Explosives and explosive danger zone
Explosion danger area "refers to the entities explosive dangerous gas or (liquid, steam) mixed with air to form explosive gas mixture, when have set off the source, can produce explosion or burning area (hereinafter referred to as" hazardous area ").
The state of the explosive material is divided into two kinds: one kind is a gas, liquid or vapor and air mixture and form explosive gas in the danger zone, area known as the first one. The other is a dust explosive danger zone, known as the second area.
Explosive gas mixture detonating capability, marks its explosion hazard degree of high and low, the greater the explosive power, the higher risk. Explosive mixture detonating capacity available maximum test security said on the sidelines. At the same time, the explosive gas and liquid to the difficulty of the steam, the mist was lit also marks its explosion hazard degree of discretion, it USES the minimum ignition current than said. Class II flameproof electrical equipment or intrinsically safe electrical equipment, according to the applicable to the biggest test of explosive gas mixture security clearance or minimum ignition current ratio, further divided into type IIA, IIB, IIC class. See table 1.
The ignition temperature of explosive gas mixture is the temperature limit value can be lit. Electrical equipment according to its maximum surface temperature can be divided into T1 ~ T6 group, makes the corresponding T1 ~ T6 group of electrical equipment of the highest surface temperature cannot exceed the corresponding temperature classes permitted. Temperature group and the relationship between the ignition temperature, see table 2. See from table 2, different explosive gas ignition temperature is different. For T1 gas ignition temperature of the highest temperature classes. And for T6 gas temperature classes are most likely to be lit.
Select a product engineering business considerations
Product selection must conform to the use place of safety standards, such as explosion-proof type and level of flameproof and category. When area there are two or more than two, group explosive mixture, at the same level should be according to the dangerous degree appropriate to the higher level and group selection explosion-proof type.
Some petrochemical factory of corrosive gas and liquid is relatively serious, should choose stainless steel explosion-proof camera;
Have a safe hidden trouble, do not use explosion-proof camera, such as lack of fastening screws, cable into the device sealing ring without clamping device or sealing ring has been lost, explosion-proof surface wear, nameplate has serious corrosion or lost;
Used in outdoor explosion-proof camera must possess strong waterproof performance;
Explosion-proof products have signs and marks, signs, nameplate or warning card) is to use copper. Signage content in addition to the product type, specification, manufacturer name, production date, or factory number, there are the "Ex" marks, explosion-proof explosion-proof certificate number. Mine explosion-proof electrical products to be "Ex" marks, "MA", explosion-proof marks and explosion-proof certificate number, MA of coal mine safety signs shall apply mutatis mutandis to card number;
Imported from abroad of explosion-proof electrical products must pass China explosion-proof quality inspection institutions accredited inspection;
Carefully identify fake and inferior products. Main show is no explosionproof qualification card number, sign in fake explosionproof qualification card number, no manufacturer, coarsely.
Explosion-proof camera installed pipeline installation
Level 1-1 of low voltage wiring construction within the hazardous locations
Level 1-1 low voltage wiring construction requirements within the hazardous locations with flameproof tube construction or cable. Portable electrical equipment (often or with the continuously moving equipment), should be used with a grounding conductor of the neoprene insulation cable or other cable performance is the same. In metal tube wiring, from electrical equipment area of the junction box to level in 1-2 dangerous or hazardous area border seal joint between the wire line, all needs to make flame-proof structure of pipeline.
In addition, grade 1 to grade 1 dangerous area, also can use cable wiring. Due to the layout of major accident, at the end of the cable connection, therefore, in addition to the ends of the cable into the flameproof terminal box, to choose to suit and laying cable, so as to avoid external injury.
The external wiring connection with electrical equipment
Flameproof thread the introduction of the method: the effective part of the mesh should guarantee the above 6 buckle, to comply with the technical requirements for "thread explosion". In order to ensure thread engagement, completely with a nut lock.
Flame-proof packing type: the insulated wires through the wall part with packing seal, in order to achieve the flame-proof function. Generally with asbestos, glass fiber, synthetic rubber, or other appropriate elasticity, good heat resistance and insulation materials. On the outside of the packing gland is equipped with cable clamp and cable protection tube, etc., avoid packing part damage by external force. By introducing flame-proof packing type steel tape armoured cable (including corrugated steel tube armored), should be peeled off through the junction box guide at the entrance of anti-corrosion layer and steel tape armoured.
