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18 chapter four DELIVERY AND DISTRIBUTION PROCESSES The concept of the fuel supply chain from refinery to an aircraft is fairly simple and straightforward. From the refinery and bulk oil company storage facility, the fuel is transmitted to the airport by one of several transport modes: pipeline, ship or barge, railcar, or transport truck. The fuel is then trans- ferred to an airport-related storage facility through similar transport modes and is eventually placed into the aircraft. Although the concept may appear simple and straightforward, the actual delivery of clean fuel within the standards and required specifications involves numerous steps, components, and processes, along with the related opportunities for mistakes and error. The possibility of fuel contamination exists every time fuel is transferred. For that reason, fuel is filtered and checked every step of the way, as illustrated in Figure 3. TRANSPORT The transport of fuel to an airport generally has two stages: primary and secondary. Primary transport will be the shipment and transport of fuel from the refinery to a âpre-airfieldâ supply terminal, as described by the International Civil Aviation Organization (ICAO; Manual on Civil Aviation Jet Fuel Supply 2012). In some circumstances, primary transport can bypass a pre-airfield storage facility and go directly to an airfieldâs storage facility from the oil refinery. The majority of airports receive fuel through a secondary stage involving intermediary storage of fuel at a pre-airfield terminal facility. An airport operator is interested in any disruption in the supply chain that can affect airport opera- tion and any changes in the quality and specification of fuel; these are concerns for both primary and secondary stage transport. The quality of fuel and its transfer through different modes is a concern because once a fuel deliv- ery is accepted from another party, the receiving party takes responsibility for the fuelâs condition and use. For this reason, fuel quality tests are performed at each stage of the fuel delivery process before introduction into an established clean fuel system. ATA 103 states it is important that a facility operator sample inbound deliveries upstream of the receiving filtration point for any potential contamination or excessive levels of water and/or dirt (Standard for Jet Fuel Quality Control at Airports 2009). According to interviews and the literature, this is done for two reasons: (1) to prevent cross-contamination of fuel, and (2) to isolate responsibil- ity, accountability, and liability for any fuel that may be contaminated. Both reasons have operational implications and economic costs associated with them. The design of a fuel system will include filters and water separators to help ensure the proper qual- ity of fuel. The introduction of large amounts of contaminants into a system can affect the service life or functionality of system filters and can increase the maintenance and cost of operation. The issue of where or how a fuel becomes contaminated points to the need for proper testing and documentation in the event of a dispute over a âbadâ batch of fuel. Significant economic and operational costs can be incurred through the need to refilter all the fuel, defuel, clean tanks, and dispose of the bad fuel as a hazardous waste; other costs include those related to delayed flights and the additional worker-hours needed to rectify the situation.
19 DEDICATED FUEL TRANSPORT The use of segregated and dedicated transport systems is considered important in minimizing the potential for cross-contamination of any fuel. Per ATA 103, âunacceptable operational and economic issues based on upstream jet fuel purity levels are to be resolved between applicable shipper, facil- ity operator and/or customer.â To help reduce the possibility of contamination in the delivery of aviation fuel, fuel suppliers consider it a most effective practice to use dedicated transport vehicles. A dedicated transport is one that transports only one type of product, whether it is jet fuel or avgas (Figure 4). If a nondedicated transport is used or a different grade of fuel was previously transported in the container, a higher risk for cross-contamination exists unless the tanker has been cleaned according to acceptable standards, such as Joint Inspection Group (JIG) 3, American Petroleum Institute Recom- mended Practice (API RP) 1595, and Energy Institute (EI) Standard 1530 (Manual on Civil Aviation Jet Fuel Supply 2012). Because of the higher possibilities for fuel contamination from residual fuels, it is the policy of one FBO in the study to reject any fuel shipped in a nondedicated transport that has not been properly cleaned according to acceptable standards, and for all quality checks to prove the fuel is on-specification, clear and bright (R. Hartwein, personal communication, Aug. 27, 2014). Fuel that does not meet acceptable quality standards is called off-specification (off-spec) fuel and is to be disposed of properly. The off-spec fuel can be sold to a recycler or otherwise disposed of per environ- mental hazardous waste regulations. Refinery Clay Filter F/W Separator F/W Separator F/W Separator F/W Separator Pre-airfield Terminal F/W Separator Pipeline Tanker Truck Rail Car Barge or Ship Microfilter Airport Fuel Storage Airport Hydrant System Hydrant Monitor, F/W Separator & Dispenser Refueler with F/W Separator Refueling Nozzle Helicopter Prop-jet aircraft Jet Aircraft Shutoff / Isolation Valve Transfer Points F/W Filter / Water Separator FIGURE 3 Fuel delivery diagram from refinery to aircraft showing filtration points and transportation modes. (Courtesy: FAUDI Aviation.) Used with permission.
