There are several types of safety barriers; what are their functions?

There are those of the Zina type and those with isolation. . There are those that go in twice and out twice, and those that go in once and out once!

Ours are German KNICK safety barriers, isolated safety barriers, with one inlet and one outlet

Zener-type safety barrier: Fast fuses, current-limiting resistors, or voltage-limiting diodes are used in the circuit to limit the amount of electrical energy entering, thereby ensuring that the amount of energy delivered to the hazardous area is controlled. Its principle is simple, its circuit implementation is easy, and it is inexpensive. However, due to flaws in its underlying principle, its reliability in practical applications is greatly affected, which limits its scope of use. The reasons are as follows: 1. The installation location must have a very reliable grounding system, and the grounding resistance of this Zener-type safety barrier must be less than 1Ω; otherwise, it loses its explosion-proof safety capabilities. Clearly, such requirements are quite stringent and difficult to meet in actual engineering applications. 　　2. The field instruments located in hazardous areas must be isolated; otherwise, when the grounding terminals of the Zener safety barrier are connected to the ground, the signals cannot be transmitted properly. Moreover, grounding the signals reduces their resistance to interference, thereby affecting the stability of the system. 　　3. Zener safety barriers have a significant impact on the power supply, and they are also prone to damage due to fluctuations in the power supply. 　　4. Since the circuit principle of the Zener safety barrier requires it to absorb energy from the input circuit, it is prone to cause instability in the output. Isolated safety barrier: It features a circuit structure that provides electrical isolation between the input, output, and power supply, while also meeting the energy limitation requirements of intrinsically safe systems. Compared to Zener-based safety systems, although it is more expensive, its superior performance advantages bring greater benefits to users: 1. Thanks to the three-way isolation mechanism, no system grounding wires are required, which greatly simplifies design and on-site installation. 　　2. The requirements for instruments in hazardous areas are significantly reduced, and isolated instruments are not necessary on-site. 　　3. Since the signal lines do not require a common ground, the stability and interference resistance of the signals in the detection and control circuits are **enhanced**, thereby improving the reliability of the entire system. 　　4. Isolated safety barriers possess stronger input signal processing capabilities; they can accept and process signals from thermocouples, thermal resistors, frequencies, etc., something that zener safety barriers cannot do. 　　5. The isolated safety barrier can output two mutually isolated signals, which are provided for two devices that use the same signal source, ensuring that the signals from these two devices do not interfere with each other. It also enhances the electrical insulation between the connected devices. 　　Therefore, by comparing the characteristics and performance of Zener-type and isolated safety barriers, it can be seen that the isolated safety barrier has significant advantages and a wider range of applications. Although its price is slightly higher than that of the Zener-type safety barrier, its overall cost may actually be lower when taking into account design, installation, commissioning, and maintenance costs. Isolated safety barriers are used almost without exception as the primary intrinsically safe explosion-proof instruments in projects with high requirements. These isolated safety barriers have gradually replaced Zener-type safety barriers and are being employed more and more widely in the field of explosion protection.
Definition of intrinsically safe equipment markings
Where: EX – Explosion protection marking
(iiA) – Explosion protection category
IIC – Gas group 　　

