Patent Description:
Tubing systems in refining furnaces, boilers, fired heaters and the like typically have a sinusoidal path to optimise the exposure of the contents of the tubing systems to heat. Such a sinusoidal path is frequently referred to as being serpentine. In a typical tubing system, a product to be treated usually passes through the tubing system that has horizontally and/or vertically set tubes, and the passage of the product through the tubing system may be in a horizontal direction, a downward direction, an upward direction, or a combination thereof. Some tubing systems may include a section of closely packed tubes that may be used to, for example, raise a temperature of the product to be treated by way of convection heating. The pre-heated product may then be passed to a subsequent section of the tubing system in which there is more space between the tubes, and such tubes may be heated by way of radiant heating. Typically, in both sections, the tubing system includes straight tube sections joined by bent tube sections, which may be semi-circular (also known as U-bends) or may be box headers with sharp bends in the form of <NUM> degree turns, sometimes referred to as "horseshoes" and/or "mule ears". Other tubing systems may include at least one helical coiled tube or at least one arbour coiled tube.

The term "pig" is used to refer to devices that are passed through a pipe or tubing whether for cleaning purposes or for monitoring the condition of the pipe or tubing. Pigs may be used for aiding separation of product from the pipe or tubing, in particular material buildup on interior walls of the pipe or tubing, for fluid transport separation, etc..

Pigs may be used to inspect, detect and record conditions of a pipe or tubing from the inside to check the surface conditions of the interior and/or exterior of the pipe or tubing, to check for material deposits on the interior and/or exterior walls of the pipe or tubing and to check for degradation and irregularities in the pipe or tubing. This is important because, if a pipe or tubing is blocked, breached or has a compromised structural integrity during its operation, it could not only lead to costly and disruptive unscheduled downtime but also result in life threatening conditions for nearby people.

In addition it is known to wrap or encase pipelines in insulation material. Carrying out inspection of such pipelines from the inside may avoid costly time and effort in removing the insulation material for the purpose of exposing the pipeline's outer surface.

In order for efficient and safe operation of a tubing system, it is important that the tubing system is not only periodically cleaned and free from deposits, but also inspected to ensure the walls of the tubing system are free from undesirable deposits, tube material condition anomalies, wall thinning and/or various forms of metallurgical degradation. Inspection of a pipe or tubing may be performed to assess the need for cleaning and/or repair or to assess the effectiveness of previous cleaning and/or repair.

Conventionally inspections of a pipe or tubing have been performed online through viewing windows and/or by inspecting the pipe manually during shutdown of the pipe or tubing. Monitoring of the condition of a pipe or tubing have also been conventionally carried out by radiography, precision monitoring of flow and pressure, thermal imaging, and hand-held non-destructive testing (NDT) such as ultrasonic testing (UT). However, each of these techniques is limited in its usefulness and has its disadvantages. Manual NDT can be time consuming, for example taking <NUM>-<NUM> days fully to inspect an entire furnace, and also requires abrasive cleaning of the outer wall of the tubing system of the furnace in order to enable successful inspection. Furthermore, a furnace would normally need internal scaffolding to enable the inspection to be carried out, thus wasting time. Thermal imaging usually involves searching for hotspots as an indication of contamination, but is not suitable for inspecting closely packed tubes such as seen in convection heating sections. When monitoring is carried out whilst the furnace is in operation, some areas of the tubing system may not be visible through the viewing windows. Furthermore, the far side of the tubing system is either difficult or impossible to monitor using the conventional monitoring techniques. Accordingly it may be necessary to replace one or more sections of the tubing system according to a supplier-provided lifetime warranty, which can result in not only unnecessary replacement of tube sections but also unnecessary and costly downtime of the tubing system.

It is known to provide a tethered pig with monitoring equipment and to send it through a pipe. Operation of the equipment is controlled from outside the pipe via a cable. Responses detected by the on-board monitoring equipment are transmitted back along the cable to an external monitoring unit. <CIT> discloses an un-tethered sensor unit for use in a pipeline.

According to a first aspect of the invention, there is provided an apparatus for tracking a pig travelling inside a tubular object, the apparatus comprising:.

