US20080310920A1

US20080310920A1 - Secondary containment for liquid

Info

Publication number: US20080310920A1
Application number: US11/762,261
Authority: US
Inventors: Bruce Allen; Leonard Konechny; Garry Konechny
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-06-13
Filing date: 2007-06-13
Publication date: 2008-12-18

Abstract

In secondary containment of a liquid in a tank which has pipes or posts extending into the ground, a liner covering the ground within a containment wall has a hole surrounding each pipe. Each hole is sealed by a boot which surrounds the pipe and connects from the pipe to the liner and includes a sleeve portion clamped to the pipe and a flange surrounding the sleeve portion at one end which is welded to the liner. A frusto-conical or accordion shape expandable portion is provided allowing longitudinal movement of the flange relative to an upper part of the sleeve of the boot such that the expandable portion allows the liner lies to move downwardly relative to the pipe. The expandable portion is of larger diameter than at the upper part of the sleeve so as to allow the flange to move horizontally with the liner relative to the member.

Description

This invention relates to a secondary containment system for liquid storage and transfer systems which include generally tanks and the like which includes a containment wall surrounding the system and a liner covering the ground surrounding the system up to the containment wall so that any escaping liquid from the system is contained to prevent ground contamination.

BACKGROUND OF THE INVENTION

Examples of secondary containments systems of this general type are shown in U.S. Pat. Nos. 5,800,091 (Van Romer) issued Sep. 1, 1998, 5,882,142 (Siglin) issued Mar. 16, 1999 and 4,765,775 (Kroger) issued Aug. 23, 1988. In each of these a containment wall is suitably supported and receives a liner which extends across the ground to an outer edge which is sealed to the wall at a height part way or wholly up the wall so that the liquid escaping from the tank either gradually or catastrophically is contained.
In Siglin and Kroger, it appears that the tank is merely located resting upon a fill material inside the wall and on top of the liner. In Van Romer the tank appears to be standing on legs with base plates resting on the liner.
In practice this support of the tank is not suitable and commonly the tank is supported on pilings extending into the ground in the area inside the containment wall. Also there may be pipes from the tank which extend into the ground at the area within the containment wall. Thus the liner must be perforated at these locations so that the element concerned passes through the liner.
Pipe boots in the form of a cylindrical sleeve with a disk attached at one end are commonly used to form a seal between the pipe pilings, or other penetrating member, and the secondary containment liners that are used to contain spills. One end of the boot is clamped to the pipe by a surrounding clamp and the other is welded to the liner.
Material used in the pipe boots is similar to the liner material and exhibits the same properties. The most important feature is compatibility with the contained product, and the ability to be sealed to the liner and the penetrating member such as the piling. The manufacturing process must be capable of maintaining a minimum thickness, as this is often specified by governing bodies. As a result of this requirement, specialized manufacturing procedures must be utilized.

