Pulse-Time Positioning Used for Safety Control of High Speed Tester

The operation and fail-safe features of the safety devices for a high speed bearing and shaft seal testing machine, operating between 10,000 rpm and 110,000 rpm, are discussed in this paper. The machine consists of an air turbine which drives a load through a flexible quill shaft. The safety devices interrupt the turbine air supply by a valve when either a predetermined torque or a preset speed is exceeded. Magnetic pickup signals genrated by magnetic pins attached to the rotating shaft operate the safety devices. An electrical shutoff signal is developed during the first revolution of overtorque or overspeed. These safety devices, including the valve, must be fail-safe and operate in approximately 27 ms to prevent possible turbine disintegration due to centrifugal forces in the event of load removal by quill breakage.