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Product family | Detectable gases |
|---|---|
ASM | Helium, hydrogen |
ASI | Helium, hydrogen |
Air series | Air, nitrogen |
Tracer gas leak detection using helium or hydrogen forming gas (a mixture of hydrogen and an inert gas, usually nitrogen) is ideal for identifying extremely low leak rates with high precision. This method is widely used across industries where accuracy, repeatability, and sensitivity are critical, such as in semiconductor manufacturing.
Air leak detectors with our patented Micro-Flow sensor are unique in the industry. These intelligent gas leak sensors measure flow, pressure and temperature to provide a numerical result that is directly proportional to the leak rate and therefore defect size. This technology brings several benefits in comparison to other leak testing methods.
A vacuum leak is an unintended or unwanted opening in a vacuum system. It allows air or other gases to enter or exit the system. The amount of air or gas that leaks out of a vacuum system is expressed as the leakage rate. Leakage rates depend on several factors, including the size and number of openings, gas type, and the pressure differential between the inside and outside of the system.
There are two types of vacuum leaks:
Vacuum leaks occur for various reasons. These include issues like faulty or old seals that have become porous, damaged components, or improper installation of vacuum equipment.
There is no average size of a vacuum leak. A leak can stem from a microscopic hole, a large tear, or anything in between, depending on what caused it. The size of a vacuum leak can be determined by measuring the leak rate, which is the amount of process gas or air that escapes from the system per second. Most technical leaks are too small to be seen with the naked eye. Helium or air leak detectors provide the most accurate method for detecting and quantifying small vacuum leaks.
There are different ways to detect leaks with a leak detector: with tracer gas or using air.
With tracer gas as a means of detection, there are three options. The spray test is suitable for components under vacuum, and sniffing leak detection is used for components under pressure. An integral leak test is a variant for components that can be put inside a vacuum chamber.
The test methods are easy to perform and deliver accurate results, making a leak detector from Pfeiffer the perfect addition to your vacuum process.
Figure 1: Spray test
Figure 1: Spray test
Figure 2: Sniffing leak detection
Figure 2: Sniffing leak detection
Figure 3: Integral leak detection
Figure 4: Integral leak detection
Figure 3: Integral leak detection
Figure 4: Integral leak detection
For an integral spray test, the test object is connected to the leak detector and placed inside a vessel (3). Just like a conventional spray test, integral spray tests are performed under vacuum. However, while a conventional spray test evacuates the test object itself, this method evacuates only the surrounding container. The vessel is then filled with a defined quantity of helium. This ensures precise test conditions and accurate results. If there is a leak, then helium will penetrate the test object due to the pressure differential. The leak detector measures the amount of helium inside the test object and determines the leakage rate. Integral leak testing methods, however, cannot localize the leak.
First, the test object is connected to the test set-up. This comprises the leak detector and an air reservoir. The test object is then pressurized with air from the reservoir to a predefined pressure level. If there is a leak, the air will leak out of the test object.
This set-up continuously replenishes the gas flow to compensate for the lost air, thus maintaining the pressure. The replenished gas flow passes from the reservoir through a specially designed sensor, the Micro-Flow sensor. This sensor is equipped with patented technology that amplifies the signal, making it possible to measure even very low leakage rates down to 5 · 10-4 mbar · l/s.
This technology is non-destructive, leaving the test object intact. It provides quantitative results without the need for daily calibration, making it highly reliable and efficient for various industrial applications.
The Mass Extraction method also uses the Micro-Flow sensor, but is carried out under vacuum. This results in an improved detection limit and ensures that there is no heat transfer due to the insulating effect of vacuum.
In the first step of Mass Extraction, the test unit is placed in a vacuum chamber. This chamber is connected to the leak detector, containing the Micro-Flow sensor, and an air reservoir. The chamber is then evacuated. The leakage rate of the test unit is determined by the flow from the reservoir to the test unit. With this method, a detection limit of down to 7 · 10-7 mbar · l/s can be achieved and defects as small as 1 μm can be detected.
Spray test and sniffing leak detection are the two most common leak detection tests that use the tracer gases helium or hydrogen.
