Products help with machine safety

A diversity of products help with machine safety. These include emergency-stops, hardguards (such as gates and fences), interlock and enabling switches, non-contact safety interlock switches, perimeter access guarding devices, safe power distribution devices, safety interlock switches, safety laser scanners, safety light curtains, safety limit switches, safety monitoring relays, and safety programmable logic controllers (PLCs), among others.


ABB calls its 'smissline' power distribution bus bar system 'finger safe.'

A diversity of products help with machine safety. These include emergency-stops, hardguards (such as gates and fences), interlock and enabling switches, non-contact safety interlock switches, perimeter access guarding devices, safe power distribution devices, safety interlock switches, safety laser scanners, safety light curtains, safety limit switches, safety monitoring relays, and safety programmable logic controllers (PLCs), among others.

ABB builds finger-safe design into its 'smissline' power distribution bus bar system, which distributes power up to 200 A at 600 V, reducing power wiring by half. Components mount on a DIN rail with a click. Single- and multi-phase devices can be mounted adjacent, on the same system. It's UL and IEC approved.

IDEC 's interlock and enabling switches can provide a secure workplace and meet all major international requirements for large machine operations and robotic construction. Utilized extensively in the robotics industry, the three-position enabling switches fully comply with ANSI and RIA requirements for working with robotic or automated equipment. The OFF-ON-OFF functionality is especially useful in hazardous conditions where operators can stop a machine by either releasing or squeezing the switch.

Two for one: Norstat Isis System combines tamper-resistant safety switches and emergency-stop monitoring in one device.

Keyence Corp. of America says it is the first to market a light curtain design that eliminates "dead zones," creating an edge-to-edge detection zone with the SL-C Series Safety Light Curtain . A new optical design allows light elements be located just 5 mm (0.20 in.) from the edge of a light bar segment, less than finger width. The 15 models offer a range of spaces; controller is built-in; four can be wired together. It complies with ANSI, OSHA, JIS, and IEC Category 4 international safety standards and regulations.

Norstat Isis System combines tamper-resistant safety switches and emergency-stop monitoring in one unit. Isis system achieves 6-mm switching in a compact, tamper resistant, resin-filled ABS plastic or stainless-steel body, with IP67 protection. Available in a range of voltages, it monitors open- and short circuit faults, and provides two NO safety contacts and one NC auxiliary contact. Isis control units can monitor up to two (or four) safety switches, depending on model. The control units also can monitor e-stop buttons or safety switches, combining multiple safety functions into one DIN-rail-mounted unit.

This Pilz Pit emergency stop pushbutton is the turn-to-release style.

Pilz Pnozmulti modular safety system suits safety applications of medium complexity, for 4-14 safety function. With safety configuration software , "you need no special knowledge" to configure e-stop switches, safety doors, light curtains, switch mats, or monitoring two-handed operation, as desired, according to Pilz Automation Safety. Pilz Pit emergency stop pushbutton suits applications up to category 4 under EN 954-1; it also meets IEC/EN 60947-5-5 and EN 418 standards. Designed to IP65, it cannot be wrongly configured, and contact elements cannot be released without detection. The photo shows the turn-to-release style; key-to-release is available.

Rockwell Automation's Allen-Bradley Guardmaster 440P IEC/Safety Limit Switch line combines two lines of limit switches.

Rockwell Automation 's Allen-Bradley Guardmaster 440P IEC/ Safety Limit Switch line combines and enhances existing 802A IEC Limit Switches and 440P Safety Limit Switches into a family competitively priced for OEMs. A 22-mm mounting in a plastic body has positive opening action and two or three circuits. A 30 x 60-mm mounting in a metal body has positive opening action for two or four circuits. Conduit options include M20 or 1/2-in. NPT-style thread options. Both come in seven operator types. Snap-acting contacts with direct opening action meet European Machine Safety Directive and Control Reliable applications. The plug-in body eases wiring and exceeds IP67 and NEMA 6P standards. Applications include machine guards, access gates or doors, cranes or hoists, transfer stations, indexing tables and robotic cells.

Safe-T-Sense makes modular machine hardguards (gates and fences) and safety control products compliant with ANSI, PFPA, and EN standards, and can develop risk assessments according to ANSI Standards project engineering.

Schmersal SLC Series has an integrated safety controller and built-in diagnostics.

Schmersal Category 4 Safety Light Curtains (SLC Series) meet "CE-Compliant Category 4 international standards for Safety Light Curtains," and meet appropriate UL, CSA, and IEC standards. Units are available with 14-mm or 30-mm resolution for protection fields of 160 mm to 1,810 mm. They have range of 18 m and response times as low as 6 ms.

