GB2585033A

GB2585033A - Hot bolting clamp

Info

Publication number: GB2585033A
Application number: GB1909109.9A
Authority: GB
Inventors: Hancock Paul
Original assignee: Boltight Ltd
Current assignee: Boltight Ltd
Priority date: 2019-06-25
Filing date: 2019-06-25
Publication date: 2020-12-30
Anticipated expiration: 2039-06-25
Also published as: GB201909109D0; GB2585033A8; GB2585033B

Abstract

A method of replacing a fastener in a pipe coupling, for instance hot bolting. The pipe coupling comprising two pipes 38 each having at their adjacent ends a flange 36a, 36b, and a plurality of fasteners 40, 42 which connect the two flanges and urge the two flanges into sealing engagement with one another. The method comprises mounting a first and second clamp 10 comprising two opposing clamp parts 12a, 12b on the flanges in between two adjacent fasteners and either side of the fastener to be replaced, tightening a clamp element 14 of the clamps to urge the clamp parts together so the flanges are clamped between the clamp parts. Also provided is a hot bolting clamp 10 having two opposing clamp parts 12a, 12b wherein each clamp part has a body portion 16a, 16b which contains an aperture therethrough which a threaded clamp element 14 extends. The threaded clamp element is provided with a right-handed screw thread and a left-handed screw thread for engaging with corresponding screw threads in the aperture associated with each body portion.

Description

Hot Bolting Clamp The present invention relates to a clamp for use in securing the inter-connected flanges of adjacent portions of pipe in a pipe-line, and thus allowing bolts used to fasten the adjacent portions of pipe together to be replaced without compromising the integrity of the coupling between the adjacent portions of pipe.

In pipe-lines such as those carrying water or other liquids, typically the pipe-line is made up of a plurality of pipes which are connected to provide a single fluid flow conduit. Typically each pipe has an annular flange at each end thereof, which flange extends generally perpendicular to the longitudinal axis of the pipe and which is provided with a plurality of apertures or bolt holes.

The adjacent flanges of two adjoining pipes are used to form a pipe coupling, and are connected together by a plurality of flange coupling bolts which each have a stem which extends through one of the bolt holes in adjacent flanges. A nut is then screwed onto the stem and tightened so that the two flanges of the adjacent pipes are clamped tight between the nut and bolt head of the flange coupling bolt. This process is repeated so that each pipe is secured to the adjacent pipe by a plurality of bolts arranged in a generally circular array around the outside of the pipe.

A seal such as a rubber 0-ring is positioned between the two flanges to ensure that fluid can flow along the pipe line and cannot leak out of the pipe-line at the joint.

The pipe coupling bolts are, however, vulnerable to corrosion, and therefore need to be replaced periodically to minimise the risk that a corroded bolt breaks, compromises the integrity of the seal and allows fluid to leak out of the pipe-line. To avoid this, it is possible to close the pipe-line in order to stop the flow of fluid past the respective joint whilst the corroded bolt or bolts are removed and replaced. However, shutting the pipe-line is likely to be costly, and so it is preferable to avoid this by using clamps to maintain the integrity of the joint while the bolt or bolts are replaced. This process is known as hot-bolting, and such clamps are generally known as hot-bolting clamps.

An example of a hot-bolting clamp is sold by Equalizer Flange Integrity Systems Ltd 30 under the name XTEGRITY. This clamp comprises a plurality of pairs of clamp parts, each clamp part in the pair being connected by a single threaded rod which extends through apertures provided in each of the clamp parts. The clamp parts are mounted on the flanges of the pipe coupling so that the two adjacent flanges are positioned between the two clamp parts. The clamping pressure required to maintain the integrity of the pipe coupling is attained by means of two nuts which are threaded onto each end of the threaded rod and screwed down until they push the clamps parts against the flanges with the desired force.

The pairs of clamp parts are joined together to form a complete circle by means of a floating frame. The floating frame comprises two pairs of generally semi-circular frame parts. One end of each of the frame parts in each pair are pivotally connected to allow the frame to be opened up to be placed around a pipeline, whilst connectors are provided at the other ends, to secure the frame in a complete circle when it is closed around the pipeline.

One of the pairs of frame parts is bolted to one clamp pail of each of the pairs of is clamps pails, whilst the other pair of frame parts is bolted to the other clamp pail of each of the pairs of clamp parts. As such, when the clamp parts are clamped to the flanges of a pipe coupling, one of the pairs of frame parts surrounds one of the two coupled pipes, whilst the other pair of frame parts surrounds the other of the two coupled pipes.

