When connecting an overflow short pipe flange to a pipeline, coaxiality accuracy is the core indicator determining the connection quality. Excessive coaxiality deviation can lead to uneven stress on the flange mating surface, causing problems such as seal failure, media leakage, and even equipment vibration. To ensure coaxiality accuracy, comprehensive control is needed across design, manufacturing, installation, and testing, forming a complete quality assurance system.
The design phase is fundamental to coaxiality control. The connection design between the overflow short pipe flange and the pipeline must clearly define the coaxiality tolerance range. Typically, the deviation between the flange axis and the pipeline axis should not exceed a specific proportion of the flange's outer diameter. Standardized flange structures should be prioritized in the design to avoid the accumulation of manufacturing errors caused by non-standard designs. Simultaneously, the connection method between the flange and the pipeline must match the operating conditions. For example, butt-welded flanges are suitable for high-pressure and high-temperature scenarios, while socket-welded flanges are suitable for small-diameter pipelines. Different connection methods have different coaxiality control requirements and must be selected based on actual operating conditions.
Manufacturing accuracy directly affects coaxiality achievement. Flange machining must be completed using high-precision CNC machine tools to ensure that key parameters such as the perpendicularity of the flange sealing surface to the axis and the coaxiality of the bolt hole distribution circle to the axis meet the standards. The machining of the pipe ends is equally important; specialized cutting equipment must be used to ensure the perpendicularity of the end plane to the axis, avoiding coaxiality deviations after connection due to end tilting. Furthermore, the welding process between the flange and the pipe must be strictly controlled, as welding deformation is a common cause of coaxiality deviations. Deformation must be reduced by optimizing the welding sequence and controlling welding heat input.
The installation process is crucial for coaxiality control. Before connecting the flange and the pipe, a pre-assembly inspection is necessary, using visual inspection or specialized tools to initially determine if the coaxiality meets the requirements. During formal installation, tools such as levels and laser alignment instruments are used to assist in positioning, ensuring that the flange and pipe axes coincide. For large-diameter or heavy pipes, specialized lifting tools are used to adjust the pipe position to prevent sagging or displacement due to its own weight. When tightening bolts, a symmetrical and uniform principle must be followed, tightening gradually in multiple stages to prevent flange tilting due to localized stress concentration, which would compromise coaxiality.
Inspection and calibration are the final guarantee for coaxiality control. After connection, feeler gauges, dial indicators, and other tools must be used to check the uniformity of the gap at the flange mating surfaces. If the gap difference exceeds the allowable value, the coaxiality must be readjusted. For overflow short pipe flange connections in critical operating conditions, non-destructive testing techniques can also be used to verify welding quality and eliminate coaxiality deviations caused by welding defects. Furthermore, during system pressure testing or operation, leakage at the flange connection must be continuously monitored. If leakage is detected, the system must be stopped immediately for inspection to confirm whether the seal failure is due to excessive coaxiality tolerance.
Material selection and heat treatment processes have an indirect impact on coaxiality control. The flange and pipe materials must be matched to avoid coaxiality changes during operation due to differences in thermal expansion coefficients. For high-temperature conditions, the creep characteristics of the material must be considered, and materials with excellent creep resistance should be selected. In addition, the heat treatment process after flange processing must be reasonable; eliminating residual stress can reduce the risk of deformation during subsequent use, thereby maintaining stable coaxiality.
Environmental factors have a significant impact on coaxiality control. Temperature, humidity, and vibration conditions at the construction site can interfere with installation accuracy. For example, high temperatures may cause uneven thermal expansion between the flange and the pipe, while low temperatures may lead to coaxiality deviations due to material shrinkage. Therefore, installation work must be carried out under suitable environmental conditions. For harsh environments, protective measures must be taken, such as erecting temporary sunshades and using heating equipment.
Maintenance and upkeep are essential for long-term coaxiality stability. During system operation, the flange connection status must be checked regularly, loose bolts tightened, and dirt cleaned from the mating surfaces to prevent coaxiality deterioration due to long-term vibration or corrosion. For easily worn parts, a replacement plan should be developed to avoid coaxiality loss due to component damage. Through full lifecycle management, the connection between the overflow short pipe flange and the pipe can be ensured to always meet coaxiality requirements, providing reliable support for the safe and stable operation of the system.