Schneider Electric Telemecanique Preventa Non-Contact Safety Interlock Switches provide non-contact gate or guard interlocking for machine safeguarding. It performs the same functions as standard mechanical safety interlock switches, but is designed to be used where no contact is desired between the switch and its actuating key. Preventa XCS-DM non-contact safety interlock can be used when the stopping time of the hazardous area is shorter than the access time of the operator opening the guard and reaching in. These devices are recommended for applications with little or no shock or vibration, where there is minimal chance of the door or guard opening unintentionally. It comes in three body sizes, including the smallest footprint in the marketplace for Category 4 applications at 0.63 x 2 x 0.28 in. It tolerates gate or guard alignment problems and has a wider temperature range for a plastic-bodied device than any other competitive product. Six approach directions allow for maximum flexibility of mounting options.

Why non-contact?

There are several reasons, according to Schneider Electric, for using a non-contact type of device:

  • Food and beverage and pharmaceutical applications require that no contaminants be trapped in or around devices.

  • Applications demanding zero operating force, such as lightweight or plexiglass doors, where cracking or breakage is possible with standard mechanical safety interlocks. Non-contact devices have no inherent operating force.

  • When there are alignment issues with the switch and actuating keys of mechanical safety interlock switches.

  • Washdown applications where a standard mechanical safety interlock switch would be more difficult to clean, especially in the actuating key receptacle.

Scientific Technologies Inc. (STI) offers the T2007 series miniature safety interlock switch , measuring 75 x 25 x 29 mm, with two sets of contacts and conduit entry. It carries the CE mark, is TÜV approved, and is UL and cUL listed. SR18A safety monitoring relay suits two-hand control, e-stop, and safety guarding applications where five safety outputs are required. SR19E safety-monitoring relay adds eight safety outputs. PA4600 Perimeter Access Guarding Device is a two-box design with no separate control box or cabling needed between transmitter and receiver. It measures 46 x 55 mm and operates with range of up to 70 m; response time as low as 16 ms. The 14-mm and 20-mm resolution versions of MiniSafe MS4600 series light curtains come in standard segmented lengths from 10 in. to 55 in. A 30-mm version is available in segments, 14-83 in. MPCE monitoring, exact channel select, floating blanking, and two PNP safety outputs are among features. [Machine primary control element (MPCE) is the last electrically powered element in the safety-stop circuit that starts or stops the machine's normal operating motion.] DeviceNet or Machine Test Signal is available. It's third-party certified to IEC 61496-1, -2, the international standard on active opto-electric protective devices.

Sick S 3000 safety laser scanner safeguards large work areas, stationary and mobile applications, point of operation, entry/exit, and hazardous work areas. It has resolution between 1.2 in. (30 mm) and 5.9 in. (150 mm) within safety zone radius of 18 ft (5.5 m) or 23 ft (7.0 m). It provides safeguarding for two to three times larger area than any other safety scanner available on the market, according to the company in June. It has been third-party certified to comply with IEC/EN 61508 SIL 2, and safety standard IEC/EN 61496, as a Type 3 safety device, Sick says. It was also designed in compliance with ANSI/RIA 15.06, CSA Z434-03 and ANSI/ASME B56.5. The 190-degree scanning range permits use of one, instead of typically two devices to cover that area. It has four levels of integrated functions and 16 user-definable protection scenarios. The corresponding warning zone radius is up to 160 ft (49 m). Safety and warning zones can be freely defined via Sick's user-friendly Configuration and Diagnostic Software (CDS) tool.

Siemens Simatic S7-400F/FH [ safety PLC ] has a failsafe control system, so immediately enters a safe state when a fault occurs or remains in a safe state thus ensuring maximum safety for man, machine, environment and process. It can also be used as a highly available control system, combining standard operating automation and safety engineering. Networking is performed by standard fieldbuses, such as Profibus-DP, where safety-orientated communication uses the ProfiSafe protocol.

For information from Banner Engineering on the Pico-Guard Fiber Optic Safety Interlock System , click here: '' Fiber-optic safety system replaces switches. ''

System integrators can provide safety-related expertise. To connect, go to Control Engineering Online Automation Integrator Guide (Registration is required).

Control Engineering Buyer's Guide Online , category, safety equipment, offers more than 85 companies; and safety systems, more than 60 companies. (Registration is required.) For more on this topic, read the November Control Engineering cover story 'Reach for Machine Safety' and online extras at Control Engineering Online .

—Mark T. Hoske, Control Engineering, editor in chief,

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