GB2430229A - Components for assembling both a single and double-walled cha mber - Google Patents

Abstract

A containment chamber assembly, for example for use in a petroleum forecourt installation, comprises inner 32 and outer 31 base portions and inner 34 and outer 33 corbel portions. The inner base portion has a lip extending around its circumference adapted to sealingly engage both a corresponding lip on the other base portion. The lip preferably incorporates an endless groove to accommodate the edge of the inner and/or outer corbel portion(s). A seal may also be provided to connect the assembly to a tank upstand which is, in use, preferably located between the inner and outer base portions. The assembly is preferably fluid tight. According to an important aspect of the invention, only one base and corbel portion may be provided for the assembly of a single-walled chamber. This invention provides the advantage that the same components may be used for either a single- or double-walled chamber.

Description

MODULAR CHAMBER

Field of the Invention

This invention relates to chambers and to methods of constructing chambers. It is particularly applicable, but in no way limited, to fluidtight underground containment chambers as found associated with subterranean fuel tanks or sumps, for example in petroleum forecourt installation.

Background of the Invention

In typical underground storage and distribution systems for hazardous fluids such as hydrocarbon fuels, the fuels are usually stored in a large storage tank or tanks buried in the ground and delivered through underground piping to delivery pumps or the like.

In recent years there has been an increasing awareness that these primary storage and distribution systems of hazardous fluids need to be contained to prevent product from leaking into the environment to prevent environmental problems such as contamination of public drinking water and making some of the food supply unusable as well as other serious environmental consequences. New laws have focused on this problem requiring improved means of storage, distribution and leak detection for all stored fluids which are characterized as hazardous. These systems can present a hazard to the environment because of poor installation practices, corrosion and structural failures producing leaks contaminating the environment.

These laws and regulations have given rise to so-called secondary containment systems which essentially provide a second barrier of protection around the primary fluid supply storage and delivery systems.

Typically, secondary containment systems have included access chambers which are an offshoot from the so-called back fill retainer. There are a variety of chambers now on the market usually comprising a base defining an enlarged chamber, a riser (or corbel) connected to the base of smaller diameter and a cover fitting over the top end of the riser which, in some instances, has access openings enclosed by an access lid which provide a means for inspecting the interior of the sump chambers.

Oil companies have been under considerable pressure to ensure that environmental concerns are given priority in the planning and installation of petrol station infrastructures. Regulations contain specific requirements that underground pumps and piping connections be provided with a means of secondary containment whereby any leaks in these plumbing connections will be contained and detected by means of a leak sensing device.

As a result of these new regulations, large containment containers have been introduced on to the market called containment chambers or sumps.

Containment chambers are typically found at fuel service stations whereby they are installed below the ground level provide a means of access to the underground piping connections, submersible pumps, leak detection sensors, fire extinguisher and other plumbing components usually found connected to the top of underground storage tanks or under fuel dispensing units. There are generally two types of containment chambers which are similar in purpose but different in design. The first type is commonly referred to as a "tank chamber" which is installed and connected to the top of an underground storage tank. The second type is commonly referred to as a "dispenser sump", which is installed under a fuel- dispensing unit.

Containment chambers are multi-purpose in function: 1. They provide a means of surface access to equipment, plumbing and miscellaneous devices, installed underground.

2. They provide a means of ground isolation for contained components to prevent corrosion and decay.

3. They provide a means of secondary containment for those contained components which handle hazardous liquids.

4. They perform as a collection sump for double wall piping entering the sump.

Dispenser sumps are installed under the fuel dispenser to provide a means of secondary containment for the dispenser plumbing and the underground piping connections located directly below the dispenser. These dispenser sumps are available in both shallow and deep versions.

Tank chambers are installed above the underground storage tank and provide a means of secondary containment from the plumbing and piping connections located above the tank. They provide access to the manway, which in turn provides access to the interior of the tank. The tank chambers are of variable length, to allow for different depths of tanks, as they need to have a height sufficient to travel from ground level down to the top of the tank.

