Application of leak detection technology for metal containers

In recent years, the manufacturing technology of China's metal containers has made great progress along with the economic development. However, compared with the development of leakage detection technology for metal containers, there has been a significant lag, especially in the leakage detection technology of steel drums. Stay at the level of the five or sixties, obviously unable to keep pace with the development of related technologies at home and abroad, therefore, China's metal container leakage detection technology needs to be improved.

In foreign developed countries, the detection of leakage of metal containers has attracted the attention of the legislature, which has made various relevant standards and norms more and more strict and clear. Therefore, in order to control and ensure the quality of the production and use of metal containers, our production companies must clearly understand the latest testing techniques and testing methods.

For metal containers, there have been many losses, pollutions, and hazards caused by leakage for a long time. With the development of society, we pay more and more attention to product quality, environmental pollution, and human health. Metal containers must reach zero permeability. leak. In terms of foreign professional technical terms, it means that "the container cannot leak, and the container must maintain its original pressure". Such a concept has a clear definition in international standards.

Leakage inspection has three main purposes: first, to prevent leakage of the contents of the container, so as not to affect the use of its products; second, to prevent environmental pollution (dangerous or harmful substances) caused by leakage; third is to prevent The contents are contaminated so that unusable ingredients (non-compliant ingredients) reach the end consumer.

For many years, the leak test of metal containers has used various forms of blisters test. The test method of this kind of test is relatively simple. It is to put the container in water or apply soapy water to the common leakage on the container. Introduce compressed air into the container to see if a container placed in the water is bubbling to determine if the container is leaking. This method is common in our national standards and has become a traditional, standard method. Although this method can detect very small leaks and find out their exact positions, this method cannot measure accurate leak rates and has the following disadvantages: First, it has low detection efficiency and labor intensity. In a modern, fully automatic production line, it is almost impossible to perform the full number of blisters leak detection in metal containers. The second is the detection of blisters leakage. After the inspection, the surface of the metal container has been contaminated by water and must be processed to enter the next process, otherwise it may cause the surface to rust or affect the quality of the subsequent coating.

Recently, a new type of container leak detection system has been successfully studied in Italy. The system selects a suitable dry air leakage sensor and is equipped with a computing system and a microprocessor-controlled test system. The system has an accurate and rapid test. The test cycle can adapt to more stringent anti-leakage specifications.

Since 1974, Italy's Bonfiglioli Engineering Company has specialized in the design and manufacture of leak testing equipment, providing leak testing methods for a variety of packaging container industries, and has earned a high reputation worldwide. He has become a worldwide container inspection company. Technical representative. In recent years, continuous research and development has enabled the company to occupy a leading position in the field of leakage testers. In order to meet the needs of various containers, they are designed and manufactured to meet the CE standards for each device, which can meet any container leak detection.

At present, in some domestic automatic barrel and can production lines, most of them are also equipped with a primary leak system, which is the result of digestion and absorption of advanced foreign technology equipment. However, in practical applications, the effects are often unsatisfactory. The method is to use the principle of pressure decay, and it is impossible to test the container with the object and sealed. The latest technology is the vacuum attenuation method. It is briefly introduced as follows.

First, the pressure decay method

In this type of test apparatus, air is continuously blown into the container until its internal pressure reaches a predetermined value or a predetermined time has passed. During the test cycle, the pressure in the container is monitored. Based on the pressure change and the pressure value compared with the predetermined critical value, the container will be determined as pass or fail.

Second, the vacuum attenuation method

In this type of test device, the container being tested is sealed and is usually filled with liquid leaving only a pore at the top of the container. A test head with a gas seal ring is inserted into the mouth of the container. When pressurized, the gas seal ring tightly adheres to the wall of the container to create a strong seal. In the sealed test cell, vacuum is generated due to the suction of air. During the entire test cycle, the special sensor controls the degree of vacuum in the test cell from beginning to end.

Third, radon gas detection method

This type of test apparatus is based on the principle that helium gas can be used as a tracking gas to react sensitively to various parts of the container. Helium gas detection equipment consists of three parts: the detection chamber, the high vacuum chamber, and the gas analyzer. During the test, helium gas was sufficiently diffused in the container. The helium-filled container enters the vacuum chamber and the vacuum pump is turned on. The gas analyzer immediately shows the percentage of helium. A small amount of helium can trigger the removal of the defective system. The bell rings and the defective container starts from another. Conveyor belts are sent out.

Fourth, load cell method

The load cell method is generally used for the air tightness test of a metal bag container, and the airtightness of the container is tested by using a load cell. The bag under test was placed on the lower conveyor. The upper conveyor was above the bag and its height was adjustable. The upper conveyor compresses the tested area of ​​the bag placed on the lower conveyor. The movement of these two transmitters is synchronized. On the lower conveyor, there is a gravity balance at the entrance and exit of the test cycle.

The gravity balance at the beginning of the test cycle is read first. The size and elasticity of the bag determines the pressure that the upper conveyor creates on the bag.

At the end of the test cycle, the gravity balance reads the second data. If the data measured by the two balances is equal to or less than the predetermined upper limit, the bag can be considered qualified. Otherwise, if the difference between the two readings is greater than the predetermined upper limit, the bag is an unqualified product.

The advanced leak detection technology not only has high production efficiency, high precision, but also has no effect on the quality of the container itself. As China's metal container packaging industry, especially its barrel making industry, is relatively backward in technology, most companies only pay attention to the production technology of metal containers, make great efforts to improve and introduce intermediate production equipment, and have not caused enough leakage detection technology. Therefore, even if it is a production equipment manufacturer, the inspection technology will remain in the original and backward state. This is an extremely abnormal phenomenon.

At present, China's metal container leakage detection technology needs to be improved. It is hoped that companies will not neglect the improvement of the leakage detection technology of containers when they are vigorously improving and purchasing advanced production equipment. It also hopes that relevant research departments and metal container production equipment Manufacturing enterprises should pay attention to the introduction, digestion, and absorption of leak detection technology from abroad and make efforts for the improvement of leakage detection equipment for the metal container industry in China as soon as possible.