TECHNICAL FIELD

[001 ] The present disclosure relates to systems and methods for pigging a pipeline.

BACKGROUND

[002] Pipeline transportation is a transportation method developed in the 1950's and has been widely employed in metal mines, coal mines and non-metallic mineral mines. Compared with other types of transportation methods, for example, automobile and train transportation, pipeline transportation has a number of advantages, such as continuous operation, increased transportation capacity, reduced environmental impact, low material loss, resistance to weather and climate conditions, low infrastructure investment, low operating cost, and so on. In addition, long-distance pipeline transportation is highly adaptable to changing terrains, and it is easier to transport materials across, for example, mountains and rivers. It is one of the most practical and economical transportation methods, and has been widely used especially with the increasing concerns over environmental protection.

[003] In mining operations, pipelines are widely used to transport slurry mixtures. In the initial stage of slurry transportation, pipelines manufactured from a single metal material, such as unlined steel or stainless steel pipelines, are generally utilised. However, these unlined steel pipelines have poor corrosion and wear resistance and tend to scale, that is, a solid or semi-solid deposit will form on an inner wall of the pipelines. The thickness of the deposit grows overtime, which can noticeably reduce the transport capacity of the pipelines. The mineral processing industry soon proposed higher standards for a pipeline’s performance, such as wear resistance, corrosion resistance, and anti-scaling. Therefore, the pipelines used for transporting slurry mixtures evolved from being manufactured from a single metal material to other forms, including pipelines manufactured from multiple materials, pipelines with wearresistant rubber or ceramics lining, UHMWPE (ultra high molecular weight polyethylene) plastic pipelines, and polyolefin composite wear-resistant pipelines in more recent years.

[004] Rubber-lined pipelines have been widely used in slurry transfer due to their improved performance in corrosion resistance and wear resistance. However, slurry pipelines with a wear-resistant rubber-liner, used for transferring slurry which contains calcium, magnesium and carbonate species, reagents, ultrafine particles, or fibrous materials, are also prone to build up of scale residue. As soon as scaling occurs on an inner surface of the pipelines, the thickness of the scaling will grow rapidly, which leads to a decrease of the flow rate of the slurry in the pipelines. In a beneficiation plant, tailing slurry transfer is essential to maintain continuous operation of production. The decrease of transfer capacity of the tailing pipeline will become the bottleneck for the whole processing plant. In the past, acidic chemicals, such as sulphuric acid and hydrochloric acid, have been used to remove the build up of calcium carbonate and magnesium hydrate. It is known that chemical cleaning methods can potentially corrode pipelines and are found to be ineffective for some residues such as fibrous material scaling. Chemical cleaning methods are also known to produce hazardous waste which is an environmental concern.

[005] Accordingly, there is a need for a system and/or a method of pigging a pipeline which ameliorates or addresses at least one of the issues mentioned above.

[006] Any reference to or discussion of any document, act or item of knowledge in this specification is included solely for the purpose of providing a context for the present invention. It is not suggested or represented that any of these matters or any combination thereof formed at the priority date part of the common general knowledge, or was known to be relevant to an attempt to solve any problem with which this specification is concerned.

SUMMARY OF THE INVENTION

[007] In a first aspect, the present disclosure provides a pipeline pigging system including: a pipeline used for material transportation, wherein the pipeline includes a rubber lining; at least one pigging device, arranged to be introduced into the pipeline at a first end of the pipeline, and caused to travel in the pipeline for cleaning purpose between the first end and a second end of the pipeline; a launching system, for introducing the at least one pigging device into the pipeline at the first end, and a receiving system for collecting the pigging device at the second end of the pipeline after decaling.

[008] In an embodiment, the pigging device includes a substantially cylindrical main body portion.

[009] In an embodiment, a diameter of the pigging device is smaller than an inner diameter of the pipeline.

[010] In an embodiment, the pigging device further includes a head portion formed in a truncated cone shape, and extends from one end of the cylindrical main body.

[011 ] In an embodiment, the pigging device is made from compressible materials, allowing dimensions of the pigging device to be varied to accommodate for different inner dimensions of the pipeline as it travels between the first and second end of the pipeline.

