| Pipe Expander: A Key Equipment for Modern Industrial Pipe Forming Under the powerful hydraulic thrust and precise temperature control, sections of metal pipes are expanded to the required dimensions and shapes, meeting the demanding requirements of various fields from petrochemicals to aerospace. In the industrial manufacturing sector, the demand for pipe systems is increasing, especially for large-diameter, thin-walled, and high-strength steel pipes. However, traditional pipe rolling techniques face issues such as large equipment, high investment, and technical difficulties when producing large-diameter thin-walled pipes. To address this challenge, pipe expanders emerged and have gradually become an indispensable key equipment in modern pipe processing. This article will comprehensively introduce the working principle, classification, application, and development prospects of pipe expanders, providing systematic introductory knowledge for beginners. 01 Basic Concepts and Development History of Pipe Expanders As the name suggests, a pipe expander is a specialized equipment used to expand the diameter of pipes. It is a finishing rolling process for large-diameter thin-walled pipes using the cross-rolling or drawing method to expand the pipe diameter. With the development of industrial technology, especially in the oil and chemical industries, the demand for large-diameter seamless steel pipes for oil and gas transportation, pressure vessels, structural, and mechanical components has been increasing year by year. The development of pipe expansion technology began in the early 20th century. In the late 1920s and early 1930s, the United States and Germany respectively developed roller cross-rolling hot pipe expanders and drawing hot pipe expanders, which were put into industrial production. These early devices laid a solid foundation for the development of modern pipe expanders. The maximum diameter of seamless steel pipes that can be produced on automatic pipe rolling machines is 426-529 mm, and large periodic pipe rolling units can only produce seamless steel pipes with a diameter of less than Φ660 mm. Therefore, to obtain seamless steel pipes with larger diameters, the expansion method must be used. 02 Working Principles and Classification of Pipe Expanders According to their working methods and application fields, pipe expanders can mainly be classified into several different types, each with its unique working principle and characteristics. Cross-rolling Pipe Expander The cross-rolling pipe expander has two cantilevered conical rolls installed in a box-shaped frame. The centerlines of the rolls intersect at an angle of 60-80 degrees in the horizontal plane. The two rolls are driven by DC motors and rotate in the same direction. The conical rolls have an entrance cone before the working cone to reduce the diameter of the pipe to a certain extent after it is bitten in, improving the biting conditions, and then the pipe wall is expanded by spreading. The characteristics of cross-rolling pipe expansion are large deformation, fast deformation speed, and high output, suitable for the production of large-diameter and medium-thin-walled seamless steel pipes with high dimensional accuracy of various steel grades; however, the equipment is large, the investment is high, and it cannot produce irregular and variable cross-section pipes. Drawing Hot Pipe Expander Drawing hot pipe expansion is carried out on a hot drawing pipe expander. First, a bell mouth is expanded at the end of the pipe, with the expanded diameter being about 100 mm larger than the diameter after hot expansion, to facilitate the clamping of the pipe end by the inner and outer rings during hot expansion and water cooling. Then, the pipe is expanded and thinned, and its length is shortened through the deformation process by the chain pulling the draw bar and driving the top head to pass through the rough pipe from the inside. Hot drawing pipe expansion is generally heated three times, with each heating followed by 1-4 passes of expansion, and the total relative expansion amount is ≤ 45%. The characteristics of drawing expansion are that the pipe expander can both hot expand and hot draw, and can hot expand round pipes as well as hot draw irregular and variable cross-section pipes; the drawing pipe expander has a light weight, low investment, and easy tool replacement. Hydraulic Pipe Expander Modern pipe expanders mostly adopt hydraulic technology, featuring stable pressure output and precise control. The equipment is usually equipped with a PLC control system, supporting preset expansion parameters, and is suitable for batch production of different specifications of pipe fittings. The two-step pipe expanding machine is a typical representative of hydraulic pipe expanding machines. It integrates cone die expanding technology, medium-frequency induction heating technology, and hydraulic technology into one machine. It is renowned for its reasonable process technology, simple equipment structure, low energy consumption, extremely low construction investment, excellent product quality, and wide applicability of raw materials and product specifications. 