GB2072790A

GB2072790A - Pipe leak repair muff

Info

Publication number: GB2072790A
Application number: GB8008691A
Authority: GB
Original assignee: E Peart and Co Ltd
Current assignee: E Peart and Co Ltd
Priority date: 1980-03-14
Filing date: 1980-03-14
Publication date: 1981-10-07
Also published as: GB2072790B

Abstract

A leak repair muff comprises two hemicylindrical body portions 2a and 2b which can be clamped together onto a pipe 1 and include end seals 3 with flexible but relatively harder end seal pipe followers 4 which have lips 8 initially holding the end seals 3 out of contact with the pipe until the muff is tightly clamped down onto the pipe whereupon the seals are compressed axially and radially so as to be extruded longitudinally between the interior of the muff body and the exterior of the pipe to seal the area of a leak 1a contained within the body 2. The followers 4 may comprise two semi-circular components having a frusto-conical camming surface 6. In an alternative emodiment (Fig. 8 not shown) the surface 6 extends radially of the pipe 1 and the seals 3 are compressed by screw (23) lying axially of the pipe. <IMAGE>

Description

SPECIFICATION Pipe leak repair muff The present invention relates to a pipe leak repair muff which provides a sealed enclosure around a pipe leak, to prevent further loss of liquid or gas from the pipe.

In accordance with the present invention we provide a pipe leak repair muff comprising a tubular muff body composed of a plurality of segmental body portions; means for clamping the segmental muff body portions together about a pipe; side seals effective, upon clamping of the segmental muff body portions, to seal the longitudinally extending joints between adjacent said segmental body portions; end seals arranged, in use, to extend around the body portion in engagement with a part of the radially inwardly facing surface of the body; flexible end seal followers arranged to extend, in use, around the body adjacent to and in contact with the end seals, each end follower having an annular lip extending axially of the end seal follower adjacent the radially innermost part of the end seal follower and adapted to extend axially along at least a part of the radially inwardly facing surface of the associated end seal so as to be capable, in use, of maintaining an associated one of said end seals out of contact with a pipe exterior which, by virtue of the flexibility of the follower, the follower lip may intimately engage; and means effective to displace the end seal pipe followers axially of the muff body to compress the end seals axially on clamping of the muff.

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawings in which:~ FIGURE 1 is a side elevational, partly sectional, view of a pipe leak repair muff in accordance with the present invention, before the clamp is tightened; FIGURE 2 is a view corresponding to Figure 1 but showing the arrangement after tightening of the muff; FIGURE 3A is a composite view showing on the righthand side a section taken on the line 3-3 of Figure 1, and on the lefthand side an end elevational view of the muff of Figure 1 as viewed from the left; FIGURE 3B is a detail of the side seal arrangement shown in Figure 3A;; FIGURES 4A and 4B are views corresponding to Figures 3A and 3B but showing the configuration after the muff has been clamped onto the leaking pipe; FIGURE 5 is a longitudinal sectional view of the end seal follower used with the muff of Figure 1, and taken on the section line V-V of Figure 6; FIGURE 6 is an end elevational view of the end seal follower shown in Figure 5; FIGURE 7A is a top plan view of the side seal follower shown in Figures 1 to 4, when viewed along the direction of arrow 7 shown in Figure 4A; FIGURE 7B is a side elevational view of the side seal follower shown in Figure 7A; FIGURE 7C is an end elevational view of the side seal follower shown in Figures 7A and 7B; and FIGURE 8 is a view corresponding to Figure 1 but showing an alternative embodiment of leak repair muff in accordance with the present invention.

Referring now to Figures 1 to 7, there can be seen a pipe leak repair muff engaged around a pipe 1 having a schematically illustrated fracture 1 a to typify the leak. The muff body 2 comprises two hemi-cylindrical muff body members 2a, 2b which can be drawn together to clamp onto the exterior of the pipe 1, and in so doing cause compression of two soft annular end seals 3 disposed one at each end of the muff, and of four longitudinally extending side seals 1 5 to be described later with references to Figures 4A, 4B, 5A and 5B.