[012] In an embodiment, the compressible materials have a compression rate of about 30%, that is, the diameter of the pigging device is able to be reduced by about 30% when it is compressed. [013] In an embodiment, the pigging device is made of high density open cell polyurethane.

[014] In an embodiment, the pigging device includes a polyurethane outer coating, wherein the outer coating comprises surface formations that assist in lifting or removing the scales as the pigging device travels within the pipeline.

[015] In an embodiment, the polyurethane outer coating is attached and wrapped around at least a substantial outer surface of the pigging device.

[016] In an embodiment, the surface formations include raised structures which are evenly distributed around the outer surface of the pigging device.

[017] In an embodiment, the surface formations are arranged in an array and in a crisscross pattern.

[018] In an embodiment, the polyurethane outer coating is of a thickness of 2 to 5 mm.

[019] In an embodiment, the pigging device further includes one or more gripping portions arranged to assist with moving or carrying of the pigging device by an operator or by a machinery when required.

[020] In an embodiment, the one or more gripping portions include one or more ropes.

[021 ] In an embodiment, the one or more gripping portions are located near a front end of the pigging device and/or at a back end of the pigging device.

[022] In an embodiment, the one or more gripping portions additionally include a recess, or a channel, formed at, or near the back end and/or a front end of the pigging device, allowing the pigging device to be lifted by engaging the recess or the channel.

[023] In an embodiment, the pigging device includes one or more bores which extend in a lengthwise direction of the pigging device, allowing a material to move from a front end of the pigging device to a back end of the pigging device and be discharged therefrom as the pigging device moves within the pipeline.

[024] In an embodiment, the material includes water, or build up of materials removed from an inner surface of the pipeline.

[025] In an embodiment, the pigging device includes a location tracking device, enabling positions of the pigging device to be detected and forwarded to an electronic position receiver. [026] In an embodiment, a plurality of pigging devices which are of different diameters and/or surface formations and are arranged to be introduced into the pipeline in a predetermined sequence.

[027] In an embodiment, the plurality of pigging devices include four pigging devices: a first pigging device with a first diameter d1 , a second pigging device with diameter d1 , a third pigging device with a diameter d2, and a fourth pigging device with diameter d2, wherein d1 <d2, and wherein each of the second, third, and fourth pigging device is provided with a polyurethane outer coating with surface formations.

[028] In an embodiment, the first pigging device is used in a pigging operation first, then followed by the second pigging device, the third pigging device, and finally the fourth pigging device.

[029] In an embodiment, the launching system is hydraulically powered.

[030] In an embodiment, the launching system includes an inlet, into which the pigging device is inserted, an outlet coupled to the first end of the pipeline to be cleaned, and a launching pipe extending between the inlet and the outlet of the launching system.

[031 ] In an embodiment, the launching pipe includes sections which are of different diameters.

[032] In an embodiment, a diameter of the launching pipe at or near the inlet is greater than a diameter of the launching pipe at or near the outlet.

[033] In an embodiment, the launching system further includes a pressure balancing pipe, which balances pressure changes between sections of the launching pipe which are of different diameters.

[034] In an embodiment, the launching system further includes: a fast opening blind valve, a pigging device passing indicator, a pressure indicator, an air bleed and an air vent, and a drain valve.

[035] In an embodiment, the pressure indicator is used to monitor a pressure inside the launching system to avoid causing personal injuries when the fast opening blind valve is opened.

[036] In an embodiment, the air bleed and air vent are arranged to release air inside the launching system.

[037] In an embodiment, the receiving system includes: an inlet, being coupled to the second end of the pipeline to be descaled, an outlet, from where the pigging device exits and is collected, a receiving pipe extending between the inlet and outlet of the receiving system. [038] In an embodiment, the receiving system further includes: a fast-opening blind valve, a pigging device passing indicator arranged to track the location of the pigging device within the receiving system, pressure indicators, an air bleed and an air vent arranged to release the air inside the receiving system, and a drain valve.

[039] In an embodiment, the receiving system includes two pressure indicators at a front end and a rear end of the receiving system respectively, arranged to monitor a pressure change inside the receiving system and to avoid any personnel injuries when opening the fast-opening blind valve.