The configuration of the apparatus of the invention enables the automatic real-time tracking of the pig travelling inside the tubular object by using the calculated pig's speed from a previous run to estimate the position of the travelling pig inside the tubular object at any given time in a subsequent run, using a minimal number of sensors. This not only minimises or removes the need for a manual search of the tubular object if the pig gets stuck but also obviates the need for the pig to be tracked by a complex system of sensors that can be intrusive, expensive and difficult to install. This is especially critical for tubular objects in dangerous or inaccessible locations.

The real-time tracking ability of the invention improves the efficiency of the pigging or inspection operation by enabling a reliable and accurate determination of the pig's position inside the tubular object. If the pig becomes stuck inside the tubular object, the ability to rapidly identify the stuck pig's position permits its recovery in a timely manner to minimise operational downtime. Furthermore, the ability to track the pig's position in real-time allows control over the pig's movement so as to concentrate on certain areas of the tubular object. For example, the pig may be controlled to move back and forth in areas with increased contamination/fouling levels, thus increasing the efficiency of a decoking process.

The configuration of the apparatus of the invention therefore provides an apparatus with the capacity to learn from one or more previous runs of the pig inside the tubular object to provide more accurate and reliable tracking of the pig inside the tubular object in one or more future runs.

The invention is applicable to various configurations of the tubular object. As stated above, the invention is preferably for use with tubular objects in the form of pipes, pipelines, tubes and tubing, and such tubular objects may come in a variety of shapes, such as straight, bent, serpentine and meandering. For example, the invention may be applied to closed-loop furnaces that feature end-to-end serpentine coils of tubing or pipework, and/or may be applied to pipelines with restricted access due to, for example, their installation on overhead structures (e.g. overhead gantries), underground or under water bodies such as a river, a lake or a water course.

The invention is applicable to various applications of the tubular object, such as pigging, cleaning and inspection.

Preferably the run is the current or most recent run of the pig through the tubular object. Alternatively the run may be any other previous run that is not the current or most recent run of the pig through the tubular object.

In a preferred embodiment of the invention, the tracking device may be configured to use a newer calculated pig's speed to replace an older calculated pig's speed and, using the newer calculated pig's speed, perform the real-time tracking of the pig's position inside the tubular object in the subsequent run of the pig through the tubular object.

Since the pig's speed through the tubular object may change over time due to various factors, the estimation of the pig's position inside the tubular object in the or each subsequent run may become less accurate if it solely relies on the previous calculated pig's speed. For example, as contamination levels inside the tubular object decrease, the pig's speed through the tubular object may increase. Continual adjustment of the calculated pig's speed enables updating of the real-time tracking of the pig's position inside the tubular object to take into account changes in operating conditions with time, thus further enhancing the learning capacity of the apparatus of the invention.

In embodiments of the invention, the tracking device may be configured to process the detected passages of the pig from multiple runs of the pig through the tubular object to determine the travel times of the pig and, using the determined travel times, calculate the speed of the pig through the tubular object. Calculating the pig's speed through the tubular object using the determined travel times from multiple runs may improve the learning ability of the apparatus of the invention to increase the accuracy of the estimation of the pig's position inside the tubular object.

Preferably the tracking device is configured to process the detected passages of the pig from multiple runs of the pig through the tubular object to determine the travel times of the pig and, using the determined travel times, calculate an average speed of the pig through the tubular object. Calculating the pig's average speed through the tubular object in this manner reduces the influence of detection errors or abnormal runs. An abnormal run is a run in which the pigging or inspection operation deviates significantly from the normal pigging or inspection operation, which may arise due to user or operator error or unexpected operating conditions.

More preferably the tracking device is configured to process the detected passages of the pig from multiple runs of the pig through the tubular object to determine the travel times of the pig and, using the determined travel times, calculate a weighted average speed of the pig through the tubular object. Calculating the pig's weighted average speed through the tubular object in this manner allows more weight to be placed on a newer run and less weight to be placed on an older run. This is because, for certain pigging or inspection operations, the tubular object's operating conditions will tend to resemble the tubular object's operating conditions in the newer run over the tubular object's operating conditions in the older run.

Optionally the tracking device may be configured to exclude at least one of the travel times in calculating the speed of the pig through the tubular object if the or each excluded travel time deviates by a predefined amount from a reference travel time. Preferably the reference travel time is the newest travel time of the determined travel times. This allows removal of the influence of one or more abnormal runs over the calculation of the pig's speed through the tubular object.

