Abstract:
An in-line inspection tool for pipeline inspection. The tool comprising a channel through which pipeline fluid can flow through the tool; a flow control valve assembly comprising a valve member which is movable between a closed position and an open position for controlling the rate of flow of pipeline fluid through the channel, the flow control valve assembly further comprising a fluid-filled chamber; and an electrical linear actuator assembly configured to control movement of the valve member from the closed position to the open position, wherein the electrical linear actuator assembly is located in the chamber of the flow control valve assembly, wherein the electrical linear actuator assembly comprises a motor configured to operate the valve member, and wherein the electrical linear actuator assembly defines a flow path to allow fluid from the chamber of the flow control valve assembly to flow through the motor.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The field of the invention relates to an apparatus for pipeline inspection, more particularly to an apparatus for in-line inspection of a pipeline (e.g. an oil or gas pipeline). The field of the invention further relates to a method of assembly for a pipeline inspection apparatus. 
         [0003]    2. Description of Related Art 
         [0004]    It is known to use electrical linear actuators in a number of applications, including various high-pressure applications. One such application is as part of a speed control system on a pipeline inspection apparatus, e.g. of the type disclosed in US2010/0212747. In that instance, the electrical linear actuator is immersed in oil, the oil serving to protect the electrical linear actuator from debris and corrosive substances. 
         [0005]    However, there are problems with the immersion of electrical linear actuators in oil. For example, the types of brushed DC motor often used in electrical linear actuators have brush current limits, and these can be exceeded if the viscosity of the oil is too high. This can be a particular problem in oil &amp; gas pipelines which pass through low temperature environments; the low temperatures may cause the oil to become can become viscous and ineffective. 
         [0006]    Further problems with immersion of an electrical linear actuator in oil are caused by the possibility of pockets of gas being trapped in the system. On decommissioning of the actuator, such gas pockets may expand rapidly and explode, increasing the risk of injury to those operating the electrical linear actuator. 
         [0007]    The disclosure overcomes or mitigates one or more of the above-discussed problems, or other disadvantages or problems, associated with known pipeline inspection apparatus. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The disclosure provides an in-line inspection tool for pipeline inspection. The tool comprising a channel through which pipeline fluid can flow through the tool; a flow control valve assembly comprising a valve member which is movable between a closed position and an open position for controlling the rate of flow of pipeline fluid through the channel, the flow control valve assembly further comprising a fluid-filled chamber; and an electrical linear actuator assembly configured to control movement of the valve member from the closed position to the open position, wherein the electrical linear actuator assembly is located in the chamber of the flow control valve assembly, wherein the electrical linear actuator assembly comprises a motor configured to operate the valve member, and wherein the electrical linear actuator assembly defines a flow path to allow fluid from the chamber of the flow control valve assembly to flow through the motor. 
         [0009]    The disclosure also provides a method of assembly of a pipeline inspection apparatus. The method comprising providing an in-line inspection tool comprising a channel through which pipeline fluid can flow through the tool; providing a flow control valve assembly comprising a valve member which is movable between a closed position and an open position for controlling the rate of flow of pipeline fluid through the channel, the flow control valve assembly further comprising a fluid-filled chamber; providing an electrical linear actuator assembly configured to control movement of the valve member from the closed position to the open position, the electrical linear actuator assembly comprising a motor configured to operate the valve member; locating the electrical linear actuator assembly in the chamber of the flow control valve assembly; and providing a flow path within the electrical linear actuator assembly for the flow of fluid from the chamber of the flow control valve assembly to flow through the motor. 
         [0010]    The disclosure further provides an in-line inspection tool for pipeline inspection. The tool comprising a channel through which pipeline fluid can flow through the tool; a flow control valve assembly comprising a valve member which is movable between a closed position and an open position for controlling the rate of flow of pipeline fluid through the channel, the flow control valve assembly further comprising a fluid-filled chamber; and an electrical linear actuator assembly configured to control movement of the valve member from the closed position to the open position, wherein the electrical linear actuator assembly is located in the chamber of the flow control valve assembly, and wherein the chamber of the flow control valve assembly is filled with Nyswitcho  3   x  oil. 
