GB2138903A - Improvements in sealing pipe and like flanged joints - Google Patents

Abstract

A clamp is made up of two generally semi-circular parts 12, 14 to constitute an enclosing ring. Each part 12, 14 has a plurality of holes 28 extending radially inwardly from an outer surface 30 of the respective part. Each hole is tapped and, in use, capped by an injection nut to allow injection of a sealant compound into the space between confronting flanges 34 and the space between each flange bolt 32 and also each bolt clearance hole. The clamp ring is located relative to the confronting flanges by locating, as a close tolerance sliding fit, a rib 38 between the flanges. The rib is formed from the stepping of each generally T-section part 13, 14. Bridges 40 are positioned to bridge between the confronting flanges and the clamp ring to prevent relative movement of the flanges. <IMAGE>

Description

SPECIFICATION Improvements in sealing pipe and like flanged joints This invention relates to improved couplings for and methods of forming fluid-tight joints between flanged pipe ends or like structures, or flanged connexions on pressure vessels or like structures.

The process of sealing leaks by the formation of an injection moulding around the defective gasket of a flanged connexion is well known and has been in use since the mid 1 920's. Present day techniques that have been developed enable leaks at all normal operating temperatures to be sealed.

We have previously proposed a specific process and means by which leaks in plant of steam, boiler feed water, gas hydrocarbons and many chemicals can be sealed whilst the plant remains at full production and the pipeline at normal operating pressure. The process relies on injecting a compound for forming moulded seals around, for example, defective pipeline flanges or gaskets say through means comprising T-section members between and adjacent pairs of confronting spaced flanges or the like.

It is recognised that the process of leak sealing will result in a small increase of the stress level in the fasteners of the assembly particularly on those fasteners in the sector of the assembly adjacent to the leak. The additional stress should not, with correct techniques, exceed approximately 15% of the yield stress. On an assembly, where the fasteners have been tightened to recognised and controlled stress levels, the additional stress should easily be accommodated at least using our previous process and means, without any danger to the security of the assembly. In practice, however, we do find many occasions where attempts have been made initially to deal with the leak by uncontrolled retightening of the fasteners which can raise the stress levels considerably above specification or code limits.In this case the additional stress due to leak sealing can bring the total stress in the fasteners close to yield and it is an object of this invention to provide a way of containing additional stress from leak sealing.

According to a first aspect of the present invention, there is provided a method of forming a fluid-tight joint between two flanged pipe ends or other structures having annular flanges in confronting spaced relationship which comprises positioning relative to the space between the flanges, substantially to close that space, cooperating clamp members that preferably engage and enter between edges of the confronting flanges, providing separation restraint for said flanges by way of bridge parts associated with the clamp members and extending over and bearing against non-opposed faces of the confronting. flanges, and, usually after separation restraint, injecting sealant compound into the space between the flanges to form a fluid-tight seal between the parts forming the joint.

In practice, the invention is preferably, but not exclusively, intended for use with 4 and 8 bolt flanges. Flanges having greater numbers of bolts are on average less affected by additional stress from leak sealing as it is only the bolts adjacent to the leak that are affected to the full extent.

According to a second aspect of the present invention, there is provided a coupling or set of parts suitable for carrying out the method of the first aspect, comprising clamp members to fit about a space between confronting flanges or the like and associated bridge parts to engage over such flanges.

Suitable bridge parts are members separate from the clamp members but secured or securable thereto, usually by bolting then preferably as registering pairs of bridge members, one of each pair to each side of the clamp and using the same bolt.

Suitable cooperating clamp members are of generally T-section, say as two semi-circular parts having end abutment faces, usually aligned with respect to a diameter of the ring formed by the parts, and themselves usually affording passageways through to the space between the flanges, say via a plurality of radial bores (preferably adapted to receive an injection nut) extending radially inwardly from an outer surface of the head of each part and through its stem. A suitable T-section has a stem preferably to be a sliding fit between confronting flanges, but with sloping shoulders to fit wider spaces, and a thick head to take bridge member bolt holes. Moreover it is preferred that each clamp part directly carry actual clamp means, say as bored lugs to receive a clamping bolt passing through the lugs of two adjacent ends, rather than be as inserts indirectly clamped by outer members.

The latter is, however, feasible, even with bridge parts associated with such outer members.

It will be appreciated that, instead of providing specific injection bores in the clamp members, other access for injection may be used, say through bolt clearances from their nut ends, or via holes drilled through the flanges themselves (then usually tapped for nipples and/or plugs.

Specific implementation of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is an end view of a coupling according to the invention for forming fluidtight joints between two flanged pipe ends; and Figure 2 is a sectional view in the plane A-A of Fig. 1.

Referring to the drawings, a clamp 10 is made up of two generally semi-circular parts 12, 14 to constitute an enclosing ring for the clamp. The parts 12, 14 have end abutment faces 16 and 18 respectively which are substantially co-planar with a diameter of the enclosing ring of the clamp when the two parts 12, 14 are assembled together.

