WO2013167094A2

WO2013167094A2 - Robotic platform for in-pipe inspection

Info

Publication number: WO2013167094A2
Application number: PCT/CO2013/000001
Authority: WO
Inventors: John Faber ARCHILA DÍAZ
Original assignee: Universidad Industrial De Santander
Priority date: 2012-05-11
Filing date: 2013-05-14
Publication date: 2013-11-14
Also published as: CO6790240A1; WO2013167094A3

Abstract

The invention relates to an inspection robot for pipes used to transport different types of fluids (liquids or gases). The robot considers the interaction between the fluid, the pipe and the robot in order to prevent: overpressure in the pipe above the maximum operating pressures, and pressure drops below vapour pressure, thereby preventing cavitation in the case of liquids. The robot extracts energy from the fluid and uses said energy to move itself, the speed of the robot also being controlled such that it can move at a constant speed, eliminating variations in speed typical of fluid transport. The reconfigurable constant speed is achieved using a control system which maintains the speed at a reference value and evaluates the interaction between the robot, the pipe and the fluid in order to maintain safe operating conditions.

Description

ROBOTIC PLATFORM FOR INTERNAL INSPECTION OF PIPES

1. Field of the Invention The present invention relates to robotic devices and more particularly, but not exclusively, to robotic devices adapted to travel through pipes or other types of tubular ducts of different diameters, propelled by the flow carried by said ducts. , to perform inspection, cleaning and other maintenance activities. 2. Description of the state of the art

The integrity of pipelines for transporting liquids and gases is of the utmost importance for cities and industries. When it comes to pipelines for transporting hydrocarbons, the standard inspection tool corresponds to the PIG, its acronym in English Pipeline Inspection Gauge, used for maintenance and inspection. In these tasks (maintenance and inspection) it is necessary to take into account various parameters when conducting the inspection with PIGs. The first is the maximum operating pressure of the pipe where the inspection will be carried out, due to the interaction between the fluid, the PIG and the pipe. It is possible to reach pressures above the operating pressure causing major damage to the pipe. The second corresponds to the speed with which the inspection is carried out, since high speeds or accelerations in the path reduce the efficiency of the inspection and increase the possibility of damage to the PIG and the pipeline. The third corresponds to generating pressures below the vapor pressure. In the case of working with liquids, this pressure generates the known phenomenon of cavitation generating damage to the pipe.

US Pat. No. 864,544 discloses a method for fluid-driven pipe cleaning without considering the effects that said activity generates on the integrity of the pipe and the inspection option. US Patent 1,547,440, like the previous patent used for cleaning, does not consider its interaction with the pipeline and the possibility of inspection. US Patent 3,292,197, unlike the previous ones, used a Magnetic cleaning system even without taking into account the PIG - pipe interaction. US Patent 3,755,908 discloses a PIG that inspects the pipe wall for deviations in its internal diameter by recording the data mechanically. This patent includes the inspection function without considering the influence of the robot with the pipe. Current inspection PIGs use measurement methods such as MFL (Magnetic Flux Lckeage), present in US 4,789,827, US 5,864,232, US 7,218,102 B2, and other patents that use Eddy ultrasound and currents, such as in US patent 4,153,875 . The inspection methods used in the aforementioned patents are sensitive to changes in the speed of movement of the PIG within the pipe, a fact that is taken into account in the present invention, but does not consider the interaction between the robot and the pipe. It is important to highlight that the inspection methods by means of PIGs generate variations in the internal operating pressures of the pipe and could even cause damage to them. The US patent 6,370,721 B 1, granted in 2002, is composed of a series of passages each with a venturi-like configuration, which allow the fluid to flow through the robot body. The size and shape of the passages may change to vary the pressure drop in the PIG body, varying the speed of the PIG in the pipe. This patent obstructs in a greater percentage the passage of the fluid and does not consider the effect of the robot in the variation of fluid pressure; It also does not have a locomotion system operated by the capture of energy from the fluid, and does not control the contact force of the wheels with the pipe or adapt its shape to it.

