GB2392715A

GB2392715A - Improvements in secondary containment pipe fitting

Info

Publication number: GB2392715A
Application number: GB0220519A
Authority: GB
Inventors: Richard Statham
Original assignee: Glynwed Pipe Systems Ltd
Current assignee: Glynwed Pipe Systems Ltd
Priority date: 2002-09-04
Filing date: 2002-09-04
Publication date: 2004-03-10
Also published as: GB0220519D0

Abstract

A fitting 4 for a secondary containment pipeline 1,1',2, 2', 3, 3' comprising; at least two open end portions 5a, 5b each configured to receive an end of a secondary pipe 2, 2' of a secondary containment pipeline, a body portion 10, narrower than the end portions 5a, 5b, configured to receive ends of primary pipes 1, 1' of a secondary containment pipeline and at least two stepped portions 6a, 6b extending between the body portion 10 and each end portion 5a, 5b of the fitting 4, at least two of the at least two stepped portions 6a, 6b being provided with a port 8a, 8b, extending from an inner surface to an outer surface of the fitting 4 for connecting with a bypass conduit 9. The fitting may comprise a unitary piece or may be comprised of a plurality of component pieces connected for the purpose of providing a join or bend between adjacent lengths of the secondary containment pipeline.

Description

239271 5

IMPROVEMENTS IN SECONDARY CONTAINMIINT PIPE FITTING

This invention relates to the secondary containment of pipes, for example pipes used in pipeline systems for conveying petrol or other flammable hydrocarbons, in order to minimise the risk of leakage to the environment surrounding the pipeline.

It is known, where fluids which may cause ecological damage if exposed to the natural environment are conveyed through a pipeline, to contain the main conveying pipe within a second pipe. Should there be a failure of the main conveying pipe, then any fluid escaping from the damaged pipe is contained by the outer pipe. This provision of a second, outer pipe is known as secondary containment.

Some technical improvements on the basic principle of secondary containment have also been made. These include, the introduction of an inert gas, for example Nitrogen,

into the interstitial space. The pressure of the gas can be monitored and any unexpected changes in the pressure can provide an indication of failure of the primary (conveying) pipe. Repairs can then be initiated, without delay, so as to minimise any loss of the conveyed fluid and any subsequent risk of environmental contamination. If the gas introduced is at an elevated pressure, the pressure of the gas itself can help contain fluid in the primary pipe in the event of a pipe failure.

Manufacture of a secondary containment pipeline is relatively straightforward for a straight line. The primary (or fluid conveying) pipe is inserted into a secondary containment pipe of greater diameter. However, the task becomes more complex when there is a need to include bends, tee junctions, elbow joints and the like to convey the fluid from its source to its final destination. Such joints or bends are typically moulded and it will be understood that to provide an interstitial space for secondary containment of a fluid within a moulded joint or bend is a complex manufacturing problem.

Consequently, whilst secondary containment is provided around pipes in pipeline

systems for conveying hazardous materials, such secondary containment may not be provided at joints or bends of such systems. One significant downfall of such arrangements is that continuity of gas pressure or a fluid pathway in the interstitial space or between consecutive interstitial spaces of the secondary containment system cannot be maintained as each length of pipe between the joints or bends necessarily has a self contained space.

The present invention aims to alleviate some of the problems identified for the prior art

secondary containment systems.

In accordance with the present invention, there is provided a fitting for a secondary containment pipeline comprising; at least two open end portions each configured to receive an end of a secondary pipe of a secondary containment pipeline, a body portion, narrower than the end portions, configured to receive ends of primary pipes of a secondary containment pipeline and at least two stepped portions extending between the body portion and each end portion of the fitting, at least two of the at least two stepped portions being provided with a port, extending from an inner surface to an outer surface of the fitting for connecting with a bypass conduit.

The fitting may be selected from (but is not strictly limited to); elbow joints of various angles, T joints, Y pieces, reducing bushes, plain couplers and valves.

Whereas the fitting and conduit may comprise separate pieces assembled together, equally, a fitting in accordance with the invention might be provided as a unitary piece into which the ports and conduit are integrally moulded. The aforewritten statement of

invention is intended to encompass such unitary piece embodiments.