The presence of the floating frame means that the clamp assembly can only be used with pipe-lines having flanges with a relatively narrow range of outer diameter. Moreover, as each clamp pail needs to have both an aperture to receive the threaded rod, and an aperture to receive the bolt by means of which the floating frame is secured to the clamp parts, the clamp extends for quite some distance from the flanges of the pipe coupling in a direction generally parallel to the longitudinal axis of the pipe-line. This is not a problem when the coupling is provided between two generally straight pipes, but can make the installation of the clamp difficult if the pipe coupling is close to a bend, in particular a right-angle bend, in the pipe-line.

An alternative hot-bolting clamp is supplied by Hydratight under the name MorSafeTM 30, and described in GB2468976. This is a flange clamp with a pair of opposing clamp parts connected by clamp bolts which are used to pre-load the clamp, and contraholders which work as a back-stop to absorb the pre-load and prevent overloading of the seal between the flanges of the pipe coupling.

The MorSafeTM is supplied with two pairs of semi-circular clamps parts which together, when mounted on the pipe coupling form a complete circle around the flanges. The number of clamp bolts in each pair of clamp parts depends on the number of bolts in the pipe coupling. A version for 4-bolted flanges has two clamp bolts in each pair of clamp parts, whilst versions with four and six clamp bolts in each pair of clamp parts are also available.

The contraholders are grub screws which are mounted in apertures provided in one clamp part of each pair, and butt up against the other clamp part in the pair. To ensure that the load across each clamp bolt is balanced, at least a pair of grub screws is provided for each pair of clamp parts. Typically, however, a pair of grub screws is provided for every clamp bolt, with each clamp bolt being located between two grub screws.

In use, the clamp parts are fitted around the flange coupling, and nuts mounted on the clamp bolts tightened until the clamp parts have full contact with the pipe flanges. The contraholders are then adjusted so that they are in contact with both clamp parts, before the nuts mounted on the clamp bolts are tightened further to pre-load the clamp to a higher force level than the existing force level of the flange coupling bolts. The flange coupling bolts can then be changed and the new coupling bolts preloaded to the required level, after which, the flange clamp can be removed.

The use of semi-circular clamp parts also means that it is necessary to provide a range of clamps to cover the full range of pipe outer diameters.

It is an object of the present invention to provide an alternative configuration of hot bolting clamp.

According to a first aspect of the invention we provide a method of replacing a fastener in a pipe coupling, the pipe coupling comprising two pipes each having at their adjacent ends a radially outwardly extending flange, and a plurality of fasteners which connect the two flanges and urge the two flanges into sealing engagement with one another, the method including mounting a first clamp comprising two opposing clamp parts on the flanges in between two adjacent fasteners and next to the fastener to be replaced, tightening a clamp element of the first clamp to urge the clamp parts together so the flanges are clamped between the clamp parts, and mounting a second clamp comprising two opposing clamp parts on the flanges in s between the two adjacent fasteners and next to the fastener to be replaced on the other side of the fastener to be replaced to the first clamp part, tightening a clamp element of the second clamp to urge the clamp parts together so the flanges are clamped between the clamp parts, wherein the first and second clamps are separate to the extent that their separation is not fixed, and they can be mounted on the flanges one after the other.

The method may further comprise, after mounting the clamps on the pipe coupling, fastening a strap or belt around the radially outwardly facing surfaces of one of the clamp parts of both the first and second clamps. In this case, the method may also comprise, after mounting the clamps on the pipe coupling, fastening a strap or belt is around the radially outwardly facing surfaces of the other one of the clamp parts of both the first and second clamp.

The method may alternatively comprise, mounting the clamps on a strap or belt such that movement of the clamps along the strap or belt is permitted, before mounting the clamps on the pipe coupling, and after mounting the clamps on the pipe coupling, tightening the strap or belt around the radially outward facing surfaces of the clamps.

The method may include mounted one clamp in every space between adjacent fasteners around the pipe coupling.

Each clamp may include only one clamp element.

The step of tightening the clamp element may include rotating the clamp element about its longitudinal axis.

The method may further include, after tightening the clamp element, mounting a lock nut on an end of the clamp element to substantially prevent any further rotation of the clamp element about its longitudinal axis.

