Helicopter Refueling Systems

How an offshore fuel system works

Jet A-1 arrives in certified transit tanks lifted from the supply vessel. Fuel settles so water and dirt drop out, and the crew takes samples before any transfer. A pump then moves it through a filter vessel to a dispensing cabinet with a meter and hose reel next to the helideck. The filters remove dirt and water, the last defence before fuel reaches an engine.

CAP 437 describes two layouts.

• A transportable tank system delivers fuel from the transit tanks straight to the aircraft.
• A static storage system transfers fuel from the transit tanks into a fixed tank first, with its own filtration, and then delivers it.

Configurations

• Single or duty and standby pumps, driven by electric, air or hydraulic motors
• Filter water separator vessels to EI 1581, the primary filtration CAP 437 now expects
• Optional extra filtration, such as EI 1588 water barrier filters, or EI 1599 dirt defence filters paired with EI 1598 electronic water sensors
• Open-line gravity nozzles, or pressure refuelling where the aircraft allows it
• Stainless steel or lined mild steel tanks and pipework

Key specifications

Standards and certification

CAP 437 sets the layout, sampling and inspection regime for UK installations. The EI 1500-series standards govern the filtration, vessels and hoses. The EI withdrew EI 1583, the filter monitor element standard, and JIG standards dropped monitor elements from 1 July 2023. Filter vessels should be built to EI 1596, and CAP 437 says new systems should not use combined three-stage vessels. On a legacy system, the monitor vessel is replaced with a spool, or left in place with its elements removed or with through-flow dummy elements.

Transit tanks are IMDG portable tanks with a five-year periodic test and an intermediate test every 2.5 years, including the pressure and vacuum relief valve. Their frames must be certified as offshore containers to DNV-ST-E271 (formerly DNV 2.7-1), EN 12079 or ISO 10855. BS 7072 framed tanks have been banned on the UK continental shelf since 1 January 2015. Mild steel tanks need an internal epoxy lining to EI 1541 or Def Stan 80-097, and product markings follow EI 1542.

Failure modes and inspection

• Water and microbial growth in tank sumps and filter vessels. Inspect sumps, drain valves and sample records.
• Lining breakdown in mild steel tanks, which releases rust and coating flakes into the fuel.
• Filter differential pressure gauges stuck or out of calibration, hiding a blocked element.
• Hose cracking, kinking and coupling damage. Check the hose date and its last pressure test.
• Meter drift. Check the calibration certificate.
• Broken bonding leads and earth reels, which raise the risk of a static discharge.

Documentation

• Tank inspection plates and the latest IMDG test certificates
• Offshore container certificates for each tank frame and its lifting set
• Filter vessel data, element type and last element change
• Hose certificates and pressure test records
• Meter calibration and pump service records
• The last service provider's report and any CAP 437 statement of compliance

Integration and compatibility

Site the package where a spill drains away from the helideck and into a bunded area. Electrical items must suit the zone the fuel system creates. The dispensing cabinet needs fire cover, often from helideck foam systems, and the package must tie into the unit's emergency shutdown. Check that the hose reaches the aircraft's fuel point from the cabinet location.

Refurbishment and recertification

A package still fitted with monitor elements needs them taken out and a filter water separator to EI 1581 as its primary filtration. Tanks with lapsed certificates need their IMDG test and a container inspection before use. Any system that has stood idle must be inspected and released by a qualified refuelling service provider before it fuels an aircraft. Used stainless tanks with in-date certificates are usually the most straightforward part of a package to reuse.