US Patent 5,208,936, issued in 1993, discloses a PIG for pipelines and contains a series of holes in the robot body with the intention of allowing the passage of gas through the PIG body. The speed is controlled with a turntable that obstructs or allows the passage of gas through the body of the PIG. This patent obstructs the passage area of the fluid to a greater extent and is only for gas. The disclosed PIG cannot interact in different fluids (liquids or gases), nor does it have a locomotion mechanism nor does it consider the robot's influence on the gas flow and its pressure. Finally, it does not control the contact force with the pipe or adapt its shape to it. Patent GB 2,305,407, granted in 2005, discloses a locomotion system and obtains the energy for its locomotion from the energy of the fluid. Said energy is taken by means of a turbine composed of a stator and a rotor, and is taken to a screw cam system which transforms the turbine's rotation movement into a cyclic translation movement which acts on brushes that they lean on the walls of the pipe generating their own locomotion. The turbine is located in the center of the pipe and has a Kaplan type configuration. It does not take into account the influence of the PIG in the variation of fluid pressure inside the pipe and does not control the contact force with the pipe or adapt its shape to it.

US Patent 7,182,025 B2, granted in 2007, discloses a robot for pipes from 2 to 6 inches in diameter, presents a power take-off system by means of a turbine, passages in the robot body and a helical movement mechanism. The PIG is limited for operation in pipes up to 6 inches. Nor does it consider the robot's influence on the pressure of the fluid in the pipe, and does not control the contact force of the wheels with the pipe or adapt its shape to it.

The foregoing patents contribute to the state of the art in the fluid intake and control of the speed of the PIG movement. They use various mechanisms such as turbines, brooms and plates, allowing the passage of fluid. However, the PIG designs ^' in these patents greatly obstruct the passage of fluid, generating configurations that could only be used for low density fluids. On the other hand, they focus on the energy intake of the fluid to generate its movement within the pipe and do not take into account its influence on the total operation of the pipe.

3. Brief description of the Figures

Figure 1 is a sectional view of the Robot.

Figure 2 is a turbine for harnessing the energy of the fluid.

Figure 3A is a normal force generation system. Figure 3B is the detail of the normal force generation mechanism.

Figure 4 is the front view of the power generation system and adaptation of various geometries for 4 contact points or supports.

Figure 5 is the front view of the power generation system and adaptation of various geometries for 3 contact points or supports.

Figure 6 shows the steering system for the robot.

Figure 7 shows the robot control scheme for inspection.

Figure 8 shows the complete assembly of the robot for inspection. 4. Brief description of the invention

The present invention consists of an inspection robot for pipes that carry different types of fluids (liquids or gases). The robot considers the interaction between the fluid, the pipe and the robot, in order to avoid overpressures in the pipe above the maximum operating pressures and the pressure drops below the vapor pressure, thus preventing the Cavitation in the case of liquids. The robot takes the energy from the fluid and with it generates its own locomotion also controlling its speed so that it can move at a constant speed eliminating the speed variations typical of fluid transport.

Given the characteristics described above, overpressures and vapor pressures that significantly damage the pipes are avoided and a constant and reconfigurable robot movement speed is provided, reducing the error of current inspection methods (MFL, Eddy currents, ultrasound, between others) thanks to the robot speed control and therefore the inspection speed. The robot of the present invention allows the incorporation of different inspection techniques making it flexible to the use of different types of instrumentation.

The constant and reconfigurable speed is achieved through the control system which is responsible for maintaining the speed at a reference value and assessing the interaction between the robot, the pipe and the fluid in order to maintain safe operating conditions (avoid overpressures, vapor pressures or sudden changes in speed).

5. Detailed description of the invention

Referring to Figures 1 to 8, the robot of the present invention consists of 5 main systems:

• the tubular body (Figure 1);

• the system to take energy from the fluid flow in order to convert it into mechanical energy (Figures 1 and 2);

• the normal force generation system (Figures 3A, 3B, 4 and 5);

• the helical routing or transmission system (Figure 6); Y

• the control system (Figure 7). 6. Detailed Description

Referring to Figure 1, the tubular body of the robot is described. The tubular body of the robot is placed inside the pipe where the inspection will be carried out so that the axis of the tubular body is parallel to the longitudinal axis of fluid flow. The robot of the present invention is contemplated for pipes that carry different types of fluids (liquids or gases) inside. The tubular body consists of at least two modular sections joined through a smaller diametral section (8), where a system for taking energy from the fluid flow is located. Each section has a series of clamping mechanisms that allow the union between said sections.

