Page 12 - MetalForming December 2009

SafetyUpdate A Checklist for Installing Safety Light Curtains
Information provided by Mike Carlson, safety products marketing manager, Banner Engineering; www.bannerengineering.com.
Installed near a press, robotic cell or other piece of manufacturing equip- ment, a safety light curtain detects the presence of an opaque object such as a finger or hand and sends a stop signal to the safety-related controls of the machine to stop the hazardous motion before the person can reach the hazard. Light curtains must be installed between the machine hazard and all personnel, in accordance with requirements speci- fied in accepted standards. Metalform- ers installing light curtains should:
1) Review procedures and manuals, including the light-curtain installation manual and the company’s procedures for performing work on the particular machine being safeguarded.
2) Identify the hazard or hazardous area to be guarded, ensuring that addi- tional hazards have not been overlooked.
3) Determine the separation (safety) distance, where the sensing field is no closer to the hazard than the deter- mined distance, as described in the installation manual. Generally, the sens- ing field should not be less than 4 in. from the hazard and typically is more than 12 in. away.
4) Ensure the hazards cannot be accessed by reaching over, under, around or through the sensing field; additional guarding may be required.
5) If the safety light curtain or inter- face to the machine control is configured for a manual reset, ensure the switch or the means to perform the reset is outside the guarded area, located to allow the switch operator unobstructed view of the entire guarded area, out of reach from within the guarded area and protected against unauthorized or inadvertent oper- ation. If any areas within the guarded area are not visible from the reset, provide additional safeguarding.
When mounting the light curtains,
installers should
ensure that the
mounting surface
can support the
weight of the
sensors, brack-
ets, cables and
hardware. Mount
the emitter and
receiver so that
the sensing field
is no closer to
the hazard than
is determined by
the safety dis-
tance, and
ensure they are
aligned in a com-
mon plane and
level/plumb and
square to each
other (vertical,
horizontal or inclined at the same angle and not tilted front-to-back or side-to- side). Avoid locating the sensing field near a reflective surface, which could reflect sensing beams around an object or per- son and prevent its detection.
Attach the required cables to the sensors and route the sensor cables to the junction box, electrical panel or other enclosure housing the safety com- ponents of the control system. Ensure that power is not available to the actu- ators or any other device that can cause a hazard prior to making any electrical connections to the machine. Then set configuration options—depending on the model, some options may have been previously set; refer to the installation manual. Make initial electrical connec- tions as detailed in the installation manual; do not connect the safety out- puts until performing the initial alignment and checkout procedures.
Apply power to the safety light cur- tain and make final optical-alignment adjustments as described in the instal- lation manual. To ensure the sensors are pointed squarely at each other, use a straight edge to determine the direction
the sensor is facing. The sensor face must be perpendicular to the optical axis. Once the indicator(s) verify a clear or aligned condition (usually a green light), snug, but do not tighten down the mounting hardware. To optimize align- ment and maximize excess gain, slight- ly loosen the sensor mounting screws and rotate one sensor left and right, noting the positions in each arc where the indicator(s) verify a blocked condition (usually a red light); repeat with the other sensor. Center each sensor between those two positions and tighten the mounting screws while maintaining the positioning.
When alignment proves difficult, use laser-alignment tools to assist or confirm alignment by providing a visible red dot along the sensor’s optical axis. When using mirrors to align an installation, all sensors and mirrors must be level/plumb, and the height of the midpoints of the mirrors above the floor (assuming a level floor) should be at the midpoint of the sensing field. Only one individual should move any one device at any one time.
Test the detection capability by per- forming a trip-test procedure with the
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