GB2296305A - Apparatus for and method of removing and replacing a pipeline component - Google Patents

Abstract

The component may be removed and replaced whilst maintaining the pipeline under pressure. Two diametrically opposed bolts which secure a flange of the component 4 to a flange 6 of the pipeline 1 are replaced by spring-loaded clamping devices 8, arranged to hold the flanges together against the pressure within the pipeline, the remaining bolts holding the flanges together being removed. A blade 14 is then driven between the flanges such that the blade passes between the spring loaded clamping devices 8, thereby forcing the flanges apart against the biassing force provided by the clamping devices. The blade 14 is dimensioned such that once inserted it obstructs communication between the pipeline 1 and the component 4. After its insertion it is clamped 17, 20 to the pipeline flange so as to minimise leakage between the blade and the flange. The component 4 is then removed and replaced, the replacement being secured by the clamping devices 8 to the pipeline flange such that it is biassed against the blade 14. The blade 14 is then withdrawn so that the replacement is pushed into contact with the pipeline flange by the clamping devices 8. The replacement can then be finally bolted to the pipeline flange. Although some leakage occurs during insertion and removal of the blade 14 and there may be some limited leakage after the blade has been clamped to the pipeline flange, such leakage is perfectly acceptable in many applications for example where the pipeline is carrying water. <IMAGE>

Description

UNDER-PRESSURE PIPELINE COMPONENT REPLACEMT The present invention relates to a method and apparatus for removing and replacing a component of an under-pressure pipeline.

There are certain circumstances in which it is highly desirable to be able to replace components of a pressurised pipeline system without it being necessary to first isolate that component from the pipeline system. For example, the water supply industry has extensive and aging pipeline systems incorporating components such as hydrants which over a prolonged period can deteriorate to the point at which they either leak or are inoperable. In some circumstances it is relatively easy to isolate such components from the pipeline, for example where a hydrant has been fitted on a valved branch of a mains supply pipeline. Unfortunately there are many cases where the component to be replaced cannot be easily isolated and therefore it is current practice when replacing such a component to shut off the main itself.

Shutting off a water main can affect a large number of customers supplied from that main and significant costs are incurred in warning customers of an intended shutoff, planning and implementing procedures to effectively isolate the main in question, and ensuring that guaranteed standards of supply are maintained.

The problem of replacing components of an under-pressure water pipeline is well known and various solutions to the problem have been proposed. For example, it has been proposed to freeze water in a pipeline adjacent a component to be removed such that the ice thereby formed "plugs" the pipeline during the removal and replacement of the component in question. Unfortunately this approach is not effective where components are located close to a main through which there is a substantial flow as turbulence within the pipeline prevents the reliable formation of an ice plug.

It is an object of the present invention to provide a method and apparatus for removing and replacing a component of an under-pressure pipeline and in particular a component of an under-pressure water pipeline.

According to the present invention, there is provided a method for removing and replacing a component of an under pressure pipeline, the component having a flange clamped to a flange of the pipeline by bolts extending through the flanges, wherein two diametrically opposed bolts are replaced by spring-loaded clamping devices which bias the flanges together with a force greater than the force biassing the flanges apart due to pressure within the pipeline, remaining bolts clamping the flanges together are removed, a blade is driven between the flanges such that the blade passes between the spring loaded clamping devices and the flanges are moved apart against the biassing force, the blade being dimensioned to obstruct communication between the component and the pipeline, the blade is clamped against the pipeline flange, the spring loaded clamping devices are released and the component is removed, the component is replaced and the replacement is clamped to the pipeline flange by the spring loaded clamping devices so as to be biassed against the blade, the blade is withdrawn such that the replacement moves into contact with and is biassed against the pipeline flange, and the replacement is bolted to the pipeline flange.

Preferably the blade is mounted on a support clamped to the pipeline, the blade is driven between the flanges such that its tip projects beyond the flanges, and the blade tip is clamped to the support to clamp the blade against the pipeline flange.

The invention also provides an apparatus for removing and replacing a component of an under pressure pipeline, comprising a support adapted to be clamped to the pipeline, a blade movably mounted on the support such that it may be inserted between two abutting flanges one of which is defined by the pipeline to which the support is clamped and the other of which is defined by the component and is spring biassed against the pipeline flange, the blade being dimensioned to obstruct communication between the component and the pipeline after its insertion between the flanges, and means for clamping the blade against the pipeline flange after its insertion between the flanges to enable the removal and replacement of the component.

