Radar is the fastest growing technology for level gauging in LNG tanks. No wonder – in a huge, cryogenic tank that may not be opened for years, you need a level gauging system designed to be maintenance-free and highly reliable.
No physical contact
5900S gauges measure the LNG level without any physical contact with the LNG surface, and without the need for inside-tank components that require service. Thus, the system provides continuous, reliable and highly accurate level data, for the entire service life of the LNG tank.
To reliably measure the level in an LNG tank, a radar gauge needs a sufficiently strong echo from the LNG surface. The advanced signal processing 5900S design, featuring a highly sensitive radar receiver, uses FMCW radar which gives optimum signal strength from the LNG surface. The 4-inch still-pipe guides the radar signal, resulting in a strong undisturbed echo from the liquid surface.
Verification during operation
A patented reference device mounted inside the still-pipe enables measurement verification with the tank in operation. This eliminates the need for expensive calibration chambers and large-size valves.
Vopak Chemical Logistics has made a safety upgrade of their 34 tank Mussalo terminal near Kotka in southern Finland. By combining high precision TankRadar Rex gauges with Rosemount 5400 radar level transmitters, they get state-of-the-art independent overfill protection.
Each tank, both fixed and floating roof tanks, is equipped with one Rex radar gauge plus one Rosemount 5400. The 5400 transmitter gives alarm output to the separate emergency shutdown system.
Before, the terminal used mechanical level switches. The on-off switches could only be tested at irregular intervals, and a major drawback was that you only knew they worked at the time of testing. As the terminal stores different products with varying properties in each tank, mechanical equipment with moving parts has reliability problems due to condensation and product build-up. In addition, many of the tanks are heated, and have thermal insulation making them generally unsuitable for equipment with moving parts.
By using a reliable level measurement device such as the 5400 as independent overfill alarm, on-line proof-testing during normal operation is now possible.