Bourdon Tube/Sensor

The Bourdon tube is the primary sensing element in many pressure gauges and relief valve monitoring systems. It is a C-shaped or helical tube that straightens under internal pressure, with this mechanical displacement transmitted through linkages to indicate pressure on a dial or trigger relief valve activation. This component is widely used in industrial machinery and equipment manufacturing, where accurate pressure measurement is critical for process control and safety. The Bourdon tube operates on the principle that a curved tube tends to straighten when subjected to internal pressure, producing a mechanical displacement at the free end. This displacement is then amplified through a linkage mechanism to move a pointer on a gauge scale or to activate a relief valve mechanism. The tube is available in various materials, including phosphor bronze, beryllium copper, stainless steel, and Inconel, each offering different corrosion resistance and temperature capabilities. Key parameters for selection include pressure range (0.1–100 MPa per EN 837-1), accuracy class (1.0–2.5% FS), operating temperature (-40 to 150°C, with high-temperature alloys required above 150°C), burst pressure (1.5–3 times full scale), process connection (G1/4 to G1/2), response time (≤10 ms), hysteresis (≤0.5% FS), repeatability (≤0.1% FS), and weight (0.3–1.5 kg). These values are reference ranges and must be verified for the specific model and application. The Bourdon tube is a passive mechanical component, requiring no external power, and is suitable for measuring gauge pressure of gases and liquids that are compatible with the wetted materials. It is not suitable for absolute pressure measurement without a reference vacuum. For dynamic pressure changes, response time is a critical factor. Maintenance signals include pointer drift, sluggish response, or leakage at connections. Failure boundaries include overpressure beyond burst pressure, corrosion of the tube material, and fatigue due to cyclic loading. Always consult the manufacturer or supplier to confirm model-specific specifications and compliance with applicable standards.

When pressure is applied inside the curved Bourdon tube, the tube tends to straighten due to the pressure differential between the inside and outside. This elastic deformation creates mechanical displacement at the tube's free end, which is amplified through a linkage mechanism to move a pointer on a gauge scale or activate a relief valve mechanism. The amount of displacement is proportional to the applied pressure, allowing for accurate measurement. The tube's material and geometry determine its pressure range and sensitivity.