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Method of monitoring the condition of a motor operated valve system

  • US 5,239,874 A
  • Filed: 06/19/1990
  • Issued: 08/31/1993
  • Est. Priority Date: 06/19/1990
  • Status: Expired due to Term
First Claim
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1. Method of identifying, during valve-in-use operation, an unacceptable degredation of the operating condition of a motor operated valve system, which system is comprised of a valve driven by a valve stem which is driven by a valve actuator which is driven by an electric motor, said method comprising the steps of:

  • establishing, for a specific valve system, a value (referred to as "BASE") representative of actuator output torque during baseline running conditions, baseline running conditions being defined as as near to normal, non-degraded running condition as possible for the valve;

    establishing, for the valve system, a value (referred to as "MAX") representative of the maximum actuator output torque to be allowed during running condition, based on a predefined, allowed degraded stem factor;

    determining the maximum allowed percentage increase in the actuator output torque from BASE during running condition by the formula;

    ##EQU3## wherein "safety factor" is a number greater than or equal to one;

    establishing, for the valve system, a value of a selected power related parameter of the motor during baseline running conditions;

    determining a warning value of the selected power related parameter as equal to the warning level percentage of the established baseline value of the power related parameter;

    monitoring the selected power related parameter associated with the valve system during valve-in-use conditions; and

    evaluating changes in the value of the selected power related parameter over the monitoring period,whereby, an increase in monitored power related parameter value indicates a potential problem and an increase in the monitored parameter to the warning value indicates operational readiness may be compromised.

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