Industrial machines have moving parts, sharpening edges and forging surfaces that can cause serious workplace injuries. According to OSHA, workers who operate and maintain machinery each year suffer approximately 18,000 amputations, lacerations, crushing injuries and abrasions, as well as over 800 deaths per year. Many of these injuries and fatalities are avoidable with the proper use of engineering controls or safeguards, which should be implemented on any machinery part, function or process that might cause injury.

Machine Safety at a Glance

Engineering controls or safeguards on industrial machinery are typically implemented in a hierarchy that is layered, and ranked from the highest to the lowest effectiveness and reliability. These include the following:

· Permanent guards or barriers are a fundamental, passive means by which industrial machinery is made safe. These are usually in the form of permanent, fixed guards affixed to or in front of the machine to physically prevent operators from placing any part of their bodies, clothing or foreign objects into moving or powered machinery.

· Some machines require that the operator periodically place raw materials into the machine, remove finished parts, replenish supplies or replace tooling during normal machinery operation. Switches or interlocks ensure that the machinery guard, barrier or door allows access to the machine but prevents the machine from operating.

· In some cases, it is not practical or feasible for the operator to install a physical guard during operation of the machine due to the frequency of access to the machine. In such instances, optical sensors, such as light curtains, area scanners or proximity sensors can interrupt machine operation if foreign objects or personnel enter a protected zone.

· Operators can actively start a machine in a safe manner with two-handed controls or can shut down machine operation with an emergency stop switch. These controls require that the operator be aware of potential hazards, such as other personnel or foreign objects that may be in the protected zone when the machine is operating. Because of the reliance on the operator, these safety measures are reactive and not as effective as those that will automatically halt operation of the machine.

· Industrial machines can also be outfitted with force, torque, current and position sensors that will interrupt operation if the machine must exert excessive force, which may indicate a potential malfunction in order to operate. These controls may not be effective in avoiding potential injury, but may be effective in reducing injuries and damage.

· There are numerous types of audio, visual and tactile alarms that improve operator awareness and safety by indicating the machine’s operational state. These will allow the operator to take appropriate measures to avoid potential anomalies and safety issues.

Engineering controls and safeguards are typically implemented in industrial machinery through the machine’s safety programmable logic controller (SPLC). An SPLC is an industrial digital computer that replaces hard-wired safety relays, timers and sequencers in industrial machines. They are easily programmed and emulate the functions of electromechanical relays. For small or simple systems with a limited number of inputs and outputs, they are relatively simple to wire, easy to troubleshoot and cost effective.

PLCs can provide good diagnostics; however, as the complexity of the machine or control scheme increases, PLCs become difficult to wire, reducing flexibility and increasing expense. Machine developers may therefore use series wiring for the engineering controls and safeguards, giving rise to problems like fault masking. Fault masking is a condition where failure of one control may hide the presence of another failure, or where the operation of one safeguard can reset failure detection of another (potentially unrelated) safeguard. The use of series wiring in a centralized approach toward fault detection, isolation and recovery can result in the continued operation of a dangerous machine function in spite of a fault in a safety circuit. Alternative approaches are therefore needed to ensure machine safety that does not limit flexibility or increase system cost.

Prevention or reduction of industrial accidents involving workers and machinery are manageable with appropriate safety procedures, controls and products. Euchner addresses problems such as fault masking through a decentralized or hybrid approach to the implementation of engineering controls and safeguards.

Euchner’s Solutions

Figure 1. Ethernet/IP-enabled MGB. Source: EuchnerIn this decentralized or hybrid approach, fault detection, isolation and recovery can occur at the point of failure, minimizing the likelihood of fault masking. An example of such a device is the Euchner Multifunction Gate Box (MGB) (Figure 1). The MGB is a modular system that contains a locking system for the protection of safety doors on machines, plus additional functionality, such as guard locking, escape release or other functions such as buttons for start or stop and emergency stop. The MGB is available in both an Ethernet/IP version and Profinet, which simplifies wiring as all components are connected to a centralized hub, allowing the user to define which elements are integrated and the related functions.

About Euchner

Euchner develops a wide range of electromechanical and electronic products, such as the MGB, transponder-coded safety switches and read heads, locking and non-locking safety switches, safety relays and control systems, light curtains, electronic identification and key systems. The wide range of offered products can provide design engineers and system integrators with a complete range of technologies and solutions to develop engineering controls and safeguards for automated manufacturing equipment.

Euchner products are made possible by a dedicated staff of 750, and a worldwide sales network of competent partners. More information about the company and its products can be found on the Euchner website.