Moore Industries Technical White Paper Explains the Use of Logic Solvers in Tank Overfill Protection Systems

NORTH HILLS, CA—Moore Industries-International, Inc. has released a technical white paper exploring the possibilities available to designers of Safety Instrumented Systems (SIS) using logic solvers as part of a tank overfill protection system. Available for download at, the “Logic Solver for Tank Overfill Protection” white paper provides examples of straightforward tank overfill protection system topographies and associated Safety Integrity Level (SIL) calculations.

A tank overfill protection system is an SIS that provides automated overfill control during the containment of dangerous substances. If the level in a tank rises above set limits, the logic solver initiates the final element of the SIS to make the process safe. This can include shutting off the input feed to the tank by isolating the pump and closing the input valve.

The “Logic Solver for Tank Overfill Protection” white paper guides safety engineers through the steps needed to determine the right logic solver for their needs. While many people assume that a logic solver for a tank overfill protection system must be a safety PLC, in many cases a discrete logic device in the safety loop is sufficient. This avoids the complications and expense associated with a complex programmable solution.

The white paper shows the methodology and calculations for determining applicable logic solvers in SIL 1 and SIL 2 environments. In many cases, discrete logic devices such as the STA Safety Trip Alarm are suitable for use while providing a flexible, low-cost and user-friendly solution. More information on the STA Safety Trip Alarm and other safety-related products from Moore Industries is available at

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