Banner SLLVE23-350 Instruction Manual

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each other, and are directly connected to each other; or where the possibility of such a failure can be excluded. If thiscannot 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 eachother, and directly connected with short wires• Properly installing multi-conductor cabling and multiple wires through strain relief fittings. Over-tightening of astrain-relief can cause short-circuits at that point.• Using positive-opening or direct-drive components, installed and mounted in a positive mode6.4.3 Machine Primary Control Elements and EDM InputA machine primary control element (MPCE) is an electrically powered element that directly controls the normal operation ofa 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 IEC 61496-1). 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 arecapable of immediately stopping the dangerous machine motion, irrespective of the state of the other. These two machinecontrol channels need not be identical (diverse redundant), but the stop time performance of the machine (Ts, used tocalculate the safety distance, seeCalculating the Safety Distance (Minimum Distance) on page 20) must take into accountthe slower of the two channels. Consult the machine manufacturer for additional information.To ensure that an accumulation of failures does not compromise the redundant control scheme (cause a failure to danger),a method to verify the normal functioning of MPCEs or other control devices is required. EZ-SCREEN LS Basic provides aconvenient method for this verification: external device monitoring (EDM).For the EZ-SCREEN LS Basic external device monitoring to function properly, each device must include a normally closed,forced-guided (mechanically linked) contact that can accurately reflect the status of the device. This ensures that thenormally open contacts, used for controlling hazardous motion, have a positive relationship with the normally closedmonitoring contacts and can detect a failure to danger (for example, contacts that are welded closed or stuck On).It is strongly recommended that a normally closed, forced-guided monitoring contact of each FSD and MPCE be connectedin series with the EDM input (seeGeneric Wiring Diagram—8-pin Receiver and IM-T-9A Interface Module on page 48 ). Ifthis is done, proper operation will be verified. Monitoring FSD and MPCE contacts is one method of maintaining controlreliability (OSHA/ANSI) and Category 3 and 4 (ISO 13849-1).If monitoring contacts are not available or do not meet the design requirement of being forced-guided (mechanically linked),it is recommended you:• 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 (for example, monitor the FSDs); and• Employ the use of well-tried, tested, and robust components, and generally accepted safety principles, includingfault 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 therisk 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: EDM Monitoring. If the System is configured for “No Monitoring,” it is the user’s responsibility to ensurethat this does not create a hazardous situation. Failure to follow these instructions could result in serious injury ordeath.6.4.4 External Device MonitoringEZ-SCREEN LS Basic provides two possible EDM configurations: 1-channel monitoring and no monitoring. Their functionsare described below. The most common form of EDM is 1-channel monitoring; its primary advantages is the simplicity ofwiring. The installation must prevent short circuits across the N.C. monitoring contacts and to secondary sources of power.Safety OutputClosedOpenOFFONEDM Don’t CareDon’t CareDon’t CareDon’t Care250 msMax.250 msMax.250 msMax.Figure 26. One-channel EDM status, with respect to safety outputEZ-SCREEN® LS Basic Safety Light Screenwww.bannerengineering.com - Tel: 763.544.3164 41