70 connected by lifting lines 72 to the lifting points 33a, 33b, 43a, 43b on each of the front 32a, 42a and rear 32b, 42b inner face plates of the left 30 and right 40 frame sections. As mentioned above, raising the apparatus 10 by the yoke 70 causes the bottom free ends of the left 30 and right 40 frame sections to separate, thus opening the frame 20 and allowing the apparatus 10 to be mounted on, or removed from, a section of pipeline 14. In one approach, the apparatus 10 is lowered onto a section of pipeline 16 so that the frame 20 and, in particular, the induction heating coil overlies the bare steel of the uncoated field joint 12 to be heated. The apparatus 10 is then supported on the factory coatings 14a, 14b by the support rollers 58 which may allow the apparatus 10 to be moved a small way along the length of the pipeline, if required, to adopt the correct position. When the apparatus lOis correctly positioned relative to the uncoated field joint 12 the locking clamp is operated to draw the pivotally connected left 30 and right 40 frame sections together. The stops 39a, 39b, 49a, 49b abut the bare steel between the factory coatings 14a, 14b to secure the frame 20 in relation to the uncoated field joint 12 of the section of pipeline 16.

The HMI is then operated to feed an alternating electrical current through the electrical conductors 60 of the induction heating coil to heat the underlying bare steel of the uncoated field joint 12 but not the steel underlying the factory coatings 14a, 1 4b of the section of pipeline 16. This helps to avoid undesirable detachment of the factory applied coatings 14a, 14b from the underlying steel.

When the uncoated field joint 12 of the section of pipeline 16 reaches the required temperature for the subsequent coating process, the HMI alerts the operator, ceases the alternating electrical current through the electrical conductors 60 of the induction heating coil and frees the locking clamp for release. The operator releases the locking clamp and raises the yoke 70 by way of a hoist or other suitable lifting apparatus. The lifting lines 72 open the frame 20. This allows the apparatus 10 to be removed from the section of pipeline 16. Any resistance to opening, due to friction between the electrical contacts 62, 64, may be overcome by pulling on the coil handles 36, 46. The apparatus 10 is raised away from newly heated field joint.

The bare steel between the factory coatings 14a, 14b is coated as soon as possible to minimize heat decay.

Claims

CLAIMS1. An apparatus for heating uncoated pipeline between coatings of a section of pipeline, the apparatus comprising: at least two pivotally connected frame sections rotatable between an open state in which the frame sections may be placed over or removed from a pipeline and a closed state in which the frame sections may surround a pipeline; electrical conductors mounted on the frame sections and arranged to form an induction heating coil having a central axis when the frame sections are in the closed state; support members disposed at each end of the induction heating coil for supporting the apparatus upon coatings of a section of pipeline, wherein the support members are disposed further from the central axis than the internal diameter of the induction heating coil.
2. An apparatus as claimed in claim 1 wherein the support members facilitate movement of the apparatus along the central axis.
3. An apparatus as claims in claim 2, wherein the support members comprise support rollers.
4. An apparatus as claimed in claim 3, wherein the support rollers are adjustable with respect to the central axis.
5. An apparatus as claimed in any one of the previous claims, wherein the frame sections comprise means for aligning the induction heating coil with uncoated pipeline.
6. An apparatus as claimed in any one of the previous claims, wherein the support members are connected to the frame sections via at least one pivot having a pivot axis.
7. An apparatus as claimed in any one of the previous claims, wherein the support members are connected to each other.
8. An apparatus as claimed in any one of the previous claims, wherein the frame sections depend from the support members when in normal use.
9. An apparatus as claimed in any one of the previous claims, wherein the frame sections each comprise a handle.
10. A method of heating uncoated pipeline between coatings of a section of pipeline, the method comprising the steps of: a) providing an apparatus of anyone of claims ito 9; b) disposing the at least two pivotally connected frame sections in an open state; c) disposing the frame sections adjacent uncoated pipeline; d) disposing the support members upon coatings of the section of pipeline; e) disposing the frame sections in the closed state thereby surrounding the pipeline and forming the induction heating coil around the uncoated pipeline; and 9 supplying the induction heating coil with alternating electrical current.
11. A method as claimed in claim 10, wherein the method comprises the steps of: g) ceasing supply of alternating electrical current to the induction heating coil; h) disposing the frame sections in the open state thereby facilitating removal of the electrical conductors from around the pipeline; and i) removing the support members from the coatings.
12. A method as claimed in claim 11, wherein the method comprises the step of locking the frame sections in the closed state between steps (e) and (; and optionally automatic unlocking of the frame sections from the closed state upon completion of step (g).