Dc motor operated valve remote monitoring system

Abstract

A method and apparatus for remotely monitoring the condition of a DC motor operated valve and/or valve operator by monitoring at a remote location, such as the Motor Control Center ('MCC'), the output torque of the DC motor which drives the valve operator comprises method and apparatus for monitoring the armature circuit of the DC motor at the remote location (I.E. MCC) to acquire a value of motor armature current (Ia), voltage drop across the armature (Va), and the electrical resistance of the armature (Ra); these remotely acquired electrical values of Va, Ia and Ra being utilized as input to apparatus for generating mechanical values of motor output mechanical power, armature speed, and a motor torque factor representative of the motor output torque multiplied by a constant; and the apparatus of the present invention also comprises invention circuitry for isolating the armature resistance (Ra) as a resistance value, representing that resistance value as a voltage and inputting that voltage representation of Ra into other modules of the circuitry to be used in the final generation of the DC motor torque factor; this Torque Factor being used in accordance with the present invention either: (1) alone, as a single indicator of the stem load on the valve stem of the valve operator (i.e.: by multiplying the torque factor by the known constant and also by the manufacturers' published gear efficiency values for the specific valve operator being monitored); or (2) in conjunction with other diagnostic equipment as an assist in determining the condition of the valve and/or valve operator.