Explosion-proof electric contact pressure gauge company analyzes the grounding category of the instrument system
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Summary of the characteristics of PC endurance board
1. Weather resistance: There is a UV-proof co-extruded layer on the outside to prevent the resin from fatigue and yellowing caused by the sun's ultraviolet rays. The external co-extruded layer has a chemical structure that absorbs ultraviolet light and converts it into visible light. It has an outstanding stabilizing effect on plant photosynthesis (very suitable for maintaining valuable art and exhibits, so that they are not damaged by ultraviolet rays).
2. Impact resistance: The impact strength of PC endurance board is 250-300 times that of ordinary glass, 20-30 times that of acrylic sheet, and 2 times that of tempered glass. There is almost no risk of cracking, and there is no breakage of glass and steel. It is known as an excellent material for bulletproof glass.
3. Heat resistance and cold resistance: It will not cause quality deterioration such as deformation within the temperature range of -40°C to +120°C.
4. Light transmittance: excellent lighting, light transmittance as high as 75~90%, and its transparency is comparable to glass. UV-coated panels will not cause yellowing, atomization, and poor light transmission under sunlight. After ten years, the loss of light transmission is only 6%, and the loss rate of PVC is as high as 15%—;;20%, glass fiber is 12%-20%. The PC board does not suffer from cold brittleness at -100°C, and does not soften at 135°C, and its mechanics and mechanical functions are not significantly changed in a harsh environment.
5. Light and rigidity: light weight, only half of the glass, 1/3 of the acrylic plate, outstanding adaptability and safety, easy to transfer, drilling, cutting equipment, not easy to crack, the surface system grounding is generally divided into maintenance grounding, There are four types of work grounding, intrinsically safe grounding and anti-static grounding. The grounding requirements for each grounding type are different. Please read this chapter carefully.
Maintenance grounding request
1. There are some metal casings that use electricity and the metal that is normally uncharged for automatic control equipment, which may carry risky voltage due to various factors (such as: insulation damage, etc.). The following electrical appearance and automatic control equipment should be grounded for maintenance:
①Exterior dial, exterior console, exterior cabinet, exterior shelf and exterior box;
②Appearance control system cabinet and operation station;
③Computer system cabinet and console;
④The power supply panel, power supply box, power consumption exterior shell, cable tray, maintenance pipe, junction box and armored protective layer of armored cable.
Clarification of normative provisions
This article proposes some occasions where maintenance grounding is not required. It conforms to 4.2 of the Electric Power Industry Code "Grounding Design Specification for Communication Electrical Equipment". In the meantime, the electrical measuring surface of regular equipment on power distribution panels, control panels and power distribution equipment, the housings of relays and other low-voltage electrical appliances, and the insulator metal base that does not cause risky voltage on the support when insulation damage occurs Some metals may not be grounded.
2. The metal shell of small low-voltage electrical appliances such as buttons, signal lights, relays, etc. on the metal dial of the equipment in non-explosion-proof occasions, when the electrical contact with the metal dial frame that has been grounded for maintenance is excellent, it can be used for maintenance grounding.
Clarification of normative provisions
This article proposes some occasions where maintenance grounding is not required, which conforms to the content of the electric power industry code "Communication Electrical Equipment Grounding Design Code)) 4.2. In the meantime, the electrical measuring surface of regular equipment on power distribution panels, control panels and power distribution equipment, the housings of relays and other low-voltage electrical appliances, and the insulator metal base that does not cause risky voltage on the support when insulation damage occurs Some metals may not be grounded.
3. On-site appearances, transmitters, local switches, etc. powered by less than 36V can be grounded without maintenance if there is no special requirement.
Clarification of normative provisions
The rules for safe voltage values are not exactly the same in different countries. I am also accustomed to choosing 36V and 12V, some foreign rules are 50V and 25V; and some Japanese companies rule that the power consumption below 60V can be grounded without maintenance. In this specification, the field appearance, transmitter, local switch, etc. whose power supply is lower than 36V in this specification may not be grounded for maintenance unless there is a special request. Because the condition of the on-site equipment is very complicated, the metal shells of the on-site surface with power supply lower than 36V may also touch other power sources higher than 36V. Under such conditions, the outer shells of these surfaces should also be grounded for maintenance.
4. The self-control equipment that has been grounded for maintenance can be used for electrostatic grounding. When using anti-static raised floor in the control room, static grounding should be done. Static grounding should be combined with maintenance grounding to use a grounding system.
Clarification of normative provisions
In accordance with the chemical industry standard "Chemical Enterprise Electrostatic Ground Impact Design Regulations" HG 20675-1990 Article 2.6.3 "Electrical Maintenance Grounding Trunk Lines as Static Grounding Trunk Lines" and Article 2.10.1 "In the computer (electronic instrument) room" When using an anti-static raised floor, it should be grounded statically to provide an outstanding electrical path for electrostatic charges.”