SUMMARY OF THE INVENTION

It is one object of the invention to provide a pipe boot of an improved construction.
According to one aspect of the invention there is provided a method for secondary containment of a liquid in a liquid container, where the liquid container is surrounded by a containment wall and where the liquid container has connected thereto at least one member which extends from the liquid container downwardly into the ground within the containment wall the method comprising:
providing a liner covering the ground within the containment wall and extending from the containment wall at least partly under the liquid container;
forming in the liner a hole surrounding the member;
providing a boot which surrounds the member and connects from the member to the material of the liner surrounding the hole;
providing on the boot a sleeve portion and a flange surrounding the sleeve portion at one end;
clamping the sleeve portion of the boot to the member;
sealing the flange of the boot to the liner at the hole;
and providing in the boot an expandable portion allowing longitudinal movement downward of the flange relative to an upper part of the sleeve of the boot such that the expandable portion allows the ground on which the liner lies to move downwardly relative to the member after attachment of the liner to the boot and the upper part of the sleeve of the boot to the member.
The method described above is primarily for use where the liquid container is a tank. However the method may also be used for process pipe penetrations (i.e. something other than pilings) that come up through the floor of the cell, or through the side wall. Thus there may not be a tank present.
Also, while the containment wall will generally be a steel wall which are the high use application, this may also be used with other forms of secondary containment such as dirt berms which are also lined and subject to the same conditions.
Preferably the boot has a portion at the flange which is of larger transverse dimension than at the upper part of the sleeve so as to allow the flange to move horizontally with the liner relative to the member.
Preferably the boot is connected to the flange at the bottom part of the expansion portion.
Preferably the expansion portion is frusto-conical from a lower end of the upper part of the sleeve to the flange.
Preferably the expansion portion can un-fold from a position in which the lower end of the upper part of the sleeve lies in a plane of the flange to a position in which the lower end is raised.
Preferably the expansion portion is frusto-conical with a cone angle in the range 45 to 60 degrees.
Preferably the sleeve above the expansion portion is frusto-conical at an angle less than that of the expansion portion.
Preferably the expansion portion includes an accordion wall between the lower end of the sleeve portion and the flange.
Preferably the sleeve portion is attached to the member by a surrounding clamp and is sealed to the member by a sealing grout.
The present inventors have found that the currently available pipe boots provide no provision for vertical expansion or collapsing. As a result, as the ground can settle after installation the boots will tear away from the pipe, resulting in loss of containment. This requires repair or replacement. As the space underneath the tank is often very restricted, this can prove difficult, or even impossible without costly remedial actions.
Also, the liner itself is subject to expansion and contraction due to temperature differentials. This results in lateral deflections. The existing pipe boots provide little protection against lateral movement, and tearing can result which again results in failure of the containment.
Thus in the present arrangement, in addition to the clamping area and the flange, which are incorporated into the existing pipe boot, there is also an expansion component incorporated between the two to allow for vertical and lateral expansion and contraction.
As with the current pipe boots, there are a variety of sizes to match a variety of pipe diameters.
The collapsible pipe boots are manufactured, and shipped, in the expanded configuration (as this lends itself to traditional manufacturing methods and shipping efficiencies).
Before installation the pipe boots are configured to their collapsed position by pushing down from the top.
In the collapsed position, sufficient clamping area remains exposed above the collapsed area to facilitate ease of banding and caulking (which remain consistent with current methods)
The interaction of the flange to the liner remains consistent with current processes in that the liner is welded to the boot flange.
Once installed, the boot is free to expand vertically as required for height differential caused by ground settlement, or other.
In addition, the boot provides for a certain amount of lateral flexibility as well to compensate for expansion and contraction of the liner material.
While a frusto-conical expansion section which simply folds at a position part way along its length is preferred as being simple to manufacture and ship, alternative different means of providing expansion and contraction are possible, such as a bellows arrangement, an accordion arrangement, etc. The concept herein is the vertical expansion.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:

FIG. 1 is a vertical cross sectional view through a secondary containment system and method showing a pipe boot according to the present invention.

FIG. 2 is a cross sectional view on an enlarged scale of the pipe boot of FIG. 1.

FIG. 3 is a cross sectional view on an enlarged scale of an alternative form of the pipe boot to be used in the method of FIG. 1.

In the drawings like characters of reference indicate corresponding parts in the different figures.

