Precise Monitoring of Thermal Housing Expansion

With the HEP-100 from Swiss vibration specialist MC-Monitoring, Avibia GmbH is setting new standards for the protection of rotating machinery. The new inductive displacement sensor enables reliable and highly precise measurements on gas and steam turbines as well as other industrial systems.

Reliable monitoring of thermal housing expansion is a critical factor for the safe and economical operation of gas and steam turbines, as well as other rotating machinery. With the HEP-100 from MC-Monitoring (distributed by Avibia GmbH), operators and plant manufacturers now have access to an inductive displacement sensor specifically designed for this measurement task. “Thanks to its precise measurement principle, integrated signal conditioning, and robust design, the sensor enables continuous monitoring of thermal expansion and thus supports the early detection of critical operating conditions,” explains Managing Director Frank Ringsdorf.

Precise Displacement Measurement and Easy Integration

The HEP-100 measures thermal housing expansion using the proven LVDT (Linear Variable Differential Transformer) principle. This involves detecting the position of a movable core within a coil and converting it into an electrical signal that is proportional to the actual displacement. The non-contact measurement principle ensures high long-term stability and reproducible measurement results.

Thanks to its integrated electronics, the sensor directly outputs a standardized 4–20 mA signal and can be connected to PLC, DCS, or SCADA systems without additional signal conditioning. “This direct integration into existing automation environments not only simplifies the design of new systems but also enables straightforward retrofitting of existing systems,” says Frank Ringsdorf.

With a measurement range of up to 50 mm, the HEP-100 is suitable for a wide range of thermal enclosure monitoring applications. A version with a 100-mm measurement range is already in development. Depending on requirements, the sensor can be configured with a rising or falling characteristic curve: The output current changes either from 4 to 20 mA or, conversely, from 20 to 4 mA.

High Measurement Accuracy and Robust Design

“The HEP-100 impresses with its high measurement precision. An accuracy of better than 0.5% and an extremely low temperature drift of less than 0.01% per degree Celsius ensure reliable measurement results even under changing environmental conditions,” explains Frank Ringsdorf.

With a cut-off frequency of 800 Hz, the sensor also detects dynamic changes. It is powered by 20 to 32 V DC, and the maximum current consumption is 60 mA. The 4–20 mA output is designed for load resistances up to 500 Ω.

For continuous industrial use, the outer tube and measuring rod are made of stainless steel, while the movable core is made of a nickel-iron alloy. Nickel-plated brass connectors with gold-plated contacts ensure consistently reliable electrical connections. The sensor withstands shock loads of up to 250 g and vibrations of up to 20 g RMS or 50 g peak, making it suitable for turbines, compressors, and other rotating machinery.

Designed for Demanding Industrial Environments

The HEP-100 operates within a temperature range of -20 °C to +85 °C and, with an IP66 protection rating, meets the requirements of harsh industrial environments. It also complies with applicable CE and EMC directives.

Continuous monitoring of thermal housing expansion supports modern condition monitoring concepts. Unusual expansions can be detected early, maintenance measures can be planned effectively, and unplanned plant downtime can be avoided. “With its combination of precise inductive measurement technology, integrated electronics, robust design, and easy system integration, the HEP-100 offers a high-performance solution for operators of gas and steam turbines as well as other large-scale industrial plants,” summarizes Frank Ringsdorf.