Subterranean piping systems, which are typically found at service stations, connect the remote underground storage tank to one or more above ground fuel dispensing units. At each of these connection locations are found access enclosures which provides surface access to these piping connections and other equipment such as a tanks' pump, valves and other plumbing devices.

As explained above, the underground storage and fuel dispensing system has been determined to be a source of environmental pollution, as well as a safety hazard because of product leakage into the surrounding earth. All components of that storage and dispensing system should be designed in such a manner that they prevent any leakage into the environment. Access chambers located at the tank and under the dispensing units provide a means of secondary containment for part of the entire system.

These access chambers should be of such a design that they are liquid tight preventing ground and surface water from entering the chamber, and preventing any leaking product escaping from the chamber into the surrounding environment. They should also be made of a material which is resistant to corrosion and deterioration and of sufficient strength to withstand external pressure from surface loads, backfill pressure, and high ground water pressures. They should also be designed and installed so that they flex or shift in such a manner that they do not damage the top of the tank as a result of tank, ground or surface movement. They should provide a means of effectively sealing all conduit and pipe penetrations into the chamber and provide a means for forming liquid tight and secure connections to the tank and dispensing island.

These chambers have been made from a variety of materials including metal containers made of coated steel, non-corrodible fibreglass or fusible thermoplastic materials. The chambers can house pumps and are often located at the lowest point of a sloped secondary piping system and thus are a focus of the collection of leaked fluids. They are viewed as multipurpose chambers.

Currently, not all countries or bodies which govern the regulations concerning petroleum installations stipulate that these chambers must be double- walled or include secondary containment. Since there is a considerable cost premium to provide secondary containment, at the present time manufacturers have to provide two different designs of chamber. One design has a single wall and the other design has two walls with a sealed interstitial space between the walls. This involves two sets of tooling, two separate production runs and two separate stock lines being held and monitored. This all results in a significant on-cost to the customer.

It is an object of the present invention to overcome or at least mitigate some or all of these problems.

Sum mary of the Invention According to the present invention there is provided a containment chamber assembly said assembly comprising:- (i) an inner base chamber portion; (ii) an inner corbel portion; and optionally (iii) an outer base chamber portion; and (iv) an outer corbel portion; wherein the inner base chamber portion comprises a lip extending around substantially the entire upper circumference of the outer base portion, said lip being adapted to sealingly engage with the underside of a corresponding lip on the inner base portion.

This arrangement provides the advantage that a selection from the same components can be used to construct a single walled chamber or a double walled chamber as required. Currently approximately 80% of chambers sold are single walled, and would require only the inner components.

Preferably the lip in the outer base portion incorporates an endless groove or channel adapted to accommodate the circumferential edge of the outer corbel portion and/or the circumferential edge of the inner corbel portion, or both. This provides for maximum flexibility and allows the outer base portion to be used to construct a single walled chamber.

Preferably the assembly further comprises a first sealing means adapted to seal the assembly to a tank upstand.

Preferably the assembly is adapted such that the tank upstand is located, in use, between the inner and outer base chamber portions. This arrangement simplifies construction and naturally creates a discrete interstitial space.

In an alternative preferred embodiment the inner and outer base chambers comprise a substantially fluid-tight base. This creates a chamber suitable for use as a sump.

In one version the assembly is supplied with only one base chamber portion and one corbel portion, when a single walled chamber is required.

Brief Description of the Drawings

The present invention will now be described by way of example only with reference to the accompanying drawings, wherein: Figure 1 is a partially cut-away side view of part of a petroleum forecourt installation, which includes a tank having a containment chamber, and a pair of dispensing pumps having sump chambers, the chambers in accordance with the invention; Figure 2 illustrated an expanded view of a containment chamber assembly according to the present invention showing inner and outer base chamber portions and inner and outer corbel portions; Figure 3 shows in diagrammatic format and not to scale a cross-section of the base portion once assembled; Figure 4 illustrated and alternative lip arrangement for the outer base chamber portion.

