Basic knowledge of the hottest safety barrier

Basic knowledge of safety barriers

intrinsically safe safety barriers are used in the design of intrinsically safe explosion-proof systems. They are devices installed in safe places and contain intrinsically safe circuits and non intrinsically safe circuits. The energy sent to the on-site intrinsically safe circuit is limited by current and voltage limiting circuits in the circuit, so as to prevent the dangerous energy of non intrinsically safe circuits from cascading into the intrinsically safe circuit. They are called associated equipment in the intrinsically safe explosion-proof system [see term explanation], It is an important part of the intrinsic safety system

since the safety barrier is designed as an energy limiting interface between the field equipment and the control room equipment, the safety barrier can ensure that the energy transmitted to the field equipment through it is intrinsically safe no matter the control room equipment is in normal or fault state

the national instrument and meter explosion-proof safety supervision station of China is the authority of the Chinese people's manual level adjustment experimental space to supervise the production of safe explosion-proof products in the people's Republic of China. It has strict, scientific and detailed regulations on intrinsically safe safety barrier products. Only the enterprises certified by the supervision station and the products developed and produced by them can have the safety performance that meets the standard, otherwise it may give users' equipment Immeasurable damage to personnel and production

explanation of terms: associated equipment

an electrical equipment installed in a safe place and connected between intrinsically safe electrical equipment and non intrinsically safe electrical equipment

installation position

safety barriers are installed in safe places, receive signals from dangerous areas, and output safety signals to safe areas or dangerous areas

structural form of safety barrier the common structural form of safety barrier is divided into Zener type and isolation type

Zener safety barrier

structural principle: China has built the world's first 10000 ton trans isoprene rubber device

in the circuit, fast fuses, current limiting resistors or voltage limiting diodes are used to limit the input electrical energy, so as to ensure the energy output to the dangerous area. Its principle is simple, the circuit is easy to realize, and the price is low. However, due to the defects of its own principle, its reliability in application is greatly affected, and its application scope is limited. 8.2 lime sand bricks should be stored for 3 days before leaving the factory. The products should be stored and stacked in an untidy site, graded, neat and stable. The reasons are as follows:

1. The installation position must have a very reliable grounding system, And the grounding resistance of the zener safety barrier must be less than 1. If it is not

, the explosion-proof safety protection performance will be lost. Obviously, such requirements are very harsh and difficult to guarantee in practical engineering applications

2. Field instruments from hazardous areas must be isolated, otherwise the signal cannot be transmitted correctly after being connected to the ground through the grounding terminal of Zener safety barrier, and the signal anti-interference ability will be directly reduced due to signal grounding, which will affect the stability of the system

3. The zener safety barrier has a great impact on the power supply, and it is also easy to cause damage to the zener safety barrier due to the fluctuation of the power supply

isolated safety barrier

adopts a circuit structure that electrically isolates the input, output and power supply from each other, and meets the requirements of intrinsically safe energy limitation. Compared with Zener security, although the price is slightly higher, its outstanding advantages in other aspects have brought greater benefits to user applications:

1 Due to the use of three-way isolation, there is no need for system grounding lines, which brings great convenience to the design and on-site construction

2. The requirements for instruments in hazardous areas are greatly reduced, and there is no need to use isolated instruments on site

3. Since the signal circuit does not need to be grounded together, the stability and anti-interference ability of the detection and control circuit signal are greatly enhanced, which improves the reliability of the whole system

4. The isolated safety barrier has stronger input signal processing ability, and can accept and process thermocouple, thermal resistance, frequency and other signals, which is impossible for Zener safety barrier

5. The isolated safety barrier can output two mutually isolated signals to provide to two devices using the same signal source, and ensure that the signals of the two devices do not interfere with each other, while improving the electrical safety insulation performance between the connected devices

therefore, after comparing the characteristics and performance of Zener safety barrier and isolation safety barrier, it can be seen that isolation safety barrier has outstanding advantages and wider applications. Although its price is slightly higher than Zener safety barrier, its comprehensive cost may be lower than Zener safety barrier in terms of design, construction, installation, commissioning and maintenance costs. Almost without exception, the isolated safety barrier is used as the main intrinsically safe explosion-proof instrument in the engineering site with high requirements. The isolated safety barrier has gradually replaced the zener safety barrier and has been widely used in the field of safety and explosion-proof

definition of intrinsically safe equipment signs

among them: ex explosion-proof sign

(IA) explosion-proof grade

Ⅱ C Gas Group

explosion proof grade of our company's products: ex (IA) Ⅱ C

explosion proof grade

Ia: under normal working conditions, dangerous gases will not be ignited under one fault or two fault conditions, and the circuit must ensure that safety characteristics are still guaranteed when two faults occur at the same time. Class IA electrical equipment must adopt triple design for components that are vulnerable to interference. Class Ib electrical equipment can only ensure that it will not ignite dangerous gases under one fault state

gas group

group I electrical equipment: used in coal mine environment vulnerable to methane

group II electrical equipment: it can be used in explosion hazardous environments except coal mines

group II electrical equipment is further subdivided according to the different ignition energy of flammable substances

all subgroups are distinguished by upper case English. From the table below, it can be seen that subgroup C requires the least ignition energy, that is, among the electrical equipment in this group, group C equipment is universal

grouping of common inflammable substances

regional division of explosive dangerous places

in the design of safety explosion-proof system and the selection of explosion-proof products, in addition to the classification and grouping of gases existing in explosive environment, explosive gas dangerous places should also be divided according to the frequency and duration of explosive gas: our products are applicable to zone 0, zone 1 and zone 2 at the same time

color code

the yellow end (non intrinsically safe side) wiring leads to the safe area

the blue end (intrinsically safe side) wiring leads to the dangerous area

for the installation method, see the "appearance and installation" in this manual

precautions in installation

1 The safety barrier shall be installed in a safe place, and the environmental conditions can meet the requirements of the use conditions in the general technical indicators of this manual

2. The wiring conductors of intrinsically safe end (blue mark) and non intrinsically safe end circuits of isolated safety barriers shall be laid separately in the trunking, and independent protective sleeves shall be used respectively. No other power lines are allowed in the wiring sleeve at the intrinsically safe side, including the power lines used for its intrinsically safe circuit

3. Intrinsically safe conductors with blue marks shall be selected for the conductors leading to dangerous places. The soft copper area of the conductors must be greater than 0.5mm2, and the insulation strength should be greater than 500V

4. Before energizing and debugging the isolated safety barrier, attention must be paid to whether the model, wiring method, line polarity, etc. of the isolated safety barrier comply with the provisions of the design and product requirements, otherwise it may cause injury to personnel and equipment

5. It is forbidden to use a megger to test the insulation strength between the terminals of the isolation safety barrier. If you want to check the insulation strength of the system, you should first disconnect all wiring, otherwise it may cause the quick fuse inside the safety barrier to fuse

6. Before programming the safety barrier on site, all wiring must be disconnected first, then connected to the programmer, and then powered on for programming, otherwise adverse consequences may be caused

7. The field instruments connected with the isolated safety barrier shall pass the explosion-proof test of the explosion-proof inspection department recognized by the state and obtain the explosion-proof certificate

8. When designing, installing, using and maintaining isolated safety barriers, SABIC will also make a keynote speech at this forum. The instructions in this product manual, GB3836. Electrical equipment for explosive gas atmospheres Part XV: electrical installation in hazardous places (except coal mines), and GB code for design of electrical installations in explosive and fire hazardous environments should be observed