Does the fan motor of the cooling tower of the circulating water field have to be explosion-proof?

Explosion-proof considerations are required. One is that the cooling water from the water drying tower may exchange heat for the flammable liquid when it goes to the heat exchanger, which may lead to leakage. The other is that Article 14 of Appendix B of GB 50058-2014 Design Code for Electrical Equipment in Explosive Hazardous Environments specifically talks about water-drying towers. For mechanical ventilation cooling towers that handle cooling water for production equipment (Figure B.0.1 14), when divided into explosion-risk areas, the area with the vent pipe at the top of the return pipe as the center, a radius of 1.5m and a cooling water tower and a height of 3m above it can be divided into Zone 2. The scope of the pump pit under the floor should be Zone 1.

Looking at the legend of the specification, how do you understand the text "Hydrocarbon vent pipe at the top of the return pipe"? On site, only the circulating water return main pipe goes directly to the cooling water tower and then branches into each tower. There is no hydrocarbon vent pipe. Do some cooling towers have this pipe at the top? What is his role? In addition, in the previous refining and chemical enterprises, the cooling tower fan motors of the circulating water plants were not explosion-proof, and explosion-proof motors were only installed later. Are there no requirements for this in previous versions of this specification?

I would like to ask, how do you understand the premise "when divided into an explosion hazard area" (for illustration 14) in Article 12 of Appendix B of GB 50058-2014 Design Code for Electrical Equipment in Explosive Hazardous Environments? Is it possible that the cooling water tower area is not classified as an explosion hazard area? If so, under what conditions can it not be classified as an explosion hazard area?

It is still necessary to analyze specific issues in detail to determine whether the fan motor of the cooling water tower that circulates water needs to be explosion-proof. Typical situations where explosion protection needs to be considered for cooling water tower fan motors are:: When there is a cooler or condenser for light hydrocarbons or liquefied hydrocarbons (ethane, propane, propylene, LPG, etc.) that uses circulating water to cool them in the device system, usually the operating pressure of these materials is higher than the pressure on the circulating water side of the heat exchanger. If there is a leak in the heat exchanger, a small amount of light hydrocarbons or liquefied hydrocarbons may leak into the circulating water. When the circulating water returns to the cooling tower of the circulating water station, a small amount of light hydrocarbons or liquefied hydrocarbons are insoluble in water and evaporate upward along with the evaporated water vapor, which may cause the fan motor to be in an explosive environment. Therefore, when it comes to such application scenarios, the fans of cooling water towers need to use explosion-proof motors. Setting a release pipe at the high point of the circulating water return pipe near the cooling water tower is also to guide the gaseous hydrocarbons contained in the circulating water return water to a safe place at the high point for discharge in an organized manner, and to reduce the possibility of bringing them into the cooling water tower.

Under normal circumstances, the cooling water tower fan of the circulating water station does not need to be explosion-proof, but if it is in an explosion-proof area, it still follows the explosion-proof requirements.

Personally, I think that as long as the heat exchange medium is flammable and explosive, for the sake of complete safety, the cooling tower fan area is explosion-proof. I feel that the meaning of the provisions in the specification should be the same.