Emerson A6312-8 Dual-channel Speed and Key Monitor

The Speed and Key Monitor is designed for high reliability for the plant’s most critical rotating machinery monitoring speed, phase, zero speed and direction of rotation.This 1-slot monitor is used together with the AMS 6500 monitors to build a complete API 670 machinery protection monitor. Applications include steam, gas, compressors and hydro turbo machinery.

The Speed and Key Monitor can be configured for redundant mode where automatic switchover from primary to backup tach is possible. Sensor gap voltage and pulse counting/comparison are monitored to trigger switchover. When the Speed and Key Monitor is operating in redundant mode, the main and failover key or speed displacement sensor must be installed in the same axial plane to ensure phase continuity upon failover.

Speed measurements consist of a displacement sensor mounted internally to the machine with the target being a toothed wheel, a keyway or gear rotating on the shaft. The purpose of the speed measurement is to alarm on zero speed, monitor for reverse rotation and provide a speed measurement to track process conditions for advanced analysis. Key, or phase measurements, also consist of a displacement transducer but must have a once per revolution target, not a toothed wheel or gear for a target. The phase measurement is a critical parameter when looking for machine health changes. 

Technical Specifications