Pipeline welding refers to the process of connecting two or more pipes together, and it is widely used in industries such as petroleum, chemical, natural gas, shipbuilding, and power. Pipeline welding not only requires the strength and sealing of the weld seam but also considers factors such as the material, specifications, shape, working pressure, temperature, and medium of the pipeline. Therefore, pipeline welding is a technically demanding and challenging task. This article will introduce professional knowledge of pipeline welding from the following aspects:
I. Pain points and difficulties of pipeline welding:
Due to the high quality requirements of pipeline welding, it inevitably encounters some pain points and difficulties, mainly manifested in the following aspects:
Low conversion capacity, slow market response: Due to the different requirements of customers for the material, specifications, and shape of the pipeline, the production line needs frequent adjustments and replacements, which reduces production efficiency and flexibility, affecting market competitiveness.
Difficulty in recruitment, high labor costs: Since pipeline welding is a high-demanding, harsh working environment, and high-risk job, it leads to a contradiction between the supply and demand of welders, making it difficult to recruit qualified welders. At the same time, it also requires high wages and insurance costs.
Difficulty in management, difficulty in decision-making and execution: Pipeline welding involves multiple departments and processes, such as design, procurement, production, inspection, and transportation, leading to multiple management levels, coordination difficulties, and information barriers, affecting the efficiency of decision-making and the quality of execution.
Low production efficiency, small profit margin: Pipeline welding requires a large amount of electricity, gas, welding wire, and other materials to be consumed, and also requires strict quality testing and maintenance, leading to high production costs and small profit margins.
II. What are the common methods of pipeline welding?
According to the different materials, specifications, and shapes of pipelines, the common methods of pipeline welding are as follows:
Manual arc welding: Manual arc welding is a method of melting the welding rod with the heat generated by the arc and bonding it with the welded workpiece. Manual arc welding has the advantages of simple equipment, flexible operation, and strong adaptability, but it also has disadvantages such as unstable quality, low efficiency, and large pollution. Manual arc welding is suitable for welding pipelines made of materials such as carbon steel and low-alloy steel.
Gas shielded welding: Gas shielded welding is a method of using inert gas or active gas to protect the arc and molten pool, preventing chemical reactions between oxygen, nitrogen, and other elements in the air and the molten metal. Gas shielded welding has the advantages of high quality, high efficiency, and small deformation, but it also has disadvantages such as complex equipment, high cost, and high environmental requirements. Gas shielded welding includes types such as carbon dioxide gas shielded welding (CO2 welding), inert gas shielded welding (TIG welding and MIG/MAG welding). Gas shielded welding is suitable for welding pipelines made of materials such as stainless steel and aluminum alloy.
Gas welding: Gas welding is a welding method that uses the high-temperature flame generated by the combustion of gas and air or oxygen to melt the filler metal and the welded workpiece. It is suitable for welding pipelines made of low melting point metals such as copper and aluminum. It has the advantages of flexible operation, simple equipment, and low cost. Gas welding is divided into acetylene-oxygen welding and propane-air welding according to the type of gas. Acetylene-oxygen flame is a flame generated by the combustion of acetylene and oxygen. It has characteristics such as high temperature, concentrated flame core, and fast heat transfer. Propane-air flame is a flame generated by the combustion of propane and air. It has characteristics such as low temperature, dispersed flame core, and slow heat transfer.
Laser welding: Laser welding is a welding method that uses the high-energy density generated by the laser beam to concentrate on the surface or inside of the welded workpiece, causing local melting or vaporization. It is suitable for high-strength, high-precision, and high-speed welding of pipelines. It has the advantages of automatic operation, advanced equipment, and cost savings. Laser welding is divided into transmission laser welding and reflection laser welding according to the transmission mode of the laser beam. Transmission laser welding uses transparent or translucent materials as the upper layer of the pipeline to penetrate the laser beam from the upper layer of the pipeline to the lower layer of the pipeline, melting and connecting the two layers of the pipeline at the contact surface. It is suitable for welding materials such as glass and plastics. Reflection laser welding uses opaque materials as the upper layer of the pipeline to reflect the laser beam from the upper layer of the pipeline to the lower layer of the pipeline, melting and connecting the two layers of the pipeline at the contact surface. It is suitable for welding materials such as metals and ceramics.
