Banner EZ-SCREEN Low-Profile Safety Light Curtain Systems - Manual (Page 39)

P/N 1334
37
Banner Engineering Corp. • Minneapolis, U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
Overview
P/N 140044 rev. E 37
Banner Engineering Corp. • Minneapolis, U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
EZ-SCREEN LP
Instruction Manual Installation and Alignment
The principle of fault exclusion allows the designer to design
out the possibility of various failures and justify it through the
risk assessment process to meet the required level of safety
performance, such as the requirements of Category 2, 3 or 4.
See ISO 13849-1/-2 for further information.
External Device Monitoring
EZ-SCREEN LP provides three possible EDM configurations:
1-channel monitoring, 2-channel monitoring, and no monitoring.
Their functions are described below. The most common form
of EDM is 1-channel monitoring; its primary advantages are
simplicity of wiring and the ability to use the Auxiliary output.
The installation must prevent short circuits across the N.C.
monitoring contacts and to secondary sources of power.
Two-channel monitoring has the ability to detect additional
failures, such as short circuits, and should be used when those
failures can not be designed out or reasonably be excluded.
Two-channel monitoring is also the default setting and has the
advantage of additional diagnostic capability that can identify
which specific element that has slowed or failed.
3.5.3 Machine Primary Control Elements and EDM Inputs
A machine primary control element (MPCE) is an “electrically
powered element that directly controls the normal operation of
a machine in such a way that it is the last element (in time) to
function when machine operation is to be initiated or arrested”
(per IEC61496-1). Examples include motor contactors, clutch/
brakes, valves, and solenoids.
Depending on the level of risk of harm, it may be required to
provide redundant MPCEs or other control devices that are
capable of immediately stopping the dangerous machine motion,
irrespective of the state of the other. These two machine control
channels need not be identical (i.e., diverse redundant), but the
stop time performance of the machine (Ts, used to calculate the
safety distance, see Section 3.1.1) must take into account the
slower of the two channels. Refer to Figure 3-26 or consult the
machine manufacturer for additional information.
To ensure that an accumulation of failures does not compromise
the redundant control scheme (i.e., cause a failure to danger)
a method to verify the normal functioning of MPCEs or
other control devices is required. EZ-SCREEN LP provides
a convenient method for this verification: external device
monitoring (EDM).
For the EZ-SCREEN LP external device monitoring to function
properly, each device must include a normally closed (N.C.),
forced-guided (mechanically linked) contact that can accurately
reflect the status of the device. This ensures that the normally
open contacts, used for controlling hazardous motion, have a
positive relationship with the normally closed monitoring contacts
and can detect a failure to danger (e.g., contacts that welded
closed or stuck ON).
It is strongly recommended that a normally closed, forced-guided
monitoring contact of each FSD and MPCE be connected to
EDM inputs (see Figures 3-24 and 3-26). If this is done, proper
operation will be verified. Monitoring FSD and MPCE contacts is
one method of maintaining control reliability (OSHA/ANSI) and
Category 3 and 4 (ISO13849-1).
If monitoring contacts are not available or do not meet the
design requirement of being forced-guided (mechanically linked),
it is recommended to:
• Replace the devices so that they are capable of being
monitored,
or
• Incorporate the EDM function into the circuit as close to the
MPCE as possible (e.g., monitor the FSDs),
and
• Employ use of well-tried, tested, and robust components, and
generally accepted safety principles, including fault exclusion,
into the design and installation to either eliminate, or reduce
to an acceptable (minimal) level of risk, the possibility of
undetected faults or failures that can result in the loss of the
safety function.
Safety Output
Closed
Open
OFF
ON
EDM Don’t Care Don’t Care Don’t Care Don’t Care
250 ms
Max.
250 ms
Max.
Safety Output
250 ms
Max.
250 ms
Max.
250 ms
Max.
250 ms
Max.
Don’t Care
Closed
Open
Closed
Open
EDM 1
EDM 2
Figure 3-19. One-channel EDM status, with respect to safety
output
Figure 3-20. Two-channel EDM, timing between channels
Figure 3-21. Two-channel EDM status, with respect to safety
output
Safety Output
Closed
Open
Closed
Open
OFF
ON
EDM 1
EDM 2 Must Match EDM 1 Must Match EDM 1
Must Match EDM 2 Must Match EDM 2
Must Match EDM 1 Must Match EDM 1
Must Match EDM 2 Must Match EDM 2
WARNING . . .
EDM Monitoring
If system is configured for “No Monitoring,” it is the user’s
responsibility to ensure that this does not create a hazardous
situation.