         [0011]    The disclosure further provides an in-line inspection tool for pipeline inspection. The tool comprising a channel through which pipeline fluid can flow through the tool; a flow control valve assembly comprising a valve member which is movable between a closed position and an open position for controlling the rate of flow of pipeline fluid through the channel, the flow control valve assembly further comprising a fluid-filled chamber; and an electrical linear actuator assembly configured to control movement of the valve member from the closed position to the open position, wherein the electrical linear actuator assembly is located in the chamber of the flow control valve assembly, wherein the electrical linear actuator assembly comprises a motor configured to operate the valve member, and wherein the electrical linear actuator assembly is configured to allow fluid from the chamber of the flow control valve assembly to be drawn into the motor to evacuate air pockets within the motor. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    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: 
           [0013]      FIG. 1  is a schematic cross-sectional view through a flow control valve, showing an electrical linear actuator according to an exemplary embodiment of the disclosure; 
           [0014]      FIG. 2  is a schematic side view of the electrical linear actuator of  FIG. 1 ; 
           [0015]      FIG. 3  is a schematic partial view of a motor for use in the embodiment of  FIGS. 1 and 2 ; and 
           [0016]      FIG. 4  is a schematic partial view of an encoder for use in the embodiment of  FIGS. 1 and 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    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. 
         [0018]    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. 
         [0019]    Referring firstly to  FIG. 1 , a pipeline inspection apparatus or “pig” (only part of which is indicated generally at  8 ) includes a valve assembly  10  for controlling the speed of the apparatus  8  within a pipeline in which the apparatus is travelling. The apparatus  8  defines a channel  9  through which pipeline fluid can flow through the apparatus  8 . The valve assembly  10  includes a valve member  12  moveable between an open position and a closed position, thereby controlling the rate of flow of pipeline fluid through the channel  9 . 
         [0020]    The valve member  12  is attached to a piston  14  having a longitudinal axis A. The piston  14  is contained within a sealed chamber  16 . The piston  14  has a central bore  18  into which an electrical linear actuator assembly  20  is inserted. The assembly  20  is contained within the chamber  16  and is connected to the piston  14  such that operation of the assembly  20  moves the piston  14  along axis A within the chamber  16 . 
         [0021]    The assembly  20  is shown in more detail in  FIG. 2 . The assembly  20  includes a gearbox  30 , a motor  24 , an encoder  26  and a spindle  28  arranged along axis A. The assembly  20  defines a fluid flow path through the gearbox  30 , motor  24  and encoder  26 , indicated in  FIG. 2  by the arrows X. The flow path allows fluid to flow into the assembly  20 , via an inlet  46  (described in further detail below), from the chamber  16  and to return to the chamber  16  through an outlet  49  (described in further detail below). 
         [0022]    The spindle  28  has at its end distal a threaded portion  30  to provide the connection between the piston  14  and the assembly  20 . Operation of the motor  24  causes rotation of the spindle  28 . The gearbox  30  includes a gear train (not shown) which controls the speed at which the spindle  28  is driven by the motor  24 . 
         [0023]    The gearbox defines a cylindrical housing  31 . Bearing shields  46  are removed from the gearbox housing  31 , providing an aperture or inlet  48  that puts the gearbox housing  31  in fluid communication with the chamber  16  and allows fluid to pass from the chamber  16  into the gearbox  30 . 
         [0024]    In this embodiment, the gearbox  30  and spindle  28  are such as those produced under part number 363976 by Maxon Motor UK of Finchampstead, UK. 
         [0025]    The motor  24  has a cylindrical motor housing  23  having a first end  34  connected to gearbox housing  31  and a second end  36  connected to the encoder  26 . The motor  24  consists of a stator  25  which defines bore in which an armature (not shown) is operable. The connection between the motor housing  23  and the gearbox housing  31  defines a flow path for fluid from the gearbox housing into the motor housing, i.e. into the bore of the stator  25 . 
         [0026]    The motor  24  is in this exemplary embodiment a brushed DC motor with graphite brushes (not shown) intended to resist corrosion. The graphite brushes have a relatively low current capacity and so have a current limit of 2A. The motor  24  is in this embodiment one such as those produced under part number 323890 by Maxon Motor UK of Finchampstead, UK. 