[040] In an embodiment, the receiving system includes a drain pipe to discharge a material from the receiving system.

[041 ] In an embodiment, the pipeline includes steel barrier bars to help guide movement of the pigging device within the pipeline and prevent the pigging device from being stopped at a corner.

[042] In a second aspect, the present disclosure provides a method of cleaning a pipeline using a plurality of pigging devices, the method comprising: providing a plurality of pigging devices, wherein at least one pigging device is of a smaller diameter, and wherein at least one pigging device is of a larger diameter, introducing the plurality of pigging devices into the pipeline according to a predetermined sequence, such that the pigging device with a smaller diameter is used in a pigging operation before the pigging device with a larger diameter is used to clean the pipeline.

[043] In an embodiment, the plurality of pigging devices include a first pigging device with diameter d1 , a second pigging device with diameter d1 , a third pigging device with diameter d2, and a fourth pigging device with diameter d2, wherein d1 <d2, and wherein the second, third, and fourth pigging devices are provided the surface formations.

[044] In an embodiment, the step of introducing the plurality of pigging devices into the pipeline comprises introducing the first pigging device into the pipeline first, then followed by the second pigging device, the third pigging device, and finally the fourth pigging device.

[045] In an embodiment, the step of introducing the plurality of pigging devices into the pipeline comprises:

(a) loading one of the plurality of pigging devices into the pipeline;

(b) using a hydraulic force to push the pigging device into the pipeline at a first end thereof, and to cause the pigging device to advance from the first end to a second end of the pipeline for pigging purpose;

(c) collecting the pigging device at the second end of the pipeline by a receiving system; wherein steps (a) to (c) are repeated for each of the plurality of pigging devices. [046] In an embodiment, the surface formations are formed in a polyurethane outer coating, which is permanently attached and wrapped around a main body portion of the respective pigging device.

[047] In an embodiment, d1 is approximately 10 to 15mm smaller than d2, wherein both d1 and d2 are smaller than a diameter of the pipeline.

[048] In an embodiment, the method further comprises: determining an effective diameter of the pipeline before a pigging operation is performed, determining diameters of the plurality of pigging devices, based on the effective diameter of the pipeline, wherein the effective diameter of the pipeline is determined based on a diameter of the pipeline and a thickness of scale built up on an internal wall of the pipeline.

[049] Further features and advantages of the present disclosure will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[050] Various preferred embodiments of the present disclosure will now be described, by way of examples only, with reference to the accompanying figures, in which:

Figure 1 illustrates a schematic diagram of a pigging system, according to an embodiment of the present disclosure;

Figure 2(a) shows a cross sectional view of a pigging device, according to an embodiment of the present disclosure;

Figure 2(b) shows a side on view of a pigging device, according to an embodiment of the present disclosure;

Figure 2(c) shows a front end view of a pigging device, according to an embodiment of the present disclosure;

Figure 2(d) shows a back end view of a pigging device, according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS [051 ] Figure 1 shows a schematic diagram of a pigging system 10, according to an embodiment of the present disclosure, being incorporated in an interconnected pipeline system. During normal pipeline transportation, materials are transported by the interconnected pipelines in the direction indicated in Figure 1 (i.e. from pipeline 130, to pipeline 100, then to pipeline 140, and eventually to pipeline 150). The pigging system 10 of the present disclosure is configured to clean a section of the of the interconnected pipeline system, namely pipeline 100 which has a first end 100a and a second end 100b.

[052] The components of the pigging system 10 will now be described in accordance with exemplary stages of a pigging operation, as follows:

Step 1 : preparation

[053] The first stage of pigging involves preparing the system 10 such that it is ready for pigging procedure.

[054] A suitable storage facility, for example a facility including storage tanks, is used to maintain normal production without stopping upstream equipment during the subsequent pigging operation. A transfer box is installed between the storage facility and the pump that controls material flow rate into the interconnected pipelines. During the initial preparation phase, material transfer (for example, slurry) between the storage facility and the transfer box is interrupted, and process water is filled into the transfer box, which is then ready to be pumped into pipeline 130.

