The present invention relates to secondary containment systems and especially, although not exclusively to a piping construction and a method for providing secondary containment systems for hydrocarbon storage and delivery systems.

BACKGROUND OF THE INVENTION A secondary containment system is one which functions to collect and contain the fluids leaking out of another and primary containment system. For example, a primary containment system may store and delivery gasoline at a filling station. A secondary containment system would collect and contain the same gasoline if a primary delivery pipe should rupture or otherwise spill the gasoline. Secondary containment systems have been developed to overcome the environmental problems that have been encountered with respect to leakage of hazardous fluids from tanks and pipe lines. As indicated, this has been a particular problem with respect to underground installations in which undetected leakage of hazardous fluids into the surrounding terrain over long periods of time has produced harmful conditions and extensive pollution which are difficult and expensive to clean.

Today there is great public concern because chemicals are penetrating into underground water supplies contaminating public drinking water and making some of the food supply unusable, amongst other things. The entire environment is being degraded to a serious level which tends to cast doubt on the future availability of safe water. Therefore, many government agencies have enacted and continue to enact laws which require a secondary containment system designed to capture and contain the spilled gasoline or other liquid materials thus preventing it from leaking into the surrounding

earth. The capture gasoline or other liquid material may then be pumped out of the secondary container for proper disposal. This eliminates the possibility of gasoline spillage to contaminate underground water supply. Manufacturers of containment systems have responded by developing and producing a variety of secondary containment systems for conventional underground piping which are designed to contain and prevent any leakage from escaping into the environment. Many of these systems have proven to be effective containment systems but have found to be difficult and costly to install.

One known approach to secondary containment systems, and, in particular, the secondary containment of underground conventional piping has been to line the piping trench with an impervious flexible membrane liner or semi-rigid trough. This technique can provide a measure of secondary containment of leaky product but such an approach does not allow for effective leaking detection in that it does not permit the determination of which pipe is leaking and the location of the leak in the piping line when the same occurs. It is also difficult to test such systems using air pressure testing devices. Additionally, said secondary containment systems do not provide 360° containment and therefore can fill with water and become ineffective.

Another approach toward solving the problem of underground leakage in such conventional piping systems has been to install a large semi-conventional piping system over the conventional underground piping as a means for providing the secondary containment. With such an arrangement, the outer secondary containment rigid pipe is installed simultaneously with the product piping. The outer secondary containment pipe by necessity has a larger diameter than the supply pipe to enable secondary containment pipe to slide over the smaller pipe. The secondary containment pipe fittings are of a clam shell

design adapted to fit over the supply pipe fitting and connect to the secondary containment pipe. The clam shell fitting is sealed to itself and the secondary container pipe by a variety of sealing techniques. Depending on the type of secondary containment system used, these sealing techniques could include metal or plastic fasteners used with a combination of adhesives, sealants and the like. Such secondary systems are generally expensive to install because of the cost of the components which are used and the time required to assemble both the product and the secondary containment piping systems.

Another known approach to solving the aforementioned problems is to employ a semi-conventional piping system over the conventional product piping. This type of containment system differs from the first described systems in that it is not an entirely rigid straight pipe but rather a combination of rigid straight pipe with a larger diameter convoluted plastic pipe over it which produces a telescoping effect. The convoluted section of telescopic containment pipe serves as a fitting of containment of the product, 90° and 45° fittings as well as unions, flexible connectors, swing joints, should they be so attached. The convoluted pipe is designed to be flexible and sized to be shifted around any angles in the production piping system.

Another type of secondary containment piping system has been developed which utilizes spaced access chambers interconnected by a secondary containment pipe to provide a sealed housing for a flexible fluid supply pipe, the ends of which are disposed within the access chambers and have a connector element at each end forming a section adapted to be interconnected to other fluid conduits. The diameter and bending radius of the fluid supply pipe and the size of the access chamber are such as to permit the fluid pipe, after uncoupling, to readily be removed from the secondary containment pipe through

one of the access chambers. Should a leak occur in the piping, the secondary containment system allows the piping to be removed and replaced.