Description of the Preferred Embodiments

The present embodiments represent currently the best ways known to the applicant of putting the invention into practice. But they are not the only ways in which this can be achieved. They are illustrated, and they will now be described, by way of example only. By way of terminology used in this document the following definitions apply:- Containment chamber any receptacle designed to keep a fluid in or out. This includes, but is not limited to, access manhole and sump chambers as described herein. It also includes tanks in general.

Containment chamber system - any part of the underground system, including the containment chamber, that is contained by, or attached to the containment chamber.

This includes the access chamber itself, corbel, frame neck or lid together with the underground tank, collar, manway and associated pipework.

Energy transfer means - a generic term describing any form of energy source.

Typically it takes the form of a resistance winding which heats up when an electrical current is passed through it. The term also encompasses other welding techniques including ultrasonic welding and induction welding.

Flange - any collar suitable for attaching the various sections of the containment chamber. In the examples given the surface of the flanges are substantially planar.

However, it will be understood that the flange must conform to the profile of the section to which it is to be joined. Thus the flange can adopt any suitable conformation to achieve the necessary contact with a flat or curved surface.

Fluid - whilst the examples provided relate mainly to liquids, the term fluid refers to liquids, vapours and gases. For example, should a leak occur in a secondarily contained pipe in a garage forecourt installation then petrol or petrol vapour will collect in the manhole chamber. It is essential that this petrol vapour cannot escape through the wall of the chamber and into the surrounding ground.

Pipe - where pipes are referred to herein they are generally of circular cross- section. However, the term also covers other cross-sections such as box sections, corrugated and the like and secondarily contained pipes of the "pipe-within-a-pipe" type.

Glass reinforced plastic (GRP) - The term GRP has a very broad meaning in this context. It is intended to encompass any fibre-reinforced plastic wherein a fibre of any type is used to strengthen a thermosetting resin or other plastics material.

Fusible material - The term fusible material has a very broad meaning in this context. It is intended to encompass any polymeric material which when energy is applied to it can melt and fuse together with an adjacent material and is intended to cover thermoplastics, thermosets, elastomers and adhesives.

Plastics Material - The term has a very broad meaning in this context and is intended to encompass any polymeric material including thermoplastics, thermosets, elastomeric or any other polymeric material.

The petroleum forecourt installation shown in Figure 1 comprises a pair of dispensing pumps 10 and 11 connected to a subterranean tank 12 through a pipeline 13. The pipeline 13 is formed from contiguously arranged sections of polyethylene pipe. The pipeline 13 extends from the pumps 10 and 11 through the sump chambers 14 and 15 having side walls 16 and bases 17 into a containment chamber 18 having a side wall 19 and a base 1 immediately above the tank 12.

Figure 1 shows two lines extending from the pipeline 13 into the tank 12.

These lines relate to two alternative forms of fuel supply system and are both shown for the sake of completeness. In practice, only one of the lines would extend from the pipeline 13 into the manhole chamber 18. One of those lines is a suction line 2 which is used where the dispensing pumps 10 and 11 are fitted with suction pumps.

The alternative line, reference 3, is a pressure line connected to the pipeline 13 via a pump 4 which is operable to propel fuel from the tank 12 to the pumps 10 and 11.

It can be seen from Figure 1 that the walls 16 and 19 have to be apertured in order to allow the pipeline 13 to pass into the chambers. In order to prevent water leaking from the surrounding ground (here denoted by reference numeral 5) into the chambers 14, 15 and 18 through the aperture, the pipe is sealed to the walls 16 and 19 by means of a fitting. In the event of a spillage or a leak in a supply pipe the seal also prevents fuel from escaping into the environment.

