Patent Application
20130174674
1. Field of the Invention
The disclosure relates to apparatus for pipeline inspection, more particularly, but not exclusively, to apparatus for inspection of the internal surface of a fluid pipeline, e.g. in-line inspection of an oil or gas pipeline.
2. Description of Related Art
It is known to inspect the inside of a pipeline using an inspection apparatus commonly referred to a pipeline pig. A known pig includes a radial array of sensor arms. In use, an end of each sensor arm is biased into contact with the inner wall of the pipe as the pig is driven along the pipe, in order to carry out an inspection of the inner wall of the pipe. In particular, the sensor arms provide a dimensional inspection of the pipe wall, looking for dents or other defects in the shape of the pipe wall.
Conventional pipelines are constructed from individual sections of pipe, which are interconnected to define a string of pipe sections. Typically, the joint between adjacent pipe sections defines an internal projection in the pipeline, such as a bead formed by welding the two pipe sections together. However, weld beads and other internal projections present an inspection problem, since the sensor arm will often lose contact with the pipe wall when it strikes the projection. Moreover, the sensor arm may reverberate for a period of time after the strike. Hence, inspection data may be lost until such time as the sensor arm regains more permanent travel along the pipe wall.
The disclosure overcomes or mitigates the above-discussed problem, or other disadvantages or problems, associated with known inspection apparatus.
According to one embodiment of the present invention, a sensor arm for a pipeline inspection tool is provided. The sensor arm comprises a body comprising: a first end and a second end, wherein the first end is configured for mounting the sensor arm on a pipeline inspection tool and the second end comprising a contact portion configured for contact with the internal surface of a pipe wall; and an elongate section which extends between the first end and the second end, the elongate section having an external profile which defines a top surface, a bottom surface and a main web arranged between the top and bottom surfaces, wherein the depth of the main web in cross section is greater than the width of the main web in cross-section.
According to another embodiment of the present invention, an apparatus for pipeline inspection is provided. The apparatus comprises: a base assembly for connection to an inspection tool; a sensor arm pivotably mounted on the base assembly, the sensor arm comprising a body comprising a first end and a second end and an elongate section extending between the first and second ends; and a spring connected between the base assembly and the sensor arm, wherein the spring is configured to bias the sensor arm towards an extended position for spring loaded contact with an internal surface of a pipe along which the inspection tool is travelling, and wherein the spring has a normal position arranged adjacent the elongate section when the sensor arm is in a fully extended position, the elongate section comprising a recess which extends in a direction between the first and second ends of the body adjacent the normal position of the spring.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:
The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.
Reference throughout the disclosure to “an exemplary embodiment,” “an embodiment,” or variations thereof means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in an exemplary embodiment,” “in an embodiment,” or variations thereof in various places throughout the disclosure is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
Referring firstly to
A base assembly 106 is mounted on the tool 104. The base assembly 106 acts as a support for the sensor arm 102. The sensor arm 102 is pivotably connected to the base assembly 106 by a pivot pin 105.
The sensor arm 102 is movable between an extended position (e.g. as shown in
A spring 108 (e.g. a torsion spring) is connected between the base assembly 106 and the arm 102. The spring 108 serves to bias the arm 102 towards its extended position, for spring loaded contact with an internal surface of a pipe along which the tool 104 is travelling.
In exemplary embodiments (as will be described in more detail below), limit stops on the sensor arm 102 and the base assembly 106 prevent over extension of the arm 102 beyond the extended position shown in
The arm 102 is shown in more detail in
The body 110 has an elongate section 118 which extends between said first and second ends 112, 114. As can be seen in
The main web 124 has a cross-section which is deeper than it is wide. Moreover, the distance between the top and bottom surfaces 120, 122 is greater than the distance between the first and second side faces 126, 128 of the elongate section 118.
As can be seen in
This configuration has been found to exhibit advantageous dynamic properties, reducing reverberations, flexure and other dynamic effects that occur in the event of a weld bead strike. The second moment of area cross section of the arm has been found to provide optimum stiffness in the ‘Y’ plane without unduly increasing the mass of the arm.
In exemplary embodiments, the body 110 is of injection moulded construction. Using an injection-moulded process reduces manufacturing costs and lead-time compared to conventional machined components. It also enables the arm 102 to be lightweight, compared with conventional machined arms, e.g. made from aluminium.