It is very difficult and expensive to meet all of the many different environmental and safety standards at a reasonably acceptable cost particularly in light of the many state and local governments writing individual laws that impose a wide variety of standards which the manufacturers of such systems must meet. Accordingly, an object of the invention is to provide a new and improved secondary containment system which will draw all spilled fluids that may leak from a primary supply pipe to a preselected collecting point which may be monitored. Another object of the present invention is to provide a practical secondary containment system which may be manufactured in a factory, shipped and installed at a reasonably low cost in a fully usable manner and yet one which meets all requirements of the environment within which they must be used.

It is a further object of the present invention to provide an economical, easily installed, highly durable and environmentally secure flexible piping systems. Other objects, advantages and applications of the present invention will become apparent to those skilled in the art of underground piping systems when one example of the best mode of the present invention is read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

The specification herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views and wherein: Fig. 1 is a schematic layout of an exemplary gasoline storage and delivery system;

Fig. 2 is an enlarged side view of a portion of the fuel dispensing system of Fig. 1 as seen generally along line 2-2 thereof;

Fig. 3 is an enlarged view of a portion of the system illustrated in Fig. 2;

Fig. 4 is an enlarged perspective view of the inner and outer pipes utilized in the secondary containment piping system of the present invention with layers of the inner pipe removed for illustrative purposes;

Fig. 4A is a fragmentary perspective view of the outer secondary containment pipe illustrated in Fig. 4;

Fig. 5 is a cross sectional view taken generally along line 5-5 prior to the backfilling of the trench within which the pipes are located; and

Fig. 6 is a view similar to Fig. 5 illustrating, in a slightly exaggerated manner, the secondary containment piping system after backfilling. DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and, in particular, to Figs. 1 and 2, wherein there is illustrated an underground fuel storage and dispensing system generally indicated at 10 comprising fuel tanks 12 from which a plurality of underground fuel supply pipes

14 extend for distribution of fuel to dispersion areas 16 in a conventional manner. The system includes one or more access chambers 20 which are also disposed below the surface dispensing station 16. The access chambers 20 and the fuel tanks 12 are interconnected by containment pipe segments 22 while the access chambers are connected via pipe segments 24 to a conventional drip pan 26 beneath the dispenser 16 and is connected thereto through suitable elbow connectors 28. The access chamber 20 and the pan 26 are interconnected in a fluid sealing manner through their side walls just above the bases thereof by means of the secondary containment pipe 24.

As can best be seen in Fig. 3, the side wall 30 of the access chamber 20 has an opening 32 through which the end of the pipe 24 extends. A conventional seal 34 surrounds the outer surface of the containment pipe 24 and provides a fluid tight seal for the interior of the access chamber 20.

As will be described in greater detail hereinafter, the secondary containment piping system comprises a flexible inner supply pipe 40 which is completely encased within a flexible outer containment pipe 42. It should be noted by reference to Fig. 3, that the outer containment pipe 42 extends into the access chamber 20 a sufficient distance so that it clears the interior of the wall 30 of the access chamber 20. During fabrication this will permit the insertion on the terminated end 39 of pipe 42 of a suitable air pressure device to permit testing as will be explained hereinafter. The inner pipe 40 extends past the terminated end 39 of the outer pipe 42 a sufficient distance to permit it to be coupled by suitable conventional couplings 44 to another inner pipe 40 which, in turn extends outwardly from the access chamber 20 through an outer containment pipe 42. At the drip pan 26, the pipe 40 exist therethrough and continues through a containment pipe 42 on to the next island.

The access chamber 22 has a removable cover 70 to permit easy access thereto for removal of any fuel that might be captured by the containment pipe 40. A fluid sensor 72 is disposed in the bottom of the access chamber 22 and is electrically connected to an appropriate indicator or alarm 74. When there is an accumulation of fluid, such as due to leakage from the primary pipe 40, the fluid will actuate the alarm.

