Emerson A6210 Dual-channel Thrust, Differential Expansion, and Rod Drop Monitor

The A6210 monitor operates in 3 distinct modes: thrust position, differential expansion, or rod position.

The Thrust Position mode accurately monitors thrust position and reliably provides machinery protection by comparing the measured axial shaft position against alarm set-points – driving alarms and relay outputs.

 

Shaft thrust monitoring is one of the most critical measurements on turbomachinery. Sudden and small axial movements should be detected in 40 msecs or less to minimize or avoid rotor to case contact. Redundant sensors and voting logic are recommended. Thrust bearing temperature measurement is highly recommended as a complement to thrust position monitoring.

 

Shaft thrust monitoring consists of one to three displacement sensors mounted in the axial direction parallel to the shaft at the shaft-end or thrust collar. The displacement sensor is a non-contact sensor that measures shaft position.

 

For extremely critical safety applications, the A6250 monitor provides triple-redundant thrust protection built on the SIL 3-rated overspeed system platform.

 

The A6210 monitor can also be configured for differential expansion measurements. As both the case and rotor grow due to changes in thermal conditions at turbine start-up, differential expansion delivers a measure of the relative difference between mounted displacement sensors on the case and the sensor target on the shaft. If the case and shaft grow at approximately the same rate, then the differential expansion remains close to the desired value of zero. The differential expansion measurement mode supports tandem/complementary or cone/ ramp modes.

Finally, the A6210 monitor can be configured for average rod drop mode – used to monitor rider band wear in reciprocating compressors. Over time, rider bands wear in horizontal reciprocating compressors due to the force of gravity acting on the horizontally-oriented piston in the compressor cylinder. If the rider band wears beyond spec, the piston can contact the cylinder wall and cause incremental machine damage and possible failure.

By mounting at least one displacement probe to measure the piston rod position, you will receive notification when the piston drops – an indication of rider band wear. You can then set shutdown protection thresholds for automatic trip. The average rod drop parameter can be factored to represent the actual rider band wear, or with no factor applied, rod drop will represent the actual movement of the piston rod.

The AMS 6500 includes easy integration to the DeltaV and Ovation process automation systems, including preconfigured DeltaV Graphic Dynamos and Ovation Graphic Macros to speed operator graphic development. AMS software provides maintenance personnel advanced predictive and performance diagnostic tools to confidently and accurately determine machine malfunctions early.

Technical Specifications