Standard s

A Safer Workplace

Automation continues to create hazards for employees in theworkplace, making their safety a major concern for manufacturers worldwide. This concern has led to the creation of OSHA guidelines, ANSI standards, semiconductor and robotics standards and the European Machinery Safety Directive.

OSHA Guidelines

Section 1910.12 states:(a) Machine guarding — (1) Types of guarding. One or more methodsof machine guarding shall be provided to protect the operator and other employees in the machine area from hazards such as those created by point of operation, ingoing nip points, rotating parts, flying chips and sparks. Examples of guarding methods are — barrier guards, two-hand tripping devices, electronic safety devices, etc.(2) General requirements for machine guards. Guards shall be affixedto the machine where possible and secured elsewhere if for any reason attachment to the machine is not possible. The guard shall be such that it does not offer an accident hazard in itself. E5.5 Control reliability is also known as control component failureand is not merely component redundancy. Control reliability implies “fail-safe”. However, failsafe is an order of reliability which includes any and all possible component failure combinations including multiple and simultaneous. Thus, a true fail-safe condition and this magnitude of reliability are not practically achievable.In its section B11.19-1990, ANSI states: “A component may fail open, closed or to the point that its intendedfunction is no longer viable. All failures should be considered in the evaluation of the system.Some electromechanical systems utilize relays that have contacts thatcan fail closed while the other contacts on the same relay continue to function. Other relays have contacts that can fail open while the other contacts on the same relay continue to function. Because of this fact, only relay types that prevent this occurrence from happening should be used.

ANSI Standards

ANSI (the American National Standard) B11.19-1990 Section 5.5, E5.5, and E5.51 reads: 5.5.1 When required by the performance requirements of thesafeguarding, the device, system or interface shall be designed, constructed and installed such that a single component failure within the device, interface or system shall not prevent normal stopping action from taking place but shall prevent a successive machine cycle. This requirement does not apply to those components whose function does not affect the safe operation of the machine tool.

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