Step 2: flushing

[055] Depending on the type of materials which were being transported within the pipeline 100 prior to pigging, it may be necessary to flush a cleaning agent, for example, water, through the pipeline 100 to remove any remaining materials which are still within the pipeline 100. This process may be continued until the discharge density reading becomes sufficiently low (for example, zero), which is an indication that a majority of the remaining materials has been flushed out of the pipeline 100. In some cases, the flushing step may take 25 mins to half an hour.

Step 3: launching a pigging device by the launching system

[056] Once the remaining materials have been flushed out of the pipeline 100, pigging operation may start.

[057] Cleaning of the pipeline 100 is achieved by causing a pigging device 20 to travel from the first end 100a of the pipeline 100, to the second end 100b, and as the pigging device 20 advances within the pipeline 100, scales within the pipeline 100 is loosened or peeled off the inner wall of the pipeline 100, due to physical contact between the pigging device and the scales, thereby achieving cleaning purpose. It should be noted that industrial pipelines vary in many different sizes and forms. For mining operations, pipelines could extend for a few kilometres, and the diameter of such pipelines could also be very large, for example, around or over 1 meter. Thus, care must be taken when introducing the pigging device 20 into the pipeline 100 and causing it to move through the pipeline 100, as moving the pigging device 20 too fast may cause structural damage to the pipeline 100 or injuries to the personnel operating the pigging system, whereas moving it too slow, or not providing sufficient propelling or pushing force to the pigging device 20 could result in inefficiencies or causing the pigging device 20 to stop at a point before reaching the second end 100b of the pipeline 100. To ensure that the pigging device 20 is launched safely and effectively, in the present embodiment, the pipeline 100 is coupled to a launching system 200 arranged to load the pigging device into the pipeline 100 and causing it to travel along the pipeline 100 by a hydraulic force.

[058] As shown in Figure 1 , the launching system 200 is fluidly coupled to the first end 100a of the pipeline 100, and the receiving system 300 is fluidly coupled to the second end 100b of the pipeline 100. In use, the pigging device 20 is introduced into the launching system 200 via inlet 210, and as it completes its pigging operation, it is collected at an outlet 315 of the receiving system 300.

[059] The launching system 200 includes a launching pipe 110 including sections that have different diameters. Preferably, the diameter of the launching pipe 110 at the inlet 210 is greater than the diameter of the launching pipe 110 at the outlet 220. This will allow the pigging device 20 to be more easily inserted into the launching system 200 via its inlet 210. To accommodate for the difference in pressure in the launching pipe 110 caused by changing parameters, a pressure balancing pipe 205 is provided which creates a separate fluid pathway, between sections of the launching pipe 110 having different diameters.

[060] The launching system 200 further comprises a number of valves 201 , 206, 207, 209, 211 , which are selectively opened and closed in a predetermined sequence, in order to build up a pressurised environment within the launching system 200, and to provide a hydraulic pushing force for the pigging device 20. A fluid source, such as water, is supplied to the launching system 20 via a main fluid inlet 101 in order to create the pressurised environment. The flow rate of such fluid source is controlled by a pump (not shown in Figure 1 ). A pressure indicator 202 is included in the launching system 200 which monitors the pressure within such that it is maintained within a suitable range to avoid any personnel injuries when opening and closing the valves mentioned above. Furthermore, air vents 203, 204 are arranged to release the air inside the launching system 200 when required. A pig passing indicator 212 is located near the outlet 220 of the launching system 200, to monitor whether the pigging device 20 is approaching the outlet 220 of the launching system 200 and is about to move into the pipeline 100.

[061 ] In one embodiment, the launching system 200 is arranged to go through the following steps in order to provide a sufficient hydraulic force to push the pigging device into the pipeline 100: (a) First, open drain valve 206 to empty the content of the launching system 200. The other valves retain closed during this step.

(b) After confirming the reading of the pressure indicator 202 has dropped to zero, open fastopening blind valve 201 , which opens up the inlet 210 of the launching system, and load the pigging device 20 into the launching system 200 by inserting it into the inlet 210.