The bypass conduit may conveniently be a length of tube sufficiently long to extend from the port in a first stepped portion to a port in a second stepped portion.

Optionally, a separate connector piece may be used to connect the bypass conduit with each port. In one very basic example, the bypass conduit comprises a length of flexible pipe and each port a simple drilled hole in each stepped portion. A connector consisting

of a short length of relatively rigid material and of suitable diameter to provide a gas tight seal when fitted into the port of the stepped portion and an end of the flexible pipe, is used to connect the conduit between two stepped portions of the fitting.

More complex arrangements might include more mechanically complex means for connecting the bypass conduits with the ports of the stepped portions. Such arrangements might (without limitation) use screw fittings or other mechanical fastening arrangements to provide joins suitable for withstanding pressures occurring in the interstitial space between the primary and secondary pipe of the secondary containment pipeline and consequently in the bypass conduit. Fastening arrangements may also, optionally, incorporate seals such as rubber O-rings to contain inert gas within the interstitial space and bypass conduit. Also, optionally, a connector may be secured in each port by a physical (eg welding) or chemical (eg adhesive) bonding means. It will be understood that by providing a bypass across the bend or joint and a conduit permitting the interstitial spaces of one length of secondary containment pipe to be in fluid communication with an adjacent length, the pressure of any gas or fluid in the interstitial spaces of the pipeline can be maintained relatively constant throughout the line. This permits more accurate monitoring of leak detection requiring potentially less sensors in the system and enables action to be taken at an early stage to repair or replace pipe sections where leakage from the primary pipe has occurred.

More than one conduit may be provided between adjacent lengths of secondary containment pipes. Accordingly, it is to be understood that more than one port may be provided in a stepped portion of a fitting in accordance with the invention.

In another aspect, the invention provides a method for improving flow of gas in the interstitial spaces of a secondary containment pipe system comprising providing at least one conduit between adjacent lengths of secondary containment pipe to bypass pipe connectors or fittings which otherwise enclose an interstitial space.

Preferably, the method is facilitated by providing the conduit in an appropriately adapted pipe fitting as previously described. Alternatively, the conduit may be located between ports provided in the secondary pipe of each length of secondary containment pipe. In another alternative a single port may be provided in a stepped portion at one end of a fitting and a second port in the secondary pipe fitted into another end of the fitting, a conduit again being provided between the two ports.

For the purposes of exemplification, an embodiment of the invention will now be further described with reference to figure I in which; Figure 1 illustrates a 90 elbow fitting connecting two straight pipe sections of a secondary containment pipeline.

Figure 2 illustrates in more detail an embodiment of the elbow fitting of Figure I which comprises 3 component parts.

As can be seen from Figure 1 two straight pipe sections of a secondary containment pipeline system are positioned at 90 to one another. Each consists of an inner or primary pipe 1, l', and an outer secondary containment pipe 2, 2' separated by an interstitial space 3, 3'. The primary pipes 1, 1' convey a hazardous fluid F through a pipeline. The two secondary containment sections 1,2,3 and l', 2', 3' are connected together by a 90 elbow fitting 4 generally of a conventional configuration. The elbow fitting 4 comprises a first open end portion 5a, which receives a first, secondary containment pipe 2, and a second open end portion 5b which receives a second secondary containment pipe 2'. The elbow fitting also has a body portion 10 into which are received primary pipes l and l'.

Extending from the body portion to to each open end portion Sa, Sb is a stepped portion 6a, 6b which crosses the interstitial spaces 3 and 3'.

Each stepped portion 6a, 6b is provided with a port 8a, 8b which extends from the inner

surface of the f sting 4 in communication with the fluid F to the outer surface of the fitting 4 in communication with the external environment. Secured into each port 8a, 8b is a connecting piece 7a, 7b which comprises a short length of tube protruding from the outer surface of the fitting 4. A length of flexible tube 9 is fitted at each of its open ends over a protruding end of a connector piece 7a, 7b to provide a bypass conduit. When the conduit is in position, gas in the interstitial spaces 3, 3' can flow between the two spaces freely and so pressure across the two pipe sections 1, 2, 3 and 1', 2', 3' is substantially equalised.

As can be seen from Figure 2 the fitting of Figure I may be comprised of three pieces.

