Rendering is a process that takes what normally would be animal waste and transforms it into usable product. The cycle begins by heating the animal product in a tank using steam from a boiler. Once the heat is used, the steam it's taken from is collected again and condensed in a separate tank where it starts the process over again . Level indication is necessary so technicians can monitor and maintain proper water levels in the condensate tank.

Mid South Steam Boiler Engineering Co. (Van Buren Ark.) manufactures these types of condensate tanks and fits them with level instrumentation. Ken Wormky, project manager for the company, says mechanical and pneumatic displacement-type level indicators were normally used with a sight glass showing the amount of water in the tank. These level indicators, though, were expensive and difficult to install. Over time they became cloudy and hard to read, would break, and sometimes injure technicians. This prompted an instrument change.

Mr. Wormky now equips the condensate tanks with the LevelSite magnetic flag-type level indicator from Barksdale (Los Angeles, Calif.), making the change based on several key factors. First, he says it's important for the user to see the water level in the condensate tank "at a glance." With flag-type level indicators, the brightly colored, rotating red flags are easy to read from the front or sides at distances of up to 100 ft., even when monitoring the level of a clear liquid. The indicator has no glass to cloud or break, and isolation from the measured media prevents the flags from discoloring.

Users also needed a system that was easy to install and maintain. Mr. Wormky says the LevelSite is not only easy to install, "it can be easily adjusted without bringing the system down." LevelSite is said to provide accident-proof level measurement to an accuracy of ±1/2 in. in applications with operating pressures to 6,000 psi, temperatures to 600 °F, and with liquid to a minimum specific gravity of 0.49.

Equipped with a permanent ring magnet, the float rides at the surface of the liquid contained within the float housing, rising and falling with the liquid. As the float moves up and down in its housing, its position is tracked by the rotating magnetic flags. Flags below liquid level show their red side while those above show their white side. Because of the float's permanent ring magnet design, which provides a 3608 magnetic flux field, the rotating flags, limit switches, and continuous level sensors can be located anywhere around the float housing.

LevelSite can also transmit alarms and electrical signals to remote process control panels, PLCs, or distributed control systems. A common method would be to use an externally mounted, vertical-shaft transmitter equipped with a network of magnetically activated reed switches connected to a series of resistors. As the float rises or falls, it magnetically activates the reed switches, changing the electrical resistance in the network's circuit, which thereby provides a standard 4-20 mA or 0-10 V output signal. Because nothing ever contacts the measured liquid, the transmitters are easy to maintain, accurate, and reliable, Mr. Wormky says.

For more information on Barksdale, visit www.controleng.com/info