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A6410 Valve and Case Expansion Monitor for AMS 6500 Machinery Health Monitor
The Valve and Case Expansion Monitor is designed for high reliability for the plant’s
most critical rotating machinery. This 1-slot monitor is used together with other
AMS 6500 monitors to build a complete API 670 machinery protection monitor.
Applications include steam, gas, compressors and hydro turbomachinery.
The main functionality of the Valve and Case Expansion Monitor is to accurately
monitor valve position and case expansion and reliably protect machinery by
comparing parameters against alarm setpoints, driving alarms and relays.
Valve position is a measurement of the main steam inlet valve stem position normally
displayed in percent open. The valve position measurement provides the operator with
an indication of the current load on the turbine.
Case expansion monitoring usually consists of two inductive displacement sensor
(or LVDT’s) mounted in the axial direction, parallel to the shaft, and on each side of
the turbine case. Unlike the eddy current sensor which is a non-contact sensor, the
inductive sensor is a contact sensor.
Case expansion monitoring is important at start-up, so both sides of the turbine case
can be monitored for proper expansion rates. Because the turbine is allowed to slide
on rails as it expands, if both sides are not free to expand, the turbine “crabs” (the case
bends), leading to the rotor colliding with the case.
Channel 1 can measure static values, such as case expansion, and can also be used for
dynamic quantities, such as displacement, angles, forces, torsions or other physical
quantities measured by inductive transducers. Channel 2 is left for static measurements
and relative displacements (relative to channel 1).
The AMS 6500 Machinery Health Monitor is an integral part of PlantWeb® and AMS
software. PlantWeb provides operations integrated machinery health combined with
the Ovation® and DeltaV™ process control system. AMS software provides maintenance
personnel advanced predictive and performance diagnostic tools to confidently and
accurately determine machine malfunctions early.