Fuel Tank Inspection Procedure

The following procedure is an in-vehicle, visual inspection for natural gas fuel cylinders. A one year/19,310 km (12,000 mile) (whichever occurs first) inspection interval is assumed.

Compressed Gas Association Pamphlet C6.2 can be obtained from:

Compressed Gas Association, Inc.
1725 Jefferson Davis Highway
Arlington, VA 22202-4102

PROCEDURE
1. Raise vehicle on hoist.

2. Examine vehicle underbody and chassis in the general area near the fuel tanks for any indication of collision damage, malfunction, fire or excessive mud/dirt accumulation.

3. Examine fuel tank stone/heat shield for any indication of collision damage, malfunction, fire or excessive mud/dirt accumulation.

4. Remove fuel tank stone/heat shield.

5. Examine fuel tanks and the stone/heat shield interior for any foreign objects (such as stones, gravel) or foreign materials (such as mud, salt, liquids, 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 fuel tank labels for tank expiration date. Use a light and mirror to access labels hidden from normal view. If expiration date has been exceeded, condemn the tank using the procedure in Step 12.

8. Inspect tank sidewall and dome ends following the general guidelines in Compressed Gas Association Pamphlet C6.2. Inspect for the following:
- abrasion
- dents
- cracking, blistering, peeling of clear coating
- corrosion
- cracks or gouges in metal dome
- cracks in fiberglass overwrap
- impact damage (crazing) in fiberglass overwrap
- cuts or gouges in fiberglass overwrap
- exposed fibers
- delamination (separating) of fiberglass overwrap
- discoloration of fiberglass overwrap
- fire or heat damage such as charring or discoloration

If any flaws are found, the depth and length should be measured in accordance with the CGA Pamphlet C6.2 guidelines. If any flaws cannot be measured completely in vehicle position, the tank assembly(s) should be removed from the vehicle.

Additionally, if the tanks have been or are suspected to have been exposed to a corrosive chemical spill, the tank assembly(s) should be removed from the vehicle to allow full examination 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 should be condemned and replaced with new tanks. Tanks on the Natural Gas Crown Victoria are of an NGV2-2 design and do not have to be hydrostatically tested during their 15-year service life.

9. Composite Wrap Inspection Criteria:
The acceptance criteria for cuts and abrasions are different from those listed in Section 6.5.1 of C-6.2. The tanks have extra epoxy resin and a clear coat to reduce the sensitivity to surface damage.

a. Level 1 Abrasions: These abrasions are defined as minor abrasions such as scuffs less than 0.254 mm (0.010 in) deep and are acceptable without repair.

b. Level 2 Abrasions: These abrasions have some exposed fibers or flat spots with a depth between 0.254 mm (0.010 in) and 0.762 mm (0.030 in). Level 2 abrasions must be repaired before the tank is returned to service.

c. Level 1 Cuts: These are cuts or scratches less than 0.254 mm (0.010 in) deep and are acceptable without repair regardless of length, number or direction.

d. Level 2 Cuts: These cuts have a maximum depth up to 0.762 mm (0.030 in) and a maximum length up to 203 mm (8 in). Level 2 cuts must be repaired before the tank is returned to service.

10. Repair of Damage to Composite Wrap:
Level 2 cuts and abrasions should be coated with epoxy resin. A commercial room temperature cure two-component epoxy resin should be mixed and applied according to the manufacturer's instructions. Frayed fibers should be cut away before application of the epoxy resin.

Tanks with damage exceeding Level 2 must be condemned in accordance with Step 12.

The criteria for other damage to the composite are defined in CGA C-6.2.

11. Metal Tank End External Inspection Criteria:
The metal tank ends are protected with a multi-coat system using epoxy and polyurethane coatings. Chips in the coating should be evaluated and repaired as follows:

a. Level 1 Chips: These are chips or abrasions which do not penetrate the black epoxy coating. The steel or gray primer have not been exposed. Level 1 chips require no repair.

b. Level 2 Chips: Chips or abrasions which penetrate the black epoxy coating must be repaired as follows to prevent corrosion:
(1) Sand the damaged area to remove rust and rough up the surrounding coating.
(2) Clean the damaged area with a commercial pre-paint cleaning solvent.
(3) Apply a Zinc-rich cold galvanizing compound (Rust-Oleum(r) Zinc-Rich or equivalent commercial product).

c. Dents: Tanks with dents to the metal ends which exceed 1.524 mm (0.060 in) in depth must be removed from service and condemned.

d. Gouges: Tanks with sharp gouges penetrating the coating and into the metal liner must be condemned.

12. Condemned Tanks:
Condemned tanks, whether due to damage or expiration, shall be removed from the vehicle and destroyed as follows.

a. Drain and remove the tanks.

b. Verify that the tank is empty, disassemble from the strap assembly and remove the tank valve as described.

c. Purge the tank with compressed air for 30 seconds.

d. Destroy the tank by drilling a 12.7 mm (0.50 in) diameter hole in the sidewall.

13. Fuel Tank Straps:
Examine fuel tank straps for proper position of rubber isolators. Replace isolators as necessary.

14. Reinstallation:
Reinstall fuel tank stone/heat shield and tighten fasteners to 9-12 Nm (89-106 lb in). Lower vehicle.

15. Luggage Compartment Mounted Tank Inspection:
Open luggage compartment door and examine fuel tank sight shield for any evidence of damage due to shifting luggage compartment loads, collision, etc.

a. Remove fuel tank sight shield.

b. Examine floorpan and package tray areas for any evidence of improper accessory mounting or hardware that might have damaged the fuel tank.

c. Examine vent box for any signs of damage that might indicate potential damage to the fuel tanks.

d. Examine fuel tanks as described in Steps 8 and 11, using a light and mirror.

e. Reinstall fuel tank sight shield.

16. Inspection Record:
Record date, vehicle mileage and results of fuel tank inspection.