Figure 2 shows a schematic exploded view of a containment chamber assembly 30 according to one embodiment of the invention. The assembly comprises an outer chamber base portion 31, an inner chamber base portion 32, an outer corbel portion 33 and an inner corbel portion 34. Thus far the arrangement is similar to known double skinned or secondary contained chambers. However, in this invention the same components can be used to create either a single skinned or double skinned chamber. Thus, referring to Figures 3 and 4, it will be seen that, during construction, and usually on site, a sealing means 40 is applied and sealed to the tank upstand 43. In this example the sealing means comprises an inner 41 and an outer 42 tank seal, applied to the inner and outer face of the tank upstand 43 to create an endless channel around the top of the tank upstand.

If a single walled chamber is required an inner base chamber portion 45 is inserted into the tank sealing means and embedded in sealant or resin to form a fluid-tight seal. The uppermost-in-use edge of the inner base chamber portion incorporates a lip or flange 48 which extends substantially around the entire upper, outer circumference of the base chamber portion. This lip/flange in turn incorporates an endless groove 49 designed to accommodate, and form a substantially fluid-tight seal with, a corbel portion. So to complete this form of construction, the endless groove 49 is filled with sealant/resin and a corbel portion inserted until a substantially fluid-tight seal has formed between the two components.

However, a major advantage of this invention is that the same components may be used to construct a double walled chamber. In this case, having applied a sealing means 40 to the tank upstand as described above, an outer base chamber portion is first inserted into the tank sealing means. The uppermost-in-use edge of the outer base chamber also incorporates a lip or flange 58. The upper surface of the lip/flange 58 is adapted to be sealed to the underside surface of lip/flange 48 using a sealant or resin. Once a substantially fluid-tight seal has formed between the two, then this part of the construction is complete.

It will be seen from Figure 3 that the inner and outer base chamber portions sit either side of the tank upstand. The interstitial space between the inner and outer base chamber portions may be filed with brine or glycol antifreeze or may be placed under a vacuum. In any event, the status of this interstitial space may be monitored using conventional means.

Figure 4 illustrates an assembly in which the lip of the outer base chamber portion has a slightly different configuration. In this case the lip 158 also incorporates an endless groove 159 adapted to accommodate an inner corbel portion or an outer corbel portion or both. Other components in Figure 4 are numbered using a numbering system corresponding to that used in Figure 3.

It will be appreciated that a number of different types of sealing means can be used around the tank upstand. It could be supplied with an endless groove around its upper edge. Or a flange connector could be used, including a bolted flange-type connector.

It will also be appreciated that different types of sealing and jointing arrangements can be used at the top edge of the base chamber portions. However, an essential part of the invention is that part of the inner base chamber portion is adapted to form a seal with the outer base chamber portion as well as forming a seal with a corbel portion.

Claims (7)

1. A containment chamber assembly said assembly comprising:- (i) an inner base chamber portion; (ii) an inner corbel portion; and optionally (iii) an outer base chamber portion; and (iv) an outer corbel portion; wherein the inner base chamber portion comprises a lip extending around substantially the entire upper circumference of the outer base portion, said lip being adapted to sealingly engage with the underside of a corresponding lip on the inner base portion.

2. A containment chamber assembly as claimed in Claim I wherein the lip in the outer base portion incorporates an endless groove or channel adapted to accommodate the circumferential edge of the outer corbel portion and/or the circumferential edge of the inner corbel portion, or both.

3. A containment chamber assembly as claimed in any preceding claim wherein the assembly further comprises a first sealing means adapted to seal the assembly toatankupstand.

4. A containment chamber assembly as claimed in Claim 4 wherein the assembly is adapted such that the tank upstand is located, in use, between the inner and outer base chamber portions.

5. A containment chamber assembly as claimed in any of Claims I to 3 inclusive wherein the inner and outer base chambers comprise a substantially fluid- tight base.

6. A containment chamber assembly as claimed in any preceding claim wherein the assembly is supplied with only one base chamber portion and one corbel portion.

7. A containment chamber assembly substantially as herein described with reference to and as illustrated in any combination of Figures 2 to 4 inclusive.