Clamp-type flexible pipe fittings have been widely used in more and more pipeline construction projects in China in recent years. This product has gained popularity due to its unique sealing principle and the characteristics of integrating multiple properties. Widely recognized by designers and users! With the continuous improvement of engineering technology requirements, clamp-type flexible pipe fittings are widely used in coal, thermal power generation, hydropower generation, petroleum, chemical industry, food processing, natural gas transportation, sewage treatment, cement pump trucks, construction fire protection, shipbuilding, papermaking and other industries.
Clamp-type flexible pipe fittings first originated during World War I. At that time, a large amount of materials were consumed on the frontline battlefield every day. As the frontline continued to advance, logistical supplies, especially the supply of oil products, gradually became a major problem that plagued the war process. There were also oil pipelines at that time, but the pipeline connection system generally used old-fashioned flange connection or welding, which caused great difficulties in the speed of laying pipelines-the use of flange connection and welding to connect pipelines was time-consuming and laborious, because war sites It changes at any time. Oil pipelines need to be installed and laid frequently and quickly. They also have to deal with uneven ground, damaged pipelines that require local repairs, and vibrations caused by external forces (such as nearby explosions). Clamp-type pipe joints came into being under this situation (in the United States) and were quickly used in pipeline installation during the war.
With the end of the war, clamp-type pipe joints were quickly widely used in civil and industrial construction in the United States due to their various advantages. One of the more famous companies is the American Vactaulic Company. . This product was first introduced to Japan from the United States and developed to a certain extent in Japan. Later, in the late 1970s, traces of this product gradually appeared on some imported equipment in my country. At that time, the Xi'an Coal Design and Research Institute, a subordinate unit of the Ministry of Coal, conducted research on this product as a scientific research project. Shi Xiaoxuan and An Zichou were responsible for the research. At that time, there was insufficient information, very little foreign technical information, and a blank domestic market. After repeated research, demonstration, trial production, and testing, it was finally successfully developed in 1983 and passed the discussion and approval of the expert group. At the same time, we applied for the "Oval Inner Cavity" "Section clamp type flexible pipe joint" patent. Then in 1986, the national standard "Clamp-type Flexible Pipe Joints" drafted and formulated by Shi Xiaoxuan and An Zichou was officially released and implemented. At the same time, in order to transform the technology into products as soon as possible, the Ministry of Coal took the lead, with Shi Xiaoxuan and An Zichou responsible for technical guidance. Several companies with production conditions were selected in the coal industry to guide and support production, and took the lead in promoting and applying it in the coal system, and achieved It achieved good results; subsequently, with the increase in domestic thermal power projects, this product gradually gained recognition from designers and users in the water conservancy ash removal pipelines in thermal power projects.
1. Classification of the main connection methods of pipelines in current projects:
Currently, the following connection methods are commonly used for pipe connections of metal materials:
1. Socket connection or card sleeve connection: mainly used for the connection of cast iron drainage pipes. The advantage is that the connection is simple and fast, and no special equipment is required. The disadvantages are that it cannot bear pressure, is prone to leakage, cannot absorb the deformation of the pipe base (displacement, corner, etc.), and cannot absorb the thermal expansion and contraction changes caused by temperature changes to the pipe.
2. Welding: applicable to the connection of various steel pipes. Rigid connection. The advantages are simple operation, simple equipment and low cost. The disadvantages are that it cannot be disassembled, which requires higher requirements for operators. It cannot absorb the deformation of the pipe base (displacement, corner, etc.), and cannot absorb the thermal expansion and contraction changes caused by temperature changes. It is required for later maintenance in some special places (such as refineries, etc.) Difficulty (cannot weld), difficulty in operation due to space constraints, etc.
3. Flange connection: suitable for the connection of various steel pipes. Rigid connection. The advantage is that the flange does not need to be welded on site and is removable. The disadvantage is that it cannot absorb the deformation of the pipe base (displacement, corner, etc.), and cannot absorb the thermal expansion and contraction changes caused by temperature changes to the pipe. The cost of flanges (especially medium and high pressure flanges) is relatively high, and the installation requirements for the pipe base are high. Higher, the sealing performance is average, and disassembly is difficult.
4. Threaded connection (wire connection): suitable for small diameter steel pipe connection. Rigid connection. The advantages are low cost and quick installation. The disadvantage is that it cannot absorb the deformation of the pipe base (displacement, corner, etc.), and cannot absorb the thermal expansion and contraction changes caused by temperature changes to the pipe. It has higher installation requirements for the pipe base, has average sealing performance, and is difficult to disassemble.
Affected by conditions such as processing equipment and installation equipment, it is difficult to operate large-diameter (DN ≥ 150) pipelines.
5. Clamp type pipe joint connection: suitable for various steel pipe connections. Flexible connection. The advantage is that it has good sealing performance and is flexible in connecting pipes. Each pipe joint allows a certain amount of expansion and contraction, and can absorb the deformation of the pipe base (displacement, rotation, etc.), and can absorb the thermal expansion and contraction of the pipe caused by temperature changes. Changes will not cause stress in the pipeline, eliminate pipeline vibration, reduce noise, etc.
6. There are other connection methods, but since they are rarely used, they will not be described here.