FORD W-EL4

Description / Abstract: FORD W-EL4, 2001 Edition, October 11, 2001 - LIGHT CURTAINS AND PRESENCE-SENSING DEVICES FOR MACHINE SAFEGUARDING

This Standard describes Safety Light Curtains (light curtains), which are "control reliable" electronic safety devices actuated by sensing presence, and their associated interfaces. This Standard includes using such a device to either stop the machine, or to start the machine cycle automatically when the operator and other persons have left the protected area and the machine cycle can be safely initiated. In both cases the light curtain serves as a primary safeguarding device.

Light curtains should not be confused with simple photoelectric sensors which are designed for different applications and which can be adversely affected by various environmental conditions. Light curtains are built with self-checking electronics for as close to a "fail-safe" operation as achievable. This means that (referring to ANSI B11.19 item 5.5.1):

"When required by the performance requirements of safeguarding, 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."

NOTE: In the United States, selection and application of safeguarding systems is provided in the appropriate ANSI B11 Safety Standard for the particular type of machine tool and shall take precedence over this standard.