CA2679790A1

CA2679790A1 - Double walled tanks with internal containment chambers

Info

Publication number: CA2679790A1
Application number: CA2679790A
Authority: CA
Inventors: Russell Hebblethwaite
Original assignee: Pearl Point Holdings Ltd
Current assignee: 1776074 ALBERTA Ltd
Priority date: 2009-09-22
Filing date: 2009-09-22
Publication date: 2011-03-22

Abstract

An above-ground storage tank includes a primary tank and a secondary tank, and an interstitial space; an containment chamber formed by a primary chamber wall and a secondary chamber wall, forming a chamber interstitial space therebetween, and an exterior door assembly; and at least one pipe and valve assembly wherein the pipe originates in the tank interior volume and the valve is disposed within the chamber.

Description

Double Walled Tanks with Internal Containment Chambers Field of the Invention [0001] The present invention is directed to double walled storage tanks with internal containment chambers.

Background

[0002] The storage of materials, including petroleum products and waste materials, in the upstream petroleum industry is dependent on primary containment devices, such as underground and aboveground storage tanks. Such tanks typically include secondary containment measures, which are required in some jurisdictions.

[0003] In Alberta, a single-walled aboveground storage tank must have secondary containment consisting of a dike with an impervious liner. However, the regulations permit the use of double-walled aboveground storage tanks ("DW ASTs") as an alternative to single-walled aboveground tanks and a secondary containment system. However, it has been found that DW ASTs are typically configured with manways and piping through the walls of the tanks. A majority of spills or releases from tanks are the result of operational issues such as overfilling, leaks and drips from valves and fittings, and spillage associated with fluid transfer. These releases are not being contained by the double-wall interstitial space.

[0004] The use of an internal containment chamber within single walled tanks is known.
Applicant's co-owned CA Patent No. 2,196,842 and US Patent No. 5,960,826 discloses the use of such containment chambers to contain spills and overflows from various valves used in these tanks.

[0005] There is a need in the art for double-walled tanks with internal containment chambers, which comprises an uninterrupted interstitial space.

Summary Of The Invention

[0006] In one aspect, the invention comprises an above-ground storage tank defining an interior volume and comprising:

(a) a tank roof, a tank floor, a primary tank and a secondary tank, and an interstitial space therebetween;
(b) an containment chamber formed by a primary chamber wall and a secondary chamber wall, forming a chamber interstitial space therebetween, and an exterior door assembly;
(c) at least one pipe and valve assembly wherein the pipe originates in the tank interior volume and the valve is disposed within the chamber, in which:
i. the pipe passes into the chamber without passing through the primary tank;
or ii. the pipe passes through the primary tank in a freeboard zone and into the containment chamber from the tank interstitial space; or iii. the pipe passes through the primary and secondary tank in a freeboard zone and into the chamber through the exterior door assembly.

[0007] The configuration of the containment chamber and the at least one pipe and valve assembly is arranged such that the double-walled protection of the tank is not compromised by any pipe or hatch or other opening, except in the freeboard zone.

Brief Description Of The Drawings

[0008] In the drawings, like elements are assigned like reference numerals.
The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted are but one of a number of possible arrangements utilizing the fundamental concepts of the present invention. The drawings are briefly described as follows:

[0009] Figure 1 shows a vertical cross-section through one embodiment of a tank of the present invention.

[0010] Figure 2 shows a horizontal cross-section through the embodiment shown in Figure 1, along line II-II.

[0011] Figure 3 shows a vertical cross-section through an alternative embodiment of a tank of the present invention.

[0012] Figure 4 shows a horizontal cross-section through the embodiment shown in Figure 3, along line N-N.

[0013] Figure 5 shows a vertical cross-section through an alternative embodiment of a tank of the present invention.

[0014] Figure 6 shows a horizontal cross-section through the embodiment shown in Figure 5, along line VI-VI.

[0015] Figure 7 shows a vertical cross-section through an alternative embodiment of a tank of the present invention.

[0016] Figure 8 shows a horizontal cross-section through the embodiment shown in Figure 7, along line VIII-VIII.

[0017] Figure 9 shows one embodiment of the configuration of welds connecting the primary and secondary tank walls to the primary and secondary chamber walls.

