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Abstract: It briefly introduces the functions of various pigging devices and outlines the status of pigging device research and application in China. Based on years of work experience, the future development direction of pigging devices is outlined. Keywords: Pigging devices ； Type ； In applications, pipelines used for the long-term transport of fluids such as oil, water, and gas can become clogged, requiring cleaning and unclogging. There are many types of pipeline cleaning technologies, such as ultrasonic cleaning technology, high-pressure water jet cleaning technology, laser cleaning technology, dry ice cleaning technology, plasma cleaning technology, electrolytic cleaning technology, and so on. These cleaning techniques are widely used in mechanical cleaning. I. Functions of pigging devices Pigging devices are among the equipment used for mechanically cleaning pipes, and they have four main functions. First, pipeline cleaning, rust removal, drying, sealing, and purging. This application is mainly used in gas and liquid pipelines on land or at sea. Second, wax removal, scale removal, as well as water and dust removal from pipelines during oil field production. This function is primarily designed for use in oil pipelines or pipelines transporting a mixture of oil and gas. Third, the isolation of different media. It is used when it is necessary to isolate different fluids, in order to prevent them from mixing, causing contamination, or undergoing chemical reactions. Fourth, anti-corrosion coating inside the pipeline. This internal coating technology for pipes is a new technique aimed at removing scale and sediment from within the pipes as well as providing corrosion protection for them; it has since evolved into an integrated technology that incorporates various fields such as transportation engineering, mechanics, electronics, and chemistry. Of course, these days pigging is also being used in lift oil production techniques; pigs are employed to prevent liquid from flowing back and to generate high-pressure gas, thereby increasing crude oil recovery rates. II. Types of pigging devices Pigging devices can be classified using different methods; for example, they can be divided into cleaning pigs used for descaling, and sealing pigs used for draining fluid and separation ； The aforementioned pigs with cleaning or separation functions can also be classified as practical pigs, while those with the capability to inspect pipelines can be classified as remotely controlled pigs. This article classifies them based on structure and function into conventional pigging devices and intelligent pigging devices. (1) Standard pigging pigs: Standard pigging pigs come in various structures and shapes, and can be divided into two main categories: spherical (i.e., pig balls) and cylindrical. Cylindrical pigging devices typically come in various forms, including straight-plate pigs, disc pigs, soft foam pigs, combined straight-disc pigs, straight-plate diameter-measuring pigs, disc diameter-measuring pigs, and straight-plate steel-brush pigs. The outer material of the pig is wear-resistant and oil-resistant neoprene or high-strength polyurethane. Spherical pigs with a nominal diameter of 100 mm or less are generally solid balls, while those with a diameter greater than 100 mm are hollow balls with water filled in their interior. Pigging devices are prone to getting stuck or damaged when there is insufficient water injection or a large amount of debris in the pipeline. The standard rubber cup pig has a three- or four-layer rubber cup structure. It consists of a guide rubber sleeve, a sealing rubber sleeve, and an isolation rubber sleeve, as shown in Figure 3. The material of the rubber bowl is oil-resistant and wear-resistant neoprene or polyurethane, offering good sealing properties and wear resistance. (II) Intelligent pigging devices: Intelligent pigging devices utilize high-resolution magnetic flux leakage technology to collect various data on the condition of the pipeline. This data is then processed by a computer, allowing for the acquisition of information such as pipeline corrosion, shape, deformation, wall thickness, cracks, and the location of pipe and valve fittings. The intelligent pig can also be located using a satellite positioning system during operation. Intelligent pigging devices vary in structure and principle. A supported wheel-type pig is one in which a certain number of rollers are added along the perimeter, on the inner side of the front and rear rubber cups of a regular pig. The roller supports the pig body along its circular path via a spring, resulting in rolling friction between the pig and the pipeline. This pig uses various sensors and detectors to detect information such as the pipeline’s profile, deformation, wall thickness, and cracks. The bidirectional electronic pig can operate in both directions; in cases of pipes prone to blockage, it can move backward to its original position. Polyurethane leather seals are commonly used, offering strong performance, wear resistance, and a long service life ； Its electronic positioning transmitter is a modified high-performance model that features a long operating time and high power; it is equipped with a dedicated high-performance battery that eliminates the need for charging, allowing it to operate for over 200 hours ； When a blockage occurs, a positioning receiver can be used to quickly locate the site of the blockage ； Conical rubber seals are chosen due to their strong performance and excellent sealing properties. This article is reprinted from Jilin Province Zhaoxi Petroleum Technology Co., Ltd. http://www.jilinzhao*.com/