GB2131497A - An annular sealing ring carrier - Google Patents

Abstract

A sealing ring carrier 1 comprises an annular support having flange- contacting faces 2,3 in at least one of which there is a locating recess 4, 5 for a gasket or other sealing element, together with an annular space and at least one bore 10, 12 connecting the space with the radially outermost surface of the support so that, in use, sealant composition can be injected into the space. A collapsible (soft) insert may be provided in the space. <IMAGE>

Description

SPECIFICATION Improvements in and relating to flanged connections This invention relates to flanged connections such as pipe joints which incorporate a gasket. It is normal practice to secure such connections by bolting through the flanges, both to retain/locate the gasket and to develope sealing stresses in the latter. In the event of a joint failure accompanied by leakage past or through the gasket, it has been proposed to form a back-up seal around the flange, to close the gap between the flanges, and then to inject a sealing compound radially inwardly of the back-up seal to stop the leak. The back-up seal may be formed by a circumferential clamp applied to the flange, or it may be a circumferential wrapping of a malleable metal wire. Both are in common use.

However, there is a serious and potentially very dangerous problem with this method of sealing a leak. If the pressure in the leaking pipeline is high, as it may well be in a petrochemical installation or in a steam main, for example, then a high injection pressure will be needed to inject the sealant composition into the joint against the pressure exerted by the leaking fluid. This injection pressure is applied between the confronting flanges over a very substantial portion of their surface area. It therefore constitutes an enormous additional load on the flange bolts, which may fail as a result. The blow-out which almost inevitably follows such failure is usually both extremely dangerous and impossible to repair without shutting down the associated system. There is thus a need for a better way of dealing with such flanged connections.

According to the present invention a sealing ring carrier comprises an annular support having flange-contacting faces in at least one of which there is a locating recess for a gasket or sealing element and an annular space and at least one bore connecting said space with the radially outermost surface of the support. Said radially outermost surface preferably lies within the bolt circle of a bolted flanged connection.

In normal circumstances the support will have a locating recess and space in each of its two flange-contacting faces, although the same bore may be used to connect both spaces to the outer surface. The recess and the space may be constituted by a single recess wider in a radial direction than the gasket or sealing element, or they may be constituted by a second recess spaced radially from the locating recess. It is however preferred that the space be located radially outwardly of the locating recess, to facilitate injection of sealant composition around the gasket or sealing element in the event of a leak. Location of the space radially inwardly of the gasket is feasible, but at the expense of a longer bore through the support, as well as the need to seal the bore to prevent leakage from the high pressure side of the gasket or sealing element.

A further and most significant advantage of having the space radially outside the gasket and at atmospheric pressure is that the space and the bore can be used for leak detection purposes. This is especially useful in that the condition of flanged connections embodying the sealing ring carrier of the invention can be monitored from a remote location. As soon as there is a significant pressure rise in the space (indicating gasket failure) then steps can be taken to inject sealant composition through the bore to stop the leak.

Repeated injection can be used if need be, because the flange-facing area of the space will always be significantly less than the total area of the flange, so that the effect of even high pressure injection will not overstress the joint. In this context, it is important to note that the sealing ring carrier preferably lies entirely within the bolt circle of a bolted flanged connection and that unlike prior art sealing methods, the flange area exposed to sealant injection pressure is accurately predictable; it can also be made relatively small.

As there is no need to fit clamps or apply wire caulking to the outside of the flange connection there is also no need to drill the flange (or flanges) to provide sealant injection ports. There is therefore no risk of damaging the flange or flanges to the point where they need, for example, re-machining or even replacement. As long as the sealing ring carrier lies, in use, within the bolt circle of a bolted connection, the bolts are not likely to be attacked by leaking corrosive fluid. In the prior art leak sealing processes, the bolts have always been inside the area treated by sealant injection; they have therefore always been at risk and virtually unprotectable.

Confining the fluid minimizes risk to the bolts; it therefore minimizes the risk of sudden catastrophic failure due to unseen corrosion.

In order that the invention be better understood, preferred embodiments of it will now be described by way of example with reference to the accompanying drawing in which:~ Figure 1 is a cross-sectional side view of one form of sealing ring carrier in accordance with the invention, and Figures 2, 3 and 4 are cross-sectional side views of other carriers in accordance with the invention.