Flameproof encapsulation way of introduction: the introduction of the flameproof encapsulation way, refers to fill the mixed packing to insulation wire through the wall part, through the conductor was in place. This method is only applicable to low voltage circuits. The introduction of rubber or plastic cable outlet box inlet, the seal should maintain a flame-proof performance, at the same time, also must be installed cable protection tube. The filling depth of mixed packing, should be 1.5 times bigger than the cable inlet diameter (minimum of 40 mm). Introduced inside the mouth filling amount due and said need tags. At the entrance of guide should be equipped with cable clamp plate, make the sealing part of the cable from pressure.
Mixed filling cavity structure shape and size, it should be against mixed filler completely through the wires and it is advisable to fill the cavity wall. Fill the cavity wall should show convex-concave shape, lest hardening mixed packing fall off. Through the conductor shall not exceed 9 root in general. With baffle, guide to symmetric decoration, such as through the spacing between wires, and fill the cavity wall of the interval, in principle for more than half of the wire diameter (minimum of 2 mm).
Flameproof metal bushing type: refers to with metal casing flange as the main body, with compression ring and nut of pipe fittings. A way of introducing apply to level 1 and level 2 level of explosive. Through cable with the metal sheath to cabtyre cable, cable, linen or vinyl resin insulated cable, cable also can choose other equivalent performance. Metal casing the joint between the inside and outside the cable weeks maximum allowable surface gap value, namely the difference of 0.2 mm in diameter, the minimum permissible value of 25 mm gap length, pipe diameter should be below than standard cable outer diameter of 0.15 mm.
The construction of flameproof tube
The method of a, piping:
1, threaded connections: wire tube connected to electrical equipment outlet box and its attachment, generally adopts screw connected with pipe thread (thread). The mesh part of screw thread connection for the 6 button above, and with tighten the lock nut is firm.
2, flexible connection: need to adopt flexible connection way of piping, it must use the flame-proof structure flexible connector. Its joint bending radius of the inside of the parts of the flexible joint of pipe diameter more than 5 times.
Second, the requirement of the sealing technology
When wire line through between grade 1 to grade 1 danger zones and other areas of partition wall, seal joint can be located in on any side of the partition, but between the seal joint and the partition in this piece of wire and tube can not have joint. More than 2 inches of wire in the tube seal joint in principle should be installed in the junction box or with other box class 45 centimeters of less than, and close as far as possible.
Three, mixed filler filler sealing requirements
Filled with sealing mixing should as far as possible do not breathe freely, must make the wiring and mixed packing completely applied in each wire coating and sealed joints between the lining. In any case, the effective length of filling layer shall be less than the diameter of wire and tube (minimum of 20 mm). Will be finished packing filling, confirm having fully meets the requirements, closely screwing in filling the mouth with a cock.
Cable construction
First use a room according to selecting the appropriate cable, such as with rubber, plastic sheath of the cable, or metal armored cable. On the occasion of corrosive gas or liquid, USES the cable must be considered. Way, introduced the flame-proof packing, introducing cable junction box, the cable should be circular, sheath surface can not have concave and convex inequality.
In district 1 places using cable wiring Ming fu, the cable must be copper core armored cable, in 2 places can be used in a plastic sleeve (oak) cables. Armoured cable appropriate chooses PVC insulation (core) within the inner and outer sheath steel tape armoured cable. Armoured cable into electrical equipment, its internal earthing line and equipment grounding bolt connection; External steel belt and metal case should bolt connection with external equipment, rubber seal shall not directly in armored steel band, and the other end of the steel belt must also be reliable grounding.
For the dangerous sites electrical wiring general provisions, which has two kinds of cable wiring and steel pipe wiring. Insulation in addition to the overhead wires shall not Ming fu, must by the metal wiring. Rubber or plastic sheath cable can use bridge, pallet, plywood, etc. Avoid using in cable trench (ditch water, gas, an accident). Can't be avoided in cable trench should be filling sand, when filled. Mobile devices must be set cable wiring and cable BaTuo prevention device.
