Explosion-proof electrical installation, inspection, maintenance and use of precautions, the specific content is as follows:
1 General requirements With the rapid development of China's economic construction, the scale of industrial production is increasing day by day, and the issue of explosion protection is even more important. In the petroleum, chemical, coal, military and other industries, explosion-proof electrical products with various functions and varieties are widely used. The selection, installation, use and maintenance of explosion-proof electrical appliances must strictly comply with the relevant national laws and regulations and national standards.
1.1 Distribution Requirements for Electrical Equipment 1.1.1 The power supply for explosion hazardous locations should be 3-phase 5-wire; if it is 3-phase 4-wire, it should first be converted to 3-phase 5-wire in a safe location;
1.1.2 The grounding resistance of the protective ground wire should meet the relevant standard requirements (≤10Ω);
1.1.3 should consider the impact of lightning on electrical equipment;
1.1.4 If the automatic power-off of electrical equipment may cause greater danger than ignition hazard, an alarm device should be used instead of the automatic power-off device, but the alarm of the alarm device should be obvious so that remedial measures can be taken in time;
1.1.5 In order to prevent sudden power failure and ensure reliability of power supply, explosion hazardous locations should be powered by dual power supplies and automatic switching devices should be installed.
1.1.6 In order to deal with an emergency situation, one or more measures shall be taken at a suitable location or location in a hazardous area to de-energize the electrical equipment in a hazardous area. To prevent additional hazards, electrical equipment that must be continuously operated should not be included in the emergency power-off circuit, but should be installed on a separate circuit;
1.1.7 If necessary, a leakage protector can be installed. When the leakage current exceeds the limit, the power supply is quickly cut off.
1.2 When selecting explosion-proof products, major factors such as explosive gas environment, protection class, and degree of corrosion protection should be taken care of to ensure that the selected explosion-proof products meet the requirements for use. If there is any improvement or change, the explosion-proof products of the corresponding grades and groups must be promptly replaced to ensure the safety of the environment. The specific selection principles are as follows:
1.2.1 Principle of safety and reliability: The type, level and group of equipment should be compatible with the environment used;
1.2.2 Economic Principle: The selection of equipment does not need to be highly selected. Factors such as price, longevity, reliability, operating cost, and availability of spare parts should be considered for products of the same class;
1.2.3 principles of environmental adaptability: consider ambient temperature, humidity, atmospheric pressure, enclosure protection grade, and corrosion resistance;
1.2.4 Maintainability Principle: Under the same conditions, products with simple structure and light weight should be selected; if necessary, the operational requirements of the system should also be taken into consideration. For example, continuous automation systems should preferably use intrinsically safe products.
1.2.5 Additional requirements:
a) Only Exia products are used in Zone 0, and double explosion-proof requirements may be considered when necessary;
b) It is not appropriate to use equipment and high-voltage equipment in the shell that often form an ignition source within the zone 1;
c) The equipment in Zone 2 should not use unstable temperature rise equipment, and Exd/Exp equipment should be selected when necessary.
1.3 Electrical equipment should be installed in accordance with the prescribed technical documents. Electrical equipment should be provided with appropriate protection devices to prevent the equipment from harmful effects due to overload, short circuit, open circuit or ground fault. For example, increased safety squirrel cage motor should be equipped with anti-time limit protection device. Short circuit and ground fault protection devices should be able to prevent automatic reclosing under fault conditions. Pay attention to ensure that the replacement items, such as replacing the lamp, must be of the same type and rating as the usage requirements. The installation of the equipment is completed, and the initial inspection of the equipment and installation shall be conducted in accordance with IEC 60079-17.
1.4 Explosion-proof electrical equipment shall be installed by construction personnel with professional knowledge. The installation quality should meet national standards such as GB50257 and GB3836.15. If necessary, professional explosion-proof agencies may be commissioned to implement engineering supervision or engineering installation site guidance to ensure that the project complies with the overall explosion-proof standard.
