Underground Tank

This invention relates generally to underground storage tanks, and more particularly to tanks for storing liquids such as gasoline.

Prior glass fiber reinforced synthetic resin underground tanks for storing gasoline were made of thermosetting resins such as isophthalic polyester, which resists corrosion by gasoline. However, such resins are subject to chemical decomposition by hydrolysis when water is present on the outside of the tank.

In accordance with the invention, a tank is provided having a liner comprising a thermoset resin resistant to corrosion by gasoline or alcohol, such as polyester or vinylester, and a structural wall comprising a thermoset or thermoplastic non-hydrolyzable resin such as cross-linked polystyrene, polyethylene, polypropylene, or rigid polyvinyl chloride.

The invention will be more readily understood by reference to the accompanying drawings wherein:

FIG. 1 is a view of an underground tank constructed in accordance with the invention;

FIG. 2 is an enlarged fragmentary isometric sectional view illustrating the construction of the wall of the tank of FIG. 1 and;

FIG. 3 is a view similar to FIG. 2, but showing an alternate construction.

With reference to the drawings, FIG. 1 shows a glass fiber reinforced plastic tank 10 constructed in accordance with the invention. Preferably the tank is provided with axially spaced annular reinforcing ribs (not shown) such as illustrated on the tank of U.S. Pat. No. 3,700,512. The tank is made in two halves secured together by internal and external lay-ups of resin and glass mat, such as shown in FIG. 16 of U.S. Pat. No. 3,655,468.

As shown in FIG. 2, a composite wall section 12 of the tank 10 comprises a liner or inner wall 14 and a structural outer wall portion 16. In accordance with the invention, the liner 14 comprises a resin resistant to corrosion by gasoline or alcohol, such as an unsaturated polyester or a vinyl ester, and the structural wall 16 cmprises a non-hydrolyzable resin, such as rigid polyvinyl chloride, polyethylene, polypropylene, or cross-linked polystyrene with up to 50 percent of a cross-linking agent such as divinyl benzene, trivinyl benzene, or nitrogen dioxide. A thin non-woven glass fiber surfacing mat 18 is provided in the liner 14, and optionally also in the structural wall 16. Inside the surfacing mat 18 of the liner, and also of the structural wall if it is provided with one, the resins are reinforced with chopped glass strands 20 and may contain fillers such as sand, talc, limestone dust, flyash, clay, or milled glass fibers.

Each half of the tank 10 may be formed on a collapsible mandrel, such as disclosed in U.S. Pat. No. 4,233,020, preferably having an integral end cap mold as disclosed in U.S. Pat. No. 4,225,302.

FIG. 3 shows an alternate construction wherein a wall secton 22 of the tank 10 comprises a steel tank portion 24 having a coating or outer wall thickness of a non-hydrolyzable resin 26 containing chopped glass strand 30 and suitable filler.

Various modifications may be made in the structure shown and described without departing from the spirit and scope of the invention.