Causes, prevention, detection and emergency treatment of leaks

In the production process of chemical enterprises, many materials are corrosive, especially in the long-term operating environment of high temperature and high pressure, long production chain and system. The equipment often leaks during production, storage and transportation. Leakage not only loses materials, but also pollutes the environment, causing serious accidents such as fire, explosion, poisoning, etc., which brings great harm to the production of the enterprise. It is extremely unfavorable to the long-term safe and stable operation of the enterprise and threatens the lives of the employees. Safety. According to statistics of industrialized countries, 56% of fires and staff poisoning accidents occurred in chemical companies, which were caused by material leaks that were not discovered or handled improperly. How to prevent leakage is one of the key points for chemical companies to effectively control accidents. The following is the analysis of the causes of the leakage and the precautions to be taken.

First, the cause of the leak

1. Seal failure, resulting in leakage. In chemical production, the pressure and temperature of most equipment pipelines are important factors affecting their sealing. For example, under the action of high temperature, the viscosity of the process medium is small, the permeability is increased, the dissolution and corrosion of the medium to the gasket and the flange will be intensified, and the requirements for the sealing are objectively improved. At the same time, the parts of the sealing assembly are relatively large. The temperature difference, the resulting temperature difference stress causes the thermal expansion of the components to be uneven, and the combined action of the operating temperature and pressure requires an increase in the sealing specific pressure, resulting in slack of the pressing surface and a decrease in the sealing specific pressure.

2. The equipment is inherently defective, resulting in leakage. On the one hand, due to the result of machining, the surface of the mechanical product must have various defects and shape and dimensional deviations. In the inevitable gap between the mechanical parts, the working medium will leak through the gap; on the other hand, corrosion Crack, wear, aging, external force damage, unfair design, poor manufacturing quality, incorrect installation, and changes in process conditions lead to material failure.

3, abnormal working conditions, leading to leakage. First, in the event of an emergency, the temperature rise and drop of the system causes uneven expansion of the components, which may also lead to seal failure. Second, it does not operate according to the regulations, causing the equipment to overheat and overpressure, resulting in physical explosion of the equipment body and leakage.

4. Human factors lead to leakage. First, the quality of the staff is poor, the training is not in place, the staff does not understand the rules, systems, procedures, etc., the operation is not smooth, or even mishandled. Second, the mind is paralyzed, the awareness is not strong, the violation of the rules, the mind is lucky, there are rules to follow; the third is that the governance is not in place, the responsibility is not clear, the system is not perfect, the procedures are not specific; the fourth is that the responsibility is not strong, the equipment is not pressed Maintenance is required, the inspection is carried out, and the problem is not treated in time.

Second, the prevention of leakage

The key to leakage management is to adhere to prevention and take active preventive measures. Plan to protect, inspect, renovate and update the device. After the event, plugging is preventive, which can effectively reduce the occurrence of leakage and reduce its harm. .

1. Take the essential safety and eliminate the hidden dangers from the source

In order to reduce the occurrence of leakage, we must start from the intrinsic safety. The first is to design according to the specifications. According to the appropriate design standards, according to the process conditions and the characteristics of the storage medium, the material material, structure, connection method, sealing device, etc. should be correctly selected to implement reliable measures. Secondly, the quality of the purchased materials should be selected according to the design standards. Materials that meet the requirements must be quality sampled before entering the factory. The substitute materials must be re-calculated by the design unit. It is strictly forbidden to use low grades instead of high-grade materials. Third, the quality of the on-site production and installation process of the equipment is controlled. Select qualified construction units to follow the standard construction, strengthen the management of the construction process, and immediately correct the defects to ensure that the quality of equipment and pipelines meets the requirements. Fourth, the new pipelines and new equipment must be pressure tested in strict accordance with the regulations. Pneumatic test and flaw detection, to prevent the installation of hidden dangers into production.

2. Improve the safety and reliability of equipment by improving the use and maintenance.

After the equipment is delivered for use, it must be used and maintained correctly. First, it must be strictly controlled according to the regulations. It should not be over-temperature, over-pressure, super-vibration, over-displacement, overload production, control the normal production control conditions, and reduce leakage accidents caused by human manipulation. The second is to strictly implement the equipment maintenance system, and carefully do the work of lubrication, turning, inspection, etc., so that the vibration of the running equipment does not exceed the standard, and there is no air leakage or leakage at the sealing point. When a fault occurs, it should be discovered in time, repaired in accordance with the maintenance inspection procedures in time, and defects should be eliminated in time to prevent problems, failures and consequences from expanding. The third is to strengthen governance. Strengthening the awareness of full participation and establishing prevention of leakage is the idea of ​​improving economic efficiency, improving various governance systems and operational procedures; strengthening the training of professional production and improving the skills of employees.