Two reducer portions, identified by reference characters A and B and an elbow bend portion identified by reference character C. The elbow bend portion C forms part of the body portion 10 identified in Figure 1. It is to be understood that the fitting may be comprised of a number of pieces or may be comprised of a unitary piece without detriment to the practical advantages previously discussed for the invention. The term "fitting" as used herein is intended to be construed to include unitary piece fittings as well as fittings, such as the embodiment shown in Figure 2, where the fitting comprises component parts brought together to join lengths of a secondary containment pipeline.

Accordingly, in another aspect, the invention provides a reducer for a pipe fitting, the reducer comprising a first open end portion configured to receive an end of a secondary pipe of a secondary containment pipeline, a second open end portion, narrower than the first and configured to receive an end of a primary pipe of a secondary containment pipeline and a stepped portion extending between the two end portions the stepped portion being provided with a port, extending from an inner surface to an outer surface of the reducer for connecting with an end of a bypass conduit.

It is to be understood that the foregoing represents just one embodiment of a fitting in accordance with the invention and that the distinguishing features lie in the provision, via the ends of the fitting, a conduit connecting the interstitial spaces between the primary and secondary pipe of adjacent secondary containment pipe sections in fluid communication.

The number of open ends or configuration of the body portion have little bearing on the

implementation of the invention as claimed in the appended claims.

Claims

I A fitting for a secondary containment pipeline comprising; at least two open end portions each configured to receive an end of a secondary pipe of a secondary containment pipeline, a body portion, narrower than the end portions, configured to receive ends of primary pipes of a secondary containment pipeline and at least two stepped portions extending between the body portion and each end portion of the fitting, at least two of the at least two stepped portions being provided with a port, extending from an inner surface to an outer surface of the fitting for connecting with a bypass conduit.
2. A fitting as claimed in claim I wherein the fitting type is selected from elbow joints of various angles, T joints, Y pieces, reducing bushes, plain couplers and valves.
3. A fitting as claimed in claim I or claim 2 wherein the bypass conduit comprises a length of tube sufficiently long to extend from the port in a first stepped portion to a port in a second stepped portion.
4. A fitting as claimed in any preceding claim further comprising one or more connector pieces for connecting the bypass conduit with a port.
5. A fitting as claimed in any preceding claim wherein the port, the bypass conduit and/or the optional connector piece comprises a mechanical fastening arrangement to provide a join suitable of withstanding pressures occurring in the interstitial space between the primary and secondary pipe.
6. A fitting as claimed in any preceding claim wherein the port, the bypass conduit and/or the optional connector piece comprises a seal for containing inert gas within the interstitial space and bypass conduit.
7. A fitting as claimed in any of claims 4 to 6 wherein a connector piece is secured in

one or more ports by a physical or chemical bonding means.
8. A fitting as claimed in any preceding claim further comprising one or more bypass conduits.
9. A fitting as claimed m any preceding claim wherein each stepped portion is provided with a plurality of ports each for connecting with one of a plurality of bypass conduits.
10. A method for improving flow of gas in the interstitial spaces of a secondary containment pipe system comprising providing one or more conduits between adjacent lengths of secondary containment pipe to bypass pipe connectors or fittings which otherwise enclose an interstitial space.
11. A method as claimed in claim 10 wherein the method is performed by providing the conduit in a pipe fitting as claimed in any of claims I to 9.
12. A method as claimed in claim 10 wherein the method is performed by providing ports in the secondary pipe of each length of secondary containment pipe and locating the conduit(s) between those ports.
13. A method as claimed in claim 10 wherein the method is performed by providing a first one or more ports in a stepped portion at one end of a fitting and a second one or more ports in a secondary pipe to be fitted into another end of the fitting and providing a conduit between those ports.
14. A reducer for a pipe fitting, the reducer comprising a first open end portion configured to receive an end of a secondary pipe of a secondary containment pipeline, a second open end portion, narrower than the first and configured to receive an end of a primary pipe of a secondary containment pipeline and a stepped portion extending between the two end portions the stepped portion being provided

with a port, extending from an inner surface to an outer surface of the reducer for connecting with an end of a bypass conduit.
15. A fitting for a secondary containment pipeline substantially as described herein and with reference to the Figures.
16. A method substantially as described herein and with reference to the Figures.