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Safety barrier
Release date：2019-05-15 Number of views：
Safety barrier is connected between intrinsically safe circuit and non intrinsically safe circuit. A device that limits the voltage and current supplied to an intrinsically safe circuit to a certain safe range.
introduce
Safety barrier, also known as safety energy limiter, is an important part of the intrinsic safety system.
There are mainly two types of safety barriers: Zener type and isolated type.
The core components of Zener barrier are zener diode, current limiting resistor and fast fuse.
The isolated safety barrier not only has limited energy function, but also has isolation function. It is mainly composed of loop energy limiting unit, signal and power isolation unit and signal processing unit.
The main function of the safety barrier is to limit the current and voltage, and ensure that the energy available to the field instrument is within the safe range.
Another name
Another name
Safety barrier is also called safety retainer. The safety interface of intrinsically safe circuit can transmit electric signals in two directions between safety zone (intrinsic safety) and danger zone (non intrinsic safety), and limit the energy transmission from danger zone caused by fault to safety zone. General safety barrier has Zener type and isolation type.
Intrinsically safe safety barrier is used in the design of intrinsically safe explosion-proof system. It is a device installed in a safe place and contains intrinsically safe circuit and non intrinsically safe circuit. In the circuit, the energy sent to the intrinsically safe circuit on site is limited by current limiting and voltage limiting circuit, so as to prevent the dangerous energy of non intrinsically safe circuit from cascading into intrinsically safe circuit. It is called associated equipment in intrinsically safe explosion-proof system, It is an important part of the intrinsic safety system.
Intrinsically safe explosion-proof system associated equipment refers to the electrical equipment installed in a safe place and connected between intrinsically safe electrical equipment and non intrinsically safe electrical equipment.
Since the safety barrier is designed as an energy limited interface between the field equipment and the control room equipment, it can ensure that the energy transmitted to the field equipment through the safety barrier is intrinsically safe no matter whether the control room equipment is in normal or fault state.
structural style
Exia IIC
1. In the circuit, fast fuse, current limiting resistor or voltage limiting diode are used to limit the input electric energy, so as to ensure the output energy to the dangerous area.
2. The installation position needs a very reliable grounding system, which is obviously very harsh and difficult to guarantee in practical engineering application.
2. The installation position needs a very reliable grounding system, which is obviously very harsh and difficult to guarantee in practical engineering application.
3. Zener barrier has great influence on power supply, and it is easy to damage Zener barrier due to fluctuation of power supply.
4. Because the circuit principle of Zener barrier needs to absorb the energy of the input circuit, it is easy to cause the output instability.
Isolated barrier
The circuit structure of electrical isolation between input, output and power supply is adopted, which meets the requirement of intrinsically safe limited energy. Compared with Zener security, although the price is more expensive, its outstanding advantages in performance bring great benefits to users
1. Due to the use of tripartite isolation, there is no need for system grounding line, which brings great convenience to the design and field construction.
2. The requirements for instruments in hazardous areas are greatly reduced, and there is no need to use isolated instruments on site.
3. Because the signal circuit does not need common ground, the signal stability and anti-interference ability of the detection and control circuit are greatly enhanced, so as to improve the reliability of the whole system.
4. The isolated safety barrier has strong input signal processing ability, and can receive and process signals such as thermocouple, thermal resistance and frequency, which is beyond the capability of Zener safety barrier.
5. The isolated safety barrier can output two mutually isolated signals to provide for two devices using the same signal source, ensure that the signals of the two devices do not interfere with each other, and improve the electrical safety insulation performance between the connected devices.
Therefore, comparing the characteristics and performance of Zener type and isolation type safety barrier, it can be seen that the isolated safety barrier has outstanding advantages and wide application. Although its price is slightly higher than that of Zener type safety barrier, the comprehensive cost may be lower than that of Zener safety barrier from the perspective of design, construction installation, commissioning and maintenance costs. Isolation barrier is used as the main intrinsically safe explosion-proof instrument in the high-demand engineering site, and the isolated safety barrier has gradually replaced the zener type safety barrier, and has been widely used in the field of safety and explosion protection
Definition of intrinsically safe equipment marking
Including: ex - explosion proof mark
(IA) - explosion proof grade
Ⅱ C - Gas Group
Explosion proof grade of our products: ex (IA) Ⅱ C
working principle
working principle