1.5 Correct installation of electrical equipment. For existing installations or expansion of existing installations, the following points must be noted:
1.5.1 Location classification documents;
1.5.2 equipment installation and connection instructions;
1.5.3 Explanatory documents for the intrinsic safety system;
1.5.4 Manufacturer/qualified personnel statement.
1.6 When installing or maintaining, you must cut off the power supply of the previous stage, and follow the warning requirements such as “Limiting energizing the lid†or “Disconnecting the lid after power off for XX minutes†in the product instruction manual. Open the lid after cooling to avoid electric shock, burns, etc. accidental damage.
If you are subjected to vibrations, special attention must be paid to the fastening of the device bolts and cable entries. When cleaning non-metallic electrical equipment, care must be taken to avoid static electricity.
1.7 The installation and use of explosion-proof electrical equipment shall prevent external factors (such as: chemical action, mechanical action and thermal, electrical, and humidity) from adversely affecting the explosion-proof performance, and shall prevent foreign matter from falling vertically into the vertical mounting motor vents. Measures.
1.7.1 moisture, waterproof measures:
In outdoor places, explosion-proof electrical equipment should be placed under the rainproof shed as far as possible, and direct rain and direct sunlight should be avoided, and products with higher protection levels should be selected as far as possible. Seal the electrical circuit inlet. And take measures to prevent the accumulation of water near the explosion-proof appliances. Apply waterproofing agent at the threaded joints of the installed wiring ducts;
1.7.2 Anti-corrosion measures:
According to the corrosive gases, liquids, and vapors present in the environment, in addition to the explosion-proof electrical appliances that are resistant to corrosion, the wiring piping must be treated with corrosion protection.
1.7.3 heat protection measures:
Try to keep explosion-proof electrical appliances away from heat sources, and choose explosion-proof electrical appliances with higher temperature levels as much as possible.
1.7.4 Anti-shock measures:
As far as possible, copper core insulated flexible conductors or copper core multi-strand cables are used. When wiring with metal pipes, flexible connecting pipes can be installed at the connection between the explosion-proof electrical apparatus and the electrical circuit as required. Spring washers and double nuts are used on loose-to-vibrate bolt fasteners to prevent loosening.
1.8 Requirements for wiring and grounding:
1.8.1 Connections and grounding terminals shall have sufficient mechanical strength and ensure a reliable connection. Despite the influence of temperature changes, vibrations, etc., there shall be no contact failures. If aluminum core cables are used, transition joints are required to avoid electrolytic corrosion.
1.8.2 The terminal box of the metal enclosure of the electrical equipment and the armored cable shall be provided with an external grounding bolt and marked with a grounding symbol. Portable grounding bolts are not provided for portable and mobile equipment, but cables with a grounded core must be used.
1.8.3 Electrical equipment The internal terminal box shall have a dedicated internal grounding bolt and shall be marked with a grounding symbol. When the direct introduction method is used, it is inside the main chamber. However, the inner and outer grounding bolts may not be provided in the electrical equipment on the electric vehicle.
1.8.4 It is not possible to use a pipeline that carries flammable gas or liquid as the grounding wire. If the equipment is installed on a grounded metal frame, or if the equipment is installed with a properly grounded conduit wiring, it can be considered as having an external ground. Electrical equipment should be provided with grounding connections beside the circuit connections in the wiring cavity.
1.8.5 The connection of electrical equipment and grounding wire should adopt multi-strand soft-twisted wire, and the minimum cross-sectional area of ​​its copper wire should not be less than 42, and the protective tube should be installed in the parts that are vulnerable to mechanical damage.
1.8.6 The diameter of the inner grounding bolt should meet the following requirements:
a) When the cross-section of the conductive core is not more than 35mm2, it should be the same as the diameter of the terminal bolt;
b) When the cross section of the conductive core wire is greater than 35mm2, it shall not be less than the bolt diameter connecting half of the cross section of the conductive core wire, but at least equal to the bolt diameter of the 35mm2 conductive core wire.
1.8.7 The specifications of external grounding bolts shall meet the following requirements:
a) The power is 250w ~ 5kw equipment, not less than M6;
b) Equipment with a power no greater than 250W and a current no greater than 5A, not less than M5;
c) Intrinsically safe equipment and instrumentation, the external grounding bolt can press the grounding core wire;
d) The grounding bolt should be made of stainless steel or electroplated for rust prevention.
