Machine Primary Control Elements And External Device Monitoring - Banner SX5 Instruction Manual

SX5 Safety Laser Scanner
For this reason, single-channel control interfacing should be used only in installations where FSD safety stop circuits and
the MPCEs are mounted within the same control panel, adjacent to each other, and are directly connected to each other; or
where the possibility of such a failure can be excluded. If this cannot be achieved, then dual-channel control should be
used.
Methods to exclude the possibility of these failures include, but are not limited to:
• Physically separating interconnecting control wires from each other and from secondary sources of power.
• Routing interconnecting control wires in separate conduit, runs, or channels.
• Locating all elements (modules, switches, and devices under control) within one control panel, adjacent to each
other, and directly connected with short wires.
• Properly installing multi-conductor cabling and multiple wires through strain relief fittings. (Over-tightening of a
strain-relief can cause short-circuits at that point.)
• Using positive-opening or direct-drive components, installed and mounted in a positive mode.
4.3.3 Machine Primary Control Elements and External Device
Monitoring
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 (they could also be diverse redundant), but the stop time performance of the
machine (Ts, used to calculate the safety distance, see
take into account the slower of the two channels. See
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. The Scanner provides this
function only when configured for manual start/restart (reset) with MPCE monitoring contacts wired in series with the reset
(start/restart) switch as shown in
When the SX5 is configured for Automatic Start/Restart (Reset), to properly monitor the MPCEs an External Device
Monitoring (EDM) function must be provided by an external means from the Scanner. One example using the UM-
FA-9A/-11A safety Module is shown in
manual or automatic reset and provide the required EDM function.
For 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
Wiring Diagrams
to EDM inputs (see
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.
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.
WARNING:
• Notice Regarding MPCEs
• Failure to follow these instructions could result in serious injury or death.
• Each of the machine primary control elements (MPCE1 and MPCE2) must be capable of
immediately stopping the dangerous machine motion, regardless of the state of the other. The
two machine control channels need not be identical, but the machine's stop time performance
(TS, used to calculate separation distance) must be based on the slower of the two channels.
44
Minimum Safety (Separation) Distance Formula
Wiring Diagrams
Wiring Diagrams
on page 46 (see also
Wiring Diagrams
on page 46. The UM-FA-9A/-11A can be configured for both
on page 46). If this is done, proper operation will be verified. Monitoring FSD and
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on page 46
Reset Switch Location
on page 32).
on page 30) must