State-of-the-art metering technology in LNG facilities

LNG is playing a crucial role in the transition to an economically and environmentally sustainable energy future. This is evidenced in part by the tremendous growth in global LNG production capacity over the past and coming years. These facilities use state-of-the-art technologies for processing, liquefaction, transportation, storage and vaporization of the gas. But what does it look like in the field of leveling technology? 

The automation of an LNG plant has safety, availability and reliability as its primary goals. To ensure stable operation, the metering technology used must be able to deal with various challenges. On the one hand, these include product properties such as cryogenic temperatures, low dielectric values, fluctuating specific masses and turbulent processes. On the other hand, there are demanding installation conditions such as high nozzles, standpipes or stabilization tubes, valves and insulation systems. For historical reasons, conventional differential pressure systems predominate. In addition to conventional differential pressure gauges, modern pressure sensors with oil-free ceramic-capacitive measuring cell are gaining ground. The CERTEC® measuring cell from SaphirKeramik® is one of the most mechanically robust and dynamically highly loadable pressure measuring cells. It excels through its excellent long-term stability, its high chemical resistance, its resistance to extreme overloads and pressure shocks, and its excellent resistance to abrasive wear. 

Radar technology for lower TCO

With pressure transmitters, the challenges include complex piping, maintenance costs and fluctuating specific gravity. In these areas, non-contact measuring radar sensors or conductor radar sensors have proven to be a real alternative. Although often more expensive to purchase, they are virtually maintenance-free and bring down the total cost of ownership due to their reliability and flexibility. With the new high-frequency 80GHz sensors, standpipes or stabilization tubes (fitted to eliminate turbulence, among other things) can be dispensed with. Especially in processes where production interruption is associated with a lot of work and high costs, valves are mounted directly on the tank. The very good signal focusing of non-contact 80GHz radar sensors makes it possible to mount them on a ball valve without causing interference reflections. A reliable measurement is guaranteed. Other pluses include:

• Accurate measurement results, unaffected by fluctuations in specific gravity and temperature;
• Insensitive to fouling and condensation on the antenna;
• Chemically highly resistant PTFE antennas ensure long life;
• The high accuracy of +/- 1 mm easily meets industry requirements;
• Easy commissioning and diagnostics, also from smartphone or tablet.

Level measurement in standpipes, stilling wells and by-pass systems 

Because of their low operating frequency, guided radar sensors are ideally suited for use in standpipes, stilling wells and bypass systems. Various rod, cable and coaxial versions are available, selected according to the desired installation situation and process requirements. Environmental conditions in LNG applications are often variable. The metering technology is exposed to rapid level changes, volatile atmospheres due to evaporation and fluctuations in temperature, pressure and specific gravity. Know-how is crucial, the continuous development of sensor software enables safe and reliable use of conductor radar sensors, even in critical applications. Other strengths include:

• Accurate measurement results, unaffected by fluctuations in specific gravity and temperature;
• Maintenance-free because no mechanical moving parts;
• Flexible mounting options, e.g. for easy replacement of existing displacement systems;
• Reliable interface measurement between two fluids;
• Easy commissioning and diagnostics also from smartphone or tablet.

Overfill or dry run protection

In addition to level measurements, switching levels are often measured, as overfill protection in tanks or as dry-running protection for pumps. Vibration level switches are universally applicable and suitable for all liquids. In compact versions or with pipe extensions, they reliably detect the switching level to the mm. The wide application range in terms of process temperature (-196 °C ... 450 °C) and process pressure (-1 ... 160 bar) is unique. Vibrating forks can also be used for switching with products with a specific gravity from 0.42 g/cm³. Other pluses of this measuring principle:

• Low commissioning costs because plug-and-play solution, so no commissioning required;
• Precise, reliable operation thanks to a switching point that does not depend on the product;
• High operational reliability through continuous monitoring of the sensor element for corrosion, damage, cable breakage and vibration frequency;
• Maximum plant availability because function test at the push of a button during the ongoing production process in accordance with IEC 61508 and 61511.

Right technology, right partner

The key to increased safety, higher availability and maximum reliability lies in choosing the right technology, the ideal configuration and proper commissioning of the sensors. Certain applications may be more likely to qualify for radar sensors, others for pressure transmitters. While in some cases, a simple level switch may suffice. VEGA sensors are used all over the world in the largest and most modern LNG plants. We will gladly provide you with advice, show you solutions and share our experience with you so that you can make the best possible decision in the field of measurement technology. We feel at home wherever intelligent sensors with high functionality and high-quality materials are needed to do their job in demanding processes.