1.9 When the wire or cable is introduced into or removed from the explosion-proof product, the original rubber seal ring and retaining ring must not be discarded and it must be directly connected by a copper pipe or a flexible pipe. The seal must be fully compressed. The outer diameter of the wire and cable should be compatible with the inner diameter of the seal (users should ensure that the minimum size of the selected cable, including the tolerance, is greater than or equal to the required value of the cable seal), rubber seal material should comply with the relevant type test Aging test, and its shape is suitable for installing the cable used. Redundant cable inlets use dead mats or metal plugs to block the seal. Do not allow multiple cables to pass through the same lead-in device at the same time. Cables used in hazardous locations must not have intermediate connectors.
1.10 The flameproof surface of the explosion-proof product is the basic guarantee for the flameproof performance of the product. Careful protection shall be taken to avoid bruising, scratches, scratches, and there shall be no trachoma. The explosion-proof surface of each product must be coated with anti-rust oil at the time of shipment. Painting is strictly forbidden to prevent oxidation and rust on the flameproof surface. Pads can only be used when the document regulations permit. Joints must not be treated with hardened materials. If rust-proof oil is found to be dried or reduced, it should be replenished promptly to ensure normal operation of the explosion-proof. The fastening bolts of the flameproof joints shall not be arbitrarily replaced and the spring washers shall be complete.
1.11 Junction box used for external wire or cable wiring should pay attention to the clearance and creepage distance to meet the requirements of the corresponding standards. (It should meet the relevant requirements in GB3836.3-2000 and GB/T14048.1-2000)
1.12 All fasteners are equipped with spring washers as a measure to prevent loosening. They must not be discarded. They must be fully pressed each time and flattened with spring washers. The fasteners necessary to ensure an explosion-proof type or to prevent exposure to live parts are only allowed to be loosened or removed by tools.
1.13 The fitting clearance of the explosion-proof products of the end-pieces, cylinders and threaded flameproof structures is usually between 10 and 20 μm, and the average surface roughness of the flame-proof joint surfaces does not exceed 6.3 μm, which is very precise. Therefore, attention should be paid when opening or separating the cover. Keep balance, lightly separate, forbid pulling hard pull, to avoid destruction of explosion-proof performance.
1.14 When installing the equipment, precautions shall be taken to prevent the distance between the flameproof joints and solid obstacles (such as steel frames, walls, sheaths, mounting plates, pipes or other electrical equipment) from being not less than the values ​​specified in the following table. The distance can be smaller except.
1.15 When reassembling the flameproof enclosure, all joint surfaces should be completely cleaned and coated with suitable grease to prevent corrosion and increase climate protection. Bolt holes should not be coated with grease. Only non-metallic and non-corrosive cleaning fluids can be used when cleaning flanges. The clearances of the spigots, shafts, levers and threaded joints are generally not checked, except when signs of wear, deformation, corrosion or other damage occur. In this case, refer to the manufacturer's documentation.
1.16 For the purpose of inspection and maintenance, the following up-to-date documents should be provided: a) Classification of hazardous locations;
b) equipment level and temperature group;
c) Records of the explosion-protected electrical equipment being maintained in compliance with its type of protection (eg equipment list and equipment configuration, spare parts, technical data and manufacturer's instructions);
1.17 The entire installation or equipment should be inspected initially before being put into operation. To ensure that the electrical device is in good condition, it can be used in hazardous locations for a long period of time. One of the following two checks should be performed:
a) Regular inspections b) Continuous supervision by professionals and maintenance if necessary.
The specific inspection items can be conducted with reference to relevant standards (see Appendix 1 and Appendix 2).
At any time, if the classification of hazardous locations has changed or the location of electrical equipment has changed, inspections should be carried out to ensure that the type of explosion protection, the type of equipment and the temperature group are adapted to the changed conditions. If the device or equipment needs to be removed during the inspection, measures should be taken to ensure that the overall type of protection is not damaged during reassembly.
Where specialists have stated where environmental conditions have changed (eg, solvent intrusion or increased shocks), the components of explosion-protected equipment that are affected by these changes should be checked more frequently.
1.18 The North American standard NPT thread cannot be connected with the inch thread. When the NPT thread is connected, it should have reliable and tight-proof measures.
