Abstract
Trouble-free operation of motor-driven valves (MDV) is one of the key factors behind the operating safety of NPPs. As critical components, MDVs are a part of a safety system and a safety-related system. This imposes the highest possible requirements on the MDV reliability. MDVs are the most numerous category of the NPP components. Depending on design, one power unit contains 1500 to 3000 motor-driven valves alone. It follows from an analysis of the NPP failures that many of these are caused by failed motor-driven valves of safety and safety-related systems. The paper presents a description of an automated system for diagnostics of shutoff and control MDVs used in the NPP pipelines. The developed diagnostic algorithms make it possible to take into account the variability of the MDV technical parameters, while taking into account, at the same time, rated restrictions on diagnostic parameters, if any.
Highlights
In the process of operation, motor-driven valves (MDV) are exposed to impacts from a large number of factors, infrequently of a random nature, e.g. variation of the fluid and environment parameters
The higher is the variation of the technical condition parameters, the less efficient are the maintenance and repair routine charts, since, in this case, there is always a factor of uncertainty regarding the technical condition of the respective item
After the permissible intervals are determined for diagnostic signs, the diagnostic system is capable to generate the diagnosis for each particular cyclogram
Summary
In the process of operation, MDVs are exposed to impacts from a large number of factors, infrequently of a random nature, e.g. variation of the fluid and environment parameters. According to (MT 1.2.3.02.999.0085-2010), the paper uses the following terms with respective definitions: The active power cyclogram calculated based on the current and voltage signals using the formula below plays the key role in diagnostics of failures. The experience of the MDV operation and an analysis of the electrical machine failures show that the motor current and/or active power signal measured for one or three phases is informative enough for identifying the technical condition type (serviceability evaluation) for the CHP plant or NPP unit process system valves (MT 1.2.3.02.999.008520103). The motor (three-phase) stator winding and limit switch current and voltage signals are recorded in real time by measuring modules in the cabinets of the unilateral-maintenance three-phase distribution assembly for gate valves (RTZO) to the database of the data acquisition system. The architecture of the data acquisition system is described in (Matveyev et al 2009)
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