Each relatively soft end seal 3 sits on a respective end seal pipe follower 4 which is in the form of two semi-circular follower components which together form an annular follower body sitting on the cylindrical exterior of the pipe 1 at the respective end of the muff. The end seal 3 is similarly in the form of two semi-circular portions.

Each body shell half 2a, 2b has at each end one half of each end seal 3 glued in place, and one half of each end follower 4 glued to the thus captive end seal half. The shell halves 2a, 2b can thus be assembled, complete with end seals 3 and followers 4, onto the pipe 1 at any location remote from both ends of the pipe I (as will usually be necessary).Figure 1 shows four chordally extending holes 5 on one side of the muff, complimented by a further set of four slic#lThtl larger, stepped apertures (not shown) on the other side of the clamp, in which holes bolts 13 are engaged in order to draw together the top body half 2a and the bottom body half 2b ol th6 muff body and thereby to compress the end seals and the side seals.

As shown clearly in Figures 1 and 2, the particular embodiment of end seal pipe follower 4 used in this embodiment of ieatx repair muff has a frusto-conical rear surface 6 which conforms with a frusto-conical wall 7 of an annular groove machined in the two body halves 2a and 2b of the clamp body 2.The engagement o this frustoconical surface 6 of each end seal pipe follower 4 with the corresponding frusto-conical wells 7 of each of the annular grooves in the muff body 2 results in movement of the two end seal pipe followers 4 towards one another as the two muff body halves 2a and 2b of the muff are pulled together by tightening of the bolts 13 in the holes.

Before the muff body halves 2a, 2b are drawn together, each of the end seals 3 is held out of contact with the cylindrical exterior of the pipe 1 by virtue of a lip 8 formed on the associated end seal pipe follower. Thus, before the muff body halves 2a, 2b are clamped together, and while they are then loosely held in the Figure 1 configuration, it is possible for the entire muff to be moved axially along the pipe from a first location where it is convenient to assemble the muff loosely on the pipe exterior to a second location where the bolts 13 are to be tightened in order to achieve sealing of the muff on the pipe exterior.

As the muff body halves 2a and 2b are drawn together, the radially outermost portion of each of the end seal pipe followers 4 comes closer to the radially outer cylindrical wall (i.e. the floor) of the groove which receives the seal 3 and seal follower 4, and thus diminishes the space 9 into which, in any case, the relatively soft material of the respective end seal 3 is caused to extrude by the effective radial compression of each seal as the respective body half 2a, 2b closes down onto the pipe exterior.

As can be seen in Figure 1, the axially inwardly facing face 1 1 of each end seal 3 is flat and adheres to a flat side wall of the groove in the muff body 2. Thus the two end seals 3 will be compressed both radially as the muff body halves 2a and 2b are drawn together and axially due to the wedging action of the frusto-conical surfaces 6 driving the two end seal pipe followers 4 axially inwardly towards one another. This causes both extrusion of the radially outer part of the end seal 3 into the gap 9, so as substantially to fill the gap, and also extrusion both radially inwardly and axially inwardly onto the cylindrical exterior of the pipe 1 near the lip 8.This serves two purposes, namely (a) the filling of the ends of the chamber 12 between the pipe exterior and the interior of the muff body 2 and (b) pressing the lip 8 of the seal follower more firmly into contact with the pipe exterior so making it substantially impossible for the high pressure which may build up in the chamber 12 around the leak from forcing material of the seal 3 to become extended along the now eliminated clearance between the follower lip 8 and the cylindrical pipe exterior. Both of these actions serve to achieve an effective seal which will prevent fluid under pressure in the chamber 12 from being able to escape.

As will be appreciated from the above, the muff body 2 is formed in two separate halves 2a, 2b which at their junction could provide a leakage path for the fluid contained by the compressed end seals 3 of Figure 2. To further contain any leakage fluid in the chamber 12, side seals are formed in the muff body halves 2a, 2b and are located on the opposing faces of the two muff body halves 2a and 2b aa can clearly be seen from Figures 3A and 4A. figure 3A shows the arrangement before the two muff body halves have been clamped tightly together, i.e.

corresponding to the configuration depicted by the longitudinal section of Figure 1, and Figure 4A shows the corresponding configuration after the muff has been tightly clamped to the configuration depicted by the longitudinal section of Figure 2.

