Industrial leak testing and leak detection are not simple issues. Even the choice of the appropriate test method must be carefully considered. Which method is ideal for a specific application depends on many factors.
Sensitivity plays a role, as well as the marginal leak rate of the method used and the cycle times that can be achieved in integral testing on the production line. The repeatability and reliability of the testing process also should be considered along with the capital expenditure and operating costs, which are all based on the particular test method.
Leaks in vacuum systems are mostly specific types of defects which can have a significant influence on the safety and performance of systems and installations. Many systems and products will have a reduced reliability if they contain leaks.
ITIS can provide you the following techniques for vacuum testing:
- Helium vacuum testing
With the helium sniffer probe technique the object to be examined for leaks is evacuated internally after which its exterior is ‘sprayed’ with a tracer gas. Mostly helium is used as test gas for this method. The test gas enters through any defects present in the object and is detected by a leak detector, sometimes in combination with a separate vacuum pump. A critical part of the vacuum method is to determine not only whether or not the part is leaking, but to determine the exact location of the leak. For tests where the exact leak rate is specified, the object can be placed in a test chamber filled with test gas and tested for leaks.
- Vacuum box testing
The objective of the vacuum box technique is to locate leaks in a pressure boundary that cannot be directly pressurized. This is accomplished by applying a soapy solution to a local area of the pressure boundary surface and creating a differential pressure across that local area of the boundary. If a defect is present in the test area, the formation of bubbles (caused by gas passing through the solution) will indicate the location of potential leakage. This method is one of the most widely applied test methods to detect leakage and defects and is widely used in testing the plating (specifically the welds) of tanks and ships.
- On Stream Leak Testing (Air ingress)
Condenser Systems (Power plant)
The efficiency of condenser systems is dictated by the pressure gradient across the turbine and condensing system. Leaks in the system degrade the pressure differential and can easily result in power loss in excess of megawatts per turbine.
If the vacuum pressure deteriorates due to air-in leakage, leaking valves, or cooling tower problems, the efficiency of the entire vacuum system declines rapidly.
If even small amounts of non-condensable gas (air) are allowed to accumulate, they will inhibit heat transfer in the condenser and adversely affect performance.
Large amounts can virtually block the condensation process, which of course will cause a substantial rise in back pressure. To prevent excessive accumulation, most power plants use steam jet air ejectors and/or liquid ring vacuum pumps to remove the non-condensable gases. When these methods cannot keep pace with the rate of air in-leakage then the leaks must be found and repaired.
- Vacuum systems
Air ingress in your vacuum system can lead to reduced product quality, production loss, environmental damage or dangerous situations.
Helium leak testing your vacuum system can significantly speed up your process, will verify the integrity of components, and keep your vacuum system operating efficiently.
A helium leak detector will be connected to the vacuum system, unfortunately this equipment generally operates at vacuum levels lower than vacuum systems in installations. Therefore a special auxiliary vacuum pump system is used to create the right set up to perform the leak test. Our test set-up allows the flexibility for a test engineer to perform leak tests while the plant is operating, without the need to isolate the section under test.
Helium is ‘sprayed’ around portions of the vacuum system, while a mass spectrometer continuously samples the vacuum system and detects (low) concentrations of the test gas in case of leakage.
In some cases, a permeable membrane will be used in an extractor, connecting the leak detector to the vacuum system. This ensures no water vapor or any liquids (which severely damage the detector) will be ingested by the leak detector.
Although finding leaks in vacuum systems presents a challenging set of problems, our engineers have developed leak test solutions specifically designed for the demanding conditions found in vacuum systems.
Please contact ITIS, your leak detection solutions partner, with any questions you may have.