(c) Close the fast-opening blind valve 201 and drain valve 206, reduce pump speed, which reduces the flow rate of water being supplied to the launching system 200. In a preferred embodiment, the speed of the pump is reduced to 40-50% of its normal operational speed.

(d) Preferably, the position of the pigging device is also monitored by a location tracking device which is embedded in the pigging device. The next step involves confirming the location tracking device 25 of the pigging device 20 is operating, then open valve 207 to allow process water to start flowing into the launching system. Next, air vent valve 204 is opened to release any remaining air within the launching system, and process water is feed into the pipeline 100. Then, close the air vent valve 204, open the valve 209 such that a pathway is opened between the launching system 200 and the pipeline 100, and close the valve 211 . After the pig passing indicator 212 detects that the pigging device 20 has moved passed it, the pigging device has successfully entered the pipeline 100 and may start its pigging operation.

(e) Next, the pump speed is slowly and cautiously increased in different stages. In a preferred embodiment, each time the speed of the pump is only increased by around 2 to 5%, and the pipeline 100 inlet pressure is maintained at a level equal to, or less than

1 ,6MPa, at a flowrate of around 6000 to 6500m ³ /h.

(f) As the pigging device approaches the receiving system 300, the flowrate of the pipeline is reduced to 2500-3000m ³ /h.

(g) Open the drain valve 206 to discharge all water in the launching system and then close drain valve 206.

Step 4: pigging

[062] Once the pigging device is launched, that is, it has left the launching system 200 and has entered the pipeline 100 which requires cleaning, it is pushed along the pipeline 100 by the hydraulic force from a back end of the pigging device 20. Due to the physical forces (e.g. friction) between an outer surface of the pigging device 20, and the scale residue on the inner surface of the pipeline 100, the scale residue is loosened and/or peeled off from the surface of the pipeline 100, which is then flushed away by the water flowing in the pipeline 100.

[063] Figures 2(a) to 2(d) show a cross sectional view, a side on view, a front view, and a back end view of an exemplary pigging device 20 according to embodiments of the present disclosure respectively.

[064] The pigging device 20 includes a main body portion 21 , which is of a substantially cylindrical shape, and a head portion 22 extending from a front end of the main body portion 21 , wherein the head portion 22 is formed in a truncated cone shape. The head portion 22 is aerodynamically designed in a truncated cone shape such that the resistance encountered by the pigging device 20 as it moves along the pipeline 100 is reduced. To further reduce the resistance encountered by the pigging device 20 as it is moved along the pipeline 100, a plurality of through holes 27 extending in a lengthwise direction of the pigging device 20 are provided in the main body portion 21 of the pigging device. These through holes 27 are arranged to discharge some peeling scales to the back end of the pigging device 20 as it travels. The through holes 27 improve the effectiveness of pigging operation and reduce the risk of the pigging device

20 being stuck in the pipeline 100. In a more preferred embodiment, 4 to 6 of such through holes 27 are provided in the pigging device.

[065] Due to the size and the substantially cylindrical profile of the pigging device 20, it would be appreciated that a number of gripping portions are provided in the pigging device 20, which would allow easier handling and moving of the pigging device 20. For example, at the back end of the pigging device 20, a channel or recess 23b is formed in the main body portion 21 , which provides a suitable gripping or engaging means for lifting or moving the pigging device 20. Similarly, a channel or recess 23a may also be provided to the front end of the pigging device 20 as shown in Figure 2(b). To further assist with the lifting or moving the pigging device 20, additional gripping portions 24a and 24b, such as pulling ropes, are provided at both ends of the pigging device 20.

[066] Preferably, the pigging device 20 is made from a high density open cell polyurethane foam. The compression rate of the foam is preferably around 30% to accommodate variation of the diameter of the pipeline 100 while still having enough rigidness to remove the scales and preventing any damage to the rubber liner.

