What Are Explosion Proof Overhead Crane Application Conditions?

The LB-type explosion-proof electric single-girder crane is a piece of safe material hanlding equipment that uses an HB-type explosion-proof electric hoist as its lifting mechanism. The primary function is to complete the displacement of objects through the hook or other handling device in an intermittent and cycle working way, and it is an important tool and equipment for realizing production mechanization and automation, relieving heavy labor, and improving labor productivity in the modernized industrial enterprise.

The LB-type explosion-proof electric single girder crane is designed and built to withstand explosions. On the basis of an ordinary electric single girder crane, an explosion-proof motor and explosion-proof electrics are installed, followed by other auxiliary mechanical explosion-proof measures to ensure that electric sparks, heat, or combustible dust caused by the crane and working environment do not cause a fire, explosions, or other hazards.

The motors and electrics of the explosion proof crane are flameproof, according to the provisions of GB3836.1 "Explosive Atmosphere Part 1: General Requirement for Equipment" and GB3836.2 "Explosive Atmosphere Part 2: the Equipment Protected by Flameproof Enclosure "d"". When the explosion-proof degree is Exd II CT4, the running mechanism will take spark-proof measures, and the complete crane system will conform to the provisions of JB/T 10219 "Specification for explosion-proof cranes with electric wire rope hoist."

Classifications

According to the provisions of Chapter 4 in GB3836.1, the explosion proof crane is divided into class I and class II electrical equipment based on the explosive gas atmosphere. According to the provisions of GB 12476.1, the electrical equipment used in a combustible dust environment are only divided into a class, and the corresponding crane classification is as follows.

• Class I: Exproof crane for coal mine
• Class II cranes are used in other explosive gas environments other than coal mines.
• Dust class: A crane used in a combustible dust environment.

According to the explosive gas characteristics, class II flameproof "d" explosion-proof crane and intrinsically safe I explosion-proof crane can be divided into class IIA, class IIB, and class IIC crane. When acetylene is present in the IIC environment, it should be noted in the contract. The class IIB explosion-proof hoist crane's operating conditions apply to class II A, while the class IIC explosion-proof hoist crane's operating conditions apply to both class II A and class IIB.

Dust type cranes are classified as A-type or B-type based on the dust-proof capacity of their electrical equipment. B-type cranes have higher heat cycle test requirements than A-type cranes and are denoted by DIPA and DIPB. A type of dust-proof enclosure of electrical equipment used in an explosion-proof electric single girder crane is recommended.

Temperature group

The surface temperature of class I crane electrical equipment or components should not exceed:

• —150°C, when the surface of the electrical equipment or components may deposit coal dust.
• —450°C, when the surface of electrical equipment or components cannot deposit coal dust or when precautions have been taken to prevent coal dust deposit (such as sealed against dust or ventilation).

Table 1 shows the maximum surface temperature group of electrical equipment of class II and dust type explosion-proof crane.

Table 1 the maximum surface temperature group

Division of explosive gas explosion-proof hazardous area

Under normal conditions, the 0 zone is the location where explosive gas mixtures appear continuously in a very short time or exist for a long time.

• 1 zone: the location where an explosive gas mixture may appear under normal conditions.
• 2 zone: under normal conditions, the location where the explosive gas mixture cannot appear, but under unusual conditions, it may appear in a short time when equipment is out of order or is operated incorrectly.

At the moment, explosion-proof electric single girder cranes are only applicable to zones 1 or 2, and not zone 0.

• 20 zone: during normal operation, the location where combustible dust appears continuously or frequently, in sufficient quantity to form a mixture of combustible dust and air and/or possibly form an uncontrollable and thick dust layer.
• 21 zone: During normal operation, the location where the amount of dust is sufficient to form a mixture of combustible dust and air is not divided into 20 zones. This zone includes the area immediately adjacent to places filled with or discharged dust, the area where the dust layer appears and possibly forms a combustible mixture of combustible dust and air during normal operation.
• 22 zone: Under abnormal conditions, combustible dust may occasionally appear and exist in a short period of time, or combustible dust may occasionally deposit or exist in the dust layer, resulting in a mixture of combustible dust and air. If combustible dust deposits or dust layers are not avoided, it should be divided into 21 zones.

