As manufacturing continues to become increasingly automated, manufacturers continue to look for ways to protect their most important asset: the workforce. Robots, autonomous ground vehicles, material handling equipment and more complex systems can create more dangerous workspaces than ever before without the proper safeguards installed on the production floor. There are many forms of safety devices. These devices are just a few examples to get you thinking about the options available.
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Emergency stops
Emergency stops (e-stops) are one of the most recognizable and most thought-of safety devices on the production floor (Figure 1). Think of them as the immediate interface to stop a machine. The e-stop is typically in a normally closed position within a circuit that, when pressed, opens the circuit and cuts power to the device. To re-engage the circuit, the e-stop must be pulled out or in a twist to open configuration returning the circuit to operational.
According to OSHA, ANSI, NFPA 79 and ISO 13850, IEC 60204-1, e-stops are required to be installed where they are easily accessible to the operator and resetting the e-stop should not allow operations to resume. A second redundant action is required such as an all-clear function through a circuit on the programmable logic controller (PLC).
Safety interlocks
Door interlocks are another physical safety device commonly integrated on the production floor. Safety interlocks are used on physical barriers such as gates and doors. The safety interlock, much like the e-stop, operates in a normally closed circuit. When the gate or door is opened, the circuit is interrupted, and all work is halted. Interlocks are required to meet ISO 14119 and ISO 13849.
Safety mats
Operator presence triggers come in many shapes and sizes. For example, a safety mat is activated by the presence of someone standing on the mat. It may trigger a machine to stop, go in reverse or deactivate when presence is detected. This helps to ensure that human workers are out of the way, allowing the machine to operate.
Laser scanners
Laser safety scanners have become very popular with the rise of cobots. The scanner uses a 360° beam that indicates how close a worker or an object are in relation to the robot. Usually with set zones, the robot will decrease speed depending on the closeness of the individual or object. In the orange or yellow zone, the robot is slowed to collaborative speed until the object or person has exited. If the red zone is triggered, the robot will then slow or even stop completely until safe (Figure 2).
Light curtains
Light curtains are especially effective in areas where crushing or pinching hazards exist such as hydraulic presses. The light curtain uses photoelectric beams that project from a transmitter to a receiver. If the beam is broken, all work stops immediately until the obstruction is cleared. Light curtains are particularly effective when solid gates or barricades are impractical. They come in a variety of sizes and levels of sensitivity to fit the needs of the manufacturer in meeting OSHA standards.
Safety PLCs
Safety PLCs are control systems designed to monitor and manage safety-critical functions and serve as a way to program in safeguards to monitor the health of a line. Through redundancies, the safety PLC is designed to run diagnostics to determine if a part of the line or a component is faulty. If an event such as a broken wire or motor is running outside of spec, the safety PLC will immediately shut down the entire affected system to help prevent injury or damage. The safety PLC must adhere to a specific safety integrity level (SIL) and must meet IEC 62061, ISO 13849-1 and IEC 61058.
These are just some of the many safety devices available to manufacturers and installers. When automating a process, it is necessary to seek advice from a safety expert and consultant to ensure you have covered all the possible hazards within your facility to protect your workforce and investment. These experts and consultants can help you to navigate OSHA, ANSI and all other safety regulatory agencies.
