Machine safety is about keeping workers out of harms way and keeping machines from harming themselves or the products they produce. In the U.S., OSHA is the primary organization that sets rules for machine safety. To be in line with OSHA requirements at their basic levels, employers should comply with the following rules.
- Rotating and moving equipment parts and pointed objects, such as fan blades or power saws, should be guarded from contact with workers.
- Machinery, pits, holes and hazardous procedures must be sufficiently guarded.
- Metal components of electrical equipment must be bonded and grounded.
- Electrical equipment that creates flames, sparks, arcs or molten metal should be enclosed and placed far from combustible substances.
- Guards should be placed on chains and gears.
- Machinery should be maintained and kept clean and secure.
- Emergency stop buttons should be red in color.
As globalization has increased, other standards, driven mostly by the European community, can cause some confusion among U.S. machine builders and add costs to machines headed to markets overseas. Clearly, machine builders must consider safety requirements in the initial design phase of the product. It no longer can be an afterthought.
There are an ever-increasing number of products on the market to aid safer machine design. Safety networks have been introduced and, as Joe Lazzara, president and CEO of Scientific Technologies says, The newest versions of safety networks have integrated the safety and control system as one common unit. Theres no need for a separate safety bus or safety PLC. This saves costs in design, materials and installation. There are safety networks on the boardall adopted from existing control networkswith safety functions added on through extended system architecture and hardware. The evolution of the safety bus networks has spurred new developments in intelligent safety devices with improved diagnostics.
One requirement for these new devices is that they are easy to use much like the old on/off switch. With reduced plant personnel, the devices should be easy to commission and easy to troubleshoot. The products that follow are a sample of safety devices on the market today that can reduce risks to men, machines and the environment.
Just Stop It
Family of emergency stop (e-stop) switches with integrated Safety at Work (SaW) functionality is anchored by the AS-Interface and mounts in field or panel-mount applications. Both are available in high-intensity, wide-angle, illuminated versions, as well as non-illuminated versions. The field-mountable version eliminates all wiring to eliminate the possibility of incorrectly wiring the e-stop switch.
Pepperl + Fuchs
Series S900 tensioning device works with the companys family of emergency cable-pull wire switch installation accessories. It is designed to speed the installation of emergency-pull switches by replacing the turnbuckle and most of the wire clamps. The device has an onboard wire clamp and an anti-slip design to minimize the need for readjustments.
More Than Just On/Off
SM enabling switch is a single-handed pendant station that complies with safety standards NFPA 79, ANSI/RIA R15.06-19999 for industrial robots and robot systems, ANSI B11, European Machinery Directive and Canadian Safety Standards. It has two-position (off-on or dead-man switch) and three-position (off-on-off or live-man switch) versions. There also is a vibratory feedback and key selector switch. The switch can be configured to include LED displays, a mini joystick, a key-operated switch and more.
UL 508-listed Square D MD50 motor disconnect switch provides safe and quick power connections in industrial facilities and prevents process interruption by cutting power to a motor if necessary, while not affecting the main circuit. IEC 60309-compliant technology helps the Square D brand MD50 increase safety on a plant floor by making it virtually impossible to plug in a power receptacle having different voltage and ampere ratings, while a mechanical interlock forces an operator to insert a plug before power can be turned on and to turn power off before the plug can be removed.
D4JL IP67-rated, locking safety door switches provide holding force of 3,000 N (674 lb) for safely locking heavy doors. Two safety circuits and two monitor contacts provide an array of monitoring patterns including monitoring the open/closed status of the door and the status of the lock. Models are available with rear release buttons that allow workers to unlock the switch inside the protected area and exit the hazardous areas.
Omron Scientific Technologies
Signal50 50-mm, CE-compliant warning tower lights indicate when a particular defined action should be initiated. Choose from 100 combinations of lenses, voltages and illumination types including incandescent, LED, strobe, flashing and more.
C4000 Select safety light curtain lets users use DIP switches for configuration. It has an integrated laser alignment tool, diagnostics and can cascade three C4000 Select pairs or S300/S3000 safety laser scanners. Designed for point-of-operation safeguarding, it also can be used for perimeter and area guarding applications.
Smart Safety Net (SSN) is a data bus for safety systems to reduce wiring. Users dont need to replace devices such as safety relays installed in the various machines partsthey can connect single safety relays to each other through the SSN network, which also makes it possible to build safety groups. It is possible to turn off one part of a facility or cell to carry out maintenance, while the rest of the manufacturing is maintained.
Operator On Guard
Guardmaster GuardShield PAC safety light curtain provides functional safety where a Type 4 safety device is sufficient, including palletizing systems, robotic weld cells, spray booths, automatic process machines, shrink wrap machines and automated assembly lines. It allows products to pass through its sensing field but will stop the machine if an operator is detected in the sensing field.
SafetyEye camera-based system for three-dimensional monitoring and guarding contains a sensing device with grey scale cameras to give 3D coverage and a control unit that evaluates software-defined zones for safeguarding people from hazardous operations. If a person enters a warning zone, an alarm is sounded and the hazardous machinery is slowed down; if the detection zone is entered, the machinery is brought to an immediate standstill.
Pilz Automation Safety
Swinging Door Safety
SI-HG63 Series hinge safety interlock switches offer NC safety contacts. When the hinge switch is activated, these NC safety contacts are forced open by a non-resilient, mechanical means, interrupting the electrical circuit and sending a stop signal to the machine control.
KL6904 TwinSafe bus terminal contains a safety-rated controller, four safety-rated outputs and interfaces with Profibus and EtherCat. KL1904 has four digital inputs with potential-free contacts rated at 24 Vdc. KL2904 has four 24 Vdc digital outputs rated at 0.5 A. If more safety I/O points need to be controlled, multiple KL1904s can be used to handle up to 4,000 I/O points.
LazerSafe LZS-003-HS safeguarding system developed for hydraulic press brakes makes complex bends with a minimum of settings while maintaining press speeds. Two flat bands of 40-mm-wide laser light continuously monitor the zone below the punch. It can detect obstructions to 4 mm, while remaining tolerant to inherent vibration.
Honeywell Wintriss Controls
Reduce ARC_Flash Hazards
Quik-Spec safety switch uses IP-20 finger-safe CubeFuse integration which has current-limiting Class J performance to reduce dangerous arc-flash hazards, both in energy and incident levels. The flange operated handle is easy to operate with electrical gloves and is lockable with up to three padlocks to protect maintenance workers.
Sirius 3TK28 safety relays from Siemens Energy & Automation are used whenever shutdown is required in dangerous situations. Permanent function monitoring and low-wear operations promise a higher reliability and increased electrical lifetime. The safety relays with DIP switches on the front facilitate configuration of up to eight parameters.
Siemens Energy & Automation