Dry Burning Failure Analysis of Pipeline Heaters and Flow Interception Prevention Technology
Pipeline electric heaters are widely used in fluid heating of industrial pipelines, and flow interruption and low flow are the core inducements of pipeline heater dry burning. Different from tank heating equipment, pipeline heaters rely on continuous flowing medium to take away heat. Once the medium flow is interrupted, blocked or lower than the safe flow rate, the heating tube will lose heat dissipation conditions and form rapid dry burning failure. Pipeline dry burning has the characteristics of fast failure speed and thorough damage, and most pipeline heaters are completely scrapped within tens of seconds after flow interruption. Thermocouple linkage flow detection system is the core technical means to prevent pipeline heater dry burning.
The working principle of pipeline heaters determines their extreme sensitivity to flow changes. Pipeline heating tubes are installed in closed pipeline cavities, with narrow internal space and no medium storage capacity. Under normal working conditions, the flowing fluid continuously takes away heat to maintain stable tube temperature. When the pipeline is blocked, the valve is closed abnormally or the pump stops conveying, the internal fluid is static instantly, and no new low-temperature medium is supplemented. The heat generated by the heating tube accumulates rapidly in the closed cavity, and the temperature rises sharply to form dry burning.
Low-flow hidden dry burning is the main hidden danger of pipeline heating systems. Many pipeline dry burning faults are not complete flow interruption, but long-term operation below the safe flow rate. When the medium flow is insufficient, the heat taken away per unit time is less than the heat generated by the heating tube, resulting in continuous heat accumulation and slow temperature rise. This low-flow dry burning develops slowly and has no obvious abnormal signs in the early stage, which will eventually lead to insulation carbonization and tube burnout after long-term cumulative operation.
Pipeline structure defects aggravate dry burning risks. Elbow dead zones, filter blockage and pipeline diameter mutation will form local low-flow areas. The heating tubes arranged in dead zones cannot obtain effective fluid scouring and heat dissipation, forming local dry burning overheating. Closed-loop pipeline static pressure retention also leads to intermittent low-flow dry burning during equipment interval operation.
Single temperature protection has obvious defects in pipeline heater protection. The closed pipeline has good thermal insulation performance, and the temperature rise has a certain delay. When the thermocouple detects over-temperature and cuts off power, the heating tube has already suffered serious dry burning damage. Temperature post-protection cannot avoid equipment loss, which can only reduce subsequent safety accidents.
Flow linkage pre-protection is the fundamental solution for pipeline heater dry burning. Install high-sensitivity flow switches at the pipeline inlet, set the minimum safe flow threshold, and realize interlock control between flow signal and heating power. When the flow is lower than the standard or interrupted, the system automatically locks the heating function and cuts off power in advance. Cooperated with thermocouple over-temperature backup protection, it forms dual safety guarantee, completely eliminating flow-induced dry burning faults of pipeline heating equipment.
