How is the high-level interlock for instruments represented?

HH refers to a high value; it seems to have little to do with choosing among 12 options. The selection is carried out through logical commands, and the operator cannot see this process.

In industrial process control, “H” is commonly used to denote a high-limit alarm (High), while “HH” denotes a high-high limit alarm (High-High). Correspondingly, “L” represents a low-limit alarm (Low), and “LL” represents a low-low limit alarm (Low-Low). Here, you only mentioned the high limit and the very high limit cases, so we don’t need to use “HHH”. Based on the information you provided, the various thresholds can be indicated on the graph as follows: 1. For the temperature alarm threshold of 290 degrees, you can mark “H” next to each temperature measurement point and indicate 290 degrees alongside it, to show that reaching this temperature will trigger a high-limit alarm. 2. For the high-limit interlock value of 300 degrees for a 12-select-3 setup, a “H” can be marked in the diagram, along with the notation “12-select-3”, to indicate that when any 3 out of these 12 temperature measurement points reach 300 degrees, a high-limit interlock action will be triggered. 3. For the high-high limit interlock at 320 degrees, “HH” can be marked on the diagram, with 320 degrees indicated next to it, to show that reaching this temperature at any temperature sensing point will trigger the high-high limit interlock. The illustrations may vary depending on the specific industry and manufacturing processes, but generally, you can create legends to explain the meaning of these abbreviations and symbols, ensuring that users can clearly understand what each symbol represents. It is essential to ensure that these markings are clear and accurate, so that operators or engineers can quickly identify and respond to potential process deviations. In actual P&ID diagrams or control interface designs, it may also be necessary to use colors, sounds, and other visual elements to provide more intuitive alarm alerts. For example, red may be used for visual warning in the case of high or very high limit alarms ； At the same time, some systems also use sound alarms to draw the operator’s attention. .

Well, the requirements for this are quite simple: it involves a 12-to-3 interlock, as well as an interlock that triggers when either one reaches a higher temperature. The first issue now is how to represent interlocking – should we use that diamond shape with “3 of 12” written in it? Secondly, H is used for alarms, and HH is used for 12-out-of-3 interlocks; then, is HHH used for higher-level interlocks?

Because there are 12 temperature measurement points inside the reactor.

Hello, thank you very much for getting back to me. Is this acceptable? Or should we not write HHH? But there is a list of alarm interlocks, and it’s best to have them correspond.

That 290-degree alarm of yours should be an alarm value from the DCS, right? 300 degrees and 320 degrees correspond to high and very high interlocks in the SIS system. Couldn’t you simply distinguish between the DCS and SIS systems in the logic diagram? Why bother using letters to make distinctions? If the DCS and SIS systems are visually distinguished from each other, then you won’t have this problem to worry about.

12 choose 3: is it the one that reaches a 300-degree interlock? Will it still trigger the 320-degree interlock? ?

For 12 choose 3, it is 300 degrees; if either value reaches 320 degrees, there is also an interlock, meaning this temperature corresponds to 12 choose 1.

Since I majored in engineering and don’t work with logic diagrams, I want to express things more clearly using flowcharts

High alarm TIA+ SP=290°C High interlock TIS+ 12oo3 SP=300°C High-high interlock TIS++ 12oo1 SP=320°C