3.6 Reducing or Eliminating Pass-Through Hazards
A
pass-through
hazard is associated with applications where personnel may pass through a safeguard, such as the SX
Series Safety Laser Scanner (which issues a stop command to remove the hazard), and then continues into the guarded
area. This is common in access and perimeter guarding applications. Subsequently, their presence is no longer detected,
and the related danger becomes the unexpected start or restart of the machine while personnel are within the guarded area.
A pass-through hazard typically results from large safety distances calculated from long stopping times, large minimum
object sensitivities, reach-over, reach-through, or other installation considerations. A pass-through hazard can be generated
with as little as 75 mm (3 in) between the sensing field and the machine frame or hard (fixed) guarding.
Eliminate or reduce pass-through hazards whenever possible. While it is recommended to eliminate the pass-through hazard
altogether, this may not be possible due to machine layout, machine capabilities, or other application considerations.
One solution is to ensure that personnel are continually sensed while within the hazardous area. This can be accomplished
by using supplemental safeguarding, such as described by the safety requirements in ANSI B11.19 or other appropriate
standards.
An alternative method is to ensure that once the safeguarding device is tripped it will latch and will require a deliberate
manual action to reset. This method of safeguarding relies upon the location of the reset switch as well as safe work
practices and procedures to prevent an unexpected start or restart of the guarded machine. The SX Series Safety Laser
Scanner provides a configurable Manual Start/Restart (Latch Output) function for these applications.
WARNING:
•
Use of the Banner device for Access or Perimeter Guarding
•
Failure to observe this warning could result in serious injury or death.
•
If a Banner device is installed in an application that results in a pass-through hazard (for example,
perimeter guarding), either the Banner device or the Machine Primary Control Elements (MPCEs)
of the guarded machine must cause a Latched response following an interruption of the defined
area.
•
The reset of this Latched condition may only be achieved by actuating a reset switch that is
separate from the normal means of machine cycle initiation.
WARNING:
•
Perimeter guarding applications
•
Failure to observe this warning could result in serious injury or death.
•
Use lockout/tagout procedures per ANSI Z244.1, or use additional safeguarding as described by
ANSI B11.19 safety requirements or other applicable standards if a passthrough hazard cannot be
eliminated or reduced to an acceptable level of risk.
3.7 Reset Switch Location
Mount the reset switch at a location that complies with the warning and guidelines below.
If any hazardous areas are
not in view from the switch location, additional means of safeguarding must be provided. The switch should be protected from
accidental or unintended actuation (for example, through the use of rings or guards).
A key-actuated reset switch provides some operator or supervisory control, as the key can be removed from the switch and
taken into the guarded area. However, this does not prevent unauthorized or inadvertent resets due to spare keys in the
possession of others, or additional personnel entering the guarded area unnoticed. When considering where to locate the
reset switch, follow the guidelines below.
WARNING: Reset Switch Location
When considering where to locate the reset switch, you must follow the guidelines outlined in this section.
If any areas within the guarded area are not visible from the reset switch, additional safeguarding must be
provided, as described by the ANSI B11.19 series or other appropriate standards.
Failure to follow these instructions could result in serious injury or death.
All reset switches must be:
•
Outside the guarded area
•
Located to allow the switch operator a full, unobstructed, view of the entire guarded area while the reset is performed
•
Out of reach from within the guarded area
•
Protected against unauthorized or inadvertent operation (such as through the use of rings or guards).
SX Safety Laser Scanner
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