Banner SC22-3E Safety Controller with Ethernet - Manual (Page 114)

2x Complementary (PNP device): This circuit can meet ISO
13849-1 category3 or category 4 requirements depending on the
design and installation of the enabling device. This circuit can de-
tect a short circuit between channels. In the actuated condition
(e.g., S1 OFF/S2 ON) a short across the closed contact can cause
the response time to increase based on the debounce time. In this
situation, the response time could be longer than specified, based
on the (selected) debounce time, see section
4.3.2 Safety Input
Device Properties on page 28.
ON OFF ON OFF
S1 S2
10.10 Bypass Switches (Bypassing Safeguards)
The Safety Controller may be used to monitor switches that initiate the bypassing of a safeguarding device.
“Bypassing” or “overriding” a safeguarding device is the manual interruption or suspension of the normal function of a safeguard under
supervisory control. It is typically accomplished by selecting a bypass mode of operation using a key switch to facilitate machine setup,
web alignment/adjustments, robot teach, and process troubleshooting.
See section 4.6.5 Bypass Function on page 38 for more information.
10.10.1 Requirements of Bypassing Safeguards
Requirements to bypass a safeguarding device include*:
• The bypass function must be temporary.
• The means of selecting or enabling the bypass must be capable of being supervised.
• Automatic machine operation must be prevented by limiting range of motion, speed, or power (e.g., only used in inch, jog, or slow-
speed modes). Bypass mode must not be used for production.
• Supplemental safeguarding must be provided. Personnel must not be exposed to hazards.
• The means of bypassing must be within full view of the safeguard to be bypassed.
• Initiation of motion should only be through a hold-to-run type of control.
• All emergency stops must remain active.
• The means of bypassing must be employed at the same level of reliability as the safeguard.
• Visual indication that the safeguarding device has been bypassed must be provided and be readily observable from the location of
the safeguard.
• Personnel must be trained in the use of the safeguard and in the use of the bypass.
• Risk assessment and risk reduction (per the relevant standard) must be accomplished.
• The reset, actuation, clearing, or enabling of the safeguarding device must not initiate hazardous motion or create a hazardous situa-
tion.
* This summary was derived from the following and other sources: ANSI NFPA79, ANSI/RIA R15.06, ISO 13849-1 (EN954-1),
IEC60204-1, ANSI B11.19
Bypassing a safeguarding device should not be confused with “muting,” which is the temporary, automatic suspension of the safeguard-
ing 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 “blank-
ing,” 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).
Safe Working Procedures and Training
The user must also address the possibility that an individual could bypass the safeguarding device and then either fail to reinstate the
safeguarding or fail to notify other personnel of the bypassed condition of the safeguarding device; both cases could result in an unsafe
condition. One possible method to prevent this is to develop a safe work procedure and ensure personnel are trained and correctly follow
the procedure.
SC22-3/-3E Safety Controller Instruction Manual
114 www.bannerengineering.com - tel: 763-544-3164 P/N 133487 rev. C