Fuel Tank Inspection
FUEL TANK INSPECTION1. NOTE:
- The following procedure is an in-vehicle, visual inspection for natural gas fuel cylinders. A 1-year/19,310-km (12,000-mile) (whichever occurs first) inspection interval is assumed.
- The Compressed Natural Gas Pamphlet C6.2 can be obtained from the Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202-4102.
Raise and support the vehicle.
2. Examine the vehicle underbody and chassis in the general area near the fuel tank(s) for any indication of collision damage, malfunction, fire or excessive mud/dirt accumulation.
3. Examine the fuel tank stone/heat shield for any indication of collision damage, malfunction, fire or excessive mud/dirt accumulation.
4. Remove the fuel tank stone/heat shield.
5. Examine the fuel tank(s) and the stone/heat shield interior for any foreign objects (such as stones or gravel) or foreign materials (such as mud, salt, liquids or chemical residue).
6. Remove any foreign material, using only a clean, dry cloth. Remove all foreign objects. Do not use water or any cleaners.
7. Examine the fuel tank labels for the tank expiration date. Use a light and mirror to access labels hidden from normal view. If the expiration date has been exceeded, condemn the tank, using the procedure in Step 14.
8. Inspect the tank sidewall and dome ends, following the general guidelines set forth in the Compressed Gas Association Pamphlet C6.2. Inspect the tank(s) for the following:
- abrasions
- dents
- cracking, blistering or peeling of clear coating
- corrosion
- cracks or gouges in the metal dome
- cracks in the fiberglass overwrap
- impact damage (crazing) in the fiberglass overwrap
- cuts or gouges in the fiberglass overwrap
- exposed fibers
- delamination (separating) of the fiberglass overwrap
- discoloration of the fiberglass overwrap
- fire or heat damage, such as charring or discoloration
9. If any flaws are detected, measure the depth and length of the flaw in accordance with the Compressed Gas Association Pamphlet C6.2 guidelines. If any of the flaws cannot be completely measured in the vehicle, the tank must be removed from the vehicle for further inspection.
10. If the tanks have been or are suspected of having been exposed to a corrosive chemical spill, the tank must be removed from the vehicle for further inspection of the complete composite surface, including the area under the tank straps. If there is any indication of chemical attack, such as blistering, cracking or delamination, the tanks must be condemned and replaced with new tanks. Tanks on the Natural Gas Econoline are of an NGV2-2 design and do not have to be hydrostatically tested during their 15-year service life.
11. The acceptance criteria for cuts and abrasions are different from those listed in Section 6.5.1 of the Compressed Gas Association Pamphlet C6.2. These tanks have extra epoxy resin and a clear coat to reduce the sensitivity to surface damage. The following are the composite wrap inspection criteria:
- Level 1 Abrasions: These are defined as minor abrasions, such as scuffs less than 0.254 mm (0.010 inch) deep, and are acceptable without repair.
- Level 2 Abrasions: These are defined as abrasions having some exposed fibers or flat spots with a depth between 0.254 mm (0.010 inch) and 0.762 mm (0.030 inch). Level 2 abrasions must be repaired before the tank is returned to service.
- Level 1 Cuts: These are defined as cuts or scratches less than 0.254 mm (0.010 inch) deep and are acceptable without repair regardless of length, number or direction.
- Level 2 Cuts: These cuts have a maximum depth up to 0.762 mm (0.030 inch) and a maximum length up to 203 mm (8 inches). Level 2 cuts must be repaired before the tank is returned to service.
12. Repair of the damage to composite wrap is as follows:
- Level 2 cuts and abrasions are to be coated with epoxy resin. Mix and apply commercial room temperature cure, two-component epoxy resin according to the manufacturer's instructions. Frayed fibers must be cut away before application of the epoxy resin.
- Tanks with damage exceeding Level 2 must be condemned in accordance with Step 14.
- The criteria for other damage to the composite wrap are defined in the Compressed Gas Association Pamphlet C6.2.
13. The metal tank ends are protected with a multi-coat system using epoxy and polyurethane coatings. Chips in the coating must be evaluated and repaired. The metal tank end external inspection criteria are as follows:
- Level 1 Chips: These are chips or abrasions which do not penetrate the black epoxy coating. The steel or gray primer has not been exposed. Level 1 chips require no repair.
- Level 2 Chips: These are chips or abrasions which penetrate the black epoxy coating and must be repaired as follows to prevent corrosion:
- Sand the damaged area to remove rust and rough up the surrounding coating.
- Clean the damaged area with a commercial pre-paint cleaning solvent.
- Apply a zinc-rich, cold galvanizing compound (Rust-Oleum(TM) Zinc-Rich or equivalent commercial product).
- Dents: Tanks with dents to the metal ends which exceed 1.524 mm (0.060 inch) in depth must be removed from service and condemned.
- Gouges: Tanks with sharp gouges penetrating the coating and into the metal liner must be removed from service and condemned.
14. Condemned tanks, whether due to damage or expiration, shall be removed from the vehicle and destroyed as follows:
1 Vent and remove the fuel tanks.
2 Remove the fuel tank solenoid valve.
3 Purge the fuel tank with compressed air for 30 seconds.
4 Destroy the fuel tank by drilling a 12.7-mm (0.50-inch) diameter hole in the fuel tank sidewall.
15. Fuel Tank Straps: Examine the fuel tank straps for proper positioning of the rubber isolators. Replace the rubber isolators as necessary.
16. Inspection Record: Record the date, vehicle mileage and the results of the fuel tank inspection.