20 FUEL FACILITY DESIGN The design purpose of a fuel system is to receive, store, monitor, filter, and transfer fuel in accordance with quality standards (Lahey and Heilbron 2008). The primary difference between a fuel system at a large hub airport or a small GA airport is the scale of infrastructure and the number of components. Little difference exists in the actual components that are used because standardization of components exists throughout the industry. Fuel storage can be located on or off airport property, depending on factors related to the land available, such as environmental and site preparation costs, and the efficiency of methods for final delivery to the aircraft. From an airport storage facility, the fuel is piped to a central dispensing pump or a decentralized underground hydrant fuel system with a pit at each aircraft gate, or is loaded into refueler trucks or dispensers for final delivery to the aircraft. The focus of this study is on the fuel processes, facilities, and equipment that are located or situ- ated within the property lines of the airport. Once fuel crosses onto airport property, its environmental safekeeping ultimately becomes the responsibility of the airport operator, no matter who is involved in the receipt, storage, or delivery of the fuel to aircraft. To that extent, an airport can specify the type of fuel facility and its location, even over the objection of a tenant (Docket No. 16-07-06 2008). A fuel farm is the consolidated location of bulk fuel storage and equipment on or off an airport. The design of a fuel farm normally includes an area large enough to meet tank separation standards and contain all associated piping, filter assemblies, and pump equipment; a containment dike or bund; a fire protection system, including separate water storage for foam; a control room or similar building; security fencing; and a truck loading/unloading platform (also known as a rack system) to include adequate maneuvering area and room for the parking of service vehicles. Backup emergency generators can also be included. A modern control room or building will house test equipment; an area for quality control testing, manuals, and documentation; a computerized management system that controls and monitors aspects of the fueling system, such as tank levels, motor operated valves, pump operations, emergency shut- down of fueling operations, alarms, pump runtime, system pressure and flow instrumentation; and other items as required by the individual system. With the exception of a dedicated control building, similar facility and equipment requirements are needed for smaller airports, although within a much smaller land footprint. Some fuel tanks installed FIGURE 4 Example of a dedicated Jet A tanker delivering fuel to an airport tank farm. (Courtesy: S. Quilty, SMQ Airport Services.)
21 at GA airports are modular, with the pump, filters, and meter equipment self-contained with the tank or are on skids for easy or temporary transport (Figure 5). ACRP Report 113 provides an overview for the planning of fuel facilities at general aviation airports (Sander et al. 2014). Fuel Piping The size of pipes and hoses used in a hydrant fueling system is based on peak demand requirements. Aircraft operators and engineers make volume calculations as to how many and what types of aircraft are expected to be fueled over a given time period. Fuel flow delivery rates to an aircraft determine how long it will take to service an aircraft, which affects turnaround times and variable operating costs for the airlines. To prevent corrosion and contamination, pipes for jet fuel systems can be made of coated or epoxy-lined carbon steel or nonferrous epoxy-lined or stainless steel. Metals in pipes, valves, equip- ment, and accessories that interact negatively with jet fuel are zinc and copper, including alloys with either of those metals. To mitigate leakage, underground piping and hydrant fuel system designs often incorporate a line leak detection system. Standards exist for the marking of pipes (EI 1542 and API 1637) and for the testing of hydrant pipe systems (EI 1594, API RP 1540, and UFGS-33 58 00). Fire Suppression Of major consideration in the design of a fuel facility is the provision for a fire protection system and emergency response (NFPA 11 2010). At a minimum, portable fire extinguishers are required under NFPA, FAA, and state or local codes. The provision of a particular fire suppression system is based on the overall fuel storage capacity or flow rate of the system and outlined in adopted codes or standards. For aboveground storage tank (AST) systems, fire protection systems normally consist of a water supply with fixed or semifixed foam fire suppression capability (Figure 6). For hydrant fuel systems, consideration is given to aircraft rescue and firefighting response to a ramp incident. Considerations include the impact of access to hydrants and equipment, fuel and isolation cutoff locations, and sur- face and storm water drainage. Electrostatic Protection Provisions are made in the design of a fuel system to minimize the potential for static electricity generation. The Coordinating Research Council (CRC) has a number of publications addressing the FIGURE 5 Example of a modular fuel tank. (Courtesy: S. Quilty, SMQ Airport Services.)
