Safety Integrity Levels - Hip or Hype?

Yesterday I attended a seminar on "Safety Integrity - Life cycle approach", organised by ISA at IIT, Madras.The IEC 61508 and 61511 standards were discussed. Having interacted with many users, I think the problem with the safety integrity approach lies somewhere between hip and hype. When I mean hip, many users think that just be implementing a SIL 3 capable system, everything will be hunky dory. Not so! It requires a lot of operations and maintenance inputs throughout the life cycle of the system to ensure that it maintains its reliability. While instrument manufacturers often tend to go overboard to sell their ides to the client and engineering, procurement and construction companies also tend to recommend such systems to their clients, ultimately it is the the client who has to decide what level of risk is he prepared to take and whether existing instruments will be sufficient, without going in for a detailed SIL study. Unfortunately many clients do not have the technical support requires to make such decisions and rely on the designer. I go back to the analogy I had given in my earlier posts - We had operated a pneumatic controlled ammonia plant (no DCS, no smart transmitters, no fieldbus, no HART) quite successfully in the eighties for over a decade without an instrument failure that caused a spurious trip or fail dangerous undetected state. The answer to the question whether safety integrity is Hip or Hype lies in the understanding of risks by the client and is solely based on his decision. So the answer lies inbetween!!