In further embodiments of the invention, the sensor arrangement may include at least one pressure sensor for measuring a pressure parameter of the interior of the tubular object. The tracking device may be configured to, using the calculated pig's speed and the or each measured pressure parameter, perform the real-time tracking of the pig's position inside the tubular object in the subsequent run of the pig through the tubular object.

In still further embodiments of the invention, the sensor arrangement may include at least one flow sensor for measuring at least one flow parameter of the interior of the tubular object. The tracking device may be configured to, using the calculated pig's speed and the or each measured flow parameter, perform the real-time tracking of the pig's position inside the tubular object in the subsequent run of the pig through the tubular object.

As the pig travels inside the tubular object, changes in pressure and/or flow may take place. This may be due to, for example, the pig transitioning between sections of the tubular object of different shapes and/or sizes or due to the pig approaching a bend or end section of the tubular object. Hence, the pressure and/or flow measurements may be used to aid the real-time tracking of the pig's position inside the tubular object.

Optionally the apparatus may include a display device. The display device may be configured to display an image of the real-time tracking of the pig's position inside the tubular object. The display device may be a display screen, a touchscreen, a television, a monitor, a projector or a beamer. The display device may form part of an electronic or computing device. The display device may form part of, or may be separate from, the tracking device. In such embodiments, the image may include a dynamic graphic of the pig (such as an icon that represents the pig) overlaid on a static graphic of the tubular object (such as a graphical layout of the tubular object).

The visualisation of the real-time tracking of the pig's position inside the tubular object makes it easier for a user or operator to observe the real-time tracking while carrying out other tasks, such as controlling equipment for the pigging or inspection operation.

The apparatus of the invention may include a propulsion device configured to automatically propel the pig inside the tubular object in response to information obtained or derived from the real-time tracking of the pig's position inside the tubular object. The apparatus of the invention may include a controller for controlling the propulsion device. The controller may be, for example, the tracking device.

The obtained or derived information may provide insight into an interior condition of the tubular object. When such information is obtained or derived, the propulsion device may act to automatically change a speed or direction of the pig inside the tubular object and/or may act to automatically drive the pig to move back and forth inside a particular section of the tubular object.

Configuration of the apparatus of the invention in this manner enables certain levels of automation through which data from the real-time tracking of the pig's position inside the tubular object is used to automatically control the propulsion device in driving a movement (e.g. speed, direction) of the pig inside the tubular object.

The propulsion device is preferably a fluid propulsion device for propelling the pig inside the tubular object using fluid pressure, but in other embodiments may be any other device that is capable of propelling the pig inside the tubular object, such as an on-board motor.

In embodiments of the invention, the tracking device may be configured to process at least one physical parameter of the tubular object and the determined travel time of the pig to calculate the speed of the pig through the tubular object. The or each physical parameter of the tubular object may be selected from any one of, but is not limited to:.

The location(s) and number of position sensors of the sensor arrangement may vary depending on various requirements of the apparatus (such as ease of sensor installation, measurement accuracy, measurement reliability, etc).

In embodiments of the invention, the sensor arrangement may include at least two position sensors, each position sensor corresponding to a respective location inside the tubular object, each position sensor configured to be capable of detecting the passage of the pig at the respective location inside the tubular object. For example, the sensor arrangement may include first and second position sensors, the first position sensor arranged at or adjacent a first tubular end of the tubular object, the second position sensor arranged at or adjacent a second tubular end of the tubular object.

It will be understood that the sensor arrangement may include one or more further position sensors (e.g. a third position sensor, a fourth position sensor, a fifth position sensor and so on) that may be arranged at other locations along the tubular object. The inclusion of the or each further position sensor is particularly useful for obtaining additional tracking information about the pig's position inside a tubular object having a complex shape, such as serpentine tubular objects, which in turn can be used to provide more accurate real-time tracking of the pig's position inside the tubular object in a subsequent run of the pig through the tubular object.

The apparatus may include at least one pig launcher arranged at either or both of tubular ends of the tubular object, the sensor arrangement including at least one position sensor arranged at or adjacent the or each pig launcher to detect a launch of the pig from the or each pig launcher. In such embodiments, the tracking device may be configured to initiate the real-time tracking of the pig's position inside the tubular object upon detection of the launch of the pig from the or each pig launcher.

The apparatus may include at least one pig receiver arranged at either or both of tubular ends of the tubular object, the sensor arrangement including at least one position sensor arranged at or adjacent the or each pig receiver to detect a receipt of the pig by the or each pig receiver.