Each clamp part may have a body portion which contains an aperture through which the clamp element extends, and the clamp element may have a longitudinal axis and be provided with two threaded portions, one of which carries a right-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of one of the clamp parts, and the other of which carries a left-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of the other of the clamp parts, wherein the step of tightening the clamp element may include rotating the clamp element about its longitudinal axis.

io The step of tightening the clamp element may include engaging a tool such as a wrench with a tool engagement formation provided on an end of the clamp element, and using the tool to rotate the clamp element about its longitudinal axis.

The method may further include inserting an elongate reaction element such as a rod or bar, into a socket provided on one of the clamp parts so that a longitudinal is axis of the reaction element extends generally perpendicular to the longitudinal axis of the clamp element, and exerting a force on the reaction bar during tightening of the clamp element to prevent the clamp part from rotating with the clamp element.

According to a second aspect of the invention we provide a system for replacing a fastener in a pipe coupling, the pipe coupling comprising two pipes each having at their adjacent ends a radially outwardly extending flange, and a plurality of fasteners which connect the two flanges and urge the two flanges into sealing engagement with one another, the system including a first clamp and a second clamp, each having two opposing clamp parts which are connected by a single clamp element which is operable to move the clamp parts to increase or decrease their separation, wherein the first and second clamps are separate to the extent that their separation is not fixed, and they can be mounted on the flanges one after the other.

Each clamp part may have a body portion which contains an aperture through which the clamp element extends, and the clamp element may have a longitudinal axis and be provided with two threaded portions, one of which carries a right-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of one of the clamp parts, and the other of which carries a left-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of the other of the clamp parts The threaded portions of the clamp element may be separated by an unthreaded portion.

Each clamp part may further comprise a flange engagement portion which extends from the body portion and which provides a clamping face which is generally perpendicular to the longitudinal axis of the threaded clamp element.

Each clamp may further comprise a guide which maintains the clamp parts in an aligned position in which the clamp face of one clamp part is directly aligned with the io clamping face of the other clamp part whilst the clamp element is operated to alter the separation of the clamp parts.

The clamp element may have a first end which is provided with a tool engagement formation which is adapted, in use, to be engaged with a tool to assist in rotating the clamp element about its longitudinal axis.

is The system may further comprise a retaining strap or belt which can be fastened around the radially outwardly facing surfaces of one of the clamp parts of both the first and second clamps. In this case, the system may also comprise a further strap or belt which can be fastened around the radially outwardly facing surfaces of the other one of the clamp parts of both the first and second clamp.

The clamp may further comprise a strap or belt retainer whereby the clamps may be mounted on a strap or belt such that movement of the clamps along the strap or belt is permitted.

According to a third aspect of the invention we provide a hot bolting clamp having two opposing clamp parts which are connected by a threaded clamp element which is operable to move the clamp parts to increase or decrease their separation, wherein each clamp part has a body portion which contains an aperture through which the threaded clamp element extends, and the threaded clamp element is provided with two threaded portions, one of which carries a right-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of one of the clamp parts, and the other of which carries a left-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of the other of the clamp parts.

The threaded portions of the threaded clamp element may be separated by an s unthreaded portion.

The hot bolting clamp may further comprise a guide which maintains the clamp parts in an aligned position in which the clamp face of one clamp part is directly aligned with the clamping face of the other clamp part whilst the threaded clamp element is operated to alter the separation of the clamp parts.

The threaded clamp element may have a first end which is provided with a tool engagement formation which is adapted, in use, to be engaged with a tool to assist in rotating the threaded clamp element about its longitudinal axis.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying figures, of which FIGURE 1 shows an perspective view of an embodiment hot bolting clamp according to the third aspect of the invention, suitable for use in the method according to the first aspect of the invention, and suitable for use in the system according to the second aspect of the invention, FIGURE 2 shows an alternatively perspective view of the hot bolting clamp illustrated in Figure 1, and FIGURE 3 shows the hot bolting clamp of figure 1 in use, clamped on the flanges of a bolted pipe coupling.

Referring now to Figures 1 and 2, there is shown a hot bolting clamp 10 having two opposing clamp parts 12a, 12b which are connected by a clamp element 14. The clamp element 14 is operable to move the two opposing clamp parts 12a, 12b towards or away from one another. In this embodiment of the invention, the clamp element is a threaded rod, hereinafter referred to as the threaded clamp element.

