I urge experts to clarify the alarm values and interlock values!
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I’m asking the experts: regarding the control of operating conditions during the process, we have high and low alarm values, as well as interlocks. There are also high-high and low-low alarms, but the values for high-high and low-low alarms are generally set to be the same as those for the interlocks. Is there any clear regulation specifying the boundaries between these high-high/low-low alarm values and the interlock values? What’s the relationship between SOL and COL? Is it greater or greater than or equal to?
Different design institutes use different notation methods; in some, HH LL denotes the interlock value, while in others, the symbol S is used to indicate the interlock value. When HH LL matches the interlock value, it can be regarded as an interlock value rather than an alarm value. In this case, when HH LL is triggered, the interlock system has already responded; the DCS interface merely provides an alarm alert, but the operator does not have time to take action, so it is not considered an alarm value
There is no explicit specification; it is mainly determined based on the process parameters in your production