Using the or each position sensor in this manner provides information about the timing of the launch or receipt of the pig, which can be used by the tracking device to determine a travel time of the pig between separate locations inside the tubular object. In addition, the accuracy of the real-time tracking of the pig's position inside the tubular object is improved by initiating the real-time tracking upon detection of the launch of the pig from the or each pig launcher.

Optionally the sensor arrangement may be configured to be in wireless communication with the tracking device. This enables remote collection of the detected passage of the pig and thereby permits remote tracking of the pig's position inside the tubular object. This is not only beneficial for monitoring a pig travelling inside a tubular object in a dangerous or inaccessible location but also provides a user or operator with ready access to the real-time tracking information from a chosen location, such as a control room where the operator is required to control equipment for the pigging or inspection operation.

The wireless communication may be carried out using wide area network (WAN), Bluetooth™ or Wi-Fi equipment. It will be appreciated that, in other embodiments of the invention, the sensor arrangement may be alternatively or additionally configured to be in wired communication with the tracking device.

Further optionally the apparatus may include a data recordal device configured to record data about the pig's travel inside the tubular object. This enables automatic generation of log sheets with details about the pig's travel through the tubular object, e.g. quantity of runs, duration of runs, operating parameters, etc. As a result, the user or operator would not be required to manually input the data into a log sheet.

The tracking device may include a processor and memory including computer program code, the memory and computer program code configured to, with the processor, enable the tracking device at least to:.

The tracking device may be, may include, may communicate with or may form part of one or more of an electronic device, a portable electronic device, a portable telecommunications device, a microprocessor, a mobile phone, a personal digital assistant, a tablet, a phablet, a desktop computer, a laptop computer, a server, a cloud computing network, a smartphone, a smartwatch, smart eyewear, and a module for one or more of the same.

According to a second aspect of the invention, there is provided a computer-implemented method of tracking a pig travelling inside a tubular object, the computer-implemented method comprising the steps of:.

The features and advantages of the first aspect of the invention and its embodiments apply mutatis mutandis to the features and advantages of the computer-implemented method of the second aspect of the invention and its embodiments.

According to a third aspect of the invention, there is provided a computer program comprising computer code configured to perform the computer-implemented method of any one of the second aspect of the invention and its embodiments.

The features and advantages of the first and second aspects of the invention and their embodiments apply mutatis mutandis to the features and advantages of the computer program of the third aspect of the invention and its embodiments.

It will be appreciated that the use of the terms "first" and "second", and the like, in this patent specification is merely intended to help distinguish between similar features, and is not intended to indicate the relative importance of one feature over another feature, unless otherwise specified.

Preferred embodiments of the invention will now be described, by way of non-limiting examples, with reference to the accompanying drawings in which:.

The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic form in the interests of clarity and conciseness.

The following embodiments of the invention are described with reference to their use in cleaning of tubes and tubing, such as fired heater, furnace or boiler process tubes, but it will be appreciated that the following embodiments of the invention may also be used in other pigging and inspection operations and other tubular objects, such as pipes and pipelines.

During a decoking or "pigging" operation, it is beneficial to monitor the real-time location of a pig inside a heater tube for several reasons.

The interior of the heater tube may be more heavily contaminated in one particular section. Consequently it may be desirable to operate the pig to move back and forth inside the particular section to remove the heavy contamination. This requires an operator to know the location of the pig inside the heater tube.

The pig may become stuck if it enters a section of the heater tube with reduced internal diameter, which may be caused by internal fouling, use of an oversized pig or a change in tube internal diameter. If a pig becomes stuck, it is sometimes necessary to place a heat mat around the section of the tube where the pig is located. The purpose of the heat mat is to heat up and melt the pig, thereby allowing it to be flushed out. Knowing the location of the pig inside the heater tube is critical to ensure correct placement of the heat map.

During the pigging operation, a pig's movement may become temporarily restricted due to, for example, internal fouling or another anomaly. It would be beneficial for the operator to know if the pig is moving or has stopped so that they can take remedial action, such as increasing fluid pressure (e.g. water pressure), to keep the pig moving.

Pressure and flow sensors may be utilised to respectively measure pressure and flow parameters of the interior of the heater tube. An operator has access to the measured pressure and flow parameters in the form of continuous line charts.

