First, the explosion-proof structure
Electric sparks and arcs can ignite explosive mixtures. The gap-proof flameproof structure established by Germany is a more reliable method of preventing arcs and Other ignition of surrounding explosive mixtures. The re-explosive danger zone of the electrical equipment with explosion-proof structure is extremely widely used. It can not only prevent the explosion of fire, but also the housing can withstand a certain over-voltage. It has a sufficiently strong enclosure capable of withstanding 1.5 times the maximum explosion pressure of the internal explosive gas mixture and not less than 3.5 x 105 Pa of impact, ensuring no deformation or damage, no permanent deformation, and having a certain structural gap for ejection The combustion products are cooled down to a temperature below the autoignition temperature of the external explosive mixture by a certain length of the flange. The structure gap may be composed of a plane joint surface or a cylinder joint surface, and may also be a structure composed of a curved road, a thread, or a barrier type. In addition to this. Such as micro-holes, nets, laminations, sand and other structures also belong to the explosion-proof form of this principle. Flameproof electrical equipment used underground in coal mines must be stronger.
Equipment used for Class I mining face shall be made of steel plate or cast steel. Class I equipment for non-excavating face shall be available with a brand no less than HT25-47 grey cast iron; Class I portable equipment and Type II equipment can be made of a light alloy with a tensile strength of not less than 117.6N/mm2 (12kg/mm2) and a magnesium content of not more than 0.5% (by weight).
1. Increased safety structure The increased safety mechanism is also widely used in explosion-proof electrical equipment such as motors, transformers, lamps, and electrical equipment with inductive coils. It adopts a series of safety measures on the equipment, such as the use of high-quality insulating materials, lowering the temperature rise, increasing the electrical clearance, and improving the quality of the wire connection so that it will not generate sparks, arcs or dangerous temperatures to the maximum extent possible. Or, using an effective protective element to produce a spark, arc or temperature that does not ignite the explosive mixture to achieve explosion-proof purposes.
Another type of explosion-proof measure similar to the increased safety type is the so-called non-spark type, which is an electrical device that does not generate sparks and dangerous high temperatures during normal operation, and it cannot generate detonation faults. Compared with the safety-enhancing type, there is no provision for additional additional measures to improve the safety and reliability of the equipment. Therefore, the safety of the sparkless type is lower than that of the increased safety type, and it can only be used in the dangerous environment of Zone 2.
2. The positive pressure type structure The explosion protection principle of the electrical equipment of this structure is to ensure that the pressure of the internal protective gas is higher than the surrounding to prevent the explosive mixture from entering the enclosure, or that a sufficient amount of protective gas passes through the enclosure to reduce the concentration of the internal explosive mixture to the lower explosion limit the following.
Under normal circumstances, there must be no dead angle inside the electrical equipment that affects safety. During normal operation, the air pressure or inflation pressure at the air outlet must not be lower than a certain value, otherwise an alarm or power cutoff will be issued immediately. Sparks and arcs inside the equipment must not be blown out from any gap or outlet.
The positive pressure type structure is not related to the level of explosive substances in use, and is often used in equipment or large electrical equipment in which internal components are easily damaged, or electrical equipment in which the self-ignition point is T4 or T5 is difficult to make in the form of other explosion-proof structures. on.
3, sand-filled structure The sand-filled structure is filled with sand or other specified characteristics of the powder material in the shell, so that under the conditions of use, the arc or high temperature generated within the shell can not ignite the surrounding explosive gas environment structure.
When the medium used for the granular solid (usually quartz sand) as the isolation medium, known as the sand-filled electrical equipment; and the medium used when the curing material filler (usually epoxy resin), the ignition source sealed in Inside the packing, and when the outer explosive mixture is isolated, it is also called a potting type electrical device.
4. Intrinsically safe structure The intrinsically safe structure is only suitable for weak current loops, such as test instruments, control devices and other small electrical equipment. Irrespective of whether it is under normal circumstances or under abnormal conditions, EDM or dangerous temperature will not detonate the explosive substances. Therefore, an explosion-proof structure with higher safety, in which the surface temperature of all components on the circuit or equipment must be less than the specified To prevent ignition caused by thermal effects.