In a preferred embodiment shown in Figure 1, the tubular body has essentially conical sections found which together adopt a venturi-like shape. This configuration is determined by the input contraction (1), a throat section (2) and an output expansion (3). This configuration of sections harness the energy of the fluid generating a venturi effect. The body shape of the venturi-type robot allows the flow energy to be exchanged for kinetic energy of the fluid, increasing the same in the throat section (2) of the system, where a system is located to take energy from the flow of the fluid coupled to the tubular body.

This system for taking the kinetic energy of the flow to convert it into rotational mechanical energy in the preferred mode is a turbine (9) (illustrated in Figure 2). The shape of the tubular body of the robot also intervenes in the thrust force generated by the fluid and allows a flow to the outlet with decrease of the possible vortices generated by the internal geometry of the robot body. The turbine (9) and the normal and steering force generation system are integral, so that when the flow of fluid passes through the robot, the turbine (9) moves harmoniously at the same time as the mentioned systems and these in turn drive the entire tubular body of the robot. The cylindrical configuration of the tubular body of the robot shown in Figure 1 and the venturi-like configuration in the inner part of the tubular body allows to house an inspection system (5). This cavity is intended to accommodate the necessary instrumentation that will be responsible for the inspection of the pipe. The inspection system (5) can perform the inspection of the pipe according to need; It can be geometric, visual, pipe thickness, corrosion, coating thickness, etc. Depending on the type of measurement to be performed, the instrumentation equipment can be located in the inspection area (5) around the pipe. In some embodiments where corrosion inspection is desired, MFL (Magnetic Flux Lekage) instrumentation located around the tubular body above the inspection system area (5) can be used. Any type of instrumentation necessary to make these measurements is adapted in the robot body, specifically in the inspection system chamber (5). In embodiments where the inspection is geometric, probes or inductive sensors are used. Therefore, the present invention acts as a platform for different inspection techniques. Following Figure 1, the tubular body of the robot has a plurality of discs (6) that facilitate the movement of the robot through the pipe. These disks (6) usually they have the same diameter to the nominal diameter of the pipe where they are going to move, this with the purpose of generating a radial interference and a pressure force between the disks and the pipe and thus allow the axial alignment of the robot inside the pipe. The discs (6) generate a force opposite to the direction of movement as a function of the radial interference between the discs and the pipe. Said force is compensated by the normal force generation system and the helical locomotion system, contemplated by the robot's motion control system.

Referring to Figure 2, a system is described, to take the energy from the fluid flow in order to convert it into mechanical energy, which consists of a turbine (9). The turbine (9) is responsible for taking the flow energy from the throat section (2) (see Figure 1) to convert it into rotational mechanical energy. The angle of the blades (11), its shape and the diameter of the turbine is variable depending on the fluid through which it is transported and the diameter of the pipe in order to obtain the speed of rotation appropriate to the needs of the inspection To make. For example, for a pipe that carries water, Kaplan turbine blades are used; For gas transport, the blades have the shape of gas turbines while retaining a similar geometry.

Referring to Figures 3, 4 and 5, a normal force generation system is disclosed. The normal force generation system is responsible for generating the contact force between the robot and the pipe to allow helical locomotion. Said locomotion depends on the generation of normal force on the pipe and the angle (16) of the selective friction points which gives the advance and translation speed. The selective direction points can be formed by any element that allows the bearing between the robot and the pipe walls, which in preferred embodiments of the present invention are addressable wheels (7). For example, so that the robot can reach a speed of 5m / s, the angle α can vary between [-45 to 45] degrees, where said angle is a function of the desired inspection speed. It should be understood for a person versed in the art, that the configuration of the normal force generation system allows varying the values of the angle of rotation (16) of the addressable wheels (7), varying the speed of movement of the robot, and so both the turn values of the addressable wheels (7) of this example are not limiting allowing a much wider range of motion.

Additionally, in the preferred embodiment, the normal force generation system consists of a set of articulated bars (13) driven by a motor that governs a gear system (17) and cogwheel (18). This gear system, which is part of the normal force generation system, is responsible for transmitting the force to the articulated bars (13) which in turn generate the force on the walls of the pipe. The gears (17) can be conical, straight or helical, with the straight gears being the preferred embodiment of the present invention. In turn, a screw (14), shown in Figure 3B, is integral to the gear (17) and nut (15), which are responsible for opening and closing the mechanism of articulated bars (13) increasing the contact force between the robot and the pipe also adapting it to geometric variations present in pipes of the same commercial standard diameter. The force generation system is integral to the turbine (9) rotating with it, taking advantage of the flow energy, as shown in Figure 1 (9) and (7).