The sectional views of Figures 3A and 4A are both taken through one of the four muff clamping screws 13 which are arranged along the junction on one of the pairs of opposing sides of the muff body halves 2a and 26. A further set of four bolts 13 will be located on the lefthand side of Figures 3A and 4A but only the shank of the first bolt 13 (the bolt in the righthand hole 4 of Figure 1) can be seen on the lefthand side of Figure 3A because the lefthand side of the drawing is in elevational form rather than sectional.

As can be seen clearly from Figures 3A and 4A, each of the holes 5 shown in the lower half of Figures 1 and 2 is a tapped hole to receive the shank of the clamping bolt 13 whereas a clearance hole 5b coaxial with the hole 5 is formed in the upper muff body half 2a and coaxial with this hole 5b is a further hole 5a which is wide enough to accommodate the head of the bolt 13.

Thus when the clamping bolt 13 is tightened down, its head bears downwardly on the washer 14, and thus pulls the upper muff body portion 2a downwardly towards the lower muff body portion 26. Tightening of the further set of clamping bolts 13 on the lefthand side of Figure 3A will achieve an exactly similar effect, although in order to simplify construction of the muff body halves, the holes 5a and 5b (not shown) appearing on the lefthand side of the body 2 in Figure 3A may be in the lower body portion 2b and the holes 5 will then be in the upper portion 2a. Alternatively the body shell portion 2a may have four holes 5a, 5b on each side and the other body shell portion may have two arrays of four holes 5.

The two longitudinal side seals 15 and their respective side seal followers 16 are more clearly illustrated in the detail comprising Figure 3B, and the way in which these side seals 1 5 deform when the opposing faces of the muff body halves 2a and 2b are drawn together by tightening of the clamping bolts 13 is more clearly illustrated in the detail view comprising Figure 4B.

From Figures 3B and 4B it can be appreciated that each of the two opposing faces of the muff body halves at each side of the body 2 is stepped and comprises a first surface portion 1 7a and a second surface portion 1 7b lying radially outwardly of the groove in which the respective side seal 15 is adhesively located.

Each of the side seal followers 16 is of Lshaped cross-section and is shown in more detail in Figures 7A, 7B and 7C. From these latter Figures it will be appreciated that one wall 1.6a of the follower extends the full length of the follower 1 6 whereas the other wall 1 6b is cut short so as to provide end recesses into which the end seals 3 can fit in order to provide a fluid-tight joint where the side seals 15 meet the end seals 3, when the clamp has been tightened into the configuration depicted by Figures 2, 4A and 4B. In this configuration the face 11 at each end of each end seal 3 abuts sealingly against the adjacent ends of the adjacent side seals 15. The rectangular crosssection side seals 15 have a length equivalent to the length of the wall 1 6b as shown in Figure 7A.

When the muff of Figures 3A and 38 is tightened by screwing up the clamping bolts 13, the side seals 1 5 are extruded laterally to fill the gaps 18 and also extruded both laterally and radially inwardly in order to come into contact with one another and to creep radially inwardly along the space between the opposing faces 1 7a of the muff body portions 2a and 26. In this way the side seals 15 prevent any radially outward seepage of fluid from the chamber 12 at the side joints of the muff in the tightened configuration.

The side seal followers 16 are glued to the respective side seals 15 and are preferably made from the same material as the end seal pipe followers 4, which in this case is a plastic material which is sufficiently hard to be able to exert the required camming action of the frusto-conical surfaces 6 and 7 of the end seal pipe followers 4 and the muff body 2, respectively. In order to ensure that the lips 8 are capable of very closely following the cylindrical exterior of the pipe 1, the wedge-shaped body portions 20 (Figure 6) of the end seal pipe follower 4 are slit at 19 along equiangularly spaced radial planes, thus leaving the two halves of each end follower 4 (which come close together to leave two diametrically opposed gaps 12) relatively flexible and able to accommodate either slight eccentricities or slight variations in diameter of the pipe 1 on which the follower is to fit.It will be understood that if the diameter of the pipe 1 is slightly undersized then the curvature required of the follower 4 is likely to be tighter, and equally if the mean diameter is correct but the shape of the pipe cross-section slightly eccentric (i.e. ovalled) then in each case the flexible follower 4 will be able to engage the pipe with its lip 8 very close to the exterior of the pipe 1.