The electrical circuit of the intrinsically safe explosion-proof structure must be isolated from other circuits in order to prevent electromagnetic or electrostatic induction of the mixed wire. In particular, the external wiring of the structure must take careful measures to ensure the explosion-proof performance of electrical equipment and wiring.
5, Explosion-proof oil-filled structure Explosion-proof oil-filled structure has nothing to do with the boost level, suitable for small-scale operation switch. The filled fluid should have high chemical stability. In order to observe the height of the oil level, the equipment should be equipped with an oil level indicator or oil level signal device.
Oil-immersed explosion-proof switches, controllers, and other equipment, due to deterioration or leakage of oil, are difficult to repair and require special attention. In addition, the equipment can no longer be used when the explosion-proof performance is impaired due to tilting or shaking of the oil surface.
6. Explosion-proof structure of explosive dust environment The dust explosion-proof electrical equipment is to limit the maximum surface temperature of the enclosure and use dust-tight or dust-proof enclosures to restrict the entry of dust to prevent ignition of flammable dust. This kind of equipment will install live parts in a protective enclosure, which limits the entry of dust and isolates the ignition source from the dust to prevent explosions. According to the difference in the dust-proof structure of the device, the device is divided into Type A device or Type B device. According to the dustproof level of the equipment shell, the equipment is divided into 20, 21 and 22 grades, which are applicable to dust dangerous places in 20, 21 or 22 zones.
II. Selection of explosion-proof types of electrical equipment in explosive gas atmospheres
For explosion-type gas environments in different regions (Type II environment), different types of explosion-proof types need to be selected according to actual needs.
1. Types of explosion-proof symbols applicable to explosion hazardous areas Zone 0 intrinsically safe (ia level) ia
Other electrical equipment specially designed for Zone 0
Zone 1 applies to zone 0 explosion-proof type flameproof d
Increased safety e
Intrinsically safe ib
Oil-filled o
Positive pressure type p
Sand filling type q
Zone 2 is suitable for explosion-proof zone 0 zone or zone 1 zone 2 spark-free type n
It may be easy to see in normal practical use that many explosion-proof electrical products use a variety of explosion protection methods in one product. For example, Lighting fixtures may employ increased safety protection (housings and terminal boxes), flameproof protection (switches), and encapsulation type protection (ballasts). This will enable manufacturers to use the most suitable composite explosion protection method. One thing to note is that the order of the explosion protection methods listed on the product nameplate will often tell the user the structure of the product. If a product is identified as Exde, it is most likely to be a flameproof type with increased safety components. Another product, labeled Exed, is most likely not a flameproof enclosure (such as stainless steel or reinforced polyester glass) with a flameproof switch or component mounted in it. Both products may be suitable for use in Zone 1, but they use different explosion protection measures to achieve the same purpose. Be three flag-proof equipment according to their actual needs and know the information to select the best available to achieve a balance in غير مجاز مي باشدt, performance, and security aspects of the type of protection products
1. Explosive Gas Environment Explosion-Proof Equipment Marks Class II explosion-proof equipment is marked in the order of explosion-proof utility signs, equipment explosion-proof types, equipment environmental groups, gas groups, and temperature groups.
Explosion-proof public sign - International Electrotechnical Commission (IEC) mark "Ex";
CENELEC logo "EEx"
Explosion-proof type mark: flameproof type - "d";
Increased safety - "e";
Positive pressure type - "p";
Sand filling type - "q";
Intrinsic safety - "i", also refined to "ia" and "ib" level;
Oil-filled type - "o";
No spark type - "n";
Casting type - "m";
Special type - "s"
Equipment Environment Group Logo - Class I, Class II Gas Group Logo - A, B, C
Temperature Group Flags - T1 to T6
Such as ExdIICT6, indicating explosion-proof explosion-proof equipment, can be used in explosive gas environment, C gas group, temperature group T6.
2. Explosion-proof dust environment Explosion-proof equipment signs The marks of Class I explosion-proof equipment are marked in turn according to the order of dust-proof public signs, equipment types, equipment levels, and temperature groups.
Anti-dust lit public signs - "DIP"
Equipment type - "A", "B"
Equipment level - "20", "21", "22"
Temperature Group Flags - T11 to T13
Such as DIPA21T13, said it can be used for 21 District A equipment, temperature group T13.
Color Glass
Glass Tube,Lab Glassware Co., Ltd. , http://www.nsglasstube.com
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