What are the potential safety hazards in using explosion-proof electric hoists?

With the vigorous development of the chemical industry, there are more and more explosion-proof electric hoists and various explosion-proof lifting tools. In recent years, there have been frequent explosions in chemical plants. Among them, the explosion-proof electric hoist accident is caused by a variety of reasons, and the supervision of pressure equipment may also be involved. Below is an example:

After the accident:

In November 1998, two explosion-proof electric hoists were used in the renovation project of the acetylene station of a certain factory. Since the electric hoist is used on the acetylene gas generator, it has no explosion-proof effect on acetylene gas, water gas, hydrogen and other gases, so the electric hoist is put into use in the first ten days of each month. When the lifting calcium carbide is added to the acetylene generator, the acetylene gas rushes to the top of the electric hoist and penetrates the explosion-proof junction box of the contactor on the electric hoist, causing a strong explosion. All electrical wiring at the scene burned down.

Cause Analysis:

the measures taken:

In order to make the explosion-proof electric hoist operate safely in the production place full of acetylene gas for a long time, the four AC contactors on the motor must be moved to the explosion-proof or explosion-proof power distribution room. Among the electrical components on the electric hoist, in addition to the frequent electrical sparks between the contacts of the AC contactor, other explosion-proof electrical components (such as electromagnetic brake coils, limit switches, motors, etc.) will not produce electrical sparks during normal operation. If a method can be found to distinguish between the AC contactor and the explosion-proof contactor on the electric hoist, this electric hoist will be able to operate safely for a long time in a production environment full of acetylene gas.

The acetylene station did not take the above measures due to improper selection of explosion-proof products. At the same time, moving the AC contactor on the explosion-proof electric hoist to the explosion-proof or explosion-proof power distribution room also facilitates the daily maintenance of electrical equipment. The switches of the original explosion-proof electric hoist installed at the production site are often not overhauled and regularly inspected. The practice of the new product proved that after the switch was moved into the explosion-proof power distribution room, the accident rate was reduced by more than 80%.