Another characteristic of the end seal pipe follower 4 is that the lip 8 is arranged to hold the rectangular cross-section respective end seal 3 away from contact with the exterior of the pipe 1, and consequently once the muff has been assembled into the configuration depicted by the longitudinal sectional elevational view of Figure 1 and the transverse sectional elevational view of Figures 3A and 38, the entire muff is able to be moved axially along the pipe to a location straddling the rupture 1 a (Figure 1).This has the advantage that where the rupture has occurred at a location which does not provide much surrounding space for accessibility to assemble the muff, the muff can be assembled on a remote part of the same pipe and can be moved axially along the pipe into the correct location at which the only further manipulation necessary is tightening of the various clamping bolts 13 (Figure 3A), for example using a hexagonal key which does not require much surrounding access space. This sliding movement of the muff along the pipe can occur without any contact of either the side seal 15 or, more importantly, the end seals 3 with the pipe, and consequently without any risk of damage to the vital radially inwardly facing sealing surfaces of the end seals 3.

Any suitable elastomeric material, for example Buna-N (R.T.M.), can be used for the side seals 1 5 and the end seals 3, and equally any suitable material can be used for the side followers 16. The material used for the end followers 4 can be any one of a number of possible materials, but the requirement of flexibility of the end seal pipe followers will avoid the use of any hard metals.

Soft metals or plastics materials can be used provided, as indicated above, they are hard enough to exert the required camming action to cause the followers to move radially inwardly as the muff body 2 is tightened.

It is envisaged that the sealing action provided by the end seals 3 and the side seals 1 5 will be adequate to withstand the likely pressures to be encountered in the chamber 12, although if necessary the ends of the muff can be welded to the pipe surface once the muff has been tightly clamped down.

An alternative embodiment of the muff is illustrated in Figure 8, which corresponds to Figure 2. The essential difference between the two different embodiments can be clearly appreciated by reference to Figures 1 and 8.

Whereas in Figure 1 the end seal pipe follower 4 was of frusto-conical form on its rear surface at each end of the body 2, in the body 2' of Figure 8 the groove accommodating the end seal pipe follower 24 is of rectangular cross-section and is at each end of the muff body 2' communicated with the exterior of the axially outwardly facing end surface 21 of the muff body by way of an array of twelve equiangularly disposed axially extending threaded bores 22 each receiving a grub screw 23 which can be rotated, from the outside, in order to screw it axially inwardly along the bore 22 to press the end seal pipe follower 24 leftwardly and thereby to compress the end seal 3 axially.Before compression, the end seal 3 occupies the same position as the end seal 3 of Figure 1, but during the tightening of the clamp it is necessary to carry out a two-stage process comprising firstly tightening the various clamping bolts 13 (Figures 3A and 4A) to compress the seal radially, and then to rotate the twenty four compression screws 23 in order to compress the end seals axially and to cause the seal material to extrude axially along the gap between the land 25 on the interior of the body 2' and the external cylindrical surface of the pipe 1.

Apart from the fact that the end seal pipe followers 24 are shaped differently to the end seal pipe followers 4 of Figure 1, and the fact that the additional screws 23 are necessary in order to compress the end seals 3 axially, the construction and functioning of the muff illustrated in Figure 8 is in all other respects similar to those of the embodiment of Figures 1 to 7.

Because there is in the Figure 8 embodiment, no longer quite the same requirement on hardness of the follower in order to achieve the camming action necessary in the embodiment of Figures 1 to 7, the followers 24 in the Figure 8 embodiment can be of a slightly softer material, although they must still be sufficiently strong to withstand and spread the effects of localised compression at various areas spaced around the axis of the pipe, in such a way as to provide a substantially uniform compression of the end seal 3.

