Servo Level Measurement

Servo Level Measurement

Servo level measurement (servo tank gauging) is a high-precision method for liquid level, interface, and density measurement in tanks. It is strongly associated with tank inventory management and loss control, and is optimized for safe operation and total cost considerations in custody transfer and critical storage applications. This category is especially relevant where measurement accuracy and repeatability directly impact product accounting, reconciliation, or transfer documentation.

The measuring principle uses a small displacer suspended on a measuring wire wound onto a finely grooved drum. A servo motor positions the displacer accurately in the liquid. When the displacer contacts the liquid, buoyancy reduces its apparent weight, changing torque in a magnetic coupling; the instrument measures that change using multiple Hall sensors. This control loop enables precise detection of liquid surface, and supports interface and density-related measurements depending on configuration and application setup.

Key benefits include high precision and performance that is described as unaffected by medium properties such as conductivity or dielectric constant. Servo tank gauging instruments are used for custody transfer and inventory control, and are cited as meeting established requirements and approvals (including references to OIML R85 and API 3.1B, and related approvals). These characteristics align servo measurement with applications where traceability, standardization, and measurement confidence are essential.

Typical applications include high-accuracy custody transfer measurement in crude oil, gasoline, diesel, petrochemicals, and chemicals, as well as broader inventory management use in terminal and tank farm environments. Because servo systems can support level, interface, and density duties, they are often deployed where stratification, water bottoms, or product layering must be monitored and where reconciliation depends on precise measurement under varying operating conditions.

Implementation planning typically addresses mechanical installation, stilling well or guide arrangements where required, and the operational implications of displacer movement within the tank. Output integration should support both real-time control visibility and inventory accounting systems, with attention to alarm thresholds and proof-test strategy if used in protective functions. Configuration and maintenance practices are commonly aligned with metrology/custody transfer procedures to preserve long-term accuracy and defensibility of measurement results.

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