Making machines safe is one way of reducing the risks of accidents. But there can be many other situations that do not involve machineries yet possess high risk elements and safety hazards. None of the known safety measures of machineries can be used in such cases. This is particularly evident in chemicals, oil and gas industries and electrical installations where there are high chances of accidents arising from human error. In all environmental and safety incidents that occur, human error plays a significant role. As it is not possible to eliminate human error, the focus of safety shifts to the system which is incorporated with safety devices that can automatically shut down the system should anything go wrong.
Trapped interlocking is the answer
In order to ensure a safe sequence of actions in the process industry trapped key interlocks are widely used. Trapped key interlocks are mechanical devices used for locking. Trapped interlocking systems can be incorporated in various control devices like access doors, power switches and all types of valves. To make the system functional, there are two keys that have to be used in sequence from one interlock to the other. The operator is not allowed to skip the system and has to adhere to the pre-set operational sequence thereby eliminating the possibilities of any safety hazard.
Areas of application
In the process industry where valves are critical for system safety, any wrong operation of valves arising from mistimed sequence can have disastrous results. Similarly, in the manufacturing industry that uses moving machineries, there may be the necessity of intermittent manual lubrication of machines. At such times, the machines have to be switched off in such a manner so that it can never be switched on even accidentally. In both scenarios, using trapped key interlocking system can ensure complete safety whenever it is required to shut down the system.
Industrial safety fencing that is used to create a physical barrier around dangerous machines can be further strengthened by using trapped interlocking. However, for maintenance of machines workers have to access the area with precaution. A trapped key interlock can be used to lock the guards in its place so that the machine can be safely accessed. To open the guards and unlock it one has to switch off the power because the key for unlocking is inside the isolating switch of machine power.
Since trapped interlocking is a purely mechanical system that involves the use of two keys that have to be inserted sequentially in the systems, it is considered to be an infallible system. Since the system does not depend on any external resources like power and electronics there is absolutely no chances of malfunctioning. Using the keys is a human activity that can be completely trusted.
The reliability of trapped key interlocking that was first introduced in England is evident from the fact that the system has been in use for more than hundred years and is still as reliable as it used to be then.