THE RIGHT LEVEL MEASUREMENT FOR LIQUEFIED GAS

Emerson’s Johan Sandberg explains how radar gauges support inventory management and overfill prevention in LNG and LPG tank storage applications Level measurement technology is a key component of tank gauging systems for vessels containing liquefied natural gas (LNG), liquefied petroleum gas (LPG), or other liquefied gases. Reliable liquid level measurements inside complex full containment tanks are vital for inventory management and custody transfer purposes, and to prevent overfills. In liquefied gas applications, level measurement has often been performed with servo technology. A small displacer suspended by a thin wire is connected to a servo gauge on top of the tank. A weighing system in the servo gauge senses the tension in the wire and sends signals to control an electric motor in the servo unit, making the displacer follow the liquid level. In more recent times, readings from these devices have been automated. Servo technology has some major shortcomings. Servo gauges have many moving parts that are susceptible to mechanical wear, increasing their maintenance requirements and likelihood of failure. Because the displacer and the wire are in contact with the liquid,...