The meaning of choosing one out of two interlock pressure conditions for the same measurement point
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This post was last edited by Qingse Nianhua on 2019-1-22 at 10:46. I have been looking into a new manufacturing process recently, and I noticed that for many pressure interlock conditions at the same measurement point, the option is either two out of three or one out of two. In my opinion, choosing two out of three can enhance the safety of the instruments and reduce the likelihood of failures. On the other hand, does choosing one out of two increase the probability of instrument failures and raise investment costs, thus yielding poor results? This is just my humble opinion; I hope experts can help analyze it.
Your first half sentence and the second half sentence don’t match! Improving safety and reducing failure rates helps to minimize unexpected shutdowns caused by instrument failures. Is a shutdown really worth the cost of just a small investment in instruments?
Generally, in situations where a choice between two options is required, it is either a place with strict pressure control, or one where it is possible to choose which gauge to use for interlock purposes
A choice between two options isn’t as safe as a choice between three, but it’s still better than a choice between just one option. The specific amount of redundancy required depends on the SIL level of your safety instrument system. The higher the SIL level, the more redundancy is required.
By using a two-out-of-one mechanism, interlock action is triggered as long as one alarm occurs, thereby improving the safety of the system. However, this same two-out-of-one approach increases the likelihood of false alarms leading to interlock actions, which reduces the system’s availability
I also think that in places where safety requirements aren’t very high, such a setting actually reduces the practicality of the system.
The probability of instrument failure has no relation to binary or ternary options; it is determined by the quality of the instrument and the manufacturing conditions. Binary options offer the best safety levels but the worst availability. Among the three options, two have good safety and usability
Therefore, designers must have a thorough understanding of safety and risks; they need to treat them separately and analyze them in context – the worst thing is to apply a one-size-fits-all approach
Agreed; therefore, during the design process it is necessary to communicate as much as possible with the client in order to find a balance between safety and investment. Of course, if it’s a critical location, safety comes first.