AADvance Safety Manual - Tuv-fs.com

Chapter 4 AADvance System ArchitecturesSIL2 Fault Tolerant Input and High Demand ArchitectureA SIL2 fault tolerant I/O architecture or High Demand architecture has dual input, dualprocessor and dual output modules. In a dual arrangement the input modules operatein 1oo2D under no fault conditions, degrade to 1oo1D on the detection of the firstfault in either module, and will fail-safe when there are faults on both modules.A triple input module arrangement can also be configured if it is required to increasethe fault tolerance of the input. When a triple input module arrangement is configuredthe input modules operate in a 2oo3D under no fault conditions, degrade to 1oo2D ondetection of the first fault in any module, then degrade to 1oo1D on the detection offaults in any two modules, and will fail-safe when there are faults on all three modules.The processor will operate in 1oo2D under non-faulted conditions and will degrade to1oo1D on the first detected fault. For high demand applications the processor must berepaired within the MTTRFor High Demand applications you must use a minimum of a dualprocessor configuration.For de-energize to trip operation, the output modules operate in 2oo2D under nofault conditions, degrade to 1oo1D on the detection of the first fault in either module,and fail-safe when there are faults on both modules. For energize to action operationthe output modules operate in 1oo2D under no fault conditions, degrade to 1oo1D onthe detection of the first fault in either module, and will fail-safe when there are faultson both modules. For both requirements the output module must be repaired orremoved within the MTTR.Document number 553630 Issue 7: February 2010 4-5