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Code for on-site explosion-proof safety inspection in dusty areas

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| 2019-12-12|Return

1、 Specification for explosion-proof safety inspection in dust explosion areas

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 2、 General items for on-site explosion-proof safety inspection in dusty areas

1Structure and layout of buildings

(1) Process equipment with dust explosion hazards or buildings with combustible dust should be separated from other buildings, and their fire separation distance should comply with the relevant provisions of GB50016

(2) The building should be a single story building, and the roof should be a lightweight structure

(3) The structural requirements for multi story buildings are as follows:

A. Multi story buildings should adopt frame structures

B. Buildings that cannot use frame structures should have explosion-proof outlets on the walls that meet the requirements

C. If a window or other opening is used as an explosion vent, it should be calculated and ensured that it can effectively release the explosion during the explosion

(4) The requirements for evacuation routes are as follows:

A. The work area should have evacuation routes, and the number and location of evacuation routes should comply with the relevant regulations of GB50016

B. The door should open outward and no threshold should be set

C. Evacuation routes should have detailed road signs and emergency lighting.

2Process equipment

(1) If there is a risk of dust explosion in the factory building, the process equipment should be located at a higher position of the building and close to the outer wall.

(2) Process equipment with explosion hazards should be located in outdoor areas outside buildings

(3) Equipment or devices that come into direct contact with dust (such as light sources, heating sources, etc.) should have a surface allowable temperature lower than the minimum ignition temperature of the corresponding dust.

(4) In places with combustible dust, the transmission mechanism of equipment and devices should comply with the following regulations:

A. The bearings of process equipment should be dustproof and sealed. If there is a possibility of overheating, detectors that can continuously monitor the temperature of the bearings should be installed

B. Belt drive is not suitable. If belt drive is used, speed difference sensors and automatic anti slip protection devices should be installed. When sliding friction occurs, the protection device should be able to ensure automatic shutdown

(5) At the feeding point of the process flow, magnets, pneumatic separators or screens that can remove impurities from the mixed materials should be installed to prevent collisions between impurities and equipment

(6) Effective measures should be taken to prevent sparks from friction between metal powders such as aluminum, magnesium, zirconium, or powders containing these metals and rust steel

(7) To achieve protective parking during an explosion, several power supply control boxes that can interlock with each other should be installed according to the size of the workshop. In emergency situations, all motors should be able to be cut off in a timely manner.

(8) The joints, inspection doors, baffles, and explosion vent covers of process equipment should be tightly sealed

(9) The equipment casing should be made of non combustible materials

(10) The running parts of the equipment should operate flexibly and there should be no scraping, collision, jamming, or rubbing.

(11) When the strength of the process equipment is not sufficient to withstand the overpressure generated by internal dust explosions under its actual working conditions, an explosion vent should be installed, and the size of the explosion vent should comply with the relevant provisions of GB/T15605

(12) The position of the explosion vent should be close to the potential source of explosion, and it should be opened at the top or upper part of the enclosure as much as possible. It should not be directed towards flammable and explosive hazardous areas to prevent ignition of other combustibles, and should not be directed towards public places to prevent explosion and injury to people.

3Lightning protection and anti-static measures

In areas with dust explosion hazards, corresponding lightning protection measures should be taken in accordance with the relevant provisions of GB50057. When there is a risk of static electricity, the following regulations should be followed:

(1) All metal equipment, device casings, metal pipes, brackets, components, etc. are generally grounded directly using anti-static methods. If it is inconvenient or the process does not allow direct grounding, it can be indirectly grounded through anti-static materials or products

(2) Instruments directly used for storing electric powder, pipelines (belts) for conveying powder, etc. should be made of metal or anti-static materials

(3) All metal pipeline connections should be cross connected.

(4) Operators should take anti-static measures.

(5) Static electricity should not be eliminated by directly grounding metal conductors or screens in contact with high-speed flowing powder,

4Explosion proof electrical equipment

Electrical equipment used in dust explosion hazardous areas should comply with the relevant provisions of GB12476.1, and electrical design should be carried out in accordance with the relevant provisions of GB50058. Explosion proof electrical equipment should be selected based on the level of the explosive hazardous area and the category, level, and group of explosive hazardous substances.

(1) Options for explosion-proof electrical equipment. Except for the dust explosion-proof electrical equipment with dustproof structure (marked as DP) used in the 11 zone environment of combustible non-conductive dust and combustible fibers, the explosive dust environment 10 zone and other explosive dust environments 11 zone all use dust dense structure (marked as DT) dust explosion-proof electrical equipment, and different ignition temperature groups of electrical equipment are selected according to the different ignition temperatures of the dust.

(2) The wiring steel pipe should be galvanized welded steel pipe for low-pressure fluid transportation

(3) The connection between steel pipes, between steel pipes and electrical equipment, and between steel pipes and steel pipe accessories should use threaded connections. Sleeve welding shall not be used and shall meet the following requirements: the thread processing shall be smooth, complete, and free of embroidery corrosion. The thread shall be coated with electric composite grease or conductive rust proof grease. Do not wrap hemp or insulating tape or apply other paint on the threads. Steel pipes with a diameter of 25mm and below should not be less than 5 buckles, and steel pipes with a diameter of 32mm and above should not be less than 6 buckles.

(4) Explosion proof flexible connecting pipes should be installed at the following locations for steel pipe wiring: the inlet buckle of the motor, where it is difficult to directly connect the steel pipe to electrical equipment, and where the pipeline passes through expansion joints and settlement joints of the building.

(5) Mobile electrical equipment should not be used in zones 20, 21, and 22. If mobile electrical equipment must be used, YC or YCW rubber cables should be used for the wires.

Note: GB50058-1992 "Design Code for Electrical Equipment in Explosive and Fire Hazardous Environments" divides dust explosion areas into 10 zones and 11 zones

AQ3009-2007 "Electrical Explosion Protection Safety Code for Hazardous Areas" divides dust explosion areas into 20 zones, 21 zones, and 22 zones

5Ventilation and dust removal

(1) It is advisable to set up relatively independent dust removal systems in sections according to the process

(2) All dust producing points should be equipped with vacuum hoods

(3) There should be no dust settling in the air duct

(4) It is advisable to use bag type dust collectors and prioritize the use of external filter types

(5) The dust collector should be installed outdoors. If installed indoors, its explosion-proof pipe should be directly connected to the outdoors, with a length of less than 3 meters, and whether to install an explosion-proof device should be determined based on the dust properties.

(6) Isolation valves should be installed at the inlet and outlet of the dust collector, and temperature monitoring devices should be installed

(7) Pulse jet ash bag type dust collectors should use nitrogen, carbon dioxide, or other inert gases as the cleaning gas source.

6Fire protection

(1) Fire extinguishers should be selected correctly based on the physical and chemical properties of dust

(2) When extinguishing a fire, it is necessary to prevent dust from rising and forming dust clouds

(3) If the combustible material can generate explosive gas in contact with water, water should not be used to extinguish the fire.

7Work safety

(1) When dust clouds can be ignited by sparks generated by collisions, measures should be taken to prevent collisions from occurring. At the same time, explosion-proof tools should be used during maintenance,

(2) Rotating grinding wheels and cutting discs should not be used for grinding and cutting without equivalent protective measures for open flame operations

(3) All production workshops and storage rooms that may accumulate dust should be cleaned in a timely manner.

(4) Compressed air should not be used for underground blowing.

(5) In the workplace, production personnel should not wear synthetic clothing or pants close to their bodies
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