9.1 Bypass and Mute-Dependent Override
"Overriding" or "Bypassing" a safeguarding device is the manual interruption or suspension of the normal function of a
safeguard under supervisory control. Typically, an Override/Bypass is needed to clear an object that is "stuck" within the
light curtain defined area, such as on an entry/exit application.
Overriding or bypassing a safeguarding device should not be confused with "muting," which is the temporary, automatic
suspension of the safeguarding function of a safeguarding device during a non-hazardous portion of the machine cycle.
Muting allows for material to be manually or automatically fed into a machine or process without issuing a stop command.
Another term commonly confused with bypassing is "blanking," which desensitizes a portion of the sensing field of an
optical safeguarding device (e.g., disabling one or more beams of a safety light curtain so that a specific beam break is
ignored).
When Override or Bypass is used, the following precautions must be taken:
• Prevent exposure to any hazard during an Override/Bypass; supplemental safeguarding must be provided per ANSI
B11.19, ANSI NFPA79, IEC/EN60204-1, and ISO13849-1
• The means of overriding/bypassing and visual indication must be provided and be readily observable from the
location of the safeguard
• The reset, actuation, clearing, or enabling of the safeguarding device must not initiate hazardous motion or create a
hazardous situation
The Override/Bypass switches must be supervised and must prevent automatic operation. This function requires
complementary inputs; one normally open switch connected to the Reset/OR1 input (violet wire, pin 12) and one normally
closed switch connected to the ME/OR2 input (pink wire, pin 6). Also, one or more of the following must be true:
• Motion should be initiated by a hold-to-run or similar device
• If a portable control station, for example, an enabling device, with an emergency stop device is used, motion may be
initiated only from that station. All emergency stops must remain active.
• Automatic machine operation must be prevented by limiting range of motion, speed, or power, for example used
only in inch, jog, or slow speed modes)
Mute-Dependent Override function (mute configuration option 5, 6, and 7) allows the user to manually force the OSSD
outputs On for up to 60 seconds. To initiate an override, the light curtain defined area must be blocked with the OSSD
outputs Off, and at least one mute device must be blocked. When the conditions for an override are met, the external mute
lamp will flash. At this time, the normally open switch on Reset/OR1 must close, and the normally closed switch on ME/OR2
must open within 3 seconds of each other. If these requirements are met, the external mute lamp will turn ON steady to
indicate an override has occurred and the OSSDs will be On.
Bypass function (mute configuration options 3, 4 and 8) allows the user to manually force the OSSD outputs On for up to 5
minutes. To initiate a bypass, the light curtain cannot be in Lockout (fault) state, the normally open switch on Reset/OR1
must close, and the normally closed switch on ME/OR2 must open within 3 seconds of each other. If these requirements
are met, the external mute lamp will turn On to indicate a bypass has occurred and the OSSDs will be On.
WARNING: Limit Use of Bypass and Override Function
The Bypass and Override functions are not intended for production purposes; they are to be used only
for temporary or intermittent actions, such as to clear the sensing field of a safety light screen if material
becomes "stuck". When used, it is the user's responsibility to install and use it according to relevant
standards (such as ANSI NFPA79 or IEC/EN60204-1).
EZ-SCREEN Low-Profile System with Integral Muting
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