Application of Hydrogen Leak Detection Technology in Refrigeration and Air Conditioning Industry
First. The basic principle of hydrogen leak detection method
1. The basic principle of hydrogen leak detection method
The hydrogen leak detection method is a leak detection method using a mixture of 5% hydrogen and 95% nitrogen as the tracer gas, which is called the hydrogen-nitrogen mixture leak detection method, or the hydrogen leak detection method. The mixture of 5% hydrogen and 95% nitrogen is non-flammable (ISO10156 international standard), non-toxic and corrosive, and will not adversely affect equipment and the environment. Hydrogen has many unique advantages as a tracer element for leak detection.
The molecular weight of hydrogen is close to that of helium, and it is the smallest and lightest element in all chemical elements. It has good diffusivity, strong escape, and low adsorption and viscosity. Since hydrogen molecules move faster than other molecules, using safe low-concentration hydrogen as tracer gas can have faster response speed and better leak detection accuracy. The basic working principle is to use a specially developed hydrogen sensor, which only has a response signal to hydrogen and no response to other gases, which is a unique leak detection method. Once there is a signal response, it means that hydrogen gas enters the test piece through the leak hole, thereby indicating the position and size of the leak hole. At the same time, since the concentration of hydrogen in the general environment is very low, it will not cause false alarms due to background pollution.
2. Main equipment of hydrogen leak detection method
(1) Leak detector: The special hydrogen leak detector manufactured by the above working principle, due to the above properties of hydrogen, its sensitivity can reach the same level as helium detection.
(2) Tracer gas filling controller: For mass production users, it is best to use the tracer gas filling controller for vacuuming/inflating/exhausting operations, which can complete the automatic control of the filling and exhausting process of the detection pipeline .
3. Process and method of hydrogen leak detection method
Mass production users use the above controller to fill the tracer gas. When the pressure is reached, the controller will give a prompt. At this time, the operator can perform the leak detection operation, and then discharge the gas through the controller. Note that it is not possible to directly discharge the gas to the leak detection position, because this will cause background pollution, making the subsequent leak detection impossible.
Engineering installation and maintenance providers can use a hand-held nitrogen and hydrogen leak detector (there is a set of products with gas cylinders/meter sets to choose from). Hydrogen + 95% nitrogen tracer gas, use a hand-held nitrogen-hydrogen leak detector for patrol leak detection. Since hydrogen is lighter than air, the leaked hydrogen will run up along the pipeline and other components, and can penetrate the insulation material. The user can check the leak at the highest position of the component, which is much easier than finding leaks in other ways. , the success rate is also much higher.
Second, the advantages of hydrogen leak detection method
Current status of leak detection technology in refrigeration and air-conditioning industries: In the production process of product components, helium leak detection technology is often used to find small leaks, while pressure-holding test and water bath method are often used to detect larger leaks. After the product is assembled and charged with refrigerant, the entire product may be leak-tested again with a halogen leak detector before leaving the factory. Since the pressure-holding test and the water bath method can only detect leaks of about 10-3 mbar·l/s at the highest, for a long time, helium leak detection technology has been the only way to detect small leaks in the refrigeration and air-conditioning industries. The leakage technology can generally detect the leakage of about 10-7mbar·l/s. However, using helium as a leak-indicating gas also has some shortcomings. For example, organic materials such as rubber and plastic often absorb helium and release it slowly after absorption; all the ion collection of helium leak detection instruments It will have a memory effect on the helium, that is, the helium ions hit the ion collecting plate, and are stored for a certain period of time, and then slowly released, causing problems such as background noise.
Whether it is in leak location or in leak testing applications, this leak detection method has been widely used in various industries. The use of low-density safe hydrogen as a tracer gas for leak detection has many advantages over helium. It is very inexpensive and readily available from various gas suppliers. Today's hydrogen-nitrogen mixed gas leak detection technology can detect leaks as low as 5*10-7mbar/s, which is equivalent to 0.1g/y, and the gas usage cost is only 1/10 to 1/20 of that of helium. The gas leak detection method needs to add some auxiliary equipment, such as helium recovery system.
Third. Application and Prospect of Hydrogen Leak Detection Method in Refrigeration and Air Conditioning
Today, many refrigeration and air-conditioning customers around the world are using various types of hydrogen leak detectors. Hydrogen leak detectors have a very reliable sensitivity and measurement indication based on their unique technology in handling the background hydrogen concentration in the environment. Hydrogen leak detectors can bring you a more flexible leak detection solution that traditional leak detection cannot meet. For example, a customer can first use the pressure drop method to check for leaks, and then use a hydrogen leak detector to find the location of the leak. Customers can also directly use the hydrogen leak detector for highly sensitive leak detection to avoid the influence of temperature changes on the pressure drop method leak detection. In modern leak detection methods, if the workpiece to be tested is not suitable for contact with water, or there is an influence of temperature in the detection environment, or the workpiece to be tested is an elastic body that cannot be detected by the blister method and the pressure drop method, the hydrogen leak detection method is used. A cost-effective option.
In various leak detection applications, the emergence of hydrogen leak detection method brings you greater opportunities to improve performance and efficiency. The hydrogen-nitrogen mixed gas leak detection method has been widely used in refrigeration, air conditioners, auto parts, engines, gearboxes, reducers, valves, pharmaceutical packaging, aircraft fuel tank oil circuits and other seals or pipeline leak detection at home and abroad. The hydrogen leak detection method has high detection sensitivity, cost saving and easy operation, which will be the development trend of leak detection technology in the future.
