How To Choose A Suitable Explosion-proof Crane?

How to choose a suitable explosion-proof crane?
 

Definition of explosive hazardous area: Under atmospheric conditions, a mixture of gas, vapor or mist, dust or fibrous combustible substances and air, after being ignited in the combustibles, combustion or explosion will spread throughout the unburned mixture .

 

Our company will give you different design solutions according to the different environments provided by customers. There are many environments that can cause explosions.
 

Fires in gas stations, warehouses, and storage tanks often cause explosions;
 

The raw materials and products in the production process of chemical enterprises have low boiling points, and most of the substances are flammable and explosive. After a fire, the burning speed is very fast, and it is very easy to form a sea of fire;
 

In dust containers, cyclone dust collectors, mixers and other equipment, combustible dust clouds in the air appear continuously or for a long time or frequently in explosive environments, which are very likely to cause explosions. . . .
 

Depending on the environment, the explosion-proof bridge cranes and supporting explosion-proof motors designed by our company will also be different. How to choose the explosion-proof motor that suits you?

 

 

1. Isolation type motor
 

It uses a flameproof enclosure to separate the electrical parts that may generate sparks, arcs and dangerous temperatures from the surrounding explosive gas mixture. However, this casing is not airtight, and the surrounding explosive gas mixture can enter the interior of the motor through the gaps between the joint surfaces of the various parts of the casing.
 

Explosion may occur when it comes into contact with ignition sources such as sparks, arcs, and dangerous high temperatures in the casing. At this time, the flameproof casing of the motor will not be damaged or deformed, and when the explosion flame or hot gas passes through the joint surface gap, Nor can it ignite the surrounding explosive gas mixture.

 

Its main features are:
 

(1) The corresponding relationship of power level, installation size and rotational speed is consistent with DIN42673. At the same time, considering the inheritance of YB series and the interchangeability of Y2 series, necessary adjustments have been made to make it more effective and applicable.
 

(2) The whole series adopts Class F insulation, and the temperature rise is assessed by Class B.
 

(3) The noise limit is lower than that of the YB series, close to the Class I noise of the YB series, and the vibration limit is equivalent to that of the YB series.
 

(4) The enclosure protection level is increased to IP55.
 

(5) The whole series adopts low-noise deep groove ball bearings, and the center height of the machine base is above 180mm. The motor is equipped with an oil injection and discharge device.
 

(6) There are two types of motor cooling fins: parallel horizontal distribution and radiation distribution, and the parallel horizontal distribution is the main one.
 

(7) The main performance indicators have reached the international advanced level in the early 1990s.

2. Increased safety motor is a motor structure that will not produce arcs, sparks or dangerous high temperatures under normal operating conditions, and then take some mechanical, electrical and thermal protection measures to further avoid normal or approved overload conditions. There is no danger of arcing, sparks or high temperatures, thereby ensuring its explosion-proof safety.

 

Its characteristics are:
 

(1) It meets the requirements of increased safety explosion-proof motors, adopts a series of reliable measures to prevent sparks, arcs and dangerous high temperatures, and can safely operate in explosion-hazardous places in Zone 2.
 

(2) Brushless excitation is adopted, and a rotating rectifier disc and a static excitation cabinet are installed. The excitation control system is reliable; the polarity slip is accurate, and there is no impact; the excitation system has reliable out-of-step protection and strong re-stepping ability; the circuit design is reasonable , The discharge resistor does not heat up during work; the excitation current has a wide adjustment range.
 

(3) The synchronous machine, the AC exciter and the rotating rectifier are coaxial. The rectifier disc is located between the main motor and the exciter, or placed outside the bearing housing.
 

(4) The enclosure protection grade is IP54.
 

(5) Class F insulation is adopted, and the temperature rise is assessed by Class B.
 

(6) Change the traditional lower water cooling to upper water cooling, that is, the water cooler is placed on the upper part of the motor.
 

(7) Install an increased safety type moisture-proof heater, which is fixed in the cover at the bottom of the motor, and is used for heating and moisture-proof when the motor is stopped.
 

(8) Select high-quality raw materials, and leave a large margin in electrical and mechanical calculations, which can meet the operational reliability and temperature requirements of increased safety motors.
 

(9) There are perfect monitoring measures; the main junction box is equipped with an increased safety self-balancing current transformer for differential protection; the stator winding is embedded with platinum thermal resistance for work and backup, and the graduation number is Pt100; water leakage monitoring is installed The instrument monitors the leakage of the water cooler; the sliding bearings at both ends are equipped with on-site temperature display instruments and remote signal terminals.

 

3. Positive pressure motor is a kind of positive pressure electrical equipment.
 

Its structural characteristics are:
 

(1) Equipped with a complete ventilation system, there is no structural dead space inside the motor that may affect the ventilation.
 

(2) The casing and piping are to be made of non-combustible material and have sufficient mechanical strength.
 

(3) Maintain a sufficient positive pressure in the casing and the main pipe relative to the outside atmosphere.
 

(4) The motor must have safety protection devices (such as time relays and flow monitors) to ensure sufficient air exchange, and must also have automatic protection or alarm devices for underpressure in the shell.
 

(5) The quick-opening door or cover on the enclosure must have an interlocking device with the power supply. At present, there is no unified series of positive pressure motors in our country.

 

5. Non-spark type motor: refers to the motor that will not ignite the surrounding explosive mixture under normal operating conditions, and generally will not cause ignition failure.

 

6. Dust explosion-proof motor: refers to the design and manufacture of its casing according to the specified conditions, which can prevent dust from entering the motor casing or can not completely prevent the dust from entering, but the amount of entry does not hinder the safe operation of the motor, and the accumulation of internal dust is not easy to cause ignition hazards. Motors that also do not cause explosions of surrounding explosive dust mixtures.
 

Its characteristics are:
 

(1) The casing has a high degree of sealing to reduce or prevent dust from entering the casing, and even if it enters, the amount of entry will not cause an ignition hazard.
 

(2) The allowable maximum surface temperature of the control enclosure shall not exceed the specified temperature group.
At present, it has been used in the mechanized equipment of the national grain reserve. The national standard for dust explosion-proof electrical equipment is GBl2476.1-90 "Explosion-proof Electrical Equipment for Explosive Dust Environments".