As a device for conveying liquid or gas medium between equipment, pipeline occupies a very important position in the construction of petrochemical production units. In particular, the quality of pressure pipeline design directly affects the safety and economy of pipeline design. Pressure pipeline combined pipe fittings refer to two or more adjacent pipe fittings (pipes) commonly used in engineering that need to be connected by field welding As an assembly designed and processed as a whole, pipe fittings are an important accessory for connecting the penstock system, and most of them are connected by on-site welding. However, due to the complex on-site situation, poor welding environment and difficult to ensure the welding quality, many hidden dangers are caused to the safety. The use of penstock assembly pipe fittings can not only reduce the workload of on-site welding, Improving the integrity, continuity and consistency of pipeline system, reducing potential safety hazards caused by welding defects and reducing safety accidents of pressure pipeline will bring great social and economic benefits to improve the utilization rate of steel, save resources and product costs, and speed up the project progress.