Discussion on SIS interlock design (the content of the previous post was incorrect; revised)
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This post was last edited by wx_Wang81529 on 2022-12-9 08:52. Design Code for Safety Instrumented Systems in the Petrochemical Industry GBT50770-2013: 11.1.1 The logical design of application software should preferably use positive logic. Design Code for Chemical Process Automation HGT20511-2014: 4.3.1 Positive logic can be used for the logical design of non-safety interlock systems, while negative logic can be employed for the logical design of safety interlocks. How do you understand the fact that one of these two codes recommends positive logic for SIS interlocks and the other recommends negative logic?
Are the design specifications for petrochemical safety instrumented systems based on independent SIS systems, while the design specifications for chemical process control are based on non-independent SIS systems? You can take another look at the scope of application of the two standards
This post was last edited by Chuxin_E8JnK on 2025-2-4 20:27. Personal understanding: 1. According to 11.1.1 of GBT50770-2013, the logical design of application software should adopt positive logic； Understanding: it refers to the display on the host computer screen, not the underlying logic ； 2. HGT20511-2014 4.3.1 Positive logic can be used for the logical design of non-safety interlock systems, while negative logic can be employed for the logical design of safety interlocks ； The following sentence is: For the design of safety interlock logic, negative logic should be employed; in other words, negative logic is recommended for use at the lower-level logic level