22 electro static properties of fueling systems (see Appendix A). NFPA 77, ATA 103, and AC 150/5230-4B provide guidance for reducing static electricity potential; routine testing of ground rods and bonding cables; and conductivity testing of filters, hoses, equipment, and piping. Standards and require- ments exist for both bonding and grounding. Bonding is the creation of an electrical path between two components to establish a neutral electrical potential, such as between a refueler truck and an aircraft. Grounding (also known as earthing) is the creation of a neutral electrical path between a vehicle, equipment, or component and the earth, such as an aircraft to ground or a refueler truck to ground. Fitness Testing and Fitness for Service Fitness testing is a quality control measure used to determine if a fuel system component meets acceptable standards before it is placed or returned to service. Fitness testing for hydrant fuel systems is periodically necessary, according to API/EI 1594 standards. The piping system is to be pressure tested for leaks every 5 or 10 years. For newly installed tanks, a soak test determines if a new tank is suitable for the storage of jet fuel or if a tank can be brought into service after repairs have been completed (EI 1540 and Jig Bulletin 35). Should damage occur to a fuel system component, an assessment for âfitness for serviceâ (FFS) can be made as to whether replacement is needed or if the component can remain in service (API 579-1). For repairs that are performed on a fueling system, an FFS test is performed on it before the system is returned to service. FFS is a means for performing a quantitative engineer- ing evaluation that demonstrates the structural integrity of an in-service component containing a flaw or damage (Fitness for Service 2007). The API guide provides examples of what fueling mechanisms and component types can incur damage. Equipment manufacturers can also provide guidance in an evaluation. FFS tests normally are performed by third-party, state-qualified or authorized firms. Local requirements can exist for placing a new or refurbished fuel truck into service. A certificate of FFS from a company that refurbishes or otherwise provides refueler trucks would certify that no contaminant exists in the fueling system and that the fuel tank system, components, and piping have been properly flushed and tested. FIGURE 6 Foam suppression inlet point for aboveground tanks. (Courtesy: S. Quilty, SMQ Airport Services.)
23 Security Protection from intentional damage or attack is critical to the prevention of malfunctioning of or seri- ous damage to the airport fueling system, which can cause major disruption to communities, trans- portation networks, and economic markets. The TSA has published guidelines for the security of fuel delivery and storage facilities on airports (Security Guidelines for General Aviation Airports 2004). Threat and vulnerability assessment methodologies, guidelines, and standards have been developed by U.S. government agencies, including DoD, DHSâs Federal Emergency Management Administration (FEMA) and TSA, and U.S.DOTâs FAA. Beyond the installation of security fencing, gates, and locks, security measures that can be used include access control devices and requirements, intrusion detection, video surveillance, patrols, blast protective screens, lighting, barricades and terrain obstacles, and security patrols. STORAGE TANKS The storage of a particular fuel necessitates keeping it segregated from other types of fuels, keeping it free of contamination, and having adequate amounts of fuel to meet the needs of the airport users. NFPA 30A provides guidance on the design of fuel storage facilities (NFPA 30A 2015). International Air Transport Association (IATA) provides guidance for assessing the amount of fuel storage capac- ity needed by an airport (IATA Guidance on Airport Fuel Storage Capacity 2008). For delivery by fuel truck to an airport, IATA suggests adequate storage would provide reserves of 3 to 10 days. For pipeline delivery to the airport, the amount of reserve time can be less. Settling Tank Settling time is a factor in the delivery and use of fuel. Settling time is the length of time the industry has established for allowing sediment and moisture to settle to the bottom of a fuel. Depending on the vertical height of a tank, settling time can be anywhere from as little as 1 hour for avgas to several days for jet fuel (Refueling and Quality Control Procedures for Airport Service and Support Operations 2000). For jet fuel, the normal allowable settling time is 1 hour for each foot of tank depth. For avgas, allowable settling time is 15 minutes for each foot of tank depth (AC 00-34A 1974). The tank volume and daily fuel consumption rate dictate the number and volume of tanks needed. Settling time also applies to transport vehicles. Once a vehicle has arrived at the airport, standard practice is to provide a wait time before fuel is transferred to allow for settling of the fuel, which is jostled during transport. Airports that produce a high turnover of jet fuel on a daily basis normally have three or more stor- age tanks (IATA Guidance on Airport Fuel Storage Capacity 2008). One tank is designated as the receiving tank and is used for accepting a load of fuel. A second tank is a holding and settling tank and is used to allow time for contaminants to settle. The third tank is called the operating tank and is the one from which fuel is drawn for daily use. The designated use of the tanks is routinely rotated, or fuel is pumped from one tank to another. Should a tank require maintenance or cleaning, the airport can continue to function with just two tanks. For GA airports having just one jet or avgas fuel tank, industry practice is to plan delivery and use carefully to ensure adequate time for settling of the fuel before fuel is drawn from the tank. For avgas, one tank usually is sufficient because of the shorter settling time required. In either case, good risk man- agement practices assess the likelihood of any one tank being unavailable for extended periods of time and determine a plan for actions to take in the event of a tank becoming contaminated or not usable. Aboveground and Underground Tanks The categories of permanent large capacity bulk storage facilities are known as aboveground storage tanks (AST) and underground storage tanks (UST). As taken from API, NFPA, and DoD standards, the determination of the tank construction material to be used is affected by a number of factors. The
24 primary factors are local or state building codes or regulations, installation and maintenance costs, environmental requirements, available land, expected design life, risk and liability exposure, insurance, security, and aesthetics. Tank material is also contingent upon the type of material to be stored. Tanks are coated or other- wise have protection from the environment, fire, and explosion. Epoxy-coated steel is the standard for jet fuel, and epoxy-coated steel or fiberglass is used for avgas and mogas. A stainless steel tank eliminates the need for epoxy coatings, although such tanks can be more difficult to repair or maintain. Jet fuel storage tanks have a floating suction tube that draws fuel from several inches below the upper surface of the fuel. Avgas tanks draw from several inches above the bottom of a tank. The with- drawal point is the result of the water and contaminant settling properties of each fuel. If jet fuel is not to be used for a period of time, large jet fuel storage systems have design requirements for recirculat- ing the fuel on a regular basis. This is because of the potential for microbial growth in the fuel and to maintain thermal stability. Water precipitates into the fuel from humidity and condensation on the tanks, allowing microbial growth to occur. Avgas is not susceptible to microbial growth. Local or state regulations are to be referenced as to whether a tank is to be installed above or below ground. A literature review of several state regulations identified the requirements for the installation and inspection of ASTs and USTs, which were to be performed by tank installers with the experience, integrity, and requisite state certification approvals to do so. Both ASTs and USTs are required to meet specifications for corrosion protection, spill and overfill prevention devices, leak detection devices, and secondary containment (40 CFR 280). One consideration for AST construction is that the tanks remain below heights that penetrate obstruction clearance surfaces at airports (14 CFR Part 77). The NFPA is a primary source of information for what flammability standards are to be met for fire-rated fuel tanks, whereas the Steel Tank Institute (STI) and the Fiberglass Tank & Pipe Institute set standards for tank construction in general (see Appendix A). A number of benefits exist for ASTs. One is their ability to hold large capacities (5,000 to millions of gallons). Given their capacity to hold thousands of barrels of fuel (1 barrel equates to approximately 42 gallons), ASTs generally are more economical to construct for larger fuel volumes than are USTs. ASTs allow for easy inspection and detection of leaks. In the event of a leak, containment is provided through construction of a bund or earthen embankment. The drawbacks to ASTs are the physical expo- sure to weather, security, potential for external physical contact damage, aesthetics, and the effects of temperature change on the fuel. USTs usually are installed horizontally below ground and are prefabricated steel or fiberglass with linings and secondary containment (double-walled). Advantages of USTs include economical installation of small capacity tanks (5,000 to 80,000 gallons), compartmentalization of the tank into two or more holding capacities, less exposure to physical damage, and more stable and consistent internal fuel temperatures. The drawbacks for USTs are related primarily to the requirement for leak detection and fuel-monitoring wells, cathodic (corrosion) protection, and the cost of a double- or triple-wall construction. According to federal and state regulations, owners of USTs are to provide financial assurance infor- mation that demonstrates they have the financial ability to cover potential corrective actions or com- pensate third parties for accidental releases (The Hazardous and Solid Waste Amendments of 1984). In addition, owners and operators of new UST systems are to certify compliance with tank and piping installation, cathodic protection, financial responsibility, and release detection. All cathodic protection systems are to be tested within 6 months of installation and at least every 3 years thereafter (40 CFR 280). Determining Fuel Tank Levels The determination of fuel level is an important safety practice for preventing overfills. Different gaug- ing methods exist, including resistive tape, floats, tapes, hydrostatic, radar, and servo-mechanisms, as well as the tried-and-true dipstick measurement. Figure 7 is an example of a float-type clock
25 gauge. The recalibration of electrical or mechanical gauge equipment is accomplished according to the manufacturerâs recommendations or local codes. There are third-party companies that specialize in calibration. FUEL DISPENSING METHODS Several methods exist for dispensing fuel to an aircraft. At large and medium hub airports, hydrant fuel systems are prevalent (Figure 8). In a 2003 survey of 128 member airports in North America, Airports Council InternationalâNorth America (ACIâNA) found that 91 airports had fuel farms, and of those, 47 had underground fuel hydrant systems (General Information Survey 2003). A second method of fuel dispensing is a refueling truck. A third method is through a stationary fuel dispenser located adjacent to a fuel tank or away from the tank at a remote or island location. Hydrant Fuel System A hydrant system delivers fuel to an aircraft through an underground piping system. The piping system terminates near an aircraft parking station on the ramp. From there it can be designed as a fuel pit location or a hydrant pit. A fuel pit system is equipped with its own hose, reel, filter, and air eliminator at each pit location, thereby eliminating the need for the mobile dispenser unit. A hydrant pit is smaller and contains a connection for a hydrant service cart or similar mobile pump that con- nects the underground pipe to the aircraft (Figure 9). The service carts are small in comparison to a refueler truck or dispenser vehicle. Although towable, hydrant service carts usually are stationed at one particular aircraft parking spot (Figure 10). To service aircraft with high wing fueling points, a mobile fueling cart with a platform lifter is often used (Figure 11). Fuel is pumped through a hydrant fuel system using any number of centrifugal, positive displace- ment, or turbine pumps operating in parallel to each other (Figure 12). A design goal for a hydrant fuel system and controller interface is to minimize pressure fluctuations within the system that could damage piping or equipment, result in loss of fuel, or adversely affect the safety of operating per- sonnel. A nonfueling pump may operate to maintain pressure in the line, or the line may maintain static pressure through the use of ball or check valves. If a static pressure line is maintained, there is FIGURE 7 Fuel tank float type clock measurement gauge. (Courtesy: S. Quilty, SMQ Airport Services.)
FIGURE 8 Typical fuel hydrant delivery system. (Courtesy: Jones et al. 2000, p. 15.)
27 FIGURE 9 Example of a hydrant pit connection on a terminal ramp. (Courtesy: S. Quilty, SMQ Airport Services.) FIGURE 10 Example of a towable hydrant transfer cart. (Courtesy: S. Quilty, SMQ Airport Services.) Platform Lifter Identification Placard Filter Vessel Hose Reels Hose Control Switch Meter Bonding Cable Gauges FIGURE 11 Example of a mobile platform lifter hydrant transfer vehicle. (Courtesy: A. Villaverde, LaxFuel Corporation.)
28 a potential problem of spikes in pressure as a pump comes on line once a hydrant valve is opened. In-line accumulators or surge suppressors help to dampen pressure spikes. With a constant pressure system and several aircraft being fueled concurrently, an additional pump will start to operate as needed to maintain the volume and pressure throughout the hydrant system with minimal pressure spike. An electronic control system monitors and regulates the pres- sures and pumps. The electronic controller can be programmed to change the lead pump each day as a means for managing wear and tear on the pumps. The installed locations of hydrant systems built underground can limit the ability of an airline to use a type of aircraft at that position that is different from what the position initially was designed to serve. This limitation is because of the different location of aircraft fill positions and the range of service cart hoses (Anderson and Hirsh 2010). A most effective practice in hydrant fuel system design is to have a continuous loop, rather than a terminus point. A loop system helps to eliminate stagnant fuel and the potential for microbial or other contaminant accumulation. A properly designed hydrant system takes into account the need for maintenance, testing, shutoff, and drainage without affecting other fueling areas of the airport. The placement of isolation valves allows for easy maintenance, inspection, and emergency shutoff. One way to help mitigate the impact of a hydrant system going off-line is to install two smaller diameter pipes in parallel, as personnel at the MemphisâShelby County International airport explained in an interview. Although such a system costs more, the design allows for shutting one line down for maintenance while retaining the capability to fuel aircraft by means of the parallel line, albeit not at the same capacity as two lines. Because it is more economical to extend an existing hydrant loop than to construct a new line from the depot area, the airport designed its system with adequate capacity, pressure, and volume to be able to expand the hydrant system for added gates or service areas. In designing the throughput rate of fuel delivery systems, a minimum rate of 200 gallons per min- ute (gpm) is sought for fuel truck, barge, or railcar delivery. Higher fuel flow rates are preferred and are contingent upon system design. Considering that transport trucks often are designed to transport 8,000 to 10,000 gallons, it would take anywhere from 40 to 50 minutes to offload a single truck at a rate of 200 gpm. Pipeline deliveries can be at higher rates. Often the pipe sizes range in diameters of 8 to 22 inches. The fuel delivery system at Los Angeles International Airport pumps between 4.5 and 5 million gallons of fuel each day. With fuel capacities of aircraft such as the B-777 and A-380 ranging from 45,000 gallons to 84,000 gallons, hydrant fueling is preferred over truck filling. Todayâs jet aircraft are designed to accept flow rates of 600 to 800 gpm through multiple nozzles. It is because of the length of time required to fuel an aircraft and refuel the truck at the rack-loading platform that hydrant systems are FIGURE 12 Example of parallel pumps for hydrant fuel system. (Courtesy: S. Quilty, SMQ Airport Services.)
29 installed at airports. There is also a large impact on reduced turnaround times for aircraft occupying gates and reduced vehicle activity on the ramp. Spill Protection A properly designed hydrant system will take into account the potential for spillage and leakage. Newer hydrant designs accommodate a side entry of pipes into a hydrant pit, rather than the older style of entry from the bottom. Side entry allows for less chance of fuel migration into the soil if there is leakage or spillage than a bottom entry pipe seal. Side entry also allows for a catchment of any fuel spill and easy removal. Truck Refueler Delivery System Another method of getting fuel to the aircraft is through a self-contained refueler truck or dispenser. The fuel is stored in a chassis-mounted tank with an integral pump, filter, and meter system. The vehicle receives a load of fuel from a rack or similar loading area and is driven to each aircraft requir- ing fuel. The design allows for flexibility, but the size of the vehicle limits the amount of fuel available and the amount of maneuvering space in proximity to an aircraft. Fuel trucks have typical capacities of 1,000, 3,000, 5,000, 8,000, 10,000, 12,000, and 15,000 gallons. Capacity of avgas trucks tends to be in the range of 500 to 5,000 gallons, whereas capacity for jet fuel trucks ranges from 1,000 to 15,000 gallons (Figure 13). With gross vehicle weights of 70,000 pounds or more for the largest trucks, terminal ramps and access roadways need to be designed to accommodate truck movements. The design of a truck loading/unloading area requires secondary containment per EPA regulations (40 CFR Part 112). Stationary Fuel Dispensing System Many small airports have a remote or stationary fuel dispenser stand that allows aircraft to taxi up to receive fuel (Figure 14). The hose, pumps, meters, and filters are commonly housed in a lockable Vent Nozzle/ Enabling Switch Relief Valve Filter Separator Meter Sump Drain Backup Sensor Fuel Pump Fill Pipe Bonding Cable & Reel Reel Switch Fire Bottle Placarding As Noted Tank Drain FIGURE 13 Typical 500-gallon avgas mobile refueler. (Courtesy: S. Quilty, SMQ Airport Services.)
30 fueling cabinet. For a fuel island arrangement, the cabinet location is of low profile and is fed by underground pipes from a nearby storage tank. The island location allows for clearance of aircraft wings or helicopter rotors. Self-service fuel stations are typical of stationary fuel dispensing systems. OTHER FUEL SYSTEM COMPONENTS In addition to fuel storage tanks, the distribution of fuel to aircraft occurs using a number of different components, such as supply pumps, filters, meters, pressure and flow control valves, refueler trucks, hydrant piping, hydrant pits, hydrant carts, fuel hoses and nozzles, bonding equipment, and cutoff switches and valves. Safety officials tend to agree it is important to know all of the components of a fuel system and the correct nomenclature (Smith 2005). A most effective practice is to have a diagram and list of components for any fueling system on the airport. Having the diagram promotes understanding of how the fuel flows through the system, the location of shutoff and routing valves, the types of pumps and filters, and the capacity of each tank and pipe system. It is not uncommon for operators or managers of a fuel facility to lack facility drawings and dia- grams of a system. Generally, an airport that has a spill prevention, control and countermeasure (SPCC) plan, which is required by the Oil Pollution Control Act (OPA) of 1990, has a description of the fuel- ing facilities within the plan. The SPCC would also spell out fuel transfer procedures and the type of overflow or spill protection a fuel system has in place. The degree of detail a facility plan provides and the degree to which the equipment is adequately described can vary greatly among airports. Figure 15 illustrates a typical AST layout with bund wall containment and identification of facility components. Fuel system diagrams are also of value in training local and mutual aid emergency response crews and for those who have inspection or operational roles, such as maintenance or operations personnel. A useful diagram includes a description of the fire suppression system or location and type of fire extinguishment. Finally, the fuel farm diagram describes the location of drains and shutoffs for con- tainment in the event of a spill and the switches needed to cut off energy to circuits. For safety purposes, fuel tanks can be equipped with overfill level alarms, low level alarms, automatic product level gauging, manual gauge ports, sampling ports, floating suction units, access manways, and vents, as necessary to comply with standards and codes. The most effective practice is to describe the settings of overflow protection devices and the operation of the alarm system, and provide directional flow and other markings on the piping (Figure 16). The building or fire codes of the local or state government will dictate what is required. Additional requirements may exist for meeting a certain fire resistance level and minimum distances between separate tanks and between tanks and buildings, property lines, public areas, and dispensing equipment. Fuel Hoses and Nozzles API/EI 1529 and NFPA 407 standards set out the requirements for fuel hose material. Inspection of a fuel hose entails checking for abrasion and cracking. If the braid is showing as a result of scuffing FIGURE 14 Typical fuel island arrangement with low-profile cabinets. (Courtesy: R. Lanman, AuburnâLewiston Airport, Maine.)
31 Pipework over wall Bund big enough to contain 120% of the volume of the largest tank High level detector Truck loading and unloading area undercover Spills from hose couplings within bund area Truck unloading area Collection sump Drains to sewer or slops tank Blind collection sump FIGURE 15 Typical aboveground tank with containment and spill protection. (Courtesy: Flexibund, Australia.) Used with permission. Red External Tank Level Indicator Safety Markings Red Hi-level Alarm Amber Low-level Alarm Shutoff Valve Bund Wall Aural Alarm Speaker Tank Status Indicator FIGURE 16 Example of a fuel tankâs high-level and low-level alarms and markings. (Courtesy: S. Quilty, SMQ Airport Services.)
32 or dragging, industry practice is to replace the hose. ATA 103 establishes a maximum service life for an aircraft fuel hose of 10 years for those using that particular standard. ASTM D380 and local codes require periodic hydrostatic testing of fuel hoses. Aircraft are designed with fuel receptacles for one or both of two fueling methods: single-point pressure feed or over-the-wing gravity feed. Single-point nozzles are used for jet fueling. The nozzle is attached to a receptacle under a wing or in the fuselage of an aircraft. It is used for high volume jet fuel transfer and helps to eliminate open exposure to static and vapor buildup. Over-the-wing fueling is used for dispensing avgas into piston-engine aircraft or jet fuel into com- mercial or business jet aircraft without single-point refueling. To help safeguard against misfueling in over-the-wing situations, the industry uses safety measures including nozzle design, color coding, and placarding. The design of jet fuel nozzles can be a single-point, flared (duckbill or J-spout), or straight (rogue spout) design (Figure 17). Avgas nozzles are round. Since 1985, aircraft manufacturers have pro- duced aircraft with gravity feed fuel filler openings designed to prevent misfueling of jet or piston aircraft (AC 20-122A 1991). The fuel filler opening, ports, and nozzles are designed to meet Society of Automotive Engineers (SAE) 1852D standard. Fuel tank filler openings in aircraft using avgas have a maximum diameter of 2.3 inches. Jet or turbine engine fuel nozzle assemblies are equipped with nozzle spouts with a minimum diameter of 2.6 inches, thereby reducing the probability of introducing jet or turbine engine fuel nozzles into the filler openings of aircraft that require gasoline. In addition, a flared jet fuel nozzle design was introduced at that time to further distinguish the fuel type in use. Misfueling accidents can (and do) occur because older aircraft may not have been modified to the smaller avgas opening; operators continue to use small round diameter nozzles; operators get tired of switching out the flared nozzle for a straight nozzle when filling different types of aircraft, especially helicopters; or operators prefer the reduced flow rates of a smaller nozzle (Mooney 2006). One com- mercial operator who needs a reduced flow rate uses a 1.5-inch straight nozzle with a 2.6-inch collar attached to help prevent the introduction of jet fuel into an avgas port (Figure 18). AC 20-122A recommends that airport owners amend their airport operations manual to encourage FBOs and other suppliers to meet the SAE size specifications for jet fuel nozzle spouts. Bonding Cable Flared Nozzle StraightNozzle Meter Hose Rewind SwitchRed Shutoff Handle Fuel & Pump Pressure Gauges Single-point Nozzle Interconnect Switch FIGURE 17 Different nozzles used on jet fuel truck dispenser. (Courtesy: S. Quilty, SMQ Airport Services.)