[0018] Figure 10 shows an alternative embodiment of the configuration of welds connecting the primary and secondary tank walls to the primary and secondary chamber walls.

[0019] Figure 11 shows an alternative embodiment of the configuration of welds connecting the primary and secondary tank walls to the primary and secondary chamber walls.

Detailed Description Of Preferred Embodiments

[0020] The invention relates to double-walled aboveground storage tanks. When describing the present invention, all terms not defined herein have their common art-recognized meanings. To the extent that the following description is of a specific embodiment or a particular use of the invention, it is intended to be illustrative only, and not limiting of the claimed invention. The following description is intended to cover all alternatives, modifications and equivalents that are included in the spirit and scope of the invention, as defined in the appended claims.

[0021] In one embodiment, the invention comprises an above-ground storage tank defining an interior volume and comprising:

(a) a tank roof, a tank floor, a primary tank and a secondary tank, and an interstitial space therebetween;
(b) an containment chamber formed by a primary chamber wall and a secondary chamber wall, forming a chamber interstitial space therebetween, and an exterior door assembly;
(c) at least one pipe and valve assembly wherein the pipe originates in the tank interior volume and the valve is disposed within the chamber;
(d) wherein no part of the at least one pipe and valve assembly passes through the secondary tank in a non-freeboard zone.

[0022] The configuration of the chamber and any pipe and valve assembly which penetrates into the tank interior volume is such that the tank interstitial space and the chamber interstitial space are not compromised, in a non-freeboard zone of the tank. As used herein, the term "freeboard" means that area of the tank above the highest fluid level of the tank.

[0023] As shown in Figures 1 and 2, in one embodiment, a storage tank (10) has a primary tank (12), and a secondary tank (14), which defines a tank interstitial space (16) therebetween.
As required by regulation in Alberta, the floor (18) is also double-walled, while the roof (20) is not as it is considered part of the freeboard zone of the tank.

[0024] A containment chamber (22) is created by a chamber primary wall (24) and a chamber secondary wall (26), which define a chamber interstitial space (28). The chamber walls (24, 26) are attached to the tank walls (12, 14) in a fluid-tight manner, such as by a suitable welding process. The attachments between the tank and containment chamber primary and secondary walls may be varied, as will be described below. What is essential is that the tank interstitial space and chamber interstitial space not be compromised.

[0025] Access to the containment chamber (22) is provided by a door assembly (30) which passes through the secondary tank wall (14). The door assembly may comprise a box (32) having a door (34). The door assembly can either be formed from the tank secondary wall material, or, be a completely separate manufactured component that is welded to the exterior of the tank secondary wall, over a door opening cut through both secondary and primary walls.
The door opening must then be framed between the primary and secondary tank walls to re-seal the interstitial space. This doorway opening provides access into the containment chamber.

[0026] A tank access hatch (36) may be provided through the tank roof (20). A
pipe access hatch (38) may be also be provided which provides access the interstitial space, tank volume or chamber space which houses pipe and valve assemblies, as described below.

[0027] The tank comprises at least one pipe and valve assembly. In one embodiment, the tank comprises two pipe and valve assemblies: a suckout pipe (40) and an overflow pipe (50).

The suckout pipe (40) originates near the tank floor, rises to the freeboard zone, where it passes through the primary tank wall (12) and into the tank interstitial space (16). It then passes through the containment chamber walls and into the containment chamber, where it terminates with a suckout valve (42).

[0028] An overflow pipe (50) originates in the freeboard zone, near the fluid line marking maximum capacity of the tank, and passes into the tank interstitial space (16). The overflow pipe (50) then continues into the containment chamber, and terminates in a high level shutdown valve (52). This valve (52) may include sensors which regulate inflows into the tank, or may be connected to transmitters (not shown) which transmit a wireless or radio alarm signal, as is well known in the art.

[0029] As may be seen in Figures 1 and 2, both the suckout pipe and valve assembly and the overflow pipe and valve assembly do not compromise the integrity of the interstitial space, as they pass directly into the containment chamber, which is itself double-walled, from the tank interstitial space.

[0030] A heater (55) may be provided within the containment chamber to keep the valves, (42, 52) from freezing in the winter.