[067] In some embodiments, an outer coating 28 wraps around the main body portion 21 of the pigging device 20, as shown in Figure 2(c). The outer coating 28 is formed from polyurethane material and is generally of a thickness of around 2 to 5mm. In one embodiment, the outer coating 28 is formed separately from the main body 21 of the pigging device 20, and is permanently attached to the main body

21 prior to a pigging operation. The outer coating 28 is formed such that it provides the pigging device 20 with surface formations that assist in lifting or peeling off the scales as it travels within the pipeline 100. In one embodiment, the surface formations are formed by cutting out sections of the outer coating 28, and the cut-outs are generally arranged in an array which extend around a major outer surface of the main body portion of the pigging device, forming a crisscross pattern.

[068] In order to prevent the pigging device 20 from getting seized, steel barrier bars are installed in all T-branch pipelines along the pigging pathway of the pigging device 20.

[069] As mentioned above, it is desirable to track and monitor the location of the pigging device 20 during a pigging operation. A location tracking device or sensor 25 is provided in the pigging device 20 to achieve this purpose.

Step 5: collecting the pigging device [070] After the pigging device 20 has finished its pigging operation within pipeline 100, it will need to be removed from the pipeline 100 and collected safely without causing any damages to the system, or injuring operators that are close by. A receiving system 300 is employed to collect the pigging device 20 at the second end of the pipeline 100, as will be further described below.

[071 ] Similar to the launching system 200, the receiving system 300 also includes a number of valves 303, 307, 309, 312, 313, 314 which are opened and closed in a predetermined sequence in order to safely reduce the pressure inside the receiving system 300 before collecting the pigging device 20 at the outlet 315.

[072] The pigging device 20 may be collected as follows:

(a) After confirming the pipeline 100 is discharging water without scale, indicating that pigging operation has been successful, open air vent 303, valves 313 and 309, and close valve 314 before the arrival of the pigging device 20. Opening air vent 303 will release the air within the receiving system 300 and prevent the pressure inside the receiving system 300 from raising too quickly.

(b) After receiving a signal from a location tracking device 301 of the receiving system 300, confirming the pigging device 20 has arrived in the receiving system 300, open valve 314, close the valves 313/309 and open drain valve 312 to discharge the water in the receiving system 300.

(c) When pressure indicators 302 and 306 show zero, open fast-opening blind valve 307 and pull the pigging device out of the receiving system 300 by engaging rope 24a.

(d) Close the fast-opening blind valve 307, drain valve 312 and air vent valve 303.

[073] In one embodiment, steps 3 to 5 above are repeated multiple times until a desired amount of scale has been successfully removed. To ensure the effectiveness of pigging multiple times, it is preferred to use pigging devices which have different configurations. For example, the plurality of pigging devices may be selected such that at least one pigging device is of a slightly smaller diameter than a subsequent pigging device, and the smaller pigging device is used first before the subsequent pigging device is caused to travel in the same pipeline. Further, the plurality of pigging devices may also be configured such that they have different surface configurations provided by the polyurethane outer coating. In one embodiment, a combination of smooth and textured outer surfaces may be provided to the plurality of pigging devices.

[074] In a preferred embodiment, steps 3 to 5 above are repeated for a total number of four pigging devices to ensure pigging efficiency. The four pigging devices are configured as follows:

• First pigging device has a diameter d1 , and does not include any surface formations on its outer surface;

Second pigging device has diameter d1 , and is provided with surface formations; • Third pigging device has diameter d2, where d2 is greater than d1 , and is also provided with surface formations;

• Fourth pigging device has identical configurations to the third pigging device.

[075] The four pigging devices are used sequentially (first, second, third and then fourth) to prevent the pigging devices from being stuck in the pipeline, as well as reducing the risk of damaging the rubber lining of the pipeline 100. In some embodiments, in order to determine suitable diameters for the plurality of pigging devices, an effective inner diameter of the pipeline 100 will need to be first estimated or measured, for example, by isolating a section of the pipeline 100, and inspecting a thickness of the scales either visually or by using a suitable measuring device. The effective inner diameter of the pipeline 100 is then determined by subtracting the thickness of the scales from the actual diameter of the pipeline 100. If a rubber lining is provided to the pipeline, it should be noted that the actual diameter of the pipeline usually equals an inner diameter of the pipeline minus the thickness of the rubber lining. In a preferred embodiment, d2 is 10 to 15mm greater than d1 , and d2 is also approximately 10-20mm smaller than the effective inner diameter of the pipeline, to account for the thickness of the scales. For example, if the pipeline 100 has an effective inner diameter of 1000mm, and the thickness of the scale is estimated to be around 20mm, then d1 is around 960 - 980 mm, and d2 is around 970mm to 990 mm. In another embodiment, the effect inner diameter of the pipeline is 975mm, and the thickness of the scale is estimated to be around 20mm, then d1 is around 955mm and d2 is 965mm.