03 Structure and Key Technical Parameters of the Pipe Expanding Machine A complete pipe expanding machine consists of multiple systems, mainly including the base, the main oil cylinder support plate (including the main oil cylinder), the movable push plate, the front support plate, the automatic feeding mechanism, the discharge roller track, the mold support, the medium-frequency coil adjustment frame (including the medium-frequency heating coil), the medium-frequency power supply, and the electrical control system, etc. These systems work together to ensure the stability and accuracy of the pipe expanding process. Key Technical Parameters of the Pipe Expanding Machine Different models of pipe expanding machines have their specific technical parameters to meet different production needs. The following is a comparison of the main technical parameters of several common pipe expanding machines: Parameter Item 3"-12" Model 8"-24" Model 16"-30" Model 20"-36" Model 30"-48" Model Maximum Pressure 31.5MPa 31.5MPa 31.5MPa 31.5MPa 31.5MPa Working Pressure 25MPa 25MPa 25MPa 25MPa 25MPa Working Speed 0-1000mm/min 0-1000mm/min 0-1000mm/min 0-1000mm/min 0-1000mm/min Hydraulic Cylinder Thrust 60T×2 120T×2 250T×2 200T×2 250T×4 Motor Power 22.5kw 46kw 48.5kw 75kw 100kw Medium-Frequency Power Supply 250kwa 400kwa 600kwa 800kwa 1000kwa From the table, it can be seen that as the equipment specifications increase, the requirements for hydraulic cylinder thrust, motor power, and medium-frequency power supply also increase accordingly. This is to meet the energy and power demands for processing larger-diameter pipes. 04 Application Fields and Practical Value of the Pipe Expanding Machine As an indispensable processing equipment in modern industry, the pipe expanding machine has been widely applied in various fields: Energy Industry: With the utilization and development of energy from solid (coal), liquid (oil) to gas (natural gas), the demand for energy transmission pipeline steel pipes has increased. The pipe expanding machine has become an indispensable important production capacity to solve the shortage of large-diameter seamless steel pipes and the difficulty in perfecting the specifications of medium and large-diameter welded pipes at home and abroad. Military Industry and Aerospace: There is a large demand for high-standard, high-strength, and special specification steel pipes. The pipe expanding machine can meet the special requirements for pipes in these fields. Chemical Equipment and Machinery Manufacturing: The expansion processing of various steel pipes made of carbon steel, alloy steel, stainless steel, etc., cannot be done without the pipe expanding machine. Automobile and Refrigeration Industry: In the automotive manufacturing field, the pipe expanding machine is used to process oil pipes, air pipes, water pipes, etc.; in the refrigeration industry, it is used for the flaring operation of air conditioning pipes, including the processing of cup-shaped and bell-shaped flares. The practical value of the pipe expanding machine lies in its ability to expand small-diameter pipes to the required size, greatly expanding the application range of raw materials. For example, the two-step pipe expanding machine can handle a wide range of steel pipe specifications, with diameters ranging from φ60 to φ1420mm, wall thicknesses from 3 to 120mm, and the longest length up to 24m. This flexibility greatly improves production efficiency and reduces production costs. 05 Operation Safety and Maintenance of the Pipe Expanding Machine Operating the pipe expanding machine must strictly follow safety regulations to ensure personal safety and the stable operation of the equipment. Safety Operating Procedures Pre-startup inspection: Before starting the machine, the operator should check if there is any damage to the power line surface, whether the hydraulic oil level is below the red line, if the oil pipes are cracked, if the screws are loose, and if the sliding parts of each mold are smooth. Precautions during operation: During operation, hands must not be placed in the opening and closing area. Stay away from the dangerous area of the push shaft to prevent pinching accidents. If there is any abnormality in the equipment or circuit system, immediately press the emergency stop switch and turn off the main power supply, and find a professional for maintenance. Post-operation maintenance: