Dust explosion-proof 20 zone, 21 zone, 22 zone difference and dust explosion-proof grade

Dust explosion-proof motor knowledge

According to the characteristics of the dust explosion-proof motor, it is divided into 20 zones, 21 zones, 22 zones, and the explosion-proof grade of these 3 zones. When choosing the dust explosion-proof motor, the user can determine the motor for himself according to the characteristics of the site corresponding to the explosion-proof grade.

Dust hazard level

Zone 20: Places and inside containers where combustible dust occurs continuously or frequently during normal operation in quantities sufficient to form mixtures of combustible dust with air or where uncontrollable and extremely thick dust layers may form.

Zone 21: Places where the amount of dust that may occur during normal operation is sufficient to form a mixture of combustible dust and air but are not classified as Zone 20.

Zone 22: Under abnormal conditions, flammable dust clouds appear occasionally and only for a short time, or flammable dust occasionally accumulates or may exist dust layers and produce flammable dust air mixtures.

The customer will have doubts when choosing the explosion-proof grade of the dust explosion-proof motor, and the previous explosion-proof grade is different from the current one.

Question 1: How can DIP B21 be Extd B21 now?

Answer: According to the latest dust explosion-proof motor national standard number: Gb 12476.5-2013 "Electrical equipment for combustible dust environment" Part 5 shell protection type "tD" representative, dust explosion-proof motor grade: Ex tD A20 T130°C, Ex tD A21 T130°C, Ex tD A22 T130°C; Ex tD B20 T130°C, Ex tD B21 T130°C, Ex tD B22 T130°C for use in places with combustible dust and combustible floc.

The new dust explosion-proof class: Extd B21 replaces the old dust explosion-proof class: DIP B21

Note: At present, the latest dust explosion-proof motor explosion-proof grade is: ExtD B21 T135℃ IP65

Question 2: The level of 20, 21, 22 zone is high, which explosion-proof level should be selected?

At present, zone 21 is the highest dust explosion-proof grade of the dust explosion-proof motor, which can be used instead of zone 22, because zone 20 does not allow the electric appliance to enter.

Dust explosion-proof grade example:

The previous dust explosion-proof rating: DIP A20 TA,T4 and 20 in the dust explosion-proof mark indicate that there is continuously combustible dust in the place where the explosion-proof motor operates, and the amount is enough to form a mixture of combustible dust and air, and the coefficient of ignition detonation is particularly high. Under normal circumstances, such places do not allow the operation of connected equipment, or the motor can be used in the 21 area or 22 area with less dust through the lead. That is to say: Zone 20 is a place of continuous dust, and there can be no electrical appliances.

The previous dust explosion-proof motor grade: DIP A21 TA,T4 dust explosion-proof mark 21 indicates that the explosion-proof motor may be operating in the site of combustible dust, the amount is enough to form a mixture of combustible dust and air, but not classified into the 20 zone. The coefficient of ignition detonation is higher.

At present, the latest dust explosion-proof motor explosion-proof grade is: ExtD B21 T135℃ IP65

Question 3: What is the difference between Extd B21 and Extd A21? What is the difference between B and A in dust explosion-proof mark?

There are also previous dust explosion-proof grades: DIP B21 TA, Dust Explosion-proof mark and DIP A21 TA. The difference between being the same or not

The difference between B and A in the dust explosion-proof mark: B means that the explosion-proof bonding surface of the motor is A straight port bonding surface, and A means that the explosion-proof bonding surface of the motor is a plane bonding surface, and the two can be interused, but in fact, the explosion-proof structure of the straight port combination is safer than the explosion-proof structure of the plane combination.

The two dust explosion-proof marks should be no difference in price, but the manufacturer in the selection of flameproof structural method is different, A21 and B21 have dust environment 21 zone explosion-proof motor use grade requirements.