Preferably the clamping means comprises means for clamping the blade tip to the support. For example, an aperture may be formed in the blade tip, the aperture receiving a bolt which is secured to the support. A further aperture may be formed in the blade, the two apertures being spaced apart along the length of the blade by a distance greater than the outside diameter of the flanges. Bolts may then be inserted through both the apertures and secured to the support.

Preferably the blade tip has a tapering edge to facilitate its insertion.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view of an apparatus in accordance with the present invention mounted on a branch pipe below a hydrant; Fig. 2 is a partial view taken on the line 2-2 of Fig. 1; Fig. 3 is a view similar to that of Fig. 1 but showing the apparatus after the insertion of a blade between flanges shown clamped together in Fig. 1; and Fig. 4 is a partial view on the line 4-4 of Fig. 3.

Referring to Figs. 1 and 2, a branch pipe 1 is connected through flanges 2 to a Tpiece 3, the interior of which is in communication with a water main. A water hydrant 4 is connected to the branch pipe 1, a flange 5 of the water hydrant housing being secured to a flange 6 of the branch pipe by bolts 7. Four bolt positions are provided and each of these will receive in normal circumstances a conventional bolt. When it is desired to remove the hydrant 4, however, two diametrically opposed bolts are replaced by elongate bolts 8, the head of each bolt 8 being separated from the flange 5 by a strong compression spring 9. The bolts 8 are of high strength and are tightened such that the springs 9 are compressed sufficiently to maintain the flanges 5 and 6 in contact despite the pressure within the branch pipe 1.

A support 10 is clamped to the branch pipe 1 by a chain 11. An arm 12 projects from the support 10 and has mounted upon it a guide 13 within which a blade 14 is slidable. The blade 14 is connected to a threaded shaft 15 which passes through a threaded nut 16. Rotation of the shaft 15 in one direction advances the blade 14 out of the guide 13, and rotation of the shaft in the other direction retracts the blade 14 into the guide 13.

As indicated above, when it is desired to remove the hydrant 4 two diametrically opposed bolts are removed and replaced by the spring-loaded bolt 8. Once this has been done the remaining bolts 7 are removed and the support 10 is positioned such that the blade 14 is located in a position in which it can pass between the bolts 8. The tip of the blade 14 is tapered to define a chisel edge and that edge is aligned with the plane of contact between the flanges 5 and 6. The shaft 15 is then rotated, forcing the blade 14 between the flanges 5 and 6.

Insertion of the blade 14 forces the flanges 5 and 6 apart against the force provided by the springs 9. The blade 14 is advanced until it projects beyond the far side of the flanges 5 and 6 as shown in Fig. 3. In that position it obstructs communication between the pipe 1 and the hydrant 4. Some leakage of water will of course occur as the blade 14 is being inserted but once it has reached the position shown in Fig. 3 the springs 9 will press the blade 14 against the flange 6 and therefore leakage will be limited.

Once the blade 14 has assumed the position shown in Fig. 3, a bolt 17 is inserted through an aperture 18 provided in the tip of the blade. A similar bolt may be inserted through a further aperture 19 (Fig. 4) provided in the blade 14, the spacing between the apertures 18 and 19 being greater than the outside diameter of the flanges 5 and 6. The bolt 17 (and any further bolt inserted through aperture 19) is then secured by an appropriate means such as a chain 20 to the support 10. Thus the blade 14 is securely clamped against the flange 6. The bolts 8 are then removed, releasing the hydrant 4 which may be replaced either by a new hydrant or another pipeline component, for example a simple blank flange where for example a hydrant is no longer required. The replacement component is secured in position by the spring loaded bolts 8. A suitable gasket may be provided on the replacement component so as to rest against the surface of the blade 14. The blade 14 is then retracted, the springs 9 on the bolts 8 maintaining the hydrant in position during this manoeuvre. Once the blade 14 has been fully retracted the assembly resumes the configuration shown in Fig. 1. New bolts 7 may then be inserted into the vacant pair of holes to secure the flanges 5 and 6 together.