The spray test is the ideal test method for components under vacuum. This measurement principle has the highest sensitivity of all available methods. Helium or hydrogen is sprayed onto the outer surface of the test object. In case of a leak, the incoming molecules are drawn in by the integrated turbomolecular vacuum pump together with its backing pump. They finally end up inside an analyzer cell. This cell detects the tracer gas.
Sniffing leak detection is the perfect method for components under pressure. A test object is pressurized with helium or hydrogen. A sniffer probe, which is connected to the leak detector, is then slowly and systematically guided over the object. In the event of a leak, escaping tracer gas atoms are detected, and the leak can be localized precisely.
Qualitative leak detection determines only whether or not there is a leak in the test object. This is already possible from an inlet pressure of 100 mbar with the ASM product series. As the inlet pressure decreases, typically at 25 mbar, leak detectors are able not only to simply detect leaks but also to determine the size of the leak. This is called quantitative leak detection.
Several factors need to be considered when selecting the right scroll vacuum pump, including the specific needs of your process and the characteristics of the pumped medium.
Contact us and we’ll find the perfect dry scroll pump for your needs.
In a pressure decay test, a pressure vessel is filled with air until a target pressure is reached. Then the loss (decay) of that pressure is measured over a set period of time.
There are several types of vacuum leak testing. For example, specialized devices such as our ASM and ASI leak detectors can conduct two types of tests utilizing either tracer gas helium or hydrogen for detection. Alternatively, our air series of leak detectors can detect leaks using our innovative Micro-Flow technology.
Vacuum leak testing offers quicker results compared to pressure decay testing and is also less sensitive to external factors such as temperature variations. The results are also more accurate.
Both the spray test and sniffing leak detection are methods using tracer gas. The spray test is the ideal test method for components under vacuum. The first stage is to spray helium or hydrogen onto the outer surface of the test object. In the case of a leak, the incoming molecules are drawn in by the leak detector’s integrated turbomolecular vacuum pump together with its backing pump. They finally end up inside an analyzer cell. This cell detects the tracer gas atoms.
Sniffing leak detection is the perfect method for components under pressure. A test object is pressurized with helium or hydrogen. A sniffer probe, which is connected to a leak detector, is then slowly and systematically guided over the object. In the event of a leak, escaping tracer gas atoms are detected, and the leak can be localized precisely.
Both test methods are easy to perform and deliver accurate results.
Our Micro-Flow sensor makes our air leak detectors unique in the industry. This intelligent gas leak sensor has much higher sensitivity than conventional air leak detectors and can detect leak rates as low as 5 · 10-4 mbar · l/s. Furthermore, the testing speed is faster than alternative methods and can provide results up to 40% quicker than using pressure decay.
The Micro-Flow sensor measures the amount of air flowing from a pressure reservoir to make up for the air lost due to a leak. By measuring this flow as well as the pressure and temperature, it can provide a numerical result that is directly proportional to the leak rate and defect size.
As the measurement is made directly from the leak flow, Micro-Flow is minimally affected by environmental changes such as temperature, greatly reducing the number of false results that can occur in other leak testing methods. Alternative flow meters, for example, work on the principle of temperature transfer, where a temperature change is measured over a period of time to calculate the air flow. Others measure mechanical movements, where the degree of movement of a particular component, such as a membrane, allows the flow to be calculated.
This technology is non-destructive, leaving the test object intact. It provides quantitative results without the need for daily calibration, making it highly reliable and efficient for various industrial applications.
Mass Extraction is an additional technique using the Micro-Flow sensor. The basic principle is similar to the Micro-Flow approach, but in order to achieve higher sensitivity, the test is performed under vacuum. A test unit is placed in a vacuum chamber. This chamber is connected to the leak detector, which contains the Micro-Flow sensor, and an air reservoir. The chamber is then evacuated. The leakage rate of the test unit is determined by the airflow from the reservoir to the test unit. With this method, leak rates down to 7·10-7 mbar l/s (<1 μm) can be detected.
Dive into our resource library to understand the science and technology behind leak detectors. Learn about different methods, industry standards, and best practices to enhance your process.
We also offer expert-led webinars, interactive courses, and hands-on trainings to further enhance your skills and understanding.