When a pig traverses a return bend or plug header, a slight increase in pressure will be observed. Therefore, as the pig travels through the heater tube, a pressure line chart may appear as a series of "beats", with each spike being associated with a bend. Normally, by physically counting these spikes, the operator can assess an estimated location of the pig within the heater tube according to the number of bends that has been passed by the pig. However, a number of mechanical variables (e.g. pig size, bend size, bend type, damping effect from connection hoses) may prevent one or more of the expected pressure spikes from occurring, thus resulting in an incorrect estimation of the pig's location within the heater tube.

Also, the use of a sufficiently small pig may result in a substantially constant pressure as the pig travels through the heater tube due to fluid/flow bypass. As a result, it becomes difficult to determine the position of the pig travelling through the heater tube from the pressure line chart.

Furthermore the pig's speed through the heater tube may change over time. As the interior of the heater tube becomes cleaner, the pig's speed through the heater tube is likely to increase due to the decrease in resistance. If the pig is replaced by another pig of larger diameter, the pig's speed through the heater tube will decrease. If the operating pressure and/or flow parameters change, a corresponding change in the pig's speed will take place.

An apparatus according to an embodiment of the invention is shown in <FIG> and is for tracking a scraper pig <NUM> travelling inside a serpentine heater tube <NUM>. <FIG> shows the pig <NUM> inside the heater tube <NUM>. The apparatus comprises first and second pig launchers <NUM>,<NUM>, a sensor arrangement and a tracking device <NUM>.

The first and second pig launchers <NUM>,<NUM> are respectively connected to inlet and outlet ends of the heater tube <NUM>. The pig launchers <NUM>,<NUM> also function as pig receivers. In use, the pig <NUM> is launched from and received by each pig launcher <NUM>,<NUM>. Fluid pressure (e.g. water pressure) by a fluid propulsion device is used to drive the pig <NUM> through the heater tube <NUM>. Alternatively the pig may be driven by an on-board drive, such as a motor. The pig <NUM> is preferably driven in both directions through the heater tube <NUM> but in other embodiments may be driven in only one direction through the heater tube <NUM>.

The sensor arrangement includes a pair of position sensors <NUM>,<NUM>. A first position sensor <NUM> is arranged at the inlet end of the heater tube <NUM> and adjacent to the first pig launcher <NUM>. A second position sensor <NUM> is arranged at the outlet end of the heater tube <NUM> and adjacent to the second pig launcher <NUM>. Each position sensor <NUM>,<NUM> is an electromagnetic pig signaller that is capable of detecting the passage of the pig <NUM>. The pig <NUM> is fitted with a magnet, such as a neodymium rare earth permanent magnet. The magnet is cast inside the pig <NUM> at the manufacturing stage. It will be appreciated that other types of sensors may be used as position sensors to detect the passage of the pig <NUM> travelling inside the heater tube <NUM>. It will be further appreciated that one or more further position sensors (e.g. a third position sensor, a fourth position sensor, a fifth position sensor and so on) may be arranged at other locations along the heater tube <NUM>. For example, a pair of position sensors may be arranged at inlet and outlet ends of each section of the heater tube <NUM> and/or multiple position sensors may be arranged and spaced apart along a length of each section of the heater tube <NUM>.

The tracking device <NUM> is exemplarily a laptop computer with a display screen. In use, the tracking device <NUM> is preferably located in a control room where the operator controls equipment for the pigging operation. The tracking device may be any device that includes a processor and memory including computer program code, where the memory and computer program code are configured to, with the processor, enable the tracking device to carry out various processing functions. The tracking device may be, may include, may communicate with or may form part of one or more of an electronic device, a portable electronic device, a portable telecommunications device, a microprocessor, a mobile phone, a personal digital assistant, a tablet, a phablet, a desktop computer, a server, a cloud computing network, a smartphone, a smartwatch, smart eyewear, and a module for one or more of the same. It will be appreciated that references to a memory or a processor may encompass a plurality of memories or processors.

The pig signallers <NUM>,<NUM> are configured to be in wireless communication with the laptop computer <NUM>, which is exemplarily achieved through a low-power wide-area network (WAN) protocol that is capable of linking battery-operated units. A signal from each pig signaller <NUM>,<NUM> is transmitted through an antenna mounted directly to the pig signaller <NUM>,<NUM> and received at a receiver, e.g. a base station, that is connected to the laptop computer <NUM>.