Lugs 20 and 22 are welded to opposite ends of the parts 12 and 14, a little way inwards from the end abutment faces 16 and 18. The lugs have clearance holes formed in them to receive clamping bolts 24 which cooperate with nuts 26 to clamp the two parts 12, 14 together.

Each part 12, 14 of the clamp ring has a plurality of holes 28 extending radially inwardly from an outer surface 30 of the respective part. Fig. 1 shows schematically the line of the holes 28, and Fig. 2 shows that each hole 28 is tapped. Each hole is, in use, capped by an injection nut (not shown) which is designed to receive a nozzle of an injection gun for injecting sealant compound into the vicinity of the confronting flanges.

As mentioned hereinbefore, depending upon circumstances, other ways of injecting sealant could be employed, i.e. not using such holes 28 (which could then be omitted).

Hollow lugs or cap nuts with injector nipple accommodation have been developed by us.

Conventional flange bolts 32 are shown in Figs. 1 and 2 as connecting the two confronting flanges 34 together. The injection holes 28 are spaced in each part 12, 14 of the clamp ring in such a way as to allow ingress of a sealant compound into the space between each flange bolt 32 and also each bolt clearance hole.

The inner surface 36 of each part 12, 14 of the clamp ring is stepped so that each part 12, 14 is generally T-sectioned. The stepping forms a rib 38 which extends round the inner circumference through which the holes 28 extend. The internal diameter of the rib 38 is nominally larger than the diameter at the outside of the flange connexion bolts 32 (as shown in Fig. 2).

In use, the clamp ring 10 is located relative to the confronting flanges 34 by locating, as a close tolerance sliding fit, the rib 38 between the flanges 34 (as shown in Fig. 2). The rib also serves to enclose substantially the gap between the confronting flanges 34. The bolts 24 are inserted into the lugs 20, 22 and the nuts 26 are tightened up. Sealing compound is then injected through each hole 28 into the joint to make the joint fluid-tight.

As an additional safety measure, bridges 40 are positioned to bridge between the confronting flanges and the clamp ring. In particular, one end of each bridge bears against a surface 42 of the clamp ring, and the other end bears against a surface 44 of the substantially adjacent flange 34. The bridges 40 are arranged in flanking relationship to the clamp ring. Each bridge has a clearance hole 42 formed in it so as to receive a clamping bolt 45 which cooperates with a nut 46 to clamp the bridge onto and against the clamp ring and one of the confronting flanges. Thus, a tension load is applied to the flanges to reinforce the loading provided by the flange bolts 32.

The addition of the bridge provides a safety feature to the clamp ring and leak sealing procedure, in particular by supporting the flange bolt 32 against any additional load acting within the cavity formed by the clamp ring and the gasket 50, which may be created by escape of fluid from the pipeline via its defective gasket or from the injection of the sealant compound. Relative movement of the flanges is thus prevented and an improved fluid-tight joint is obtained.

Claims (14)

1. A method of forming a fluid-tight joint between two flanged pipe ends or other structures having annular flanges in confronting spaced relationship which comprises positioning relative to the space between the flanges cooperating clamp members substantially to close that space, providing separation restraint for the flanges by way of bridge parts associated with the clamp members and extending over and bearing against non-opposed faces of the confronting flanges, and injecting sealant compound into the space between the flanges to form a fluid-tight seal between the parts forming the joint.

2. A method as claimed in claim 1, using clamp members that engage and enter between edges of the confronting flanges.

3. A coupling or set of parts suitable for carrying out the method as claimed in claim 1 or 2, comprising cooperating clamp members to fit about a space between confronting flanges or the like and associated bridge parts each to engage over a said flange.

4. A coupling as claimed in claim 3, wherein the bridge parts are members separate from the clamp members but secured or securable relative thereto.

5. A coupling as claimed in claim 4, wherein the bridge members are secured or securable to the clamp members by bolting.

6. A coupling as claimed in claim 5, wherein the bridge members as registering pairs, one of each pair to each side of the clamp member, are secured or securable together through the clamp members by common bolting.

7. A coupling as claimed in any one of claims 3 to 6, wherein the cooperating clamp members are of generally T-section of which a stem fits between confronting said flanges.

8. A coupling as claimed in claim 7, wherein each part has sloping shoulders to fit wider spaces, and a thick head to take bridge member bolt holes.

9. A coupling as claimed in any one of claims 3 to 8, wherein the clamp members are two semi-circular parts having end abutment faces aligned with respect to a diameter of the ring formed by the parts.

10. A coupling as claimed in any one of claims 3 to 9, wherein the clamp members afford passageways through to the space between the flanges for sealant injection.

11. A coupling as claimed in claim 10, wherein said passageways comprise a plurality of bores, each adapted to receive an injection nut, and extending radially inwardly from an outer surface of a clamping member.

12. A coupling as claimed in any one of claims 3 to 11, wherein the clamp members are secured end-to-end and the bridge members also bear directly on the clamp members.

13. A coupling as claimed in claim 12, wherein the clamp members have lugs for securement end-to-end by clamping bolts.

14. A coupling as claimed in claim 10 or 11, wherein the clamping members are inserts indirectly secured end-to-end by outer members.