What Do Updated EI 1540 Guidelines Mean for Airport Hydrant Operations?
Jet fuel is supplied to aircraft either by a fueling truck or through an underground network of pipes known as a hydrant system.
Refueling can take many hours depending on the aircraft. Hydrant systems are preferred for their operational efficiency and ease of use, particularly for larger aircraft that require significant amounts of fuel. Hydrant systems minimize the need for transporting fuel via trucks across busy airfields, reducing logistical complexity and ensuring a safer, more streamlined refueling process.
Hydrant systems are essential for efficient aircraft refueling, but they come with operational challenges. In the event of a leak, without a reliable tightness monitoring system, operators may face significant fuel losses, operational delays, and environmental risks before the issue is identified. Tightness monitoring is crucial to identifying leaks early, minimizing downtime, and preventing financial and safety risks, allowing hydrant systems to operate smoothly and meet regulatory requirements.
Hydrant systems are the backbone of efficient aircraft refueling operations, and their performance depends on strict adherence to industry guidelines. The Energy Institute's Recommended Practice (RP) EI 1540 outlines the best practices for the design, construction, maintenance and testing of these critical systems.
With the release of the sixth edition, significant updates have been introduced that directly impact the way hydrant operators manage their systems. These changes aim to improve operational reliability, tighten leak detection standards, and reduce downtime. For operators, this means adopting new procedures to stay compliant and ensure seamless, safe refueling operations.
EI 1540: Then and Now
Historically, tightness monitoring for airport hydrants was addressed in two separate standards: EI 1540 and EI 1560. However, with the latest update, the key elements of EI 1560, which covered the operation, inspection, maintenance and commissioning of aviation fuel hydrant systems, have now been integrated into EI 1540.
This consolidation streamlines the guidelines, making EI 1540 the single reference point for both hydrant system design and operational best practices.
Sensitivity Requirements
Sensitivity requirements in the previous specification for EI 1540 were based on the ability to “detect leaks equivalent to 0.04 liters/hour/cubic meter at a reference pressure of 7 barg, require a fuel hydrant shutdown period of about 1 hour and can be used on a regular basis.”1
In the previous specification, the sensitivity of a pressure-based system scales with hydrant volume, so a 4 liter/hour leak in 100 m3 gives approximately the same pressure drop as an 8 liter/hour leak in 200 m3.
The same standard is applicable to hydrant volumes of any size. The reference pressure accounts for the leak rate changing with pressure (a smaller pressure difference between inside and outside the pipe section results in a smaller leakage) and thus the operational pressure of the hydrant network determines the hole size to be detected.
The new standard addresses a concern that it was possible to cover an entire hydrant network as one section of a large volume and have a correspondingly large leak that would then go unnoticed. Under the new standard, optimal volume for each hydrant section should be under 200 m3. The leak detection sensitivity threshold for hydrant sections operating with this volume should have a leak detection sensitivity threshold of 0.02 l/hr/m3 at a reference pressure of 700 kPag (7 barg). This makes the requirement twice as sensitive as the fifth edition’s specifications.
Testing Frequency
At a busy airport, finding time for tightness testing or any other maintenance activities is a challenge and most automated tightness monitoring systems can only be activated during quiet periods at the airport, which vary from region to region.
The new EI 1540 standard recommends testing every 24 hours to limit the total leak volume.
Sectionalization of Hydrant Networks
Previously, it was possible to treat an entire hydrant network as a single section with a large volume, which allowed for a larger leak to be detected while still remaining compliant with the standards.
To enhance leak detection precision and accuracy, EI 1540 recommends that pipeline sections be isolated using double block and bleed valves (DBBs), dividing the network into smaller, more manageable sections, ideally with volumes less than 200 m³.
This ensures that each segment is correctly isolated, preventing issues caused by passing valves, which can interfere with the effectiveness of tightness monitoring systems..
Revalidation Requirements
After installing a tightness monitoring system, there is a requirement to validate the system.
Typically, this is accomplished by inducing a leak and confirming that the leak is detected, details of the procedure will be available from the vendors. It is recommended under EI 1540 that revalidation of the system be completed annually as a minimum.
How Hydrant Operators Should Respond to EI 1540
The new standard tightens the minimum detectable leak size in internal, pressure-based tightness monitoring systems, and increases the testing frequency thereby reducing the risks associated with undetected leaks. To comply with these updated guidelines, operators should focus on performance improvement and optimization of their existing systems.
For hydrant sections with volumes below 200 m³, the increased sensitivity requirement targets a minimum leak of 0.02 l/hr/m³ at a reference pressure of 700 kPa. For sections above 200 m³, such as feeder lines, while the target leak rate is 4 l/hr at the same reference pressure, Atmos aims to achieve 0.02 l/hr/m³ across all volumes as best practice for optimal performance. Operators are encouraged to work closely with their tightness monitoring vendors to achieve this level of sensitivity.
Meeting the new standard may involve re-commissioning or fine-tuning current systems. Operators can use these updates as an opportunity to improve the overall reliability and efficiency of their systems, ensuring compliance while reducing operational risks.