[0031] In an alternative embodiment, as shown in Figures 3 and 4, the pipes (40, 50) pass through both the primary and secondary tank walls in the freeboard zone, thereby complying with regulations which allow such intrusions in the freeboard zone. The pipes then pass along the exterior of the tank, and enter into the containment chamber through the door box (32).
Because the pipes are accesible on the exterior of the tank, in this embodiment, a pipe access hatch into the tank is not necessary.

[0032] In an alternative embodiment, shown in Figures 5 and 6, the tank comprises an ancillary containment chamber (60) formed by a single walled enclosure (62).
The ancillary chamber is formed adjacent to the main containment chamber and has a roof portion (64).

The pipes (40, 50) pass into the ancillary chamber, preferably in the freeboard zone, and from there, pass into the main containment chamber. The overflow pipe (50) simply extends up through the roof portion (64). Because the single walled enclosure is ancillary to the double walled tank and containment chamber, the incursions into the interstitial spaces is contained by the ancillary chamber.

[0033] In an further alternative, as shown in Figure 7 and 8, the single walled enclosure of the ancillary chamber extends upwards and attaches to the tank roof (20). The access hatch (3 8) through the tank roof (20) provides direct access into the ancillary chamber, unlike the embodiment shown in Figures 5 and 6, where the pipe access hatch (38) only provides access to the roof portion (64) of the ancillary chamber.

[0034] As shown in Figures 9, 10 and 11, various configurations of attachment between the tank primary and secondary walls and the chamber primary and secondary walls are possible.
Both of the primary or secondary chamber walls (24, 26) may attach to the primary tank wall, as is shown in Figure 9. In this case, the tank interstitial space and the chamber interstitial space are separated by the primary tank wall. In one embodiment, the attachment is accomplished by a full penetration weld (W) which is fluid-tight.

[0035] Alternatively, the primary chamber wall (24) may attach to the primary tank wall (12), while secondary chamber wall (26) attachs to the secondary tank wall (14). In one embodiment, shown in Figures 10, the primary chamber wall is welded to the primary tank wall in a fluid tight manner, and the secondary chamber wall is welded to the secondary tank wall. As a result, the tank interstitial space (16) is contiguous with the chamber interstitial space (Figure 11), or there is no sealed connection between the two (Figure 10), which means the two interstitial spaces are connected but not contiguous.

[0036] In one embodiment, the tank comprises fluid detection sensors (not shown) in the tank interstitial space, the chamber interstitial space, or both. If the tank interstitial space, and the chamber interstitial space are connected or continguous, it may possible to implement only one fluid detection sensor within either the tank or the chamber interstitial space. Suitable fluid detection sensors are well known in the art.

[0037] As will be apparent to those skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the scope of the invention claimed herein.

Claims

WHAT IS CLAIMED IS:

1. An above-ground storage tank defining an interior volume and comprising:
(a) a tank roof, a tank floor, a primary tank and a secondary tank, and an interstitial space therebetween;
(b) an containment chamber formed by a primary chamber wall and a secondary chamber wall, forming a chamber interstitial space therebetween, and an exterior door assembly;
(c) at least one pipe and valve assembly wherein the pipe originates in the tank interior volume and the valve is disposed within the chamber, in which:
i. the pipe passes into the chamber without passing through the primary tank;
or ii. the pipe passes through the primary tank in a freeboard zone and into the containment chamber from the tank interstitial space; or iii. the pipe passes through the primary and secondary tank in a freeboard zone and into the chamber through the exterior door assembly.

2. An above-ground storage tank defining an interior volume and comprising:
(a) a tank roof, a tank floor, a primary tank and a secondary tank, and an interstitial space therebetween;
(b) an containment chamber formed by a primary chamber wall and a secondary chamber wall, forming a chamber interstitial space therebetween, and an exterior door assembly;
(c) at least one pipe and valve assembly wherein the pipe originates in the tank interior volume and the valve is disposed within the chamber;
(d) wherein no part of the at least one pipe and valve assembly passes through the secondary tank in a non-freeboard zone.

3. The tank of claim 1 or 2 wherein the tank roof comprises an access hatch.

4. The tank of claim 1 or 2 wherein the at least one pipe and valve assembly comprises a tank suckout pipe and valve or a tank overflow pipe and valve, or both.

5. The tank of claim 1 or 2 wherein the tank interstitial space and the chamber interstitial space are contiguous or connected.