         [0027]    A bearing shield  50  is removed from the motor first end  34 , providing an aperture  52  that puts the motor  24  in fluid connection with the chamber  14 . 
         [0028]    The second end  36  of the motor housing  23  is shown in  FIG. 3  and defines a disc-shaped end wall  37 . The end wall  37  includes two apertures  38  spaced at points approximately half way between the edge and the centre point of the end wall  37 . The apertures  38  each define an outlet for the flow of fluid from the motor housing  23 , e.g. into the encoder  26 . 
         [0029]    The encoder  26  (shown in  FIG. 4 ) is in this exemplary embodiment one such as those produced under part number 228452 by Maxon Motor UK of Finchampstead, UK. The encoder  26  has cylindrical housing  27  having a first end  40 , a second end  42  and a side wall  44 . The first end  40  comprises two apertures  46  corresponding to and aligned with the apertures  38  of the motor end wall  37 . The encoder housing  27  is thereby arranged in fluid communication with the motor  24 , allowing fluid to pass from the motor  24  to the encoder  26 . The side wall  44  defines two radial apertures  49  connecting with the two apertures  46 , putting the encoder housing  27  in fluid communication with the chamber  16  and allowing fluid to pass between the encoder  26  and the chamber  16 . 
         [0030]    In this exemplary embodiment the apertures  38 ,  46 ,  49  may be drilled in the motor  24  and the encoder  26 . 
         [0031]    Prior to use of the pipeline inspection tool, the chamber  16  and the bore  18  are filled with a low viscosity oil. In exemplary embodiments, the actuator assembly  20  is then primed. Operation of the motor  24  and gearbox  30  acts as a pump, and oil is drawn from the chamber  16  into the assembly  20  through the aperture  48  of the gearbox  30 . Oil flows into the gearbox  30 , the motor  24  and the encoder  26  via the apertures  50 ,  38 ,  46 ,  49  along the flow path indicated by the arrows X in  FIG. 2 , filling the assembly  20  and thereby eliminating any air pockets within the assembly  20  (e.g. within the gearbox or motor). In use, oil is free to return to the chamber  16  via the apertures  49 , e.g. under the pumping action of the motor and gearbox. 
         [0032]    Allowing oil to flow through the primed motor  24  ensures that all gas is evacuated from the system, reducing the risk of injury from an explosion of rapidly expanding gas during decommissioning, for example. 
         [0033]    In this embodiment, the low viscosity oil used is Nyswitcho 3x oil produced by Nynas of Stockholm, Sweden. Nyswitcho 3x is normally used as switchgear oil. However, test indicate that this particular oil is extremely well suited for use in the harsh operating conditions associated with pipeline inspection. In particular, the oil has been found to perform well at low temperatures, in terms of low viscosity and high oxidation stability. 
         [0034]    The low viscosity oil reduces friction in the assembly  20 , lowering power consumption and increasing battery life, and thus increasing pipeline inspection range. However, test indicate that the use of Nyswitcho 3x switchgear oil allows the assembly  20  to operate satisfactorily across a wide range of temperatures, e.g. at temperatures from −30° C. to 70° C., as well as at pressures up to 220 bar. Test indicate that other low viscosity oils will not perform as well, and may leads to the 2A current limit on the graphite brushes being exceeded, particularly when operating at temperatures below to −10° C. This is due to the increased viscosity of those low viscosity oils at such temperatures, which leads to an increase in the torque level required. When operating the system with Nyswitcho 3x, the 2A current limit on the graphite brushes is not exceeded, as the low viscosity properties of Nyswitcho 3x mean minimal torque is required. 
         [0035]    Existing electrical linear actuator assemblies comprising the parts or similar parts described can be easily modified by the removal of bearing shields and the drilling of holes to produce the exemplary embodiment described herein. 
         [0036]    In alternative embodiments, alternative low viscosity oils could be used. Alternative DC motors with brushes of a different material could be used. Apertures could be drilled in different areas of the motor and encoder. Further apertures may be provided. 
         [0037]    An electrical linear actuator as disclosed may be used for applications, particularly high pressure applications, other than for pipeline inspection. 
         [0038]    This written description uses examples to disclose embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of embodiments of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial difference from the literal languages of the claims.