Non-Destructive Solution for Identifying Leaks on Plate Heat Exchangers

Corrosion, thermal and mechanical stress and gasket damage are some of the conditions that can cause a plate to develop small cracks. Leak-free heat exchangers are crucial for several reasons:

• Efficiency: Leaks can lead to the loss of heat transfer fluid, which reduces the overall efficiency of the heat exchange process. By maintaining a leak-free system, operators can ensure optimal thermal performance and energy savings.
• Safety: Leaks can pose significant safety risks, including exposure to toxic substances or high-pressure fluids. Leak-free heat exchangers help mitigate these risks, protecting workers and the environment.
• Cost Reduction: Leaks can result in costly downtime and repairs. A leak-free system minimizes maintenance needs and operational interruptions.
• Environmental Protection: Leak detection avoids emissions that can harm the environment. This is especially important in industries with strict regulatory compliance requirements.

Various techniques have been used over the years to detect leaks in heat exchangers. 

• Pressure decay: This method involves filling the heat exchanger with air, pressurizing it, and then checking the pressure drop over time. Pressure decay is, however, affected by temperature changes. Furthermore, the pressure drop gives an indication of the tightness of the system, but not of the exact location of the leak. 
• Soap bubbles: After pressurizing the heat exchanger with air, a soap or detergent solution can be applied to potential leak areas. If there is a leak, bubbles generally form at the leak point. Commonly used for detecting small leaks in flanges, joints, seals and gaskets, this technique is simple and inexpensive, but the limited sensitivity makes it impossible to detect very small leaks. 
• Water bath: After pressurizing the component with air or gas, water dunk testing is performed by simply immerging it in a tank of water. Bubbles appearing at the leak site typically indicate the location of the leak. However, the large number of bubbles makes it often difficult to identify leaks with accuracy. Water bath requires visual access to all surfaces of the component, including those that are hidden from the operator's eye. 

These techniques aren’t suitable for large, complex systems or heat exchangers in use within an operating system or process, as their sensitivity is limited and they require shutdown and drying  the heat exchanger afterwards. 

A non-destructive and more sensitive leak detection method is leak detection with a tracer gas. The process involves using forming gas (5% hydrogen in nitrogen) or helium as the tracer gas. Depending on the size of the heat exchanger, the required throughput, and the leak rate requirements, accumulation test and vacuum test are suitable alternatives.

For very rapid leak tests, when extremely small leaks are expected or in all circumstances where a leak detector for both helium and forming gas is preferred, the LDS3000 AQ Leak Detector gives the highest sensitivity. The plate heat exchanger is filled with tracer gas and placed in the accumulation chamber. The LDS3000 AQ measures the speed of increase of the tracer gas level in the chamber and alerts the operator if this rises too quickly.

Vacuum Leak Test

For larger heat exchangers that need to be tested with medium to high throughput, or parts that need to be tested for refrigerant leaks, leak testing with helium in a vacuum chamber is the preferred solution. In this testing procedure, the heat exchanger is filled with helium before vacuum pumps create a vacuum in the chamber. If there is a leak, the LDS3000 Helium Leak Detector detects the helium gas as it exits the heat exchanger and gives an alarm signal. 

Look at our video or check out our solutions for accumulation leak testing!