Explosion Proof Lift
Explosion Proof Lift
The designing of electrical appliance and components for installation of explosion proof electrical system is based on a basic concept that fire is created through three elements including flammable substance (in adequate amount), oxygen, and source of ignition. Hence, to prevent an explosion, extreme heat or sparks along the surface of the cover must be prevented. However, if any sparks should occur within the cover, spreading of fire to external area must be prevented.
Hence, squirrel-caged induction motors are most commonly used in factories. If it is required in flammable areas, you must ensure that it has high safety standard and explosion or fire proof. Base on European standard, gas zone can be divided into 3 types according to its potential of fire ignition, severity, or impact of explosion as follows:
Zone 0 (ATEX 1G/1D) – This is the most hazardous gas zone as it contains gas or vapors that can potentially lead to long explosion duration or more than 100 hours per year. This includes containers filled with flammable liquid or gas, fuel tank, or gas tank for trucks. Hence, no motors are allowed in this Zone 0.
Zone 1 (ATEX 2G/2D) – This is a hazardous gas zone that may potentially lead to unexpected explosion during normal operation. This zone contains gas or vapors that can cause explosion to more than 10 – 1000 hours a year. This includes areas surrounding Zone 0, ventilation areas, access doors for transferring flammable substance, or areas surrounding flammable gas pipeline. Hence, any electrical appliance used in this zone must undergo Type Testing and approved by reliable central organizations such as PTB, BVS, US-NEC, or the new European standard called ATEX.
Zone 2 (ATEX 3G/3D) – This particular zone contains no flammable gas during normal operation. The amount of flammable gas in Zone 2 is less than 10 hours per year. Hence, explosion rarely occurs in this zone and would occur for only a short period of time. Electrical appliances under Zone 1 standard can be used in this zone without the need for certifications. However, it must not cause sparks. Meanwhile, surface temperature of equipment must be lower than 880oC. Normally, a squirrel-caged induction motor can be used in Zone 2 by determining its maximum surface temperature during operation according to each class of temperature using T1/T2/T3. Such code is used to indicate motor surface temperature to see under which gas or vapor condition it is suitable for use and what type of hazards it may cause.
When determining explosion prevention standard, all hazardous areas must be covered including flammable or explosive dusts. Based on the European standard, danger dust zones include Zone 10 and Zone 11 as follows:
Zone 10 – This zone is where explosion and fire will most likely occur and for a long period of time due to flammable dust. It is therefore considered as an extremely hazardous area. This includes inside a mixing machine, grinding machine, compressor, or dehydration machine. Hence, any electrical appliances used in this zone must undergo Type Testing and approved by reliable central organizations such as PTB, BVS, US-NEC, or the new European standard called ATEX.
Zone 11 – This zone is where explosion and fire can potentially be caused by flammable dust or dust dispersion and only occurs within a short period of time. This includes areas surrounding silo tank or Zone 10. Any electrical appliances or motor used in this zone must therefore be separated in accordance with DIN 57165/VDE0165 part 7.1.