1 General requirements With the rapid development of China's economic construction, the scale of industrial production is increasing day by day, and the issue of explosion protection is even more important. In the petroleum, chemical, coal, military and other industries, explosion-proof electrical products with various functions and varieties are widely used. The selection, installation, use and maintenance of explosion-proof electrical appliances must strictly comply with the relevant national laws and regulations and national standards.
1.1 Distribution Requirements for Electrical Equipment 1.1.1 The power supply for explosion hazardous locations should be 3-phase 5-wire; if it is 3-phase 4-wire, it should first be converted to 3-phase 5-wire in a safe location;
1.1.2 The grounding resistance of the protective ground wire should meet the relevant standard requirements (≤10Ω);
1.1.3 should consider the impact of lightning on electrical equipment;
1.1.4 If the automatic power-off of electrical equipment may cause greater danger than ignition hazard, an alarm device should be used instead of the automatic power-off device, but the alarm of the alarm device should be obvious so that remedial measures can be taken in time;
1.1.5 In order to prevent sudden power failure and ensure reliability of power supply, explosion hazardous locations should be powered by dual power supplies and automatic switching devices should be installed.
1.1.6 In order to deal with an emergency situation, one or more measures shall be taken at a suitable location or location in a hazardous area to de-energize the electrical equipment in a hazardous area. To prevent additional hazards, electrical equipment that must be continuously operated should not be included in the emergency power-off circuit, but should be installed on a separate circuit;
1.1.7 If necessary, a leakage protector can be installed. When the leakage current exceeds the limit, the power supply is quickly cut off.
1.2 When selecting explosion-proof products, major factors such as explosive gas environment, protection class, and degree of corrosion protection should be taken care of to ensure that the selected explosion-proof products meet the requirements for use. If there is any improvement or change, the explosion-proof products of the corresponding grades and groups must be promptly replaced to ensure the safety of the environment. The specific selection principles are as follows:
1.2.1 Principle of safety and reliability: The type, level and group of equipment should be compatible with the environment used;
1.2.2 Economic Principle: The selection of equipment does not need to be highly selected. Factors such as price, longevity, reliability, operating cost, and availability of spare parts should be considered for products of the same class;
1.2.3 principles of environmental adaptability: consider ambient temperature, humidity, atmospheric pressure, enclosure protection grade, and corrosion resistance;
1.2.4 Maintainability Principle: Under the same conditions, products with simple structure and light weight should be selected; if necessary, the operational requirements of the system should also be taken into consideration. For example, continuous automation systems should preferably use intrinsically safe products.
1.2.5 Additional requirements:
a) Only Exia products are used in Zone 0, and double explosion-proof requirements may be considered when necessary;
b) It is not appropriate to use equipment and high-voltage equipment in the shell that often form an ignition source within the zone 1;
c) The equipment in Zone 2 should not use unstable temperature rise equipment, and Exd/Exp equipment should be selected when necessary.
1.3 Electrical equipment should be installed in accordance with the prescribed technical documents. Electrical equipment should be provided with appropriate protection devices to prevent the equipment from harmful effects due to overload, short circuit, open circuit or ground fault. For example, increased safety squirrel cage motor should be equipped with anti-time limit protection device. Short circuit and ground fault protection devices should be able to prevent automatic reclosing under fault conditions. Pay attention to ensure that the replacement items, such as replacing the lamp, must be of the same type and rating as the usage requirements. The installation of the equipment is completed, and the initial inspection of the equipment and installation shall be conducted in accordance with IEC 60079-17.
1.4 Explosion-proof electrical equipment shall be installed by construction personnel with professional knowledge. The installation quality should meet national standards such as GB50257 and GB3836.15. If necessary, professional explosion-proof agencies may be commissioned to implement engineering supervision or engineering installation site guidance to ensure that the project complies with the overall explosion-proof standard.
