Control danger signals

Shutdown systems for processes Interlocks for dangerous machinery Fire and gas detection Instrumentation Programmable controllers Railway signaling Boiler and burner controls Industrial machinery Avionic systems... 

In potentially dangerous work situations, a worker must recognize not only the demands inherent to the work task but also hazards and danger signals. These may be components of the work task itself or of the situation exterior to the work task. Saari (1976) defines the information which must be processed during the execution of a task in terms of these same components, i.e. (a) the information needed to execute a production task and (b) the information needed to keep existing hazards under control. 

The costs of a wrong decision are loss of production, on the one hand, and failure to respond to a real emergency on the other. In order to improve his or her decision basis, the control room worker will usually dispatch others to the source of the emergency signal to declare whether it is spurious (false alarm) or whether it is real, but it is containable without need for depressurizing. This takes up valuable time, during which the situation could escalate dangerously. 

The probes are 1-mm nickel rods with square ends. They are powered by 100-V dc power supplies. The positive side of the power supply is connected to the cell body. (This makes the probes cathodic to the case.) The control modules have 12 M3 resistance so that when contact is made, less than 10 mA flows through the circuit this is not a dangerous current. (The use of a 12-V power supply and lower resistance modules did not reliably deliver a control signal when contact was made this may have been caused by the buildup of a passive film on the probe that was not cleared by the lower voltage.)... 

Voluntary skeletal muscle movements are initiated by the motor cortex in the brain. Then signals travel down the spinal cord to the alpha motor neuron to result in contraction. However, not all movement of skeletal muscles is voluntary. Certain reflexes occur in response to dangerous stimuli, such as extreme heat. Reflexive skeletal muscular movement is controlled at the level of the spinal cord and does not require higher brain initiation. Reflexive movements are processed at this level to minimize the amount of time necessary to implement a response. 

Until recently, the signal displayed by most instruments has required mathematical treatment to obtain the required result. Now, however, calibration factors are frequently built into the instrument so that the digital voltmeter or printout gives the required result. There is some danger that this may induce a false sense of security in the analyst and a reduced awareness of the limitations of the basic analytical process, which can be avoided only by continued quality control. 

These various control actions may be generated electrically, mechanically, pneumatically, or hydraulically. Pneumatic and electrical controllers are most widely used. The former are often preferred in petroleum refining and similar industries where fire hazards make electrical devices dangerous unless specially protected. Present trends are toward increased use of electrical controls, particularly where signals must be transmitted more than 200 ft. 

All automotive torque sensors form part of a system that could potentially lead to dangerous situations for the driver. Using incorrect signals that do not reflect the real torque must therefore be avoided under all circumstances. Various monitoring features within the sensors or the controllers are implemented. The data transmission from the sensor to the controller must fulfill these safety requirements, such that erroneous data transmissions are detectable. Another important... 

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