Each clamp part 12a, 12b has a body portion 16a, 16b which contains an aperture through which the threaded clamp element 14 extends. Each clamp part 12a, 12b further includes a flange engagement portion 18a, 18b which extends from the body portion 16a, 16b and provides a clamping face 20a, 20b which is generally perpendicular to the longitudinal axis A of the threaded clamp element 14. The clamp parts are arranged so that the clamping face 20a of one clamp part 12a faces the clamping face 20b of the other clamp part 12b.

io In this embodiment the depth of the body portion 16a, 16b of each clamp part 12a, 12b is greater than the depth of the engagement portion 18a, 18b (the depth being taken in the direction generally parallel to the axis A), with each clamp part 12a, 12b having one generally planar face which is generally perpendicular to axis A which is part of both the body portion 16a, 16b and the flange engagement portion 18a, 18b, is and an opposite stepped face, having a step between the thicker body portion 16a, 16b and the shallower flange engagement portion 18a, 18b. The clamping face 20a, 20b is part of the stepped face.

The threaded clamp element 14 has a first end which is provided with a tool engagement formation 22 which is suitable for engaging with a tool, such as a spanner or wrench, for rotating the threaded clamp element 14 relative to the clamp parts 12a, 12b about its longitudinal axis A. In this example, the tool engagement formation 22 is a stud with a square transverse cross-section. Any other suitable configuration of tool engagement formation 22, such as a hexagonal or star-shaped head.

The threaded clamp element 14 is also provided with two separate threaded portions 24a, 24b. Although not essential, in this embodiment of the invention, the threaded clamp element 14 has an unthreaded portion 24c which separates the two separate threaded portions 24a, 24b.

One threaded portion 24a carries a right-handed screw thread which engages with a 30 corresponding screw thread provided around the aperture in the body portion 18a of one clamp part 12a. The other threaded portion 24b carries a left-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion 18b of the other clamp part 12b. As a result of the provision of two separate, oppositely directed, screw threads. rotation of the threaded clamp element 14 relative to the clamp parts 12a, 12b about its longitudinal axis A in a first direction causes the clamp parts 12a, 12b to move together so that the separation of the clamp faces 20a, 20b decreases, whilst rotation of the threaded clamp element 14 in the opposite direction causes the clamp parts 12a, 12b to move away from one another so that the separation of the clamp faces 20a, 20b increases.

The clamp 10 may therefore be used in hot bolting a pipe coupling of the type illustrated in Figure 3 and comprising two coupling flanges 36a, 36b extending radially outwardly from the adjacent ends of two pipes 38, the two flanges 36a, 36b being bolted together using a plurality of coupling bolts 40a, 40b, 40c, 40d and nuts 42a, 42b, 42c, 42d which are located in bolt-holes spaced around the outer circumference of the pipes 38. In the example illustrated in Figure 3, four coupling is bolts 40a, 40b, 40c, 40d are provided, but it will be appreciated that this need not be the case, and fewer or (more typically) more coupling bolts may be used.

Each clamp 10 is mounted on the coupling flanges 36a, 36b between two adjacent coupling bolts 40a, 40b, 40c, 40d so that the coupling flanges 36a, 36b lie between the engagement portions 18a, 18b of the two clamp parts 12a, 12b. A torque wrench is then used to rotate the threaded clamp element 14 about its longitudinal axis A relative to the clamp parts 12a, 12b in the direction in which the clamp parts 12a, 12b move together, until the clamp faces 20a, 20b of the two clamp parts 12a, 12b engage with the flanges 36a, 36b. This rotation of the threaded clamp element 14 is continued until the clamp parts 12a, 12b are applying the required degree of compressive force to the flanges 36a, 36b to maintain the integrity of the pipe coupling when one or both of the adjacent coupling bolts 40a, 40b, 40c, 40d are removed. If desired, further clamps 10 may be mounted on the flanges 36a, 36b in exactly the same way.

Any corroded or damaged coupling bolts 40a, 40b, 40c, 40d are then removed and replaced with new bolts in the conventional manner. Once this process is complete, each clamp 10 is removed by using a torque wrench to rotate the threaded clamp 14 element about axis A in the opposite direction, to release the compressive force applied by the clamp parts 12a, 12b and move the clamp parts 12a, 21b away from one another.