[076] After the pigging process finishes, the pipelines can be used to transfer materials again.

Example

[077] Sino Iron Project, the world's largest magnetite iron ore project, is located within the mineral-rich Pilbara region of Western Australia. It has 6 milling production lines and all of them have been put into operation since 2016. The tailings transfer pipeline is 8.124km in length, DN1000 in diameter (i.e. the nominal diameter of the pipe is 1000mm, but the actual diameter of the pipe is 975mm with a rubber liner), and is used to transfer iron tailings slurry from the concentrator to the tailings storage facility (TSF). The designed capacity of the pipeline is 69 MTA (mega tons per annum). Because of the high corrosion of the process water, the pipeline has been lined inside by a layer of rubber which is approximately 9.53mm in thickness. After operation for several years, the tailings transfer flowrate was observed to gradually decrease because of scaling on the rubber liner at the beginning of 2019, resulting in substantial upstream production loss. With the scaling deteriorating, processing capacity of 67,200 tonnes of raw ore (equalling to 23,172 tonnes of concentrate at a concentration ratio around 2.9) was lost per day.

[078] Furthermore, the scaling material on the tailing pipeline contains fibrous material and ultrafine particles, inter grown together and physically adsorbed on the rubber liners. Acid washing has been tried without any success due to insolubility of the scale material. Thus, a pigging system was proposed. [079] One of the issues with the pigging of the tailings transfer pipeline is that the scale is too thick, and the scale on the top section of the tailings transfer pipeline can be up to 110mm in thickness. If too much scale is scraped off at one time or if the scale collapses and falls to a lower section of the pipeline, it will bring about excessive scale material in front of a pigging device, which will absolutely prevent the pigging device from advancing, resulting in blockage of the pipeline and further causing the breakdown of all the upstream milling lines. In order to address this problem, it is necessary to disassemble the transfer pipeline to measure the thickness of the scale, determining the effective inner diameter of the pipeline in order to select a suitably sized pigging device. A total of four pigging devices were used to remove the scales within the pipeline, with the first pigging device having a diameter of 955mm, and the diameter of the subsequent pigging devices are incremented by 10mm each time, until it reaches the inner diameter of the rubber lined pipe, which is 975mm in this instance due to the rubber lining. This measure ensures that the scale scraped off each time will not be too excessive and the pigging device will not be easily blocked by the peeled off scale.

[080] Routine pigging cleaning by temporarily switching normal slurry transfer mode to pigging operation without any interruption of processing production is conducted to ensure enough tailings transfer capacity for normal upstream production. For normal operation of tailings slurry transfer in the Sino Iron, the tailing slurry is pumped through pipelines 130, 100, 140, 150, to maintain the daily production of the whole beneficiation plant. Generally the throughput of the tailing slurry is 6700-7500m ³ /h and the slurry density is 45%-55%. Every three months, the throughput will decrease by 200-1200m ³ /h due to scaling of mainly minerals in fibrous form and ultrafine particles below 10pm.

[081 ] In the Sino Iron Project, various sections of the pipelines are descaled using the systems and methods described above. After pigging operations, the throughput of the pipeline recovers to its original value with an increase of the throughput by about 200-1200m ³ /h.

[082] In this specification, the terms ‘comprises’, ‘comprising’, ‘includes’, ‘including’, or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.

[083] The above description relating to embodiments of the present disclosure is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the disclosure to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present disclosure will be apparent to those skilled in the art from the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. The present disclosure is intended to embrace all modifications, alternatives, and variations that have been discussed herein, and other embodiments that fall within the spirit and scope of the above description.