1.5 Correct installation of electrical equipment. For existing installations or expansion of existing installations, the following points must be noted:
1.5.1 Location classification documents;
1.5.2 equipment installation and connection instructions;
1.5.3 Explanatory documents for the intrinsic safety system;
1.5.4 Manufacturer/qualified personnel statement.
1.6 When installing or maintaining, you must cut off the power supply of the previous stage, and follow the warning requirements such as “Limiting energizing the lid†or “Disconnecting the lid after power off for XX minutes†in the product instruction manual. Open the lid after cooling to avoid electric shock, burns, etc. accidental damage.
If you are subjected to vibrations, special attention must be paid to the fastening of the device bolts and cable entries. When cleaning non-metallic electrical equipment, care must be taken to avoid static electricity.
1.7 The installation and use of explosion-proof electrical equipment shall prevent external factors (such as: chemical action, mechanical action and thermal, electrical, and humidity) from adversely affecting the explosion-proof performance, and shall prevent foreign matter from falling vertically into the vertical mounting motor vents. Measures.
1.7.1 moisture, waterproof measures:
In outdoor places, explosion-proof electrical equipment should be placed under the rainproof shed as far as possible, and direct rain and direct sunlight should be avoided, and products with higher protection levels should be selected as far as possible. Seal the electrical circuit inlet. And take measures to prevent the accumulation of water near the explosion-proof appliances. Apply waterproofing agent at the threaded joints of the installed wiring ducts;
1.7.2 Anti-corrosion measures:
According to the corrosive gases, liquids, and vapors present in the environment, in addition to the explosion-proof electrical appliances that are resistant to corrosion, the wiring piping must be treated with corrosion protection.
1.7.3 heat protection measures:
Try to keep explosion-proof electrical appliances away from heat sources, and choose explosion-proof electrical appliances with higher temperature levels as much as possible.
1.7.4 Anti-shock measures:
As far as possible, copper core insulated flexible conductors or copper core multi-strand cables are used. When wiring with metal pipes, flexible connecting pipes can be installed at the connection between the explosion-proof electrical apparatus and the electrical circuit as required. Spring washers and double nuts are used on loose-to-vibrate bolt fasteners to prevent loosening.
1.8 Requirements for wiring and grounding:
1.8.1 Connections and grounding terminals shall have sufficient mechanical strength and ensure a reliable connection. Despite the influence of temperature changes, vibrations, etc., there shall be no contact failures. If aluminum core cables are used, transition joints are required to avoid electrolytic corrosion.
1.8.2 The terminal box of the metal enclosure of the electrical equipment and the armored cable shall be provided with an external grounding bolt and marked with a grounding symbol. Portable grounding bolts are not provided for portable and mobile equipment, but cables with a grounded core must be used.
1.8.3 Electrical equipment The internal terminal box shall have a dedicated internal grounding bolt and shall be marked with a grounding symbol. When the direct introduction method is used, it is inside the main chamber. However, the inner and outer grounding bolts may not be provided in the electrical equipment on the electric vehicle.
1.8.4 It is not possible to use a pipeline that carries flammable gas or liquid as the grounding wire. If the equipment is installed on a grounded metal frame, or if the equipment is installed with a properly grounded conduit wiring, it can be considered as having an external ground. Electrical equipment should be provided with grounding connections beside the circuit connections in the wiring cavity.
1.8.5 The connection of electrical equipment and grounding wire should adopt multi-strand soft-twisted wire, and the minimum cross-sectional area of ​​its copper wire should not be less than 42, and the protective tube should be installed in the parts that are vulnerable to mechanical damage.
1.8.6 The diameter of the inner grounding bolt should meet the following requirements:
a) When the cross-section of the conductive core is not more than 35mm2, it should be the same as the diameter of the terminal bolt;
b) When the cross section of the conductive core wire is greater than 35mm2, it shall not be less than the bolt diameter connecting half of the cross section of the conductive core wire, but at least equal to the bolt diameter of the 35mm2 conductive core wire.
1.8.7 The specifications of external grounding bolts shall meet the following requirements:
a) The power is 250w ~ 5kw equipment, not less than M6;
b) Equipment with a power no greater than 250W and a current no greater than 5A, not less than M5;
c) Intrinsically safe equipment and instrumentation, the external grounding bolt can press the grounding core wire;
d) The grounding bolt should be made of stainless steel or electroplated for rust prevention.