However, the non-tapering end seal pipe followers 24 of Figure 8 will of course have slits corresponding to the slits 19 of Figure 6, in order to enhance the flexibility of the followers.

Claims

1. A pipe leak repair muff comprising a tubular muff body composed of a plurality of segmental body portions; means for clamping the segmental muff body portions together about a pipe, side seals effective, upon clamping of the segmental muff body portions, to seal the longitudinally extending joints between adjacent said segmental body portions; end seals arranged, in use, to extend around the body portion in engagement with a part of the radially inwardly facing surface of the body; flexible end seal followers arranged to extend, in use, around the body adjacent to and in contact with the end seals, each end follower having an annular lip extending axially of the end seal follower adjacent the radially innermost part of the end seal follower and adapted to extend axially along at least a part of the radially inwardly facing surface of the associated end seal so as to be capable, in use, of maintaining an associated one of said end seals out of contact with a pipe exterior which, by virtue of the flexibility of the follower, the follower lip may intimately engage; and means effective to displace the end seal pipe followers axially of the muff body to compress the end seals axially on clamping of the muff.

2. A leak repair muff according to claim 1, wherein said means effective to displace the end seal pipe followers axially comprise a plurality of thrust members extending in array around said body and operable to drive the associated end seal pipe follower axially of the body.

3. A leak repair muff according to claim 2, wherein said thrust members comprise screws engaged in threaded bores extending axially of the body at the ends thereof.

4. A leak repair muff according to claim 1, wherein said means effective to displace the end seal pipe followers axially upon clamping of the muff comprise inter-engaging camming surfaces on each end seal pipe follower and on said body in order to ensure that as the segmental muff body portions are drawn together to clamp the muff body on a pipe, each end seal pipe follower is urged axially in a direction to compress the associated end seal.

5. A leak repair muff according to claim 4, wherein said camming surfaces of the body and the follower are frusto-conical.

6. A leak repair muff according to any one of the preceding claims, wherein each end seal pipe follower has longitudinally extending slits effective to enhance the flexibility of the end follower.

7. A leak repair clamp according to claim 6, wherein said slits are formed on the radially outer part of each end seal pipe follower.

8. A leak repair muff according to any one of the preceding claims, wherein said lip has a radially inwardly facing surface flush with the rest of the radially inwardly facing surface of the respective end seal pipe follower.

9. A leak repair muff according to any one of the preceding claims, wherein the muff body comprises two said segmental body portions and each end seal pipe follower comprises two semicircular follower portions.

10. A leak repair muff according to any one of the preceding claims, wherein said side seals comprise: in each of the two faces of a pair of adjacent faces defined between adjacent ones of said segmental body portions in the assembled muff body, a rectilinear seal extending along a direction parallel to the axis of said muff body; and a side seal follower of L-shaped cross-section such that when the adjacent said segmental body portions are assembled together each of the followers is arranged so that, when viewed in cross-section, one of its limbs is in contact with one of the limbs of the side seal follower of the adjacent segmental body portion and the said one limb of each of the two side seal followers is effective to hold the associated side seal out of contact with the side seal associated with the said other side seal follower.

11. A leak repair muff according to claims 9 and 10, taken together, wherein each of said segmental body portions has adhesively attached at each end a semi-circular portion of a said end seal and adhesively attached along each lateral edge a said rectilinear side seal.

12. A leak repair muff according to claim 1 1, wherein each said adhesively attached end seal portion has a said semi-circular end seal pipe follower adhesively secured in position thereon, and each said adhesively attached side seal has a said side seal follower adhesively secured in position thereon.

13. A leak repair muff according to any one of the preceding claims, wherein said means to draw the segmental body portions together to form the assembled muff body comprise an array of chordally extending clamping bolts.

14. A leak repair muff according to any one of the preceding claims, wherein said end seal pipe followers are made of a plastic material.

15. A leak repair muff according to anyone of the preceding claims, wherein said end seals and side seals are formed of an elastomeric material.

16. A pipe leak repair muff substantially as hereinbefore described with reference to, and as illustrated in Figures 1 to 7, or Figure 8 of the accompanying drawings.