It is envisaged that, in other embodiments of the invention, the wireless communication between the sensor arrangement and the laptop computer <NUM> may be carried out using Bluetooth™ or Wi-Fi equipment. It is also envisaged that, in still other embodiments of the invention, the sensor arrangement may be configured to be in wired communication with the laptop computer <NUM> or configured to be in wired and wireless communication with the laptop computer <NUM>.

After the signals are received by the laptop computer <NUM>, the signals are interpreted by a computer program that acts as a serial bus emulator. The information from the pig signallers <NUM>,<NUM> are deciphered and formatted into useable pieces of information that can be recognised and processed by the computer program.

Operation of the apparatus of <FIG> during an exemplary run of the pig <NUM> through the heater tube <NUM> is described as follows, with reference to <FIG> and <FIG>.

The exemplary run is described with reference to an initial launch of the pig <NUM> from the first pig launcher <NUM> but applies mutatis mutandis to an initial launch of the pig <NUM> from the second pig launcher <NUM>.

Before the run is started, the computer program is provided with physical parameters of the heater tube <NUM>, such as:.

This enables the computer program to not only determine the overall distance travelled by the pig <NUM> between the inlet and outlet ends of the heater tube <NUM> but also create a graphical layout <NUM> of the heater tube <NUM>.

Initially the pig <NUM> is loaded into the first pig launcher <NUM> ('<NUM>'), and the operator controls the fluid pressure to launch the pig <NUM> from the first pig launcher <NUM> ('<NUM>').

When the pig <NUM> is launched from the first pig launcher <NUM>, it will pass the first pig signaller <NUM> that will detect the magnetic field generated by the magnet in the pig <NUM> and thereby send a wireless signal to the receiver connected to the laptop computer <NUM> to confirm the detection of the passage of the pig <NUM>. At this stage the computer program is informed that the pig <NUM> has passed the first pig signaller <NUM> and entered the heater tube <NUM>, which triggers the computer program to start a timer ('<NUM>'). The pig <NUM> then travels through the heater tube <NUM> from the inlet end to the outlet end. When the pig <NUM> is received by the second pig launcher <NUM>, it will pass the second pig signaller <NUM> that will detect the magnetic field generated by the magnet in the pig <NUM> and thereby send a wireless signal to the receiver connected to the laptop computer <NUM> to confirm the detection of the passage of the pig <NUM>. At this stage the computer program is informed that the pig <NUM> has passed the second pig signaller <NUM> and left the heater tube <NUM>, which triggers the computer program to stop the timer ('<NUM>').

The laptop computer <NUM> may be programmed to identify the pig signaller <NUM>,<NUM> from which a given wireless signal originated through evaluation of:.

The time difference between the two signals will be determined as the run time (also known as travel time) for the travel of the pig <NUM> through the heater tube <NUM>. The computer program then calculates the speed of the pig <NUM> through the heater tube <NUM> in the previous run from the run time and the distance value between the inlet and outlet ends.

If the pig <NUM> is then required to be driven in the opposite direction from the second pig launcher <NUM> to the first pig launcher <NUM>, the operator controls the fluid pressure to launch the pig <NUM> from the second pig launcher <NUM> ('<NUM>'). When the pig <NUM> is launched from the second pig launcher <NUM>, it will pass the second pig signaller <NUM> that will detect the magnetic field generated by the magnet in the pig <NUM> and thereby send a wireless signal to the receiver connected to the laptop computer <NUM> to confirm the detection of the passage of the pig <NUM>. At this stage the computer program is informed that the pig <NUM> has passed the second pig signaller <NUM> and entered the heater tube <NUM> and initiates the real-time tracking of the pig's position inside the heater tube <NUM> ('<NUM>'). The display screen of the laptop computer <NUM> displays a moving icon <NUM> representing the pig <NUM> overlaid on the graphical layout <NUM> of the heater tube <NUM>, as shown in <FIG>. As the actual pig <NUM> travels through the heater tube <NUM> from the outlet end to the inlet end, the virtual pig signified by the icon <NUM> moves along the graphical layout <NUM> of the heater tube at a speed equal to the calculated pig's speed from the previous run. This provides the operator with an approximate location of the pig <NUM> inside the heater tube <NUM> at any given time. When the pig <NUM> is received by the first pig launcher <NUM>, it will pass the first pig signaller <NUM> that will detect the magnetic field generated by the magnet in the pig <NUM> and thereby send a wireless signal to the receiver connected to the laptop computer <NUM> to confirm the detection of the passage of the pig <NUM>. At this stage the computer program is informed that the pig <NUM> has passed the first pig signaller <NUM> and left the heater tube <NUM> and stops the real-time tracking of the pig's position inside the heater tube <NUM> ('<NUM>'). During the second run, the detected passages of the pig <NUM> may be recorded and used to determine the run time and calculate the pig's speed in the same way as the first run.

