Pressure decay testing is one of the most common methods for detecting leaks in production lines. It is simple, cost-effective and easy to automate.
The test instrument fills your product with air until it reaches the desired test pressure, then cuts the air source to isolate the remaining pressure and measures the drop over time; any loss indicates a leak.
Sensitivity
Pressure decay testing is one of the most reliable methods for detecting leaks in industrial parts and containers. This method involves pressurizing the product with air, locking it out to isolate the pressure, and measuring the drop in pressure over a specified test time. If the pressure drops significantly, the product is considered to be defective and must be rejected. Modern pressure decay instruments have high resolution, making them able to detect very small changes in the test pressure. This enables them to detect leaks that would be masked by noise in older systems.
The sensitivity of the pressure decay test is also affected by the instrument’s ability to measure the pressure difference between the air inside the test part and the ambient air outside it. The measurement accuracy is determined by the instrument’s ability to consistently reproduce the difference between these two values, and it is affected by both systematic and random errors. A gauge R&R study is usually performed on the tester and its associated system to evaluate these errors and determine their effect on sensitivity.
Another factor affecting the sensitivity of the pressure decay test is its load/unload and settle periods. These times are important to account for when estimating the total test cycle time. Load and unload are the times it takes to engage and disengage the test item from the pressurizing and pressure decay measuring instruments. The settling period is the time it takes for the volume of the test item to change and stabilize due to stresses introduced by the pressurizing process.
Accuracy
Pressure decay testing is one of the most reliable and cost-effective methods for detecting leaks in containers and other sealed parts. It works by filling a test part with air until it reaches a specified target pressure, then cutting off the air supply and measuring the resulting pressure loss over a set period of time. The resulting pressure curve is used to determine the presence of a leak. This method is ideal for testing railcars and other hard-to-reach components.
The accuracy of a pressure decay test depends on a number of factors, including the size of the container and the length of the test. Generally speaking, larger containers will require longer test times than smaller ones in order to detect small leaks. In addition, temperature variations along the production line can also affect the sensitivity of the test and the accuracy of the results.
TM Electronics pressure decay leak testers are designed with precision in mind. They use a low test pressure to ensure that bottles don’t deform and that the pressure decay measurement remains accurate. This allows us to identify pinholes in containers that other leak testers may miss. In fact, we can detect holes as small as 1mm – much smaller than the tip of a pencil. This enables our customers to improve the reliability of their quality control systems by ensuring that they have a consistent manufacturing process.
Reliability
Pressure decay testing is one of the most reliable and cost-effective ways to test for leaks in containers. This non-destructive test can be used on a wide variety of products, including plastic bottles, pharmaceuticals, and cosmetics. It uses air to create a known and stable internal pressure, isolates the test item from the source of pressure through valves, and then monitors the loss of pressure over time to detect a leak. The test is fast and accurate, which makes it a popular choice for high-volume industries such as automotive components and castings.
The reliability of a pressure decay instrument depends on its ability to accurately reproduce the desired test pressure, and also on the accuracy of the calibration system that it is linked to. While modern electronic pressure-decay measuring instruments can achieve resolutions down to 0.001 psi, there are many other factors that can cause inaccurate results. These factors include mechanical volume change during a test, adiabatic temperature changes in short test cycles, and flow regimes of laminar or turbulent conditions.
Another factor affecting the reliability of pressure decay testing is its sensitivity to permeability. Permeability is determined by interpreting a portion of the pressure-decay curve, and a variety of different parts of the curve can yield different results. This is a problem because it makes the test less predictable and can lead to false negatives.
Cost
A pressure decay test consists of filling a container with air until it reaches its target pressure, cutting off the supply of air to isolate the specimen, then measuring the drop in the pressure over a set period of time. The resulting measurement can be used to detect leaks in plastic or glass containers filled with liquid, oil, or powder. This method is particularly useful for vials or ampoules containing toxic products, oil-based liquid, lyo/powder, glucose/protein, and other substances that can be blocked by a vacuum pull or cause dangerous fumes when they boil under high pressure.
A pressure decay leak tester uses a custom jig or fixture to connect a test line to your product and then pressurize it. After a specified fill time the tester will isolate your test sample from the pressure source and wait for a specified amount of time to see if the pressure in the jig or fixture drops. The pressure sensor will then record the drop in pressure and the test will be considered a failure if it is not within a certain accepted limit.
Unlike other leak test methods such as blue dye or bubble testing, the pressure decay test yields quantitative information and hard data points. This allows specific accept/reject criteria to be set and removes dependency on the test operator’s impression of the test result. This method is a good choice for high-volume manufacturers that need to test a large number of small parts and products.