However, other production techniques may be used in alternative embodiments, e.g. die casting, rotational moulding or shell moulding.
The body 110 may be of single piece construction, and so can be produced as a straightforward moulding, e.g. in a simple mould cavity.
In exemplary embodiments, the injection moulded body is made from plastics material, e.g. nylon or nylon 12. Nylon 12, in particular, is a lightweight material well suited to the operating conditions associated with in-line inspection of oil and gas pipelines.
In further exemplary embodiments, the injection moulded body is made from nylon 12 having a glass content of up to about 30% by weight. An arm 102 made from this material has been found to exhibit beneficial levels of strength, reduced bending performance and improved impact resistance suitable for the operating conditions associated with in-line inspection techniques, particularly when formed with a configuration of the kind discussed above.
Tests indicate that the lightweight and dynamically improved configuration of arm reduces the impact of a weld bead strike, in terms of the kinetic energy imparted to the arm and the subsequent degree of deflection of the arm away from the wall of a pipe. Moreover, the lightweight and dynamically improved configuration is understood to contribute to the arm settling more quickly into smooth travel with the internal surface of the pipe after a weld bead strike, thereby reducing the loss of inspection data as a result of a weld bead strike.
As can be seen in
As mentioned above, the arm 102 is biased into its extended position on the tool 104 by the spring 108. During movement of the tool 104 within the pipe, the degree of extension of the arm 102 will change relative to the tool 104 (e.g. if the tool 104 deviates from the central axis of pipe). In the event of a significant change in the degree of extension, e.g. resulting from a weld bead strike, the spring 108 will deflect. Any contact between the deflecting spring 108 and the arm 102 may have a negative effect on the dynamic performance or relative positioning of the arm 102 on the tool 104. The provision of the recess 130 provides a space into which the spring 108 may deflect, thereby reducing the likelihood of significant contact between the deflecting spring 108 and the arm 102. Specifically, the recess reduces the risk of impact between the deflecting spring 108 and the side face 128 of the arm 102.
In exemplary embodiments, the recess 130 consists of an elongate groove or slot formed in the side face 128 of the elongate section 118. Hence, the recess 130 is easy to produce in a simple mould tool.
Referring back to
The tip 132 is manufactured from steel, e.g. vacuum hardened and tempered tool steel. The tip 132 prevents wear of the sensor arm 102 and inhibits the frictional heat generated from contact with the pipe wall from melting the sensor arm 102.
An aperture (indicated by the dotted lines 134) extends through the distal end 116 of the arm 102. As can be seen in
The tip portion 136 projects from the distal end 116. The tip portion 136 has an upper contact surface 142 for contact with a pipe wall. The contact surface 142 has a periphery 144 which defines a leading edge 146. The leading edge 146 defines a radius to the upper contact surface 142.
The provision of radiused leading edge on the contact tip can reduce the impact of a strike between the contact tip and a weld bead as the tool passes along the pipe, reducing the degree of deflection and wear caused by the impact. In exemplary embodiments, the leading edge may be inclined or chamfered relative to the upper surface 142, providing the same or similar effect.
The periphery 144 of the contact surface 142 also defines a trailing edge 148, which is also inclined, chamfered or defines a radius to the upper contact surface 142. The provision of an inclined or radiused trailing edge on the contact tip can reduce the impact of a strike between the contact tip and a weld bead if the tool is reversed along the pipe, reducing the degree of deflection and wear caused by the impact.
Referring back to
A magnet 154 is fitted to one side of the bush 152 (e.g. as shown in
In exemplary embodiments, the magnet 154 is fitted into a thin bush 156. e.g. of nylon 12 material, which is then glued to phosphor bronze bush 152. As shown in
Referring back to
An exemplary spring 108 for use in the arrangement of
In exemplary embodiments, the stiffness of spring (and hence, the load that the spring exerts when biasing the arm into engagement with a pipe wall) is configured to aid the dynamic performance of arm during travel along the pipeline, to reduce the degree of off-lift and the number and/or effect of reverberations induced in the arm as a result of a weld bead strike.
This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended and are understood to be within the scope of the claims.