It will be appreciated that, in the inventive clamp 10, the compressive force required to maintain the integrity of the pipe coupling is provided by loading of the threaded connections between the body portions 16a, 16b of the clamp parts 12a, 12b and the threaded clamp element 14. In contrast, in the prior art hot-bolting clamps described above the compressive force is provided by one or more nuts, and load transfer across the screw thread between the nut(s) and bolt / threaded rod. For a given compressive force applied to the pipe coupling, the pressure on the screw threads can be minimised by maximising the length of the screw thread. The length of the screw thread can be maximised by maximising the depth of the aperture around which it is provided. This means depth of the nut or nuts in the prior art arrangement, whilst in the inventive clamp 10, the full depth of the clamp parts 12a, 12b can be utilized without adding the additional bulk of one or more nuts.

is This assists in minimising the dimensions of the clamp 10 which enables the clamp to be used in conjunction with a pipe coupling close to a bend in one or both of the coupled pipes.

Where only one coupling bolt 40a, 40b, 40c, 40d in the pipe coupling is to be replaced, preferably two clamps are used -one mounted on the flanges on each side of the coupling bolt 40a, 40b, 40c, 40d in question. If more than one coupling bolt 40a, 40b, 40c, 40d is to be replaced, a clamp 10 is mounted on the flanges on each side of every coupling bolt 40a, 40b, 40c, 40d to be replaced.

It will be appreciated that, because entirely separate clamps 10 are placed on either side of each bolt to be replaced in between the coupling bolts 40a, 40b, 40c, 40d in question and the two adjacent coupling bolts 40a, 40b, 40c, 40d the inventive system is not restricted to use with a particular diameter of pipe coupling. As such, a single set of clamps 10 according to the invention can be used with any diameter of pipe coupling.

It should also be appreciated, that the inventive clamp 10 could equally be used if 30 one or more of the nuts 42a, 42b, 42c, 42d on the coupling bolts 40a, 40b, 40c, 40d is to be replaced instead of or as well as the bolts 40a, 40b, 40c, 40d. Similarly, the invention is not restricted to use in relation to a pipe coupling in which the fasteners used to connect the coupling flanges 36am 36b are nuts and bolts -any other suitable fastener could be used.

Whilst not essential for operation of the clamp 10, in this embodiment, once the threaded clamp element 14 has been rotated to produce the desired compressive force, a locking nut 26 is mounted on one of the threaded portions 24a, 24b at one end of the threaded clamp element 14. The locking nut 26 does not play a part in loading the clamp 10, but merely acts to prevent any unintended rotation of the threaded clamp element 14 about its longitudinal axis A, which could release the pressure applied to the pipe coupling during the removal and replacement of the coupling bolts 40a, 40b, 40c, 40d and/or nuts 42a, 42b, 42c, 42d. This may achieved by placing a double-acting lockwasher 28, such as the one described in W02011/161387.

In this embodiment, the clamp 10 is further provided with a guide which maintains is the clamp parts 12a, 12b in an aligned position in which the clamp face 20a of one clamp part 12a is directly aligned with the clamp face 20b of the other clamp part 12b whilst the threaded clamp element is operated to move the clamp parts 12a, 12b.

In this example, the guide is provided by two guide rods 30a, 30b which each extend from one of two guide apertures provided in the body portion 16a of one of the clamp parts 12a, to one of two guide apertures provided in the body portion 16b of the other clamp part 12b. The longitudinal axis of each of the guide rods 30a, 30b is parallel to the longitudinal axis A of the threaded clamp element 14. The guide rods 30a, 30b fit sufficiently loosely in their respective apertures that they can slide into and out of the apertures (without ever coming out of the aperture completely) as the clamp parts 12a, 12b move together or away from one another.

Moreover, in this embodiment of clamp 10, the two clamp parts 12a, 12b are each provided with a reaction bar socket 32a, 32b, which are visible in Figure 2 only. The reaction bar socket 32a, 32b comprises a generally cylindrical aperture provided in an end face of the body portion 16a, 16b of the clamp part 12a, 12b. A longitudinal axis B of each clamp part 12a 12b between from body portions 16a, 16b and the flange engagement portions 18a, 18b generally perpendicular to the longitudinal axis A of the threaded clamping element 14, and the cylinder axis C of each reaction bar socket 32a, 32b is generally parallel to this longitudinal axis B of each clamp part 12a, 12b.

