Challenges at Freezing Points: The Impact of Sub-Zero Environments on Magnetic Level Gauges and Countermeasures

Magnetic level gauges are favored in petrochemical, liquefied natural gas (LNG), refrigeration industries, and storage and transportation systems in cold regions due to their intuitive indication and robust structure. However, when ambient temperatures drop below freezing, these reliable measuring instruments face severe challenges. The low-temperature environment is like a silent battle, posing a comprehensive challenge to the stable operation of magnetic level gauges, from the medium itself to the instrument's internal components.

The primary and most direct challenge comes from the freezing of the measured medium. When the medium is water or other high-freezing-point liquids, sub-zero temperatures will cause it to solidify inside the measuring cylinder. Ice not only completely blocks the level measurement channel, but the enormous pressure generated by the volume expansion during freezing is enough to cause permanent deformation or tearing of the measuring cylinder, flange, and even the float, resulting in irreversible damage.

Secondly, the performance of the instrument's core components will severely degrade. The "heart" of the magnetic level gauge is the internal magnetic float, whose magnetism weakens significantly in ultra-low temperature environments. If the float design or material selection is inappropriate, its magnetic force may be unable to effectively penetrate the measuring cylinder wall, which has widened due to cold contraction, to drive the external flapper to rotate, leading to malfunctioning indications, false level readings, or disordered flapper display. Simultaneously, the rubber or ordinary polymer gaskets used for sealing will harden, become brittle, and lose elasticity at low temperatures, ultimately causing seal failure and media leakage.

Furthermore, physical changes in the environment itself pose a threat. Moisture in the air will condense into frost on the instrument's gauge head, connecting flanges, and other parts, forming a thick layer of ice. This ice layer may freeze the flapper mechanism, preventing it from functioning properly. In extremely cold conditions, the toughness of the instrument's metal materials decreases, reducing their impact resistance and making them more susceptible to damage during pressure fluctuations or mechanical impacts.

To win this battle against freezing temperatures, a systematic approach is essential:

Insulation and heat tracing are the core methods. The most common and effective method is to equip the magnetic float level gauge with an insulation layer and a heat tracing system. Heat loss is reduced by applying external insulation cotton, and the measuring cylinder is continuously and evenly heated using steam or electric heating cables to ensure the medium remains in a flowing liquid state. Electric heating is usually paired with a temperature controller for precise temperature management, balancing energy saving and safety.

Optimize instrument selection and design. For low-temperature conditions, low-temperature magnetic float level gauges should be selected directly. These instruments typically use low-temperature magnetic materials (such as AlNiCo magnets) to ensure the float's magnetic stability at low temperatures; low-temperature resistant metal bellows sealing structures replace rubber gaskets; and stainless steel 316L or other metals better suited for low temperatures may be used to maintain toughness.

Implement preventative maintenance. Before the onset of severe cold season, a comprehensive inspection of the heating system and the insulation layer should be conducted to ensure proper functioning. Regular inspections and manual de-icing should be performed on areas prone to freezing. Where process permits, consider installing a drain valve to promptly drain the medium from the measuring cylinder during shutdown, fundamentally eliminating the risk of freezing.

In summary, sub-zero environments pose multiple threats to the measurement accuracy and structural safety of magnetic level gauges through media freezing, component performance degradation, and environmental icing. Only by scientifically combining insulation and heat tracing, proper selection, and meticulous maintenance can these risks be effectively mitigated, ensuring that magnetic level gauges can still clearly and accurately indicate liquid levels below freezing points, thus safeguarding industrial processes in cold environments.