3. Monitor the equipment and prevent the lead in prevention

The occurrence of a leak accident is often directly related to the poor condition of the production equipment. Use the relevant instruments to carry out regular inspection and on-line inspection of the production equipment, analyze and guess the development trend, guess and discover the problems in advance, repair the equipment and pipeline before the leakage occurs, eliminate the hidden dangers in time, and make the inspections targeted to avoid disrepair or excessive maintenance. To reduce the occurrence of sudden spills and improve economic efficiency. The combination of conventional non-destructive testing techniques with ultrasonic, eddy current, infiltration, magnetic powder, ray and infrared thermal imaging, acoustic emission, holography and other monitoring techniques can make condition monitoring and fault diagnosis more accurate and faster.

4. Improve protection and monitoring facilities to ensure safe production

Complete and reliable safety valves, breathing valves, pressure gauges, liquid level gauges, rupture discs, venting tubes and other safety facilities. When abnormal conditions such as ultra-high pressure occur, emergency materials are excreted to prevent sudden overpressure and damage to the equipment. Risk of equipment explosion; take appropriate protective measures against sealing surfaces, valves, steam traps, safety valves, etc. to prevent impurities and foreign matter from entering, damage facilities and equipment, and reduce leakage; control system, TV monitoring system and alarm system Advanced information technology enables the operator to grasp the flow, pressure, temperature, liquid level and other information in the control room, and clearly observe the scene of the installation area in real time, and realize alarm and automatic control; Maintenance is required to be sensitive and reliable.

Third, the detection of leakage

In order to effectively control the leakage during the production process, it is necessary to find the leak in time, correctly determine and determine the location where the leak occurred, and find the leak point. Especially for the parts and places where leaks easily occur, by detecting early detection of leaking clues, control measures can be taken to eliminate the leak in the bud.

The first is the empirical method. This method is mainly for some obvious leakages, which can be directly perceived by watching, listening, smelling and touching. This method mainly relies on human sensitivity, experience and responsibility. The second is to use the instrument and equipment to carry out the leak detection method. In the case of dangerous situations, the leak detection instrument can diagnose the operating condition of the equipment without interrupting the production operation, determine the location of the fault, the degree of damage, the presence or absence of leakage, and correctly analyze the cause of the leak. For example, the thermal imager can clearly find the leakage abnormality at night; ultrasonic, acoustic pulse, and acoustic emission technology use a highly sensitive sensor to capture the leakage sound that is inaudible to the human ear. After processing, the adult ear can be converted. The sound that arrives, determine whether it leaks and locate it; add the easily detectable substance to the medium as a tracer (such as helium, hydrogen, odor, fuel, etc.), which can be quickly detected when a leak occurs; fiber optic sensor The detection method continuously measures the pipeline according to the change of the ambient temperature caused by the leaked substance, and can determine whether a leak has occurred.

At present, new methods and new results of pipeline leak detection technology are emerging one after another. In particular, scientific developments such as sensor technology, computer technology, control technology, and artificial intelligence technology have promoted the development of leak detection technology in an intelligent, diversified, and systematic manner, and greatly improved the detection capability, sensitivity, and accuracy. Timely protection against leakage provides a strong technical support.

Fourth, the emergency treatment of leakage

After the leakage occurs, if it can be discovered in time, take a quick and effective emergency treatment method, the accident can be eliminated in the bud. The key to dealing with leaks is three links. One is to find leaks in time and control the source of danger. Hazard source control can be carried out in two major aspects, namely process emergency control and engineering emergency control. The main measures of process emergency are: cutting off related equipment (facilities) or equipment feeding, scheduling of public works system, pressure relief, material transfer, spray cooling, emergency shutdown, inert gas protection, neutralization and dilution of leakage hazards. The main measures for engineering emergency are: emergency repair of equipment and facilities, pressure plugging, leakage and leakage of dangerous materials. The second is to rescue poisoning, injury and rescue the trapped staff. This link is an important task in the emergency rescue process. The main task is to transfer the poisoned, injured and rescued trapped staff from the dangerous area to the safe area, carry out on-site first aid, and transfer to the hospital for treatment. The third is the disposal of spills. When the materials on the site leak, it is necessary to cover, retain and dilute in time to prevent the occurrence of secondary accidents. From many accident handling experiences, if this link cannot be effectively carried out, the impact of the accident will be greatly increased. If the leak is not controlled or handled improperly, it may lose the best time to deal with the accident, and turn the leak into a more serious accident such as fire, explosion, poisoning. Chemical enterprises should formulate effective emergency plans. After the leakage occurs, effective rescue and control of leakage should be carried out according to specific conditions, and efforts should be made to avoid casualties and poisoning accidents during the treatment process and minimize losses.