Motion Monitoring Unit Permits Safe Access Without Unnecessary Downtime

March 24, 2007
Safe access to equipment with variable rundown times can be difficult to judge. The BEMF motion-monitoring device from Castell Interlocks guarantees that motor-driven equipment such as mixers, hammer mills and pellet mills has completely stopped before access is granted. Safety is increased while downtime is reduced, compared to fixed time delay systems. While an electric motor is rotating, whether powered or not, an electromotive force is generated. This force is measured by sensors in the BEMF unit. A key, corresponding to a lock on the machine’s guard hatch, will not be released until the sensors register zero speed. The key is then released and can be used to gain access to the machine. Access is granted as soon as safely possible, unlike fixed time delay systems which can overcompensate run-down times for lighter loads. The BEMF prevents access to the equipment while it is running. Entrance to the equipment is immediate after reaching zero speed. The equipment cannot be restarted until personnel has safely withdrawn, then closed and locked the guard hatch. The BEMF unit can be connected to both A.C. and D.C. motors, including soft start motors. It is designed to provide the highest level of safety at all times; like other Castell key interlock systems, it is an approved alternative method to Lockout-Tagout requirements under the ANSI Z244 Standard.