Control Systems / Industrial Safety / Industrial Automation

Fortify your machines' defenses

Sheila Kennedy says combine physical barriers and advanced technologies to keep workers safe.

By Sheila Kennedy, CMRP

Providing a safe and healthful workplace is every employer’s responsibility. The U.S. Occupational Safety and Health Administration (OSHA) advises: “(A)ny machine part, function, or process which may cause injury must be safeguarded. When the operation of a machine or accidental contact with it can injure the operator or others in the vicinity, the hazards must be either controlled or eliminated.”

Protective barriers, sensing safety controls, and advanced drives are among the many machine safeguarding tools helping protect workers today.

Physical barriers

Automatic machine safety doors prevent hazardous operations from interfering with other processes and nearby people. The new Gortite VF (vertical fabric) door from Dynatect provides dynamic protection for applications prone to welding splatter, smoke, arc flash, and other common hazards. It can include a UV-resistant window to enable visibility of the protected process.

“The barrier created by the VF door reduces the floor space required by eliminating the extra buffer needed for light curtains to create a safety zone,” says Steve Piacsek, R&D engineering manager at Dynatect. “Unlike light curtains, which can’t contain process hazards, high-speed roll-up doors isolate common workplace debris.”

For inspections of energized electrical equipment, electrical maintenance safety devices (EMSDs) such as the infrared windows or ultrasound ports from IRISS can be affixed to a cabinet surface to protect against arc flash and electrocution hazards. Combining EMSDs with critical asset surveillance technologies (CAST), including IR cameras or ultrasonic probes, allows real-time electrical condition monitoring readings to be taken safely from outside the closed cabinet.

This approach “can further enhance an equipment reliability program by ensuring that wrench-turn-type maintenance is only performed when truly warranted,” says Rudy Wodrich, VP of technical services at IRISS. Infrared windows from IRISS utilize a patented reinforced polymer optic that is rugged, durable, and optically stable and that carries an unconditional lifetime warranty.

Machine stop and restart controls

Accidental restarts often occur because machine operators assume their machinery has anti-restart protection when it does not. The Sensing-Saf-Start from Rockford Systems is designed to protect against automatic or unintentional restarts when a power interruption occurs. “These types of accidents are some of the most common on the plant floor, resulting in horrible injuries, such as crushed hands and arms, severed fingers, and blindness,” says Brian Boes, VP of operations at Rockford Systems.

The Sensing-Saf-Start has a reset button that must be pushed to restart the machine once power has been lost and then restored. It is designed for easy, fast installation by tying into e-stops on a wide variety of machines, including drill presses, tool grinders, and band saws.

Automatic machine stops with radio frequency (RF) presence sensing, or RF guarding, combine RF signal transmission with capacitive presence sensing. The PC1000 Proxagard from Gordon Engineering is an example of this technology. It can guard areas around corners for multiplane 3-D coverage; it’s immune to vibrations from machinery and other sources; and it broadcasts an adjustable signal radially out. 

“RF guarding technology uses a coupler that generates a low-level RF field around the antenna,” explains Steve Weighart, president of Gordon Engineering. “Any part of a person or object intruding into the area around which the antenna is placed attenuates the signal. The control unit senses the attenuated field and triggers a machine stop.”

Safe-speed drives

VSDs designed with machine safety and cyber-security in mind provide extra protection for an operation’s human and networked assets. Altivar Machine drives from Schneider Electric have several built-in safety features. The Altivar 320 has SIL3/PLe-rated safe torque off (STO), full monitoring functionalities with safe stop (SS1), safe limited speed (SLS), safe maximum speed (SMS), and guard door lock (GDL), says James Crook, senior staff electrical engineer at Schneider Electric. The Altivar 340 offers an embedded solution featuring STO with dual inputs compliant with SIL3/PLe and Achilles Level 2 certification for cyber-security.