The laptop computer <NUM> is preferably programmed to record the data about the pig's travel inside the heater tube <NUM> and automatically generate log sheets with details about the pig's travel through the heater tube <NUM>, e.g. quantity of runs, duration of runs, operating parameters, etc..

The calculated pig's speed can also be used for the real-time tracking of the pig's position inside the heater <NUM> in a new run that is in the same direction as the previous run.

By way of the real-time tracking of the pig's position providing the operator with the pig's approximate location inside the heater tube <NUM> at any given time, the operator is provided with information that enables them to control the decoking operation, e.g. maintain or change the movement (e.g. speed, direction) of the pig <NUM> through the heater tube, drive the pig <NUM> to move back and forth inside a particular section of the heater tube <NUM>, or change fluid pressure direction to re-launch the pig <NUM> after it is received in a pig launcher <NUM>,<NUM>.

Data from the real-time tracking of the pig's position inside the heater tube <NUM> may be used to automatically control the movement of the pig <NUM> inside the heater tube <NUM>. In this regard, operator involvement is minimal or optional. The fluid propulsion device is exemplarily configured to automatically control a propulsion of the pig <NUM> inside the heater tube <NUM> in response to information obtained or derived from the real-time tracking of the pig's position inside the heater tube <NUM>, as follows:.

The automatic activation of the fluid propulsion device may be carried out by linking the controls of the fluid propulsion device to the tracking device <NUM>, which then acts as a controller to control the activation of the fluid propulsion device.

The automatic control of the fluid propulsion device can be maintained without operator involvement until such time as, for example, the pig <NUM> needs to be replaced by a different pig, e.g. a newer pig, a sharper pig, a larger diameter pig.

Two exemplary modes of the real-time tracking of the pig's position inside the heater tube <NUM> are described as follows:
In a first exemplary mode, the real-time tracking of the pig's position inside the heater tube <NUM> is carried out using a calculated pig's speed from a previous run. The calculated pig's speed is kept unchanged until it is deemed necessary to recalculate the pig's speed through the heater tube <NUM>. The recalculation of the pig's speed through the heater tube <NUM> may be carried out as a result of an operator decision or may be automatically carried out after a fixed number of runs are completed.

After recalculating the pig's speed through the heater tube <NUM>, the newer calculated pig's speed replaces the older calculated pig's speed and is used in the real-time tracking of the pig's position inside the heater tube <NUM> in the or each subsequent run of the pig <NUM> until it is deemed necessary to recalculate the pig's speed through the heater tube <NUM>.

In a second exemplary mode, the real-time tracking of the pig's position inside the heater tube <NUM> is carried out using a calculated pig's speed from multiple previous runs to reduce the influence of detection errors or abnormal runs. The computer program calculates the pig's speed from a fixed number of multiple previous runs by taking the determined run times from the previous runs and assigning a pre-defined weight to each run time, as shown in Table <NUM>.

The second exemplary mode continually recalculates the calculated pig's speed after each completed run and thereby enables the automatic adjustment of the real-time tracking of the pig's position inside the heater tube <NUM> to take into account changes in operating conditions with time.

Optionally the computer program may exclude at least one of the run times in calculating the speed of the pig <NUM> through the heater tube <NUM> if the or each excluded run time deviates by a predefined amount from a reference run time, which may be the most recent run of the multiple runs. This allows removal of the influence of one or more abnormal runs over the calculation of the pig's speed through the heater tube <NUM>.

Alternatively the pig's speed through the heater tube <NUM> may be an unweighted average speed of the previous multiple runs, instead of a weighted average speed of the previous multiple runs.

The number of previous multiple runs may be two, three, four or more.