Whilst tightening the clamp 10 about the flanges of a pipe coupling as described above, a rod, hereinafter referred to a reaction bar, may be inserted into each reaction bar socket 32a, 23b and are held so that they do not rotate, whilst the threaded clamping member 14 is rotated about its longitudinal axis A. By doing this, it is possible to ensure that the clamp parts 12a, 12b do not rotate with the threaded clamping member 14, and instead move together to clamp onto the flanges or io separate to release the clamp force, depending on the direction of the rotational force applied to the threaded clamping member 14. It will be appreciated that, as the guide rods 30a, 30b prevent rotation of one clamp part 12a, relatively to the other 12b, it will be appreciated that it is not necessary to provide a reaction bar socket 32a, 32b in both clamp parts 12a, 12b -the clamp 10 may be tightened with a is reaction bar in a reaction bar socket 32a, 32b on only one of the two clamp parts 12a, 12b in each clamp 10.

As mentioned above, the inventive system involves mounting a plurality of separate clamps on the flanges of a pipe coupling in between pair of adjacent coupling bolts. Once mounted on the flanges in this way, it is possible for a strap or band to used to provide the user with an additional degree of reassurance that the clamps 10 cannot come off the flanges during the hot bolting process.

As such, in this embodiment, the face of the body portion 16a, 16b of each clamp part 12a, 12b which faces radially outwardly relative to the pipe is provided with a strap retaining formation 34a, 34b, the strap retaining formations being adapted to assist in retaining a strap or belt which is wrapped around the body portions 16a, 16b of all the clamps 10 mounted on the pipe coupling, and tightened to substantially prevent any radially outward movement of the clamps 10 relative to the pipe coupling. For each pipe coupling, two straps may be provided -one engaging with the strap retaining formations 34a on the body portions 16a of the clamp parts 12a on one side of the pipe coupling, and one engaging with the strap retaining formations 34b on the body portions 16b of the clamp parts 12b on the other side of the pipe coupling.

In this embodiment, the strap retaining formations 34a, 34b each comprises a pair of generally parallel lips which extend from the body portion 16a, 16b in the opposite direction to the flange engagement portion 18a, 18b and generally perpendicular to the longitudinal axis A of the threaded clamp element 14. The spacing between these lips is greater than the width of the belt or strap and so, in use the belt or strap can be located between the lips, the lips preventing the belt or strap, once tightened, from sliding off the clamp part 12a, 12b.

In an alternative embodiment of the invention, the strap retaining formations could comprise hooks or a loop formation which the strap or belt has to be threaded through before being tightened. Whilst in the preferred embodiment of the invention, the strap or belt is fastened around the clamps 10 once they are mounted on the pipe coupling, in this case, the strap or belts can already be secured to the clamps 10 before they are mounted on the pipe coupling. To ensure that the advantage of the inventive system in accommodating a variety of pipe diameters is realised, however, the belt or strap should be flexible, and the strap retaining formation configured so that each clamp part can slide along the strap or belt to the desired position. Preferably the strap is made from a woven fabric, but it could equally comprises a strip of relatively thin, and therefore flexible, metal sheet.

It will also be appreciated that it is not necessary to use two such belts or straps.

One belt or strap which is wide enough to engage with the radially outwardly facing surface of both clamp parts 12a, 12b of each clamp 10 may be used, or, since both the clamp parts 12a, 12b of each clamp 10 are connected, one belt which engages with only one clamp part 12a of each clamp 10 may be used.

Whilst in this embodiment, the clamp faces 20a, 20b are planar, this need not be the case. For example, the clamp faces 20a, 20b may be convex, i.e. slightly domed, or generally flat but oriented at an angle of slightly more or less than 90° to the longitudinal axis of the threaded clamp element 14. This can mitigate some of the problems associated with fastening the clamp 10 onto a pipe coupling in which the coupling flanges 36a, 36b, or at least the outer surfaces of the coupling flanges 36a, 36b with which the clamp faces 20a, 20b engage, are not completely flat, or are not perfectly perpendicular to the longitudinal axis of the pipe. For example, in some instances, if the coupling bolts 40a, 40b, 40c, 40d are overtightened. Depending on how close the bolt holes are to the pipe 38, this may cause the flanges to splay slightly at their radially outward edges, and the spacing between the outer faces of the flanges 36a, 36b being greater at the radially outward edge of the coupling flanges 36a, 36b than at the portion of the coupling flanges 36a, 36b adjacent the s pipe 38, or the reserve -causing the spacing between the outer faces of the flanges to be less at the radially outward edