Fuel tank

01

Fix the capacity, wall material and fittings

Transfer Flow's replacement tanks for pickups and cab-chassis trucks show the capacity range of one maker's catalogue: 40, 45, 46, 50 and 58 gallon models, built from 12- and 14-gauge aluminised steel and fully baffled to reduce fuel sloshing. [4] Its regulations page states that its tanks use high-yield 14-gauge aluminised steel as a minimum, are pressure tested for leaks, and that liquid-filled tanks are subjected to a 30-foot drop test; it warns never to apply more than 3 psi to its tanks and never to connect 12 volts directly to the sending unit, which would burn out the sender resistor. [5]

For plastic tanks, Kuraray's patent US7208210B2 describes a coextrusion blow-molded fuel container whose example 35-liter tank, with 0.85 m² surface area, has five layers — outer HDPE, adhesive resin, EVOH barrier, adhesive resin, inner HDPE — of 2500/100/150/100/2500 μm. The patent identifies the pinch-off seam and the joints where components are attached as paths for fuel permeation that a barrier member can cover. [6]

FMCSA requires the tank body to have flanges or spuds for all fittings, Dryseal taper pipe threads (SAE J476) with at least four full threads engaged, drains and bottom fittings no more than three-fourths of an inch below the tank and protected from impact, and joints closed by welding, brazing or silver soldering — not by crimping or soft solder alone. [1]

Editorial calculation: at 3.785 L per US gallon, the 40–58 gallon range above is about 151–220 L; the 95% fill limit leaves a 58 gallon tank about 55 gallons (about 209 L) of fill. The Kuraray example wall totals 2500 + 100 + 150 + 100 + 2500 = 5,350 μm (5.35 mm), with the EVOH barrier about 2.8% of it. [4] [1] [6]

Give the supplier the fuel (diesel, gasoline, alcohol blend), usable and nominal capacity, the space envelope and mounting (frame rail, side-mounted, midship), wall material, alloy and gauge or layer structure, baffles, sender type and port, withdrawal, return and vent fittings with thread standard, filler location and fill rate, venting and rollover valve, drain, finish, the rules it must certify to, test reports, marking and quantity.

02

Check the safety and emission rules the tank must pass

49 CFR 393.67 applies to liquid fuel tanks on commercial motor vehicles. Tanks must not fill beyond 95% of liquid capacity in a normal filling operation, and must carry a nonspill air vent such as a ball check. Above 25 gallons, a tank needs a safety venting system that activates in a fire test before internal pressure exceeds 50 psi, and its body and fittings must withstand 150% of the maximum pressure reached in that test. Diesel tanks above 94.75 L must accept fuel at 75.8 L/min without spillage. Filled and turned through 150°, a tank may leak no more than one ounce of fuel per minute; side-mounted tanks must also pass a 30-foot corner drop and a 10-foot fill-pipe drop. Tanks are marked with the month and year of manufacture, the manufacturer's name and an FMCSA conformity statement. [1]

Under 49 CFR 393.65, no part of a fuel tank may sit forward of the front axle of a power unit, fuel spilled while filling must not reach the exhaust or electrical systems except the fuel level indicator assembly, and an unenclosed fuel line may not extend more than 2 inches below the tank. Vehicles meeting FMVSS 301 are exempt from these requirements as they apply to the vehicle's fuelling system. [1]

FMVSS 301 (49 CFR 571.301) applies to passenger cars and to trucks, buses and multipurpose vehicles of 4,536 kg GVWR or less, and to heavier school buses. After a frontal barrier crash at up to 48 km/h, a rear moving deformable barrier at 80 km/h with 70% overlap, or a side barrier at 53 km/h, spillage may not exceed 28 g until motion stops and 142 g in the next 5 minutes; static rollover limits apply at each 90° step. Alcohol-fuel vehicles must stop a hose of at least 1200 mm length and 5.2 mm outside diameter from reaching fuel through the filler neck with the tank 90–95% full. [2]

For nonroad spark-ignition equipment, 40 CFR 1060.103 limits fuel tank permeation to 1.5 g/m²/day at 28 °C, or 2.5 g/m²/day if tested at 40 °C; fittings mounted directly to the tank, such as caps, gaskets and O-rings, count as part of the tank, and Large SI tanks are covered by the diurnal standard of 1060.105 instead. [3]

Editorial calculation: applied to the 0.85 m² surface of the 35-liter patent example, 1.5 g/m²/day corresponds to about 1.3 g of fuel per day. [3] [6]

03

Drawings and test reports to ask tank suppliers for

When requesting quotations, ask each supplier for the tank drawing with capacity and port positions, material certificates and gauge or layer structure, leak, pressure, venting and drop test reports, and the regulation each tank is certified to.

04

Shell, baffles, ports, vents and drain

05

Capacity, wall build-up and leak limits in figures

Gallon and gauge figures from the US sources are converted where the page already does so; the leak, fill and permeation rows are regulatory limits, not one tank's test results.

06

Send the vehicle, fuel and rules together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Vehicle or machine: [type; GVWR; mounting position]
Fuel: [diesel; gasoline; alcohol blend]
Capacity: [nominal L; usable L; envelope]
Wall: [steel; aluminium; HDPE layers; thickness]
Fittings: [sender; withdrawal; return; vent; drain; threads]
Rules: [49 CFR 393.67; FMVSS 301; 40 CFR 1060]
Quantity: [units]

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