As the pig <NUM> travels inside the heater tube <NUM>, changes in pressure and/or flow may take place due to, for example, the pig transitioning between sections of the heater tube <NUM> of different shapes and/or sizes or due to the pig approaching a bend or end section of the heater tube <NUM>.

The pressure and/or flow changes may be used to aid the real-time tracking of the pig's position inside the heater tube <NUM>. When the pig <NUM> enters the heater tube <NUM> from a launcher <NUM>,<NUM> as detected by a pig signaller <NUM>,<NUM>, the computer program will monitor the pressure and flow parameters of the interior of the heater tube <NUM> via pressure and flow sensors in addition to detection of the passage of the pig <NUM> inside the heater tube <NUM> using the pig signallers <NUM>,<NUM> and any other optional position sensor arranged along the heater tube <NUM> between the pig signallers <NUM>,<NUM>. For example, a significant increase or decrease in pressure and flow indicates that the pig has reached an end of the heater tube <NUM>. Also, for example, as mentioned above, as the pig <NUM> travels through the heater tube <NUM>, a pressure line chart may appear as a series of "beats", with each spike being associated with a bend. The change in pressure and flow parameters will be vastly different depending on the feature of the heater tube <NUM> towards which the pig <NUM> is travelling. If the pig <NUM> is travelling towards a section of the heater tube <NUM> of reduced size, the computer program will be searching for an increase in pressure and a decrease in flow. If the pig <NUM> is travelling towards a section of the heater tube <NUM> of increased size, the computer program will be searching for a decrease in pressure and increase in flow. Additionally the computer program may compare the current pressure and flow parameters with measured pressure and flow parameters from previous runs of the pig <NUM> through the heater tube <NUM>.

Hence, the pressure and/or flow measurements together with the calculated pig's speed may be used to carry out the real-time tracking of the pig's position inside the heater tube <NUM>. More specifically, the pressure and/or flow data may be combined with the calculated pig's speed by the laptop computer <NUM> and fed to the display screen to generate the display of the moving icon <NUM> representing the pig <NUM> overlaid on the graphical layout <NUM> of the heater tube <NUM>. Such combination improves the accuracy of the graphical representation of the pig's location, direction and speed inside the heater tube <NUM>.

The pressure and/or flow measurements may be shown on the display screen of the laptop computer <NUM> together with the graphical display of the real-time tracking of the pig's position inside the heater tube <NUM>. Alternatively the pressure and/or flow measurements may be shown on a separate display screen. In addition the pressure and/or flow measurements may be included in the automatically generated log sheets.

The configuration of the apparatus of <FIG> therefore enables the automatic real-time tracking of the pig <NUM> travelling inside the heater tube <NUM> by using the determined travel time from a previous run to estimate the position of the travelling pig <NUM> inside the heater tube <NUM> at any given time, using a minimal number of sensors. In this way the apparatus of <FIG> is capable of learning from experience in that the updating of the run time, the use of a weighted or unweighted average of run times and the ability to exclude one or more anomalous readings provide the apparatus with the capacity to learn from the previous run (or previous runs) of the pig <NUM> inside the heater tube <NUM> but also permit such learning to automatically control the propulsion of the pig <NUM> inside the heater tube <NUM> and record and report information associated with the run(s).

The invention provides time savings and performance improvements over conventional inline decoking processes, examples of which are set out as follows:.

It will be appreciated that the above numerical values are merely intended to help illustrate the working of the invention and may vary depending on the requirements of the apparatus and the associated application.

The listing or discussion of an apparently prior-published document or apparently prior-published information in this specification should not necessarily be taken as an acknowledgement that the document or information is part of the state of the art or is common general knowledge.

Claim 1:
An apparatus for tracking a pig (<NUM>) travelling inside a tubular object (<NUM>), the apparatus comprising:
a sensor arrangement including at least one position sensor (<NUM>, <NUM>) configured to detect a passage of the pig (<NUM>) travelling inside the tubular object (<NUM>),
characterised in that the apparatus further comprises a tracking device (<NUM>) configured to:
process the detected passage of the pig (<NUM>) from a run of the pig (<NUM>) through the tubular object (<NUM>) to determine a travel time of the pig (<NUM>);
using the determined travel time, calculate a speed of the pig (<NUM>) through the tubular object (<NUM>); and
using the calculated pig's speed, perform real-time tracking of the pig's position inside the tubular object (<NUM>) in a subsequent run of the pig (<NUM>) through the tubular object (<NUM>).