Before leaving work, turn off the hydraulic pump switch first, then the main power supply of the control cabinet, and clean the machine and the surrounding environment. Do a good job in daily maintenance. Common faults and maintenance strategies As a high-precision forming equipment, the stable operation of the pipe expanding machine depends on scientific maintenance and care. In actual production, problems such as mold wear, hydraulic system leakage, and electrical faults often lead to a decrease in processing accuracy and even equipment shutdown. Mold failure is a frequent type of fault, mainly manifested as scratches on the surface of the pipe and dimensional deviations. The causes include insufficient mold hardness (not reaching the HRC58-62 standard), clogging of the cooling system leading to excessive temperature rise, and poor lubrication causing metal adhesion. Solutions include regularly using a hardness tester to check the mold hardness, and conducting ultrasonic testing every 5,000 pieces processed; cleaning the scale in the cooling water channel to ensure a flow rate of ≥15L/min; using extreme pressure emulsions for lubrication, with a concentration controlled at 8%-10%. Hydraulic system faults are often characterized by unstable pressure and slow action. Common causes include hydraulic oil contamination (cleanliness below NAS 8 grade), stuck relief valves, and aging seals. Maintenance points include changing the hydraulic oil every three months, cleaning the oil tank and filter at the same time; calibrating the relief valve pressure monthly to ensure the deviation of the set value is ≤±0.5MPa; regularly checking the wear of the seal lip, and replacing it immediately if cracks are found. 06 Future development trends of pipe expanding machine technology With the continuous progress of industrial technology, pipe expanding machine technology is rapidly developing towards intelligence, efficiency, and precision. Intelligent control system: Modern pipe expanding machines have adopted intelligent constant temperature systems, which can intelligently control the medium frequency power supply to heat the steel pipe to the required temperature and maintain it constant during the pipe expanding process. Especially when expanding high-alloy steel pipes, it can effectively avoid the decline in pipe quality and mold scrapping caused by overheating (high temperature) due to human factors. Fully automatic production line: The fully automatic pipe expanding production line consists of a feeding robot, an expanding machine, an online detection device, and a sorting mechanism, achieving unmanned production. By connecting with the MES system and ERP, the equipment utilization rate and product qualification rate can be monitored in real time. After a certain automotive exhaust pipe manufacturer introduced this production line, it achieved integrated processing of expanding, punching, and cutting of φ89mm stainless steel pipes, with a cycle time of 45 seconds per piece, an annual production capacity of 1.2 million pieces, and a 60% reduction in labor costs. Widespread application of numerical control technology: Numerical control pipe expanding machines, through computer numerical control technology, have achieved the automation and precision of the pipe forming process, indicating the development direction of pipe expanding equipment. Its system consists of a numerical control unit, a servo drive, and an actuator, supporting G-code programming and CAD model import, and can directly convert design drawings into processing instructions. Environmental protection and energy-saving technology: Traditional mechanical pipe expanding and rinsing use a large amount of water-based emulsions and lubricating oils. Modern pipe expanding machines have established a recycling system for expanding water, collecting the rinsing emulsions and reusing them in the collection pool. When changing the emulsion, the waste emulsion is sent to the wastewater treatment system, and treated through processes such as adding chemicals, demulsification, flocculation, air flotation, activated carbon adsorption, and sand filtration. The treated and recovered clear water can be reused as cleaning water. With the advent of the Industrial 4.0 era, the technology of tube expanding machines is developing rapidly towards intelligence and automation. The fully automatic tube expanding production line integrates feeding robots, online detection devices and sorting mechanisms, and connects with the MES system and ERP to achieve unmanned production and real-time monitoring. As an important part of modern industrial equipment manufacturing, the advancement of tube expanding machine technology will directly promote the upgrading and development of the entire manufacturing industry. |