The normal force generation system can be driven by a stepper motor or a servomotor that acts on the gearwheel (18) that transmits movement to the gear system (17) that rotates the screws (14) inside the nut (15) which is free and moves on the axis of the screw, moving the articulated bars (13) acting on the wheels (7) which adjust the value of the normal force to a value that can range from 0 to 30,000 N depending on the boundary conditions of the pipe to be inspected. The force generation system can have at least 3 points of contact with the pipe as shown in Figure 4 where four points of contact (19a), (19b), (19c), (19d) and Figure 5 are presented which shows three points of contact (20a), (20b), (20c). Variations in the force generated by the normal force generation system, can increase or decrease its contact diameter by 5%. The person versed in the matter would understand that other designs can be seen that allow to generate normal force on the internal surface of the pipe, such as springs, pneumatic, hydraulic systems, auger. Referring to Figure 6, the steering system for the robot is described. The robot's steering system works in conjunction with the normal force system, but for purposes of understanding the figure, it does not include the sprocket (18) shown in Figure 3Λ, which would go around on the front face, opposite to the cogwheel (22) that is on the back side and that makes contact with the gears (21), which is responsible for rotating the gears (17) and modifying the force of the wheels on the pipe. The steering system shown in Figures 1, 3, 6 and 8, is responsible for changing the orientation of the wheels (7) of the robot forming an angle of attack α (16) (see Figures 3 and 6), defined as the angle (16) between the wheels of the robot and the pipe, generating a helical movement which transforms the rotational movement of the turbine into longitudinal movement along the pipe, something similar to how a screw and a nut would. The angle of attack (16) changes depending on the desired speed of movement of the robot. The steering system is initially driven by a conductive cogwheel (22) (see Figure 6) driven by a servomotor or stepper motor. When turning, the cogwheel (22) drives the driven gear system (23), which by means of a cardan (24) transmits the angular movement to the addressable wheels (7) of the robot.

Referring to Figure 7, the robot control system is disclosed. The control system is responsible for maintaining the speed at a reference value Vd (t) taking into account the interaction between the fluid, the pipe and the robot. The control system is a system based on the thrust force necessary to maintain the translation in the reference value and the monitoring of the interaction between the robot, the pipe and the fluid so as not to reach unwanted pressure values. The control system takes the speed reference value Vd (t), then through a comparator (29) generates the error signal E (t) which is transformed to normal force and angle of the addressable wheels F (t ) by means of the gain (30) by changing the movement of the robot, whose dynamic equation (3) is in the RIT (31) (acronym for Robot for Pipe Inspection). This movement generates a pressure signal P (x, t) that modifies the pressure conditions P (x, t) and fluid velocity V (x, t) preset in the control, reflected in (32). Due to the interaction of the plant (Fluid Pipe Interaction) + RIT (Pipe Inspection Robot) (32), the thrust force on the RIT robot (33) is changed generating a new angle of the addressable wheels and normal force F (t) and therefore its speed. The forces and velocities are sensed with a load cell (25) and an odometer respectively and treated by means of the block K (34) obtaining the real Speed value Vr (t) which is taken to the comparator (29) where it restarts the control cycle comparing the actual speed with the reference speed Vd (t) generating the error signal again and so on until reaching the desired reference speed. In each of the control stages (29) to (34) are the algorithms necessary to carry out the calculation and measurement of the data. These algorithms can be programmed in a DSP (Digital Signal Processor), FPGA (Faithful Programmable Gate Array), Microcontroller or Processor commercially available.

Figure 8 shows the configuration of the inspection robot in its preferred mode with all its systems, tubular body (27), contact discs (6), turbine (9) and helical locomotion system (26).