For convenience like parts in all four figures will be given the same reference numerals. Referring to all four figures the carrier 1 is generally rectangular in cross-section, with flangecontacting faces 2 and 3, which in use seat against opposed flanges of a pipe joint, (not shown). Common to all four versions is the provision of oppositely-facing recesses, 4 and 5.

In use, these receive conventional gaskets (not shown). Spiral-wound gaskets are very commonly used for high pressure duty, but the invention is not limited to such gaskets. The recesses are either bounded radially inwardly of the sealing ring carrier by a solid metal land (6 in Figure 1) or are open to the inside of the ring as in Figures 2, 3 and 4.

In Figure 1 the ring-receiving recess is made wider (in a radial direction) than a spiral wound gasket designed for the desired class of service of a particular pipe joint. This is to leave oppositelydirected annular spaces 7 either radially inwardly, or more preferably, radially outwardly of the gasket. Figures 2, 3 and 4 embody this annular space as recess 8 in its own right. Those regions where a gasket is to seat are machined to the usual, relatively rough surface finish shown, for illustration purposes, on an exaggerated scale at 9.

Common to each embodiment, is the provision of at least one port. This comprises a radial bore 10, a screw-threaded inlet 1 1 to the radial bore, and axially-directed bores 12. These serve to give access (in use) to the oppositely-directed spaces 7. The access may be through a one-way valve (e.g. a grease nipple, not shown) or it may be connected through tubing (not shown) to a leak detection sensor (not shown)), or it may be both, since it is preferred that at least two ports be provided in any one sealing ring carrier. Unused ports may of course be blocked off with a set screw, as necessary. The opposite-directed spaces in figure 2 each contain a collapsible (soft) insert 13; these serve to help form a seal on injection of composition after discovery of a leak past the main gasket.

It will be appreciated that the Figure 4 embodiment is configured for raised face flanges; the outer land 14 is of increased height in the axial direction.

In use, the sealing ring carrier is fitted with two gaskets, one one each side. This is facilitated by making the gasket a push fit, or in the case of a spiral wound gasket, by profiling a wall of the recess to receive the edge of the spiral as a snap fit, in the usual manner of a spiral wound gasket guide ring. The carrier is then assembled into a flanged pipe joint with its outer circumference serving to locate it within the flange bolt circle.

The joint is then bolted up to compress both gaskets and develop a seal. The body of the carrier serves also as a compression stop, in that it limits the overall compression of the gaskets, just as the guide ring of a spiral wound gasket would do.

The port (or one of the ports, the rest being plugged with set screws) is then connected to a leak detector, either of the kind responsive to pressure or responsive to gas/vapour of a particular variety, depending on what the pipe line is to carry. The detector will normally be connected to give an alarm signal at a remote point such as a pipe line or process control room.

On detection of a leak a technician can go straight to the leaking joint ready to inject sealant. Typical sealants are heavily-filled rubber compounds formulated to cure rapidly in situ.

Injection could be through the same port as used for detection, but more usually it will be through at least one other port. It is important to note that the pipe joint need not be readily accessible, because injection can be made through a tube connected to the or each injection port. This is useful where the pipe line is carrying very dangerous material, such as radioactive fluid and the joint itself/is buried in a protective casing, for example, of concrete, or behind a radiation barrier.

Claims (9)

Claims

1. A sealing ring carrier comprising an annular support having flange-contacting faces in at least one of which there is a locating recess for a gasket or sealing element and an annular space and at least one bore connecting said space with the radially outermost surface of the support.

2. A carrier according to claim 1 wherein said radially outermost surface lies within the bolt circle of a bolted flange connection between elements of which the carrier and associated gasket are to form a seal.

3. A carrier according to claim 1 or claim 2 wherein the carrier has a locating recess and a space in each its oppositely directed flange contacting faces.

4. A carrier according to claim 3 wherein a common bore is used to connect each space to that outermost surface of the carrier.

5. A carrier according to any preceding claim wherein the recess and the space are constituted by a single recess wider in a radial direction than that gasket or sealing element.

6. A carrier according to any one of claims 14 wherein the space is constituted by a second recess spaced radially from the locating recess.

7. A carrier according to claim 5 or claim 5 wherein the space is located outwardly of the locating recess.

8. A carrier according to any preceding claim wherein the locating recess is configured to receive a spiral wound gasket.

9. A carrier according to any preceding claim wherein the bore is, in use, connected to leak detection apparatus.