As can best be seen in Figs. 4 and 5, the inner pipe 40 is made from a fuel impervious material and is comprises of three layers of material which are extruded together and comprise an interior layer 50, which is

fabricated from a nylon 12 material; a intermediate layer 52 consisting of a nylon 6 yarn reinforcement wrap; and an exterior outer material 54 which is preferably fabricated from a polyethylene material. The inner layer 5 50 is .080" thick and the outer layer is preferably 060" thick. In the preferred embodiment, the pipe 40 has an inside diameter of 1.68" and an outside diameter of 1.960", a maximum operating pressure of 150 psi and a minimum burst pressure of 750 psi. The material is 0 flexible and has a bend radius of 12" to 24".

The inner pipe 40 is completely encased in the outer containment pipe 42 which, as can best be seen in Figs. 4, 4A and 5, comprises integrally extruded member a having a wall 60, the interior of which is provided with 5 a plurality of angularly spaced, radially inwardly extending ribs or projections 64 that define therein between U-shaped cross sections 60. The projection extends along the full length of the interior of the wall 60 (Fig. 4A) . The outer pipe 42 is sized to permit the 0 inner pipe 40 to be inserted therein with little or no resistance and is, preferably, assembled in the combined arrangement at the factory, ready for positioning in the pipe trenches when delivered onsite. The outer pipe 42 is very flexible and can bend as needed to accommodate 5 the bending of the primary inner pipe 40. The outer pipe 42 is made from a fuel impervious material such as a nylon or polyethylene, clear acrylonitrile or clear polyurethane material.

In practice, trenches are laid out and the 0 various lengths of piping are laid in the trenches and connected to the various underground access chambers 20 and drip pans 26 via the sealing members 34. Once connected, a portion of the outer pipe 42 is cut and removed so that a sufficient amount of the inner pipe 40

35 extends past the termination end 39 of the outer pipe 42 to permit the inner pipe 40 to be attached to a suitable coupling 44.

Before a coupling 44 is attached to the inner pipe 40, an appropriate seal may be placed over the outside of the inner pipe 40 to sealingly engage the outer pipe 42 whereby pressurized air may be communicated to the annular space (Fig. 5) formed between the inner and outer pipes 40 and 42 to test the same to be sure that there are no leakage points in the containment system. Obviously, the opposite ends of the pipe 42 of each of the access chambers 22 and drip pans 26 must be sealed in order to effectively perform such a test. Likewise, the inner pipes 40 can be subjected to air pressure to test their integrity. Once the installer is satisfied that the containment piping system is able to perform its function without concern for leakage, the trenches within which the containment pipes 14 have been laid are backfilled.

The weight of the earth on the flexible outer pipe 42 deforms the pipe 42 in the manner similar to that illustrated in Fig. 6 of the drawings, until the outer ends of the projections 64 abut the outer wall of the inner pipe 40. The abutment of the projections 64 with the wall 40 provides a two-fold purpose. First, it snugly and lockingly engages the pipe 40 and prevents relative movement between the inner and outer pipes providing for a more secure system, and secondly, the space between U-shaped cross sectional areas and the space between the inner and outer walls always insures a flow path for any fuel that may leak into the annular space between the inner and outer pipes. The view illustrated in Fig. 6 is exemplatory of the condition that may exist. However, it should be noted that the outer tube 42 may be deformed in a variety of different shapes. Suffice it to say, that a continuous flow path will exist in the event there is a leakage from the primary inner pipe 40. While it is preferred that the primary pipe 40 and secondary containment pipe 42 be assembled at a factory location there may be situations

in which the pipes are assembled on site before burial. The pipe 40 may be removed and either pipe may be replaced if a leak is found during testing. Once buried, the weight of the fill collapses appropriate portions of the outer containment pipe 42 around the primary pipe 40 and the primary pipe 40 may no longer be removed after burial.

While this invention has been described has having a preferred design, it should be understood by those skilled in the art of the forms of the invention may be had all coming within the spirit of the invention and the scope of the appended claims. What is claimed is as follows.