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The common structural types of safety barriers are divided into Zener-type and isolation-type. In Zener-type safety barriers, fast fuses, current-limiting resistors, or voltage-limiting diodes are used in the circuit to limit the electrical energy input, thereby ensuring the amount of energy delivered to the hazardous area. Its principle is simple, its circuit implementation is easy, and it is inexpensive. However, due to flaws in its underlying principle, its reliability in practical applications is greatly affected, which limits its scope of use. The reasons are as follows: 1. The installation location must have a very reliable grounding system, and the grounding resistance of this Zener-type safety barrier must be less than 1Ω; otherwise, it loses its explosion-proof safety functions. Clearly, such requirements are extremely stringent and difficult to meet in actual engineering applications. 2. The field instruments located in hazardous areas must be isolated-type; otherwise, once the grounding terminals of the Zener safety barrier are connected to the ground, the signals cannot be transmitted properly. Moreover, grounding the signals reduces their resistance to interference, thereby affecting the stability of the system. 3. Zener safety barriers have a significant impact on the power supply, and they are also prone to damage due to fluctuations in the power supply. 4. Since the circuit principle of the Zener-type safety barrier requires it to absorb energy from the input circuit, it is prone to cause instability in the output. Function of the safety barrier: The isolated safety barrier employs a circuit structure that provides electrical isolation between the input, output, and power supply, while also meeting the requirements for energy limitation in intrinsically safe systems. Compared to Zener-based safety systems, although it is more expensive, its superior performance advantages bring greater benefits to users in terms of application: The functions of the safety barrier – 1. Thanks to the three-way isolation approach, no system grounding wire is required, which greatly simplifies design and on-site installation. 2. The requirements for instruments in hazardous areas are significantly reduced, and isolated instruments are not necessary on-site. 3. Since the signal lines do not require a common ground, the stability and interference resistance of the signals in the detection and control circuits are **enhanced**, thereby improving the reliability of the entire system. 4. Isolated safety barriers possess stronger input signal processing capabilities; they can accept and process signals from thermocouples, thermal resistors, frequencies, etc., something that zener safety barriers cannot do. 5. An isolated safety barrier can output two mutually isolated signals, which are provided to two devices that use the same signal source, ensuring that the signals from these two devices do not interfere with each other. It also enhances the electrical safety isolation between the connected devices. Therefore, by comparing the characteristics and performance of Zener-type and isolated safety barriers, it can be seen that isolated safety barriers have significant advantages and a wider range of applications. Although their price is slightly higher than that of Zener-type safety barriers, their overall cost may actually be lower when taking into account design, installation, commissioning, and maintenance costs. In engineering sites with high requirements, isolated safety barriers are almost universally used as the primary intrinsically safe explosion-proof instruments. These isolated safety barriers have gradually replaced Zener-type safety barriers and are being increasingly employed in the field of explosion protection. Definition of intrinsically safe device markings: EX – Explosion protection mark; (ia) – Explosion protection class; II C – Gas group. The explosion protection class for our company’s products is EX(ia)II C. Explosion protection class ia: Under normal operating conditions, hazardous gases will not be ignited even in the presence of 1 or 2 counting faults; the circuit must maintain its safety properties even when both counting faults occur simultaneously. “Electrical equipment of the “ia” category must adopt a “triplication” design for components that are prone to interference. “Electrical equipment of the “ib” category can only ensure that no hazardous gases will be ignited under 1 counting fault condition. Gas group: Group I electrical equipment: Used in coal mining environments susceptible to methane. Group II electrical equipment: Can be used in explosive hazardous environments other than coal mines. Group II electrical equipment is further subdivided according to the ignition energy of different flammable substances. The various subgroups are distinguished by uppercase English letters. As can be seen from the table below, the IIC group requires the least ignition energy according to the standards of China, IEC, and Europe; in other words, among electrical devices in this group, those belonging to the IIC group have compatibility with devices from groups IIA and IIB. Classification of common flammable substances: Typical gases, classification criteria, ignition characteristics – China, IEC, Europe, North America. Methane: Group I; Acetylene: Group II C A; Hydrogen: Group II C B; Ethylene: Group II B C; Propane: Group IIA D. Zoning of explosive hazard areas: In the design of safety and explosion-proof systems as well as in the selection of explosion-proof products, it is necessary not only to classify and group the gases present in explosive environments but also to zone these areas based on the frequency and duration of the presence of explosive gases: Zone 0 – Areas where explosive gas mixtures are present continuously or for extended periods of time. Zone 1: Areas where explosive gas mixtures are likely to occur. Zone 2: Areas where explosive gas mixtures cannot occur, or if they do appear, it is only for a short period of time. Our products are suitable for Zone 0, as well as Zones 1 and 2. Installation of isolated safety barriers: Color code – The yellow terminal (the non-intrinsic side) leads to the safe area. The blue terminal (intrinsic safety side) wiring leads to the hazardous area. Precautions during installation: 1. The safety barrier should be installed in a safe location, and the environmental conditions must meet the requirements specified under \"Operating Conditions\" in the \"Safety Barrier Selection Guide\". 2. The connection wires between the intrinsically safe side (blue side) and the non-intrinsically safe side of the isolated safety barrier circuits should be laid separately in the trunking, with each using its own protective sleeve. Other power cables are not allowed in the wiring ducts on the intrinsically safe side, including those used for the intrinsically safe circuit. 3. Wires leading to hazardous areas should be intrinsically safe wires marked in blue; the cross-sectional area of the soft copper in such wires must be greater than 0.5 mm2, and their insulation strength must be above 500 V. 4. Before powering on the isolated safety barrier for testing, it is necessary to ensure that its model, wiring method, and circuit polarity meet the specifications outlined in the design and product requirements; otherwise, it may cause harm to people and equipment. 5. It is strictly prohibited to use a megohmmeter to test the insulation strength between the terminals of isolated safety barriers. To check the insulation strength of the system, all connections of the isolation safety barriers must be disconnected first; otherwise, it may cause damage to the internal circuits of the safety barriers. 6. Before programming the safety barrier on-site, it is necessary to disconnect all connections first before connecting it to the programmer, and then power it on to perform programming; otherwise, it may lead to adverse consequences. 7. Field instruments connected to isolated safety barriers shall all be those that have undergone explosion-proof testing by **authorized relevant explosion-proof testing institutions and obtained an explosion-proof certification. 8. When designing, installing, using, and maintaining isolated safety barriers, it is necessary to comply simultaneously with the instructions in this product’s user manual, as well as with GB3836.15-2000 \"Electrical equipment for explosive gas environments – Part 15: Electrical installation in hazardous locations (except coal mines)\" and GB50058-1992 \"Code for design of power supply systems in explosive and fire-hazardous environments\".

There are two main types of safety barriers: Zener-type safety barriers and isolated safety barriers. Zener-type safety barriers are characterized by their simplicity and low cost, but for applications that require a high level of safety, it is recommended to use isolated safety barriers