Turbine Overspeed Trip Logging System

Steam turbines can become unsafe if the overspeed trip becomes faulty. Regular checking of this trip must be carried out. This can be hazardous using a simple handheld tachometer. This Turbine Overspeed Trip Logging system has been developed to check the operation of steam turbines. The speed of the turbine is monitored using an optical sensor, the logging system can be mounted up to 30 meters from the sensor. This allows the overspeed trip speed to be monitored and recorded with greater safety that using a simple tachometer. The results are logged together with time and date stamp so that it can be demonstrated that the test has been carried out. The speed is logged for 5 minutes and can be downloaded to a PC. The results are stored in an Access database and a graph showing speed against time can be viewed onscreen and then printed out. 32 sets of results can be saved in the instrument for later downloading. For each set of readings the instrument will display, the maximum speed and the maximum rate of change. These can be compared against the specification for a particular turbine and an alarm raised if the values are exceeded. There is also the option at the start of a test of specifying if the test is an overspeed trip or a letby. It will also record if the test turbine is coupled or uncoupled. Tests can also be carried out to log the rate of speed reduction during spindown. This provides a useful check on the operation of the turbine.

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