Explosion-proof electric single girder crane operating conditions

• Explosion-proof electric single girder crane is operated indoors, working ambient temperature is -20°C+40°C, relative air humidity is not more than 85 percent (when ambient temperature is 25°C), altitude should not exceed 1000m. If the above-mentioned environmental conditions are exceeded, it should be determined after consulting with the user.
• When operating in an explosive gas atmosphere, the working area of an explosion-proof electric single girder crane is 1 zone or 2 zones divided in GB 3836.14.
• When operating in a combustible dust environment, the working area of an explosion-proof electric single girder crane is 21 zone or 22 zone as specified in GB 12476.3.
• The working environment should be well-ventilated and equipped with all necessary amenities.

（6）Examples of explosion-proof hoist crane motors and electrical equipment used in an explosive gas atmosphere

Table 2 shows the applicable explosive gas for each explosion-proof degree and the corresponding temperature group of flameproof motor and electrical equipment.

Table2 Explosive Gas

Table 3 shows the applicable combustible dust for each dust-proof structure, as well as the corresponding temperature group of dust explosion-proof motor and electrical equipment.

Table 3 Dust Name

Explosion-proof electric single girder cranes are outfitted with an explosion-proof motor, an explosion-proof switch box, explosion-proof pendent control, an explosion-proof limit switch, an explosion-proof over-load limiter, an explosion-proof hoist limit device, explosion-proof junction boxes, a  switch, and other safety features. The flexible cable is used for power wires, the connection between electrical equipment is made with a rubber sheath multiple copper cores cable with a ground core wire, and the wiring cable is also made with a rubber sheath multiple copper cores cable. The joints in the middle of the cable should be prohibited. Explosion-proof junction boxes are available if required. On the obvious location of the enclosure of explosion-proof electrical equipment, there is a warning board "Do not open if there is electricity."

The crane's work duty is A3. The operating mode of an explosion-proof electric single girder crane for a factory is typically ground controlling, with a maximum travel speed of 25m/min. However, remote and cab operation are also selected based on specific conditions; the basic patterns are shown in Figures 12 and 13. At the moment, the only mode of operation for this mine crane is ground control, with a traveling speed of 20m/min. The basic patterns are shown in Figures 14 and 15.

When the explosion-proof degree is EXdIICT4, the wheel tread and flange parts should be made of copper alloy or other materials that, due to impact and friction, do not ignite the explosive gas. The cable pulley's pull wire should be made of stainless steel wire rope. The hook should take precautions to avoid dangerous parts caused by impact and friction. The crane and trolley travel at a maximum speed of 16m/min.

Explosion Proof Hoist, Winch, Crane System

To reduce the risk of sparking, consider non-sparking materials such as copper, bronze, and austenitic stainless steel for coatings or as material substitutes for material handling overhead and crane equipment. These materials are not only spark resistant, but also corrosion resistant. Surface corrosion can increase friction between mating components, hence corrosion prevention is crucial when lifting in hazardous settings.

1 Ton, 5 Ton,10 Ton Explosion Proof Single Girder Overhead Cranes

Explosion proof single girder overhead crane is for mining, oil, gas, dusty applications, featured as spark proof, flame proof & explosion proof.

5 Ton - 75 Ton Explosion Proof Double Girder Overhead Crane

5 ton -75 ton explosion proof double girder overhead cranes for workshops with flammable or explosive gases. Explosion-proof grade: EXdIIBT4 and EXdIICT4.

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Air hoist explosion proof feature

Article by Bella ，who has been in the hoist and crane field since 2016. Bella provides overhead crane & gantry crane consultation services for clients who need a customized overhead travelling crane solution.Contact her to get free consultation.