Pressure block welding technology is a core process that balances the installation firmness and later maintenance convenience of sheathed thermocouples. Irregular welding operations such as full-circle welding, plug welding and random fixed-point welding are common causes of sensor jamming, dead locking of stop screws and difficult disassembly and replacement in later use. The industry-specified three-sided spot welding process is the only standardized construction method for pressure block fixation, which can ensure structural firmness while completely reserving operation space for equipment maintenance.
The standard three-sided spot welding process adopts uniform stress symmetric welding, which fixes the pressure block from three different side directions. This welding method can form stable and balanced fixing stress on the pressure block body, effectively avoiding equipment displacement and loosening caused by single-sided welding stress concentration. In long-term high-temperature and high-vibration industrial environments, the three-sided spot welding structure can resist thermal deformation stress, fluid impact force and mechanical vibration, ensuring that the pressure block does not shift, deform or fall off, and maintaining long-term fixing stability of the thermocouple.
The most critical forbidden operation in welding construction is spot welding at the thermocouple insertion port. The insertion port is the core channel for sensor assembly, disassembly, debugging and replacement. Welding at this position will cause local high-temperature thermal deformation of the port aperture, resulting in aperture shrinkage, structural distortion and welding residue blockage. Once deformed and blocked, the thermocouple cannot be inserted and extracted smoothly, and even permanent jamming failure will occur, making later equipment maintenance and replacement impossible and causing long-term production shutdown losses for enterprises.
Side spot welding construction needs to strictly avoid welding the stop screw dead. The stop screw is a key limiting component to control the insertion depth and fixed position of the sheathed thermocouple, which undertakes the core functions of positioning, locking and anti-displacement. If the stop screw is welded and fixed during side welding, the screw will completely lose its adjusting and disassembling function. The thermocouple cannot adjust the insertion depth according to working condition changes, nor can it be disassembled for maintenance and calibration, greatly improving the later equipment operation and maintenance cost.
Professional low-current and short-time spot welding technology must be adopted in actual construction to reduce welding heat input and avoid overall thermal deformation of the pressure block. After welding, all welding scars and burrs need to be polished smoothly to prevent scratching the thermocouple sheath during insertion and extraction. Repeated inspection of screw flexibility and port smoothness after welding ensures unobstructed equipment disassembly and assembly. Standard three-sided spot welding specifications perfectly balance installation firmness and maintenance convenience, which is an essential professional process for high-quality installation of sheathed thermocouples.
