Trip mechanisms speed

During the Nazi invasion of Russia in World War II, Soviet engineers were instructed to destroy turbogenerators before retreating. First, the trip mechanism was wired so that it would stay latched. Next, the turbine was run up to maximum speed. Finally, the pump circulating lube oil to the turbine bearings was switched off. 

In contrast to steam turbines, in which runaway overspeediug is always a problem, pump-turbines operating at design head go to zero torque at about 130 to 140 percent of design speed. Thus, overspeed protection may not be necessary if the pump-turbine can withstand 140 to 150 percent of design speed and it is the sole driver. When a steam-turbine helper is used, it should be provided with the usual overspeed trip-out mechanism. 

Failures which can prevent rod motion by a CRD mechanism are of concern because they might preclude a reactor trip of the associated rod. To detect such failures, redundant load cells and position sensors are installed. The load cells detect rod binding or breaking, and the position sensors measure rod position. The position sensors can be used to test all aspects of rod motion such as rod speed and rod mobility. When either the load cells or position sensors indicate a malfunction, this information is conveyed to the... 

Electronic slack rope Mechanical slack rope Rock winder inter-trip Auxiliary drive shaft shaft failure Ecam fault No start and stall Relay X check Slowdown failure GEC over speed Headgear overwind Brakes rubbing Escort fault Brakes worn... 

The control rod drive mechanisms are installed in the lower part of the reactor pressure vessel, so that the control rods are inserted from the bottom into the reactor core. There are different reasons for this layout, among others the fact that the moderator water shows a higher density in the lower part of the core which is counteracted by the partly inserted control rods, thus resulting in a better homo-genity of load distribution in the core axial direction. Movement of control rods during normal operation periods is performed by electrical or hydraulic drive mechanisms in order to initiate a reactor trip, the control rods are forced into the core by a pressurized water drive mechanism. The load control by the control assemblies which are inserted more or less into the reactor core, depending on the demand, is supplemented by a load control which is effected by the speed of the main coolant pumps. A reduction of speed results in a longer residence time of the coolant in the reactor core and, as a consequence, in an increase of the void fraction in the water-steam mixture. As a result, neutron moderation is reduced and... 

In addition to the various turbine trips, two independent and redundant overspeed trip systems, the mechanical overspeed trip (OST) system and the electronic overspeed system (EOS), are provided to trip turbines at 110% and 111% of rated speed, respectively. Therefore, this system is considered to meet the regulatory requirements. 

Figure T-87 illustrates a hydraulic trip valve used with a mechanical shaft-mounted trip. When trip speed is reached, the plunger (or ring) mounted in the trip...

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