9905-869

About the 9905-869

This overspeed protection system has a modular design. The 9905-869 system has three individual units, each with its own 24 Vdc power supply. Each of these three identical speed-sensing units is interfaced with a magnetic pickup (MPU) to monitor prime mover speed. All three units are in the same IP65-certified enclosure, which is locked with a key switch to prevent unauthorized changes and testing. The modular design of model 9905-869 permits the testing of individual units one at a time while the prime mover is online, as well as hot replacement.

9905-869 is part of the ProTech 203 Overspeed Protection System. This model is one of the de-energize-to-trip versions in the Woodward series. When an overspeed condition is detected, a trip relay is activated. The accuracy of this system is ensured through the use of a two-out-of-three voting configuration of the three speed-sensing units. The actual speed of any of the three units can be viewed on the LCD of each unit’s own operator interface. Each interface also has a keypad and LED functional status indicators.

Thanks to the hardware vote configuration, the 9905-869 will continue to operate even after one of the unit trips. Along with an overspeed condition detection, there are several possible reasons why one of the units may trip, including but not limited to the loss of an MPU signal, the unit was not reset before the turbine was restarted, or an interlock fault. More information on the trip relays and troubleshooting information can be found online in the ProTech 203 Overspeed Protection System Manual 85191 (version B)