Reaction kettles operate under high temperature, pressure, agitation, and corrosive media, so position feedback must remain stable throughout each batch. A flange-mounted magnetostrictive displacement sensor meets this field requirement by mounting directly on the kettle cover through a sealed flange. Its stainless-steel pressure tube protects the magnetostrictive waveguide, while a movable permanent magnet follows the measured part without mechanical contact. In practical field applications, the sensor monitors agitator shaft axial displacement, mechanical seal compression, baffle position, and feed or discharge valve stroke. It outputs 4–20 mA, Modbus, or SSI signals for PLC and DCS systems, enabling real-time trend analysis and alarm logic. The flange design separates electronics from process vapors, making the sensor suitable for steam cleaning, vacuum cycles, and chemical production. Maintenance teams use the data to detect shaft runout, coupling wear, bearing clearance changes, and abnormal movement before seal leakage or batch contamination occurs. Correct installation requires a clean flange seal, exact magnet alignment, and stable 24 VDC power. During commissioning, zero and span are calibrated over the actual working stroke, and vibration filtering is adjusted to avoid false alarms. This field-proven solution improves batch reproducibility, reduces downtime, and increases safety in chemical, pharmaceutical, and food processing plants. Routine inspection of the flange gasket and cable gland further extends service life and keeps measurement accuracy stable. For harsh reaction kettles, the flange-mounted magnetostrictive displacement sensor provides accurate, rugged, and low-maintenance displacement monitoring.