Is Triconex right about safety systems?

Bob Adamski, from Invensys PCS (and formerly from ExxonMobil) and Luis Duran from Invensys Triconex visited our offices yesterday, and of course the discussion centered around the question of how to meet ISA84 and the IEC standards on functional safety.layers of protection Of course, it is Bob's position, and Triconex' position that integrating an SIS with a BPCS (Basic Process Control System) removes one of the fundamental layers of protection inherent in separate systems. "People seem to have forgotten," Adamski said, "that we've been integrating safety systems into control systems for years." Duran noted that the latest Triconex hardware and software is capable of integration at a higher level with the HMI, and serves the same purpose as a BPCS that also does safety, but without the loss in layers of protection that, he claimed, inevitably results. I asked Duran if people were buying this argument, and he said, "I don't know if they are buying the argument, but I can tell you that we are experiencing unprecedented growth, faster growth than the market." So, is Triconex right?