The energy concentration, high risk level and potential risk of major hazard source enterprises are the key points of safety risk prevention and control and supervision and management of hazardous chemicals.

According to statistics, from 2011 to 2019, a total of 12 major accidents occurred in China's chemical enterprises, and 12 accidents occurred in major hazard source enterprises. Since 2015, two particularly serious accidents involving hazardous chemicals have occurred in the storage links of hazardous chemicals which constitute the critical quantity of major hazard sources.

In mid May, the Safety Law Enforcement Bureau of the Ministry of emergency management held a key training on the safety inspection of major hazard installations of hazardous chemicals, and put forward 17 key points for inspection. The following 10 key points are selected, each of which corresponds to a typical case for analysis.

Inspection key point 1: whether the storage tank of dangerous chemicals has the problems of over temperature, overpressure, over liquid level operation and random change of storage medium.

Case study:

On June 26, 2019, an explosion accident occurred in the natural flavor extraction workshop of Xumei company in Kaifeng, Henan Province, causing 7 deaths and 4 injuries, resulting in a direct economic loss of more than 20 million yuan. The direct cause of the accident is: the workers' wrong operation, so that the equipment should be operated under normal pressure.

The use of hazardous chemicals storage tank must meet the design process conditions and process control indicators. The design process conditions include storage medium, storage temperature, pressure, liquid level and other key indicators. Otherwise, it may lead to accidents.

Inspection key point 2: whether the safety valve, shut-off valve, pressure relief and discharge system and cooling and cooling facilities are in good condition and put into operation normally.

Case study:

On July 16, 2016, a fire and explosion accident occurred in Shandong Shida science and technology Petrochemical Co., Ltd. located in Rizhao City, Shandong Province. According to the accident investigation report, the manual valves before and after the safety valve on the top of the tank were closed, and the main gas vent line was separated by a blind plate at the boundary of the liquefied hydrocarbon tank farm. As a result, the consequences of the accident were expanded Big.

The safety valve cut-off valve is a shut-off valve installed before and after it. The pressure relief and discharge system refers to the system that can quickly discharge the pressure of the storage tank, usually refers to the flare system or special discharge system. The closing of the safety valve cut-off valve or adding blind plate to the pressure relief system will make the pressure of the storage tank unable to release in case of overpressure or emergency, which will cause serious accidents.

Inspection key point 3: whether the alarm and interlock system for temperature, pressure, liquid level, combustible and toxic gases in the tank farm of hazardous chemicals are put into operation, and whether the important parameters can be remotely transmitted and continuously recorded.

Case study:

On July 16, 2010, the crude oil pipeline of Dalian CNPC International storage and transportation company exploded, causing a fire and a large amount of crude oil leakage, resulting in one death and one injury. The main reason for the accident escalation is that the leaking crude oil tank is not equipped with an emergency cut-off system, which leads to the expansion of the fire.

The storage tank of major hazard source shall be equipped with continuous collection and monitoring system of temperature, pressure, liquid level and other information as well as combustible gas and toxic and harmful gas leakage alarm device, and have the functions of information remote transmission, continuous recording, accident warning, information storage, etc. The tank farm which constitutes the first or second level major hazard source has the function of emergency cut-off. Independent safety instrument system is equipped in the tank farm of primary and secondary major hazard installations involving toxic gas, liquefied gas and highly toxic liquid. Otherwise, it is easy to cause accidents.

Key point of inspection 4: whether the floating plate falls to the bottom during the operation of internal floating roof storage tank.

Case study:

On August 29, 2011, the explosion and fire accident occurred in the diesel tank of PetroChina Dalian Petrochemical Company. The main cause of the accident was that the liquid level of the accident tank was too low, and the gas phase space formed between the floating pan and the diesel liquid level, resulting in the air entering; at the same time, the operation of the upstream device fluctuated, the content of light components in the diesel oil entering the accident storage tank increased, and the explosive gas mixture was formed under the floating plate If the oil flow rate is too fast, a large amount of static electricity can not be exported in time, resulting in electric discharge, which leads to explosion and fire.

The so-called floating tray falling to the bottom refers to that the floating plate falls on the supporting leg due to the low liquid level of the storage tank; after the floating plate falls to the bottom, the gas phase space will be formed between the floating plate and the oil surface, which is easy to cause fire and explosion accidents under the condition of too fast material flow rate.

Inspection key 5: whether detection and alarm devices are set up in the places involving flammable and toxic gas leakage according to national standards and industrial standards; whether explosion-proof electrical equipment is installed and used in explosion-proof dangerous places according to national standards and industrial standards.

Case study:

On June 29, 2010, a deflagration accident occurred in the crude oil storage tank of Liaoyang Petrochemical Company of PetroChina, resulting in 5 deaths and 5 injuries. The main cause of the accident was that the hydrocarbon combustible materials in the crude oil tank reached the explosion limit during the tank cleaning operation, and the electric spark generated by the non explosion-proof ordinary lamp connected to the crude oil tank occurred.

The medium stored in the oil and gas tank area is generally flammable and explosive. The use of non explosion-proof tools, electrical facilities, communication equipment, etc. in the oil and gas tank area, there is a great potential safety hazard, which is easy to cause accidents.

Inspection key 6: whether water injection measures are set for full pressure liquefied hydrocarbon storage tank according to national and industrial standards.

Case study:

On March 5, 1998, the liquefied gas storage tank of Xi'an gas company's liquefied gas Management Institute exploded after leakage, resulting in 12 deaths. The main reason was that the sealing failure of the upper flange of the blowdown valve of the 400m ~ 3 spherical tank caused fire and explosion after the failure of plugging.

When the full pressure storage tank leaks, the liquid level of liquefied hydrocarbon will be raised by injecting water into the tank. Placing the leakage point under the water surface can reduce or prevent the leakage of liquefied hydrocarbon and eliminate the accident in the bud.

Inspection key 7: whether universal pipeline filling system is used for filling flammable, explosive, toxic and harmful liquefied gases such as liquefied hydrocarbon, liquid ammonia, liquid chlorine, etc.

Case study:

On September 18, 2015, an ammonia leakage accident occurred in Henan Zhonghong coal chemical company, causing poisoning to some villagers near the plant area. The cause of the accident was the explosion of the metal hose at the bottom of the ammonia tower in the chemical plant of Zhonghong coal chemical company, resulting in ammonia leakage.

Liquefied hydrocarbon, liquid ammonia, liquid chlorine and other flammable, explosive, toxic and harmful liquefied gas filling safety risk is high, once the leakage is easy to cause explosion combustion, personnel poisoning and other accidents. The universal pipe filling system has the advantages of flexible rotation, high sealing reliability, small electrostatic hazard, long service life, far higher safety performance than metal hose, easy operation and use, and can effectively reduce liquefaction