Introduction to Leak Testing of Fuel Tanks 

Fuel tank leak testing is an essential process that ensures the integrity and safety of fuel storage systems across various industries, including automotive, aerospace, and marine. Fuel tanks, designed to store flammable liquids such as petrol, must be secure and leak-proof to prevent potential hazards such as environmental contamination, fire risks, and economic losses. Given the critical nature of fuel tanks, leak testing is a fundamental step in manufacturing, maintenance, and quality control processes. 

Fuel tanks can be made of different materials, including plastic and metal, each presenting unique challenges in leak testing. The importance of this process cannot be overstated, as undetected leaks can lead to severe consequences, ranging from regulatory fines to catastrophic accidents. This article delves into the various methods of leak testing, their importance, the challenges involved, and the future of this vital process. 

Types of Fuel Tanks and the Driving Factors Behind Fuel Tank Leak Testing 

Fuel tanks vary in material, design, and application. The most common types are plastic and metal fuel tanks: 

• Plastic Fuel Tanks: These are lightweight, corrosion-resistant, and often used in automotive applications due to their durability and flexibility in design. High-Density-Polyethylene (HDPE) is the most widely used plastic material for fuel tanks in modern vehicles. 

• Metal Fuel Tanks: Typically made from steel or aluminum, these tanks are known for their strength and ability to withstand high pressures, making them ideal for heavy-duty vehicles and aviation. 

As automakers strive to reduce vehicle weight to meet stricter fuel economy and emissions standards, the use of plastic fuel tanks, especially HDPE, has increased significantly. This shift allows manufacturers greater flexibility in vehicle design and enhances overall vehicle performance. 

However, it has also resulted in more stringent and higher requirements for leak testing. This is because plastics are highly permeable, and the complex molding techniques used, like blow molding or rotational molding, can create weak spots that are prone to leaks. 

Why Is Conducting a Leak Test on Fuel Tanks Essential? 

The primary reasons for leak testing of fuel tanks are safety, environmental protection, and regulatory compliance: 

• Safety: Fuel is highly flammable, and any leak can lead to fires, explosions, or other catastrophic events. Proper leak testing ensures that the fuel tank can withstand the operational stresses it will encounter, thereby protecting lives and property. 

• Environmental Protection: Any leakage from a fuel tank can have significant environmental consequences, particularly the release of hydrocarbons that contribute to air pollution and smog. Given the higher risk of vapor permeation and leakage with plastic tanks, they must pass more rigorous leak tests to protect the environment. 

• Regulatory Compliance: Many industries are governed by strict regulations that mandate regular leak testing of fuel tanks. Compliance with these regulations is essential to avoid legal consequences and ensure the safety of operations. For example, UK Whole Vehicle Type Approval (UK WVTA) and UNECE Regulation No. 34 (R34) are some of the regulatory standards that automotive OEMs must adhere to, ensuring the fuel tank’s ability to withstand pressure without leaking in both static and dynamic pressure tests. 

Methods of Leak Detection Systems 

Several methods are used for leak detection of fuel tanks, each with its advantages and suitability depending on the type of tank and the required sensitivity of the test: 

• Pressure Decay Test: This method of leak detection measures the loss of pressure within a tank over time. It is widely used due to its simplicity and effectiveness in detecting leaks in closed systems. 

• Vacuum Decay Test: Similar to the pressure decay test but in reverse, this method involves creating a vacuum in the tank and measuring any loss of vacuum over time, which would indicate a leak. 

• Helium Leak Testing: Known for its high sensitivity, this method involves filling the tank with helium and using a mass spectrometer to detect any escaping gas. This makes it suitable for detecting very small leaks and helps locate the leak with a sniffer probe. 

• Bubble Test Method: This basic method involves submerging the tank in water and looking for bubbles, which indicate leaks. It’s cost-effective but only suitable for detecting larger leaks. 

Different Types of Testing That Can Be Conducted on Fuel Tanks and Their Assembly 

• Ionization Technology on Fuel Tank Caps: With the help of ionization technology, it is possible to test and measure if there are any molding faults or insufficient membrane thickness that could cause a fuel leak from the cap. The electric current discharge rate between a charged probe and a ground plate indicates the presence of weak spots on the fuel tank cap. 

• Fuel Tank Testing: Fuel tank testing varies widely based on the size and material of the fuel tanks. The testing pressure of fuel tanks can range from 50-75 mbar for motorcycle fuel tanks to 100 mbar for automobiles and sometimes over 700 mbar for large tanks used in heavy-duty vehicles. Typically, the leak rates for plastic fuel tanks are around 0.5 to 2 Pa/s, while for metal fuel tanks, they are generally lower, around 0.1 to 0.5 Pa/s. Consult with our team to learn more about fuel tank leak testing and the ideal leak rate values for your specific tanks. 

• Fuel System/Assembly Testing: Fuel assemblies in automotive applications also undergo leak testing to ensure safety and efficiency. Components such as fuel tanks, valves, fuel lines, connectors, and fuel injectors are typically subjected to leak testing. ATEQ’s F600HP is an excellent leak detection equipment which can test leak rates at high pressures. 

Transitioning to high-pressure hydrogen systems and ATEQ’s solution 

Automobile fuel tanks are increasingly transitioning from traditional gasoline or diesel storage to hydrogen tanks as the industry shifts towards cleaner energy solutions. Hydrogen tanks, typically made from high-strength composite materials, are designed to store hydrogen at high pressures, enabling fuel cell vehicles to achieve greater range and efficiency. Due to the small size and high diffusivity of hydrogen molecules, leak testing for these tanks is more stringent than for conventional fuel tanks. Advanced methods tracer gas leak detection systems using hydrogen/ helium gases facilitated leak detection at higher sensitivity. Learn more about Hydrogen fuel tank testing here. 

Leak testing of fuel tanks and assemblies is a critical process to ensure safety, environmental protection, and compliance with regulations. As technology advances, the methods and tools for leak testing continue to improve, offering even greater accuracy and efficiency in detecting leaks. Contact us to learn more about efficient leak testing and the latest advancements in the world of leak testing.