Electronics and control system:

The robot's electronic system is divided into two parts: the electronics for the control and the electronics for instrumentation or electronics used in the inspection, the latter depends on the service that is requested, for example if it is corrosion detection it is necessary to use an MFL system (Magnetic field leakage), if it is a geometric detection, you need probes or inductive sensors, these systems are located in the body of the robot in the area of the inspection system (5) according to the requested need. The control electronics consist of an odometer or encoder that gives the robot speed information. This information goes to a crocontroller (the controller can be of any technology such as DSP, FPGA, microcontroller, etc.) who infers according to the difference with the reference value and controls two servomotors one of them acts on the system of normal force generation (see Figure 3), generating the necessary contact force for the movement. The second servomotor acts on the helical transmission system (see Figure 6) by controlling the angle (16) of incidence of the addressable wheels (7) of the robot with the pipe by changing the travel speed of the robot. The controller analyzes the influence of the robot on the pressures and velocities of the fluid, since it generates changes in the flow behavior and this in turn generates changes in the drag force that acts on the robot influencing its speed. This interaction is evaluated in the controller by solving the following equations 1, 2 and 3, which describe the influence of the robot dynamics (equation 3), the amount of fluid movement (equation 2) and the boundary conditions generated by the pipe and the physical properties of the fluid, described in the continuity equation (ecu

d ² x

m (P _l - P ₂ ) A - mg sm 0 - F _e a (3)

dt ¹

Illustrative example:

In a preferred embodiment of the present invention, the robot performs an inspection on a pipeline that carries oil. The first step is to make a route through the pipeline to be inspected in order to obtain the plani-altimetric information of the route, inferring the position from equation (4):

r 'C COS Ó. .

J ₀ - ^{~ + ca} ) dt (4)

In case of having the route profile previously, it is not necessary to make the first route and the route data is loaded to the controller. Taking into account the average relative density of oil, which is between 0.8 and 0.9kg / m ³ , and the mass flow of 400 kg / s, an angle of the turbine blades (9) was determined in 30 degrees, obtaining a torque of 98 Nm and angular speed of 14.6 rad / sec. Under the above conditions the system generates a contact force with the pipe between 2,300 and 30,000 N, and an angle (16) of the addressable wheels (7) of 42 degrees for a travel speed of 5 m / s, which is The recommended speed for the MFL magnetic field leak inspection technique.

Claims

one . Device for internal inspection of pipes with internal fluid flow characterized in that it comprises:

a- a tubular body whose axis is parallel to the fluid flow;

b- a system to take energy from the fluid flow operatively coupled to the tubular body; Y

c- a steering system that allows varying the rotational and longitudinal locomotion speed of the device inside the pipe.

2. The device of Claim 1, characterized in that the tubular body has an external surface and an internal surface where the external diameter is substantially constant and the internal diameter varies in such a way that it is reduced in a throat section (2) of such so that a venturi effect is generated.

3. The device of Claim 1, characterized in that the tubular body is formed by modular sections.

4. The device of Claim 1, characterized in that the system for taking energy from the fluid flow is a turbine.

5. The device of Claim 4, characterized in that the turbine is integral with the steering system and is coupled to the tubular body.

6. The device of claim 4, characterized in that the turbine is located in a throat section (2) of the tubular body.

7. The device of Claim 4, characterized in that the angle of the turbine blades is variable depending on the fluid through which it is transported and the diameter of the pipe.

8. The device of Claim 1, characterized in that the steering system exerts a contact on the internal walls of the pipe at least 3 points.

9. The device of Claim 1, characterized in that the steering system is formed by a system of generating normal force on the internal walls of the pipe.

10. The device of Claim 9, characterized in that the normal force generation system makes contact with the internal walls of the pipe through directionally selective friction points.

The device of Claim 10, characterized in that the directionally selective friction points are addressable wheels.

12. The device of claims 9 to 11, characterized in that the addressable wheels are operatively connected to a crown-gear type transmission system that allows angular movement.

13. The device of claims 1 to 12, characterized in that the steering system allows to exert a contact of variable normal force on the walls of the pipe.

14. The device of claims 1 to 13, characterized in that the steering system is formed by an additional crown-gear type transmission system (22) that allows the articulation of a plurality of bars (13) to modify the force exerted by the addressable wheels (7) on the internal walls of the pipe.

15. The device of Claim 14, characterized in that the transmission system transmits angular movement to the addressable wheels (7) through a cardan-type joint (24).

16. The device of Claim 1, characterized in that the tubular body has a plurality of discs (6) located on its periphery than to keep the device axially aligned to the pipe.

17. The device of Claim 1, characterized in that the tubular body also has an inspection system (5) to house the instrumentation necessary for the inspection of the pipe.

18. The device of Claim 1, characterized in that it also has a control system that regulates the speed of the device in the pipe, evaluating the interaction between the device, the pipe and the fluid.