Today we will discuss the application of magnetostrictive displacement sensors in variable pitch axial flow fans. Before elaboration, it is necessary to gain a basic understanding of variable pitch axial flow fans.

Variable Pitch Axial Flow Fans

A variable pitch axial flow fan is an axial ventilation device that adjusts fan performance by changing blade angles. Featuring a wide high-efficiency operating range and high automation level, it can satisfy ventilation requirements under complex working conditions and is widely adopted in multiple key industrial sectors:

• Thermal power generation: Primary air fans, forced draft fans, induced draft fans, etc., for boiler combustion, ventilation and flue gas emission.

• Metallurgy industry: Blast furnace air supply, sintering machine exhaust, to guarantee ventilation and gas transportation during production.

• Tunnel ventilation: Ventilation and air exchange for subway tunnels and highway tunnels to improve air quality and discharge harmful gases.

• Industrial cooling: Air cooling island cooling fans, heat dissipation for large-scale equipment, enabling efficient air volume regulation to meet cooling demands.

The core performance of the fan lies in its blade pitch adjustment system. Driven by a hydraulic cylinder, the crank-link mechanism converts the linear motion of the piston rod into rotational motion of the blades, realizing continuous and precise adjustment of blade angles. Accordingly, real-time, accurate and reliable position monitoring of the hydraulic cylinder piston rod is an essential prerequisite for blade angle control and precise fan output. Conventional displacement measurement methods usually have limitations in accuracy, reliability or environmental adaptability. The TEC magnetostrictive displacement sensor delivers an optimal solution for this critical measurement task.

Application of TEC Sensors in Blade Pitch Adjustment Systems

Tailored to the characteristics and stringent requirements of variable pitch axial flow fan adjustment systems, the TEC-R series magnetostrictive displacement sensors exhibit outstanding applicability with straightforward and efficient installation. Generally, the sensor body containing the waveguide wire is mounted inside the hydraulic cylinder. The standard R-series displacement sensors support multiple installation configurations and can be easily integrated into existing hydraulic cylinder structures.

During measurement, the electronic housing of the sensor emits an interrogation current pulse. This pulse interacts with the permanent magnetic field of the magnetic ring and generates a transient torsional strain wave within the waveguide wire (the Wiedemann effect). By precisely calculating the time interval between the emission of the current pulse and the return of the torsional wave, the absolute position of the magnetic ring (i.e., the piston rod) can be directly converted, enabling non-contact measurement.

In practical applications, the R-series displacement sensors demonstrate prominent advantages:

• High Precision and Reliability: The sensor delivers micrometer-level measurement accuracy with long measuring stroke and long-distance signal transmission. The non-contact measurement mode eliminates mechanical wear, ensuring long service life and sustained high precision of the sensor.
• Resistance to Harsh Operating Conditions: The R-series sensors feature excellent anti-vibration and anti-shock performance, fully adapting to severe working environments of fans.
• Support for Intelligent Redundancy: Variable pitch axial flow fans are critical auxiliary equipment. A fault-induced shutdown may force the whole system to halt or operate under reduced load. Tailored to the structural characteristics of variable pitch axial flow fans, the R-series displacement sensor adopts a dedicated position magnetic ring with large inner diameter and uniformly distributed circumferential magnetic field. Multiple sensors can be easily installed to monitor the position of the same hydraulic cylinder simultaneously to build a redundant system. If one sensor fails, the system can still operate normally, drastically lowering the risk of unplanned shutdown and safeguarding continuous production.

Efficient and stable operation of variable pitch axial flow fans relies on precise control of blade angles. Featuring adaptive design, reliable measurement principle and redundant protection scheme, TEC magnetostrictive displacement sensors provide core support of precision, stability and durability for hydraulic cylinder position monitoring!