Electrical selection principles and environmental conditions for explosion-proof chain hoists used in explosive environments

1、 Environmental condition requirements

temperature range

Operating environment temperature: usually -20 ℃ to+40 ℃. If the actual ambient temperature exceeds this range, it should be clearly marked on the equipment nameplate, and the maximum surface temperature of the equipment should be calculated based on the highest ambient temperature.

Surface temperature limit:

Class I equipment (underground coal mine): When there is no coal powder deposition, the maximum surface temperature shall not exceed+150 ℃; If dust prevention measures are taken, the temperature can be relaxed to+450 ℃.

Class II equipment (explosive gas environment in factories): The temperature group (T1-T6) should be determined based on the ignition temperature (AIT) of the gas or vapor, and the maximum surface temperature of the equipment should not exceed the limit of the corresponding group (such as T4 group equipment with a maximum surface temperature of 135 ℃).

Local temperature limit: For components with a total surface area of ≤ 10mm ² (such as transistors or resistors), the maximum surface temperature is allowed to exceed the group temperature marked by the equipment, but it must meet the safety margin (+50 ℃ for T1-T3 group and+25 ℃ for T4-T6 group).

compressed air

Suitable for environments with air pressure ranging from 0.8 × 10 ⁵ Pa to 1.1 × 10 ⁵ Pa, covering most industrial scenarios.

Humidity and corrosive gases

Wet tropical environment: If the equipment is used in an environment with a temperature of ≥ 20 ℃ and a relative humidity of ≥ 80% for more than 12 hours in a day, it must have moisture and heat resistance performance (such as underground equipment in coal mines).

Corrosive gases: Corrosive substances such as acids, alkalis, salts, and ammonia may exist in the production environment of industries such as chemical and petroleum. Equipment with corrosion resistance capabilities (such as stainless steel casings or anti-corrosion coatings) should be selected.

Protection level (IP code)

The appropriate protection level should be selected based on pollutants such as dust and moisture in the environment. For example, for outdoor use or humid environments, IP54 or higher rating should be selected to prevent dust and rainwater from entering.

2、 Principles of Electrical Appliance Selection

Safety, reliability, and economic rationality

The selection should prioritize safety while also considering economy. Avoid excessive design leading to increased costs or insufficient selection causing safety hazards.

Matching of explosion hazard zone levels

Regional division: According to the frequency and duration of explosive gas environments, they are divided into Zone 0 (continuous occurrence), Zone 1 (possible long-term occurrence), and Zone 2 (only occurring in abnormal situations).

Explosion proof type selection:

Zone 0: Only intrinsically safe (ia) or special type (s) devices are allowed to be used.

Zone 1: You can choose explosion-proof type (d), increased safety type (e), positive pressure type (p), intrinsic safety type (ib), etc.

Zone 2: Non sparking type (n), sealed type (m), etc. are allowed, and equipment suitable for Zone 1 can also be selected.

Example: For explosion-proof chain hoists used in Zone 2, if manual operation is required and there is no risk of electric sparks, non spark type (n) equipment can be selected to reduce costs.

Explosive substance category and level matching

Category classification:

Class I: Equipment used underground in coal mines.

Class II: Equipment used in explosive gas environments other than coal mines, further divided into Class IIA, Class IIB, and Class IIC (based on maximum test safety gap (MESG) or minimum ignition current ratio (MICR)).

Selection requirements: The category and level of the equipment shall not be lower than the category and level of explosive substances in the environment. For example, if there are Class IIB gases (such as ethylene) in the environment, Class IIB or Class IIC equipment needs to be selected.

Temperature group matching

Select the temperature group (T1-T6) of the equipment based on the ignition temperature (AIT) of explosive gases in the environment. For example:

Isobutane (AIT=460 ℃): Select T1 group equipment (maximum surface temperature ≤ 450 ℃).

Butane and ether (AIT=160 ℃): T4 group equipment (maximum surface temperature ≤ 135 ℃) needs to be selected.

External impact protection

The impact of external factors such as chemical corrosion, mechanical action, thermal effect, and electrical interference on the explosion-proof performance of equipment needs to be considered. For example:

Chemical corrosion: Choose stainless steel casing or anti-corrosion coating equipment.

Mechanical damage: Avoid using explosion-proof equipment in areas prone to impact (deformation of the casing may cause explosion-proof failure).

Thermal effect: Ensure good heat dissipation of the equipment to avoid danger caused by overheating.

Mobile device restrictions

In explosive hazardous environments, the use of portable and mobile equipment should be minimized as much as possible to reduce the risk of electric sparks. If necessary, choose equipment that meets higher explosion-proof standards (such as intrinsic safety type).

3、 Practical application suggestions

Environmental assessment: Before selecting, it is necessary to comprehensively evaluate the types, concentrations, temperatures, humidity, and other parameters of explosive substances in the environment, as well as the installation location and frequency of use of the equipment.

Compliance verification: Ensure that the equipment complies with GB 3836 series standards (China) or IEC 60079 series standards (international), and obtains an explosion-proof certificate.

Maintenance and inspection: Regularly check the explosion-proof performance of the equipment (such as damage to the explosion-proof surface, aging of seals, etc.), and replace faulty components in a timely manner.

Personnel training: Operators need to receive training on the use and maintenance of explosion-proof equipment to ensure safe operation.

The main equipment produced by Hebei Makita: stage electric hoist, electric chian hoist, wire rope electric hoist，Hand chain hoist, lever hoist, pneumatic hoist and other lifting equipment