National offers a complete line of AST sensors designed to provide high level alarm contacts for above ground storage tanks. All units are fabricated in stainless steel and have a self-checking feature. For pressure tank installations, the self-check feature is magnetic, allowing the operation to be done while maintaining tank integrity. There are three types of AST sensors, each engineered to provide maximum utility unique to each tank design.
VERSA-LEVELS excel at service in internal floating roof tanks-
Available in single or dual level format, versa-level sensors live up to their name. Engineered for maximum reliability, they feature both displacer and float characteristics. This allows them to perform under normal conditions with the roof causing the sensor to operate (displacer), or in the case of a breached roof, liquid (float) operation. Versa-level sensors are independently adjustable over the length of the cable length supplied with the sensor. They may be used in cone or fixed roof tanks without floating roofs. They should not be used in tanks that have aeration or agitation, as this may compromise the bias spring mechanism in the sensor, causing false actuations. This is also a concern in open floating roof tanks, where wind and weather can cause the sensor to false actuate. The specifier should instead consider the Mono-Check, or Duo-Check sensors listed below.
VERSA-LEVEL X for open floating roof tanks
This AST sensor addresses the problems of providing reliable high-level alarms in open floating roof tanks. Being open to the environment, the tank conditions may include adverse weather, including freezing rain, snow, and icing. Physical contamination in the form of leaves, branches, and flying debris must be considered. Versa-level X will operate as a tilt sensor under most conditions, and will operate as a float operated tilt sensor if the roof is breached and floods with fluid. Operation is simple, the cable suspended sensor will topple over as the ball float is lifted, regardless of how it is lifted. They may be mounted in pairs to provide high and hi-hi contacts. Versions of Versa-Level X have been successfully installed in processes with viscous liquids such as hot asphalt.
MONO-CHECK and DUO-CHECK for cone or fixed roof tanks
Single and dual level AST sensors can provide maximum reliability in tanks with processes, agitation, and pressure. Simple and easy to install, the sensors contain magnetic self-checking systems. Most often used in conjunction with I.S. devices (intrinsically safe) they are the simplest and strongest of our AST sensors. All have sealed contacts and are built to order with customer supplied length, and actuation requirements.