Ultrasonic welding: Ultrasonic welding is a welding method that uses the mechanical vibration and frictional heat generated by ultrasonic waves to soften or melt the surface or interface of the welded workpiece. It is suitable for welding pipelines made of low melting point, high conductivity, and high thermal conductivity metals and non-metallic materials. It has the advantages of simple operation, compact equipment, and low cost. Ultrasonic welding is divided into surface ultrasonic welding and interface ultrasonic welding according to the mode of action of ultrasonic waves. Surface ultrasonic welding applies ultrasonic waves to the surface of the welded workpiece, causing relative sliding and frictional heat under pressure, forming a uniform metal connection. It is suitable for welding materials such as copper and aluminum. Interface ultrasonic welding applies ultrasonic waves to the interface of the welded workpiece, causing relative vibration and frictional heat under pressure, forming a uniform non-metallic connection. It is suitable for welding materials such as plastics and fibers.
The pipeline rack platform is a fixed offshore platform supported by the pipeline rack driven into the seabed, mainly used for offshore drilling, oil production, and transportation activities. In the manufacturing of pipeline racks, the weld seam at the truss saddle is one of the most difficult welding nodes, requiring high-altitude operations, low accuracy, poor alignment, and limited positioning. It requires the use of welding rods for the root, gas-shielded flux-cored welding wire for filling, multi-layer multi-pass welding, and large filling volume.
Shenzhen Chiwan Shengbaowang Engineering Co., Ltd. (CSE) used the Megmeet Artsen CM500C fully digital industrial heavy-duty CO2/MAG/MMA intelligent inverter welding machine in the offshore pipeline rack manufacturing project. The series of welding machines have the following characteristics:
Adopting carrier technology eliminates control lines, greatly improving overall reliability and ensuring efficient production. It can achieve remote welding of 100 meters with stable and reliable parameters.
Supports special flux-cored welding wire (E71T-1C) vertical upward straight pulling welding function, relative oscillation welding, greatly reducing the heat input to the weld seam. Suitable for vertical upward welding of ultra-large container ships and other thick plates.
It has a 100% load continuous rate at 500A, with a high wire feeding speed and high deposition rate of 24 meters per minute. It can adapt to long-term stable welding with large currents.
The wire feeder and PCBA have excellent protection design, making them more suitable for working in environments such as vibration, collision, humidity, and salt spray.
It has short-circuit overcurrent and open-circuit protection functions of electromagnetic valves, realizing automatic protection.
Through comparison, the Megmeet Artsen CM500C series welding machine has better welding effects for pipeline welding, mainly manifested in:
Stable and reliable welding with high current over long distances, the welding parameters displayed by the wire feeder greatly improve welding quality, reducing rework rates by 15%.
One welding machine meets the requirements of on-site manual operation and gas shielded welding process switching, increasing equipment utilization by 30%.
The failure rate of the welding machine has dropped significantly, and the number of welding machine repairs has decreased by 50%.
Deep welding penetration, multi-layer and multi-groove welding can reduce the risk of non-fusion and ensure the welding quality.
IV. What are the precautions for pipeline welding?
Before welding pipelines, clean the oil, rust, oxide scale, and other debris near the groove, inner and outer walls, and weld seams of the pipeline to avoid affecting the welding quality.
During pipeline welding, select appropriate welding rods, welding wires, welding machines, welding nozzles, and other equipment and materials. Determine reasonable welding process parameters and methods according to factors such as the material, specifications, shape, and working pressure of the pipeline.
During pipeline welding, ensure the quality of the pipe joint, control the dimensions such as the gap, misalignment, and overlap length of the pipe joint, and fix the pipeline with spot welding or fixtures to prevent deformation or displacement.
During pipeline welding, pay attention to uniformly heating the pipeline and fittings to the appropriate welding temperature, avoid overheating or overcooling, which may cause burn-through or lack of fusion.
During pipeline welding, control the dimensions such as the number of layers, width, and height of the weld seam to ensure the strength and sealing of the weld seam. Remove the slag and spatter from each layer and stagger the arc starting and ending points of each layer.
During pipeline welding, follow safety operating procedures to prevent accidents such as electric shock, fire, and poisoning. Use protective equipment and ventilation facilities to protect the safety of yourself and surrounding personnel.
After pipeline welding, carry out necessary inspections and tests such as visual inspection, flaw detection, pressure test, and air tightness test to ensure that the pipeline meets design requirements and construction specifications.
Pipeline welding is a technical method of connecting pipes or fittings into a whole, which has a wide range of applications in fields such as petroleum, chemical, power, shipbuilding, and construction. Common methods of pipeline welding include manual arc welding, gas shielded welding, gas welding, laser welding, and ultrasonic welding, each with its advantages, disadvantages, and applicable scope. The appropriate welding method should be selected based on factors such as the material, thickness, position, and environment of the pipeline. Pipeline welding also requires attention to groove processing, joint quality, welding parameters, heating methods, and cooling methods to ensure the quality and performance of the weld seam. Pipeline welding is a highly comprehensive technology that requires continuous learning and practice to master its essence and skills. For more welding knowledge and skills improvement, you can visit the Megmeet Welding News Center.
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