Should the SIS system be independent of the process control system?
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This post was last edited by stysqxyx on 2016-8-23 at 11:17. I’ve always found the SIS system confusing, and after looking up some information, I’m even more confused. 1.1 Selection of SIS sensors: Principle of independent setup: Level 1 SIS sensors can share resources with DCS； Level 2 SIS sensors should be separated from the DCS ； Grade 3 SIS sensors should be separated from the DCS ； Redundancy setup principle: Level 1 SIS sensors can use a single sensor ； Redundant sensors are recommended for Class 2 SIS sensors ； Level 3 SIS sensors should use redundant sensors ； 1.2 Selection of SIS logic operators: Principle of independent setup: Level 1 SIS logic operators should be separated from the DCS ； The Level 2 SIS logic operator should be separated from the DCS ； Level 3 SIS logic operators must be separated from the DCS ； Principle of redundancy setup: Level 1 SIS can use a single logical operator ； Level 2 SIS should employ redundant or fault-tolerant logic operators ； Grade 3 SIS should use redundant fault-tolerant logic operators ； 1.3 Selection of SIS actuating elements: Principle of independent setup: Level 1 SIS valves can share those used by the DCS, but it must be ensured that the SIS takes precedence over the DCS in terms of operation ； Class 2 SIS valves are suitable to be separated from the DCS ； Grade 3 SIS valves are suitable for being separated from the DCS ； Redundancy setup principle: Level 1 SIS can use a single valve ； Redundant valves are recommended for level 2 ； If a single valve is used, solenoid valves should be provided in a redundant configuration ； Redundant valves are recommended for level 3 ； A control valve and a shut-off valve can be used ； SH/T3018 states that \"3.1 The Safety Instrumented System is independent of the process control system and carries out safety protection functions on its own.\" If the safety level of the SIS system is grade 1, and sensors, actuators, and logic operators are shared, how can independence be achieved? And how can priority in operation be ensured?
Looking at the requirements in various aspects, there are no fixed rules.
Set up interlock forced action in DCS
So what exactly constitutes the installation of an SIS system? The safety supervision authorities now require that SIS systems be installed for hazardous chemical processing processes – but what qualifies as a compliant installation?
The sensors are shared, but the systems are independent. For example, temperature data measured on-site is transmitted from the DCS cabinet to the SIS cabinet through communication, yet the DCS system and the SIS system remain separate. Furthermore, if the on-site safety level is all at grade 1, it is likely unnecessary to use an SIS system. It can only be said that some areas at the scene are at level 1, while others are at level 2.3
From the DCS cabinet, communication is established to the SIS cabinet; this cabinet should contain computing modules or something similar. If it’s at the first level, can it also be shared?
For level 1, the standard only states that sensors and actuators can be shared, but specifies that the calculator should be kept separate. If we’re creating something new, it’s best for us to do it in accordance with the proper procedures. In addition, while studying this, it is necessary to determine whether your process safety level is grade 1. If it is grade 1 for all processes, then are there any regulatory requirements that mandate the use of an SIS system?
These specifications specify what types of processes are required and how many levels of safety instrument systems should be installed. Is there any relevant basis for this? Thank you very much
Are there any good textbooks? I want to learn it systematically.
AQ/T3054-2015 Guidelines for the Application of the Protective Layer Analysis (LOPA) Method – you can take a look at this