Turbine overspeed protection systems and speed sensors
Rotation velocity sensor
Main sensor properties
- Speed range: from close to zero to 12000 counts per second (response time: not more than 40 microseconds)
- Distance to object for rotating part: up to 4 mm (depending on the profile size)
- Temperature range: -40 ° C ... +125 °C (-40 ... +255 °F)
- Sensor’s differential operating principle allows to exclude possible impact of magnetic fields or mechanism vibration
- Insulated stainless steel casing (1.4305) with IP67 protection class allows sensor tip to take up pressure > 200 bar. Sensor can be connected via hermetically-sealed sleeves or using strapped-down cable (with standard or Teflon insulation)
- Strong square output signal equally high within the whole speed range. Signal level ≈ corresponds to feeding voltage level. Firm signal transmission to a distance over 500 m
- Fine and coarse profiles are allowed, including tooth wheels, cut slots, teeth, orifices in any ferrous metals, or rotating magnets
Overspeed protection systems
Main protection systems properties
E16x346 system acting as self-contained unit (without external testing by operator or distributed control system (DCS)) with emergency shutdown function complies with SIL3/IEC61508 and DIN EN ISO 13849:2008 Cat.3 PLe standards..
Overall response time for shutdown: <15 ms
Maximum safety upon maximum availability factor is achieved through:
- TMR (triple modular redundancy) with three E1667 monitors.
- Triple speed measurement and assessment of value thereof by each monitor.
- Speed increase actuation setpoint allowing to trace acceleration.
- Detection of low speed as protection against incorrect assembly or speed sensor malfunction.
- Continuous speed sensors monitoring.
- Assessment of external additional devices emergency condition, using relevant channels of each monitor. Response to signals selected for each additional diagnostic channel separately (logic function, low/high emergency condition signal level, response time).
- Permanent monitors control performed by test signals generator carrying out cyclic, fully automatic tests or external controlled tests.
- Permanent electromagnetic valves unit control performed under the 2oo3 principle by test signals generator carrying out cyclic, fully automatic tests or external controlled tests.
- Each shutdown line (emergency circuit) is created according to method 2 and 3.
- Shutdown lines I, II, III, IV, V, VI are created by the medium of safety switches with a set of contacts actuated by electromagnetic force.
- Monitoring of shutdown lines with shutdown lock function (selectable).
- Shutdown lines outputs of 2oo3 emergency valves electromagnetic relay unit are monitored on a permanent basis. If the shutdown lock function is activated when 2 and 3 shutdown lines are in open position, shutdown condition is detected and blocked.