Test & measurement


thermal stress and resisting brittleness in cryogenic conditions. LPG presents different but equally complex challenges. Stored either pressurised or semi- refrigerated, it can rapidly vaporise with temperature or pressure changes, generating turbulence and a vapour layer that can impact measurements. Density variations can further affect any technology dependent on buoyancy or hydrostatic principles. Also, because liquefied gas tanks are typically sealed throughout operation, instruments must have minimal maintenance requirements.


Q. WHICH TECHNOLOGY HAS TRADITIONALLY BEEN USED? Servo gauges were long regarded as the industry standard for liquefied gas tanks. Using a wire- suspended displacer adjusted by an electric motor, they infer level from changes in wire tension. Although widely used for decades, servos have inherent limitations stemming from their mechanical complexity. Their numerous moving parts are prone to wear, leading to a mean time between failures (MTBF) that can be as short as five years, while direct contact with the product can cause contamination. Wire breakage is a regular maintenance concern, and if a displacer falls into the tank, it may pose a risk to rotating equipment. Even isolating the gauge for service carries the possibility of mechanical damage. Furthermore,


Continued on page 50... Instrumentation Monthly February 2026 49


Non-contacting radar gauges have become the preferred level measurement technology in liquefied gas applications.


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