Typically, safety stop circuits are a series connection of at least two N.O. contacts coming from two separate, positive-
guided relays, each controlled by one separate safety output of the Safety Controller. The safety function relies on the use
of redundant contacts to control a single hazard, so that if one contact fails On, the second contact stops the hazard and
prevents the next cycle from occurring.
Interfacing safety stop circuits must be wired so that the safety function cannot be suspended, overridden, or defeated,
unless accomplished in a manner at the same or greater degree of safety as the machine’s safety-related control system
that includes the Safety Controller.
The normally open outputs from an interfacing module are a series connection of redundant contacts that form safety stop
circuits and can be used in either single-channel or dual-channel control methods.
Dual-Channel Control—Dual-channel (or two-channel) control has the ability to electrically extend the safe switching point
beyond the FSD contacts. With proper monitoring, such as EDM, this method of interfacing is capable of detecting certain
failures in the control wiring between the safety stop circuit and the MPCEs. These failures include a short-circuit of one
channel to a secondary source of energy or voltage, or the loss of the switching action of one of the FSD outputs, which
may lead to the loss of redundancy or a complete loss of safety if not detected and corrected.
The possibility of a wiring failure increases as the physical distance between the FSD safety stop circuits and the MPCEs
increase, as the length or the routing of the interconnecting wires increases, or if the FSD safety stop circuits and the
MPCEs are located in different enclosures. Thus, dual-channel control with EDM monitoring should be used in any
installation where the FSDs are located remotely from the MPCEs.
Single-Channel Control—Single-channel (or one-channel) control uses a series connection of FSD contacts to form a safe
switching point. After this point in the machine’s safety-related control system, failures that would result in the loss of the
safety function can occur, for example, a short-circuit to a secondary source of energy or voltage.
Thus, this method of interfacing should be used only in installations where FSD safety stop circuits and the MPCEs are
physically located 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 two-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
• Routing interconnecting control wires with low voltage or neutral that cannot result in energizing the hazard
• Locating all elements (modules, switches, devices under control, etc.) within the same control panel, adjacent to
each other, and directly connected with short wires
• Properly installing multi-conductor cabling and multiple wires that pass 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
WARNING:
• Properly install arc or transient suppressors
• Failure to follow these instructions could result in serious injury or death.
• Install any suppressors as shown across the coils of the FSDs or MPCEs. Do not install
suppressors directly across the contacts of the FSDs or MPCEs. In such a configuration, it is
possible for suppressors to fail as a short circuit.
WARNING: Safety Output Interfacing
To ensure proper operation, the Banner product output parameters and machine input parameters must
be considered when interfacing the solid state safety outputs to the machine inputs. Machine control
circuitry must be designed so that:
• The maximum cable resistance value between the Safety Controller solid-state safety outputs
and the machine inputs is not exceeded
• The Safety Controller’s solid-state safety output maximum Off state voltage does not result in an
On condition
• The Safety Controller’s solid-state safety output maximum leakage current, due to the loss of 0 V,
does not result in an On condition
Failure to properly interface the safety outputs to the guarded machine may result in serious bodily injury
or death.
XS/SC26-2 and SC10-2 Safety Controllers
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