What Is a Safety Instrumented System?
Safety instrumented system, referred to as SIS for short; also known as Safety Interlocking System. It is mainly the alarm and interlocking part of the factory control system. It is an important part of the automatic control of the factory enterprise to implement the alarm action or adjustment or shutdown control on the detection results in the control system.
Safety Instrumented System
Right!
- Chinese name
- Safety Instrumented System
- Foreign name
- Safety instrumentation System
- Features
- Based on IEC61508
- nickname
- Safety interlock system
- Safety instrumented system, referred to as SIS for short; also known as Safety Interlocking System. It is mainly the alarm and interlocking part of the factory control system. It is an important part of the automatic control of the factory enterprise to implement the alarm action or adjustment or shutdown control on the detection results in the control system.
(1) With IEC61508 as the basic standard, it complies with the safety standards of the instruments specified by the International Safety Association. (2) It has wide coverage, high security, and self-diagnostic functions, and can detect and prevent potential dangers. (3)
Safety instrumented systems include sensors, logic
- The main system structures of SIS are TMR (triple) and 2004D (quad).
(1) TMR structure: It integrates three-way isolated, parallel control systems (each is called a sub-circuit) and extensive diagnostics in one system, and uses three-to-two voting to provide a highly complete, error-free, non-disruptive control. TRICON, ICS, HollySys, etc. are all adopted
- Basic functions and requirements of safety instrumented systems
- 1. To ensure the normal operation of production and accident safety interlock (control system CPU scan time must reach ms
- 1. The setting of signal alarm, interlock point, action set value and adjustment range must meet the requirements of production process.
- 2. On the premise of meeting safety production, the scheme with simple circuit and few components should be selected as far as possible.
- 3.Signal alarm, safety
- Design principles of sensors
- Independence principle
- Redundancy criterion
- Design principles for final actuators
- Valve independence principle
- Valve redundancy criteria
- Solenoid valve cooperation guidelines
- Motor starter fit guidelines
- Design principles for logic cells
- Logic unit independence
- Logic unit redundancy criterion
- Design principles for communication interfaces
- IEC-61508 divides the safety level required for process safety into 4 levels (SIL1-SIL4,).
- ISA-S84.01 divides the safety level into 3 levels (SIL1-SIL3) according to the probability that the system does not respond to the safety interlock request.
- In view of the current actual situation in China, the qualitative assessment of the probability and severity of all events and the effectiveness of other security measures are generally used to determine the appropriate level of security:
- Level 1 is used for accidents that rarely occur. If an accident occurs, it will have a slight impact on the device and products, and will not immediately cause environmental pollution and casualties, and the economic loss will be small;
- Level 2 is used for occasional accidents. If an accident occurs, it will have a greater impact on the device and products, and may cause environmental pollution and casualties, and cause large economic losses.
- Level 3 is used for frequent accidents. If an accident occurs, the device and products will have a serious impact, and cause serious environmental pollution and casualties, and serious economic losses.
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