33 To further help prevent misfueling, black lettering and color coding are applied to jet fuel facili- ties (Figure 19). Red coding is applied to avgas facilities and components. NFPA 407, ATA 103, and AC 00-34A identify standards for placarding fuel trucks, piping, and storage facilities (see Figures 13 and 16). The third method for preventing misfueling is through placarding. Accepted standards for the marking of fuel systems are found in EI 1542, API 1637, NFPA 385, and AC 00-34A. Collar attachment FIGURE 18 Collar attachment to nozzle to prevent fueling of jet fuel into avgas aircraft. (Courtesy: S. Quilty, SMQ Airport Services.) FIGURE 19 Standard color coding and marking of pipes and equipment. (Courtesy: FAA Aviation Maintenance Technician HandbookâAirframe 2012.)
34 Fuel Filtering A general rule and common practice in the design of jet fuel and avgas systems is that each time fuel or gas is moved, it passes through a filtration system (see Figure 3). Fuel is filtered from the sup- plier tanker vessel to the storage tank, from one storage tank to another, from the storage tank to the hydrant or refueler truck, and from the hydrant or refueler truck to the airplane. The filtering system is intended to remove all particles, including dirt, rust, and live microbial organisms. Fungi and bacteria are prone to grow in jet fuel that has remained stagnant for a period of time. A typical large two-stage vertical fuel coalescer filtering system is shown in Figure 20. Filter Check Valve Air Eliminator Swing Bolt Closure Diï¬erential Pressure Gauge Coalescer Cartridge Liquid Level Gauge Sump Heater Sump Area Positive Drain Deck Clean Out Connection Sampling Probe INLET Main Drain Valve Water Slug Control Valve OUTLET Clean Out Connection Float Control Valve Separator Cartridge Head Lift w/ Hydraulic Jack Spacer Plate Pressure Relief Valve Coalesced Water Drops to Sump FIGURE 20 Typical fuel coalescer filter system for bulk storage. (Adapted from Precision Filtration Products.) Used with permission.
35 vessels can also be designed for horizontal installation. Fuel trucks and smaller tanks have smaller individual filter water/separator vessels. The condition of a filter media within a vessel is generally measured using a differential pressure gauge. Differential gauges can be visual, mechanical, or electrical. Standard industry practice is for a maximum differential of 15 psi when operating at design flow rates (PEI Aviation Fueling Com- mittee 2013). If flow rates are reduced from what the system was designed for, lower filter media differential pressures are to be applied per the standards or manufacturer recommendations. Other Design Components As part of a quality control management program and for environmental and operational reasons, familiarity with the function, purpose, and location of all the design components of a fuel system is important. Gaining familiarity with the system can lead to better decisions about maintenance, opera- tion, and emergency response in the event of a malfunction. The glossary provides a list of common components and terms used in the design of storage facilities, pump transfer and piping systems, and truck, stationary, and hydrant delivery systems (see Glossary and Fuel System Terminology). Figure 21 shows several system components associated with a horizontal AST. Accessible on the web and within many of the standards, suggested practices, and guidance mate- rial listed in Appendix A are detailed descriptions and functional explanations of common compo- nents used in fueling systems. Line Strainer Overfill Prevention Valve Clock Gauge w/ Alarm 12 Ft. Min. Above Grade Pressure Vacuum Valve Gate Valve Submersible Pump Line Strainer Emergency Valve Solenoid Interconnect Valve Expansion Relief Valve Overfill Alarm Check Valve Locking Ball Valves Fill Adapter w/ Cover Spill Container Fuel Dispenser Ground Connection Ground Connection Vapor Recovery Adapter w/ Cover Emergency Vent Emergency Vent Interstitial FIGURE 21 Components for a horizontal AST. (Adapted from Morrison Bros.) Used with permission.