Thereafter the bolts 8 may be removed and replaced with conventional new bolts. The procedure is then complete and the apparatus may be removed from the pipe 1 simply by releasing the chain 11.

In a typical application the blade 14 will be made from steel and have a thickness of, for example, 2mm. The width of the blade will be typically about 80mm, the width being selected to ensure that the blade can pass between the two spring loaded bolts and to ensure that the blade fully covers the bore of the branch pipe. It will be appreciated that accurate positioning of the apparatus is important.

The guide 13 as shown in the drawings is in the fonn of a pair of U-shaped channels each of which receives a respective edge of the blade 14. It will be appreciated that alternative guide arrangements could be provided. Although in the described embodiment the blade is extended and retracted by a simple threaded shaft and nut arrangement, it will be appreciated that alternative drive mechanisms may be provided and in particular there will be advantages to using a hydraulic drive mechanism as this will enable a relatively fast movement of the blade 14 to be achieved, thereby reducing the volume of water which escapes as the blade 14 is being extended and retracted.

The chisel edge on the blade 14 is arranged such that the blade goes beneath any flange gasket provided in the original coupling. This ensures that the old flange gasket can be reliably removed with the hydrant which is to be removed.

There will inevitably be some escape of water during the hydrant replacement operation but the water loss is not sufficient as to prohibit the operation. Thus it is not necessary to cut off a mains supply pipeline during a hydrant replacement operation and it is most unlikely that any contaminants will enter the pipeline during the operation given that the pipeline immediately adjacent the inserted blade is in effect flushed out as a result of the limited leakage which takes place. Thus customers are not cut off and there is no risk to the quality of the water supplied.

Claims (9)

1. A method for removing and replacing a component of an under pressure pipeline, the component having a flange clamped to a flange of the pipeline by bolts extending through the flanges, wherein two diametrically opposed bolts are replaced by spring-loaded clamping devices which bias the flanges together with a force greater than the force biassing the flanges apart due to pressure within the pipeline, remaining bolts clamping the flanges together are removed, a blade is driven between the flanges such that the blade passes between the spring loaded clamping devices and the flanges are moved apart against the biassing force, the blade being dimensioned to obstruct communication between the component and the pipeline, the blade is clamped against the pipeline flange, the spring loaded clamping devices are released and the component is removed, the component is replaced and the replacement is clamped to the pipeline flange by the spring loaded clamping devices so as to be biassed against the blade, the blade is withdrawn such that the replacement moves into contact with and is biassed against the pipeline flange, and the replacement is bolted to the pipeline flange.

2. A method according to claim 1, wherein the blade is mounted on a support clamped to the pipeline, the blade is driven between the flanges such that its tip projects beyond the flanges, and the blade tip is clamped to the support to clamp the blade against the pipeline flange.

3. An apparatus for removing and replacing a component of an under pressure pipeline, comprising a support adapted to be clamped to the pipeline, a blade movably mounted on the support such that it may be inserted between two abutting flanges one of which is defined by the pipeline to which the support is clamped and the other of which is defined by the component and is spring biassed against the pipeline flange, the blade being dimensioned to obstruct communication between the component and the pipeline after its insertion between the flanges, and means for clamping the blade against the pipeline flange after its insertion between the flanges to enable the removal and replacement of the component.

4. An apparatus according to claim 3, wherein the clamping means comprises means for clamping the blade tip to the support.

5. An apparatus according to claim 4, wherein an aperture is formed in the blade tip, and the clamping means comprises a bolt which may be inserted through the blade tip aperture and means for securing the bolt to the support.

6. An apparatus according to claim 5, wherein a further aperture is formed in the blade, the apertures being spaced apart along the length of the blade by a distance greater than the outside diameter of the flanges, and the clamping means comprises a further bolt which may be inserted through the further aperture and means securing the further bolt to the support.

7. An apparatus according to any one of claims 3 to 6, wherein the blade tip has a tapering edge to facilitate its insertion.

8. A method for removing and replacing a component of an under pressure pipeline substantially as hereinbefore described with reference to the accompanying drawings.

9. An apparatus for removing and replacing a component of an under pressure pipeline, substantially as hereinbefore described with reference to the accompanying drawings.