Common Vacuum Leak Detection Methods Introduction

Accurately and efficiently identifying leakage points is crucial in the maintenance and inspection of vacuum systems. The following are common vacuum leak detection methods:

● Helium mass spectrometry leak detection method

Helium mass spectrometry leak detection technology plays an indispensable role in the field of vacuum leak detection. It hashigh leak detection efficiency, easy operation, sensitive instrument response, extremely high accuracy, and is not easily affected by other gases, so it is widely used. The helium mass spectrometer leak detector is made based on the principles of mass spectrometry, using helium as the leak gas. It mainly consists of a mass spectrometry chamber composed of an ion source, analyzer, collector, cold cathode ionization gauge, as well as an exhaust system and electrical components.

The electrons emitted by the filament in the mass spectrometry chamber oscillate continuously inside the chamber, colliding with the indoor gas and helium gas entering through the leak, causing it to ionize into positive ions. These helium ions enter the magnetic field under the action of an accelerating electric field and undergo deflection under the Lorentz force, forming circular arc orbits. By changing the acceleration voltage, ions of different masses can be detected by passing through the magnetic field and receiving slit to reach the receiving electrode. In actual leak detection, helium injection method and helium absorption method are the two most commonly used methods for helium mass spectrometer leak detectors.

● Vacuum gauge leak detection method

The readings of some vacuum gauges are related to the type of gas, such as thermocouple gauges and ionization vacuum gauges. By utilizing this characteristic and selecting appropriate gases or liquids as leak indicators, these vacuum gauges can transform into detectors. Generally, coating machines are equipped with vacuum gauges, which are very convenient to use and are a commonly used method for leak detection. The leakage substances suitable for thermocouples include carbon dioxide, butane, alcohol, etc., but the reaction of thermocouples is slow and requires careful observation. The leakage substances suitable for ionization meters include helium, argon, alcohol, etc.

● Ultrasonic leak detection method

When gas leaks from a leak point, ultrasonic signals are generated. Ultrasonic leak detectors can capture these ultrasonic waves and convert them into audible sound signals or visual electrical signals. The operator can determine the location of the leakage point based on the strength and position of the signal. This method is suitable for detecting various vacuum systems, especially in noisy environments, but may not perform well for detecting very small leaks.

● Pressure change leak detection method

Fill the vacuum system being tested with a certain pressure of gas (usually dry air or nitrogen), then close the intake valve and observe the pressure changes in the system over time. If there is a significant decrease in pressure, it indicates that there is a leakage point in the system. The leakage rate can be roughly estimated by the rate of pressure change. This method is easy to operate and cost-effective, but its sensitivity to detecting small leaks is relatively limited.

● Halogen leak detection method

Use halogen gases (such as Freon) as leak gases. The sensor inside the halogen leak detector is very sensitive to halogen gas. When halogen gas leaks out from the leak point, the leak detector will emit signals such as sound and light alarms. This method has high detection sensitivity and is commonly used for leak detection in vacuum systems with good compatibility with halogen gases, such as refrigeration systems. However, due to the certain impact of halogen gases on the environment, environmental protection issues should be taken into account when using them.

● High frequency spark leak detection method

This method is only applicable to glass vacuum systems. When operating, first evacuate the system, and then move the spark end of the high-frequency spark leak detector along the glass surface. When the sparks concentrate into a beam and form a bright spot, it is the location of the leak hole.

● Vacuum sealing mud detection method

This method involves sealing suspicious leakage points one by one with vacuum mud, while closely observing changes in vacuum degree. If the vacuum degree rapidly increases after applying vacuum sealing mud and then significantly decreases after removing it, then this point is a leak point. However, this method is used relatively infrequently in practical applications.