DETAILED DESCRIPTION

FIG. 1 shows schematically a secondary containment system for liquid escaping from a tank 10. The containment system comprises a containment wall 11 supported on a base plate 12 and maintained upright by a brace 13, A liner 14 extends across the ground underneath the tank and is fastened to the wall so that an edge of the liner runs up the inside surface of the wall and attached to the wall at a suitable height relative thereto.
The construction of the wall and liner is shown only schematically since these can vary in arrangement and location in accordance with many designs available to a person skilled in the art.
In the arrangement shown the tank 10 is mounted on a piling or post 15 which engages into the ground 16 beneath the liner 14. The post thus extends from below the ground to the tank at a position above the ground so that the liner must be perforated to surround the post.
The liner is commonly fabricated from sheets so that an opening can be formed by cutting and by welding or sealing the edges together to form the required dimensions and shape of the liner. Preferably, the liner may be applied while the piles are exposed from the ground and before the tank is attached so that a simple hole can be cut in the liner and placed over the pile.
The hole is cut of course slightly larger than the pile so as to fit readily over the pile or around the pile.
In order to seal the liner to the pile 15, there is provided a pipe boot generally indicated at 20. The pipe boot 20 comprises a sleeve portion 21 and a flange 22. The sleeve portion 21 is attached to the outside surface of the pile 15 and the flange 22 is welded to the edge 14A of the hole in the liner 14. The sleeve portion is attached to the pile by a ring or bead of grout 32 located between the top of the sleeve portion and the pile. Around the sleeve portion is attached a clamping band 23 of conventional nature which is tightened to fasten around the sleeve portion and to squeeze it down onto the ring of grout to provide a sealing action.
The pipe boot further includes an expansion portion 25 of the pipe boot located between the sleeve portion 21 and the flange 22. The construction of the pipe boot is shown in more detail in FIG. 2. The sleeve portion 21 extends from an upper end 26 to a lower end 27. The sleeve portion is slightly conical so that the upper end 26 closely surrounds the outside surface of the piling while the lower end 27 is spaced further away from the piling. The purpose of the conical sleeve is to cover a range of pipe diameters, and wall thicknesses, which might result in a variability in pipe ODs where the sleeve can be cut to the appropriate diameter.
Between the flange 22 and the lower end 27 of the sleeve portion is provided the expansion portion 25. In the arrangement shown this comprises a simple frusto-conical section extending downwardly and outwardly from the lower end 27 of the sleeve portion to the inner edge 22A of the flange. This conical section has a cone angle lying in the range 45° to 60° which allows it to fold into the construction shown in doffed line indicated at 25A so that the lower end 27 is moved to the point indicated at 27A and is provided a fold indicated at 28. Thus the sleeve portion 21 is moved into a retracted or collapsed position by folding around two annular fold lines indicated at 28 and 28 A. The material may be weakened at these locations to provide an effective folding action at those locations. However this is not necessary. The material may be arranged so that the collapsed position defines a stable position of the structure in which it holds its position until pulled out of that position in the expansion direction.
In the collapsed position the upper end 26 of the sleeve portion is located above the height of the fold line 28 so that sufficient of the sleeve portion is available to receive the band 23 and the layer of caulking 32. The movement of the pipe boot between the expanded and collapsed conditions is of the order of 6 to 10 inches and can be greater in specific arrangements. In the collapsed position the expansion portion defines a stable position of the structure in which it holds its position until pulled out of that position in the expansion direction. In the collapsed position a component of the expansion portion, that is the bottom fold line 28A is in a common plane with the flange to locate the collapsed position when the flange is located on the ground for attachment to the liner.
The pipe boot is transported in the expanded position but when attached to the pile is moved to the collapsed position by pushing down on the upper edge 26. This causes the folding action that pushes the upper edge 26 to the lowered position where it is attached to the piling. The flange 22 is then welded using conventional techniques or is sealed using an adhesive or heat sealing to the edge of the liner.
In use, after a period of time, the ground surface surrounding the pile can often collapse or subside by distance as much as 6 to 10 inches and using the pipe boot described above, this downward movement which carries also the liner in a downward direction is accommodated by pulling on the expansion portion which then allows the construction to unfold to the expanded position shown in full line in FIG. 2.
It will also be noted that the expansion portion 25 is frusto-conical so that where it meets the flange 22A is at a significantly greater diameter than the lower end 27 of the sleeve portion. In the event therefore that there is expansion or contraction of the liner in a sideways direction tending to pull the flange in one direction or the other away from the piling, the conical shape and the larger diameter of the flange allows the flange to be pulled away from the piling by the liner movement without acting to tear the pipe boot or to tear the pipe boot away from the liner.
In FIG. 3 is shown an alternative arrangement which has a sleeve portion 21 similar to that previously described but includes as an expansion portion between sleeve portion and the flange 22 as an accordion shape generally indicated at 35. The accordion shape allows simple compression of the sleeve portion downwardly by compressing the accordion folds and allows the arrangement to be pulled upwardly in the event that expansion is required.
This arrangement is less satisfactory in view of the greater difficulty of manufacture and the greater difficulty of placing the pipe boots in stacked position for transportation. It will be noted that the arrangement of FIG. 1 and FIG. 2 allows the pipe boot to simply be stacked one on the next in the expanded condition.
It has been determined that the folding action which takes place between the expanded and collapsed condition shown in FIGS. 1 and 2 can be carried out while accommodating the forces involved without tearing the liner and also bearing in mind the thickness and rigidity of the pipe boot which is desirable to match that of the liner.
The liner thicknesses may vary with application. A liner of 30 mil is the current minimum specified by Alberta regulations for secondary containment applications. However a liner of 40 mil seems to be the standard. Since there is a thinning of material during the boot manufacturing process and for cost advantage it is preferable to maintain the minimum 30 mil for standard product offerings.
This thickness and material provides a pipe boot which is relatively stiff but can still fold to take up the expanded and collapsed positions shown in FIGS. 1 and 2.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departure from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims

1. A method for secondary containment of a liquid in a liquid container, where the liquid container is surrounded by a containment wall and where the liquid container has connected thereto at least one member which extends from the liquid container downwardly into the ground within the containment wall, the method comprising:

providing a liner covering the ground within the containment wall and extending from the containment wall at least partly under the liquid container;

forming in the liner a hole surrounding the member;

providing a boot which surrounds the member and connects from the member to the material of the liner surrounding the hole;

providing on the boot a sleeve portion and a flange surrounding the sleeve portion at one end;

clamping the sleeve portion of the boot to the member;

sealing the flange of the boot to the liner at the hole;

and providing in the boot an expandable portion allowing longitudinal movement downward of the flange relative to an upper part of the sleeve of the boot such that the expandable portion allows the ground on which the liner lies to move downwardly relative to the member after attachment of the liner to the boot and the upper part of the sleeve of the boot to the member.

2. The method according to claim 1 wherein the boot has a portion at the flange which is of larger transverse dimension than at the upper part of the sleeve so as to allow the flange to move horizontally with the liner relative to the member,

3. The method according to claim 2 wherein the boot is connected to the flange at the bottom part of the expansion portion.

4. The method according to claim 1 wherein the expansion portion is frusto-conical from a lower end of the upper part of the sleeve to the flange.

5. The method according to claim 4 wherein the expansion portion can un-fold from a position in which the lower end of the upper part of the sleeve is in a common plane with the flange to a position in which the lower end is raised.

6. The method according to claim 1 wherein the expansion portion is frusto-conical with a cone angle in the range 45 to 60 degrees.

7. The method according to claim 6 wherein the sleeve above the expansion portion is frusto-conical at an angle less than that of the expansion portion.

8. The method according to claim 1 wherein the expansion portion includes an accordion wall between the lower end of the sleeve portion and the flange.

9. The method according to claim 1 wherein the sleeve portion is attached to the member by a surrounding clamp and is sealed to the member by a sealing grout.

10. The method according to claim 1 wherein in the collapsed position an upper end of the sleeve portion is located above the height of the expansion portion so that sufficient of the sleeve portion is available to attach to the member.

11. The method according to claim 1 wherein the collapsed position defines a stable position of the structure in which it holds its position until pulled out of that position in the expansion direction.

12. The method according to claim 1 wherein in the collapsed position a component of the expansion portion is in a common plane with the flange to locate the collapsed position.