1.9 When the wire or cable is introduced into or removed from the explosion-proof product, the original rubber seal ring and retaining ring must not be discarded and it must be directly connected by a copper pipe or a flexible pipe. The seal must be fully compressed. The outer diameter of the wire and cable should be compatible with the inner diameter of the seal (users should ensure that the minimum size of the selected cable, including the tolerance, is greater than or equal to the required value of the cable seal), rubber seal material should comply with the relevant type test Aging test, and its shape is suitable for installing the cable used. Redundant cable inlets use dead mats or metal plugs to block the seal. Do not allow multiple cables to pass through the same lead-in device at the same time. Cables used in hazardous locations must not have intermediate connectors.
1.10 The flameproof surface of the explosion-proof product is the basic guarantee for the flameproof performance of the product. Careful protection shall be taken to avoid bruising, scratches, scratches, and there shall be no trachoma. The explosion-proof surface of each product must be coated with anti-rust oil at the time of shipment. Painting is strictly forbidden to prevent oxidation and rust on the flameproof surface. Pads can only be used when the document regulations permit. Joints must not be treated with hardened materials. If rust-proof oil is found to be dried or reduced, it should be replenished promptly to ensure normal operation of the explosion-proof. The fastening bolts of the flameproof joints shall not be arbitrarily replaced and the spring washers shall be complete.
1.11 Junction box used for external wire or cable wiring should pay attention to the clearance and creepage distance to meet the requirements of the corresponding standards. (It should meet the relevant requirements in GB3836.3-2000 and GB/T14048.1-2000)
1.12 All fasteners are equipped with spring washers as a measure to prevent loosening. They must not be discarded. They must be fully pressed each time and flattened with spring washers. The fasteners necessary to ensure an explosion-proof type or to prevent exposure to live parts are only allowed to be loosened or removed by tools.
1.13 The fitting clearance of the explosion-proof products of the end-pieces, cylinders and threaded flameproof structures is usually between 10 and 20 μm, and the average surface roughness of the flame-proof joint surfaces does not exceed 6.3 μm, which is very precise. Therefore, attention should be paid when opening or separating the cover. Keep balance, lightly separate, forbid pulling hard pull, to avoid destruction of explosion-proof performance.
1.14 When installing the equipment, precautions shall be taken to prevent the distance between the flameproof joints and solid obstacles (such as steel frames, walls, sheaths, mounting plates, pipes or other electrical equipment) from being not less than the values ​​specified in the following table. The distance can be smaller except.
1.15 When reassembling the flameproof enclosure, all joint surfaces should be completely cleaned and coated with suitable grease to prevent corrosion and increase climate protection. Bolt holes should not be coated with grease. Only non-metallic and non-corrosive cleaning fluids can be used when cleaning flanges. The clearances of the spigots, shafts, levers and threaded joints are generally not checked, except when signs of wear, deformation, corrosion or other damage occur. In this case, refer to the manufacturer's documentation.
1.16 For the purpose of inspection and maintenance, the following up-to-date documents should be provided: a) Classification of hazardous locations;
b) equipment level and temperature group;
c) Records of the explosion-protected electrical equipment being maintained in compliance with its type of protection (eg equipment list and equipment configuration, spare parts, technical data and manufacturer's instructions);
1.17 The entire installation or equipment should be inspected initially before being put into operation. To ensure that the electrical device is in good condition, it can be used in hazardous locations for a long period of time. One of the following two checks should be performed:
a) Regular inspections b) Continuous supervision by professionals and maintenance if necessary.
The specific inspection items can be conducted with reference to relevant standards (see Appendix 1 and Appendix 2).
At any time, if the classification of hazardous locations has changed or the location of electrical equipment has changed, inspections should be carried out to ensure that the type of explosion protection, the type of equipment and the temperature group are adapted to the changed conditions. If the device or equipment needs to be removed during the inspection, measures should be taken to ensure that the overall type of protection is not damaged during reassembly.
Where specialists have stated where environmental conditions have changed (eg, solvent intrusion or increased shocks), the components of explosion-protected equipment that are affected by these changes should be checked more frequently.
1.18 The North American standard NPT thread cannot be connected with the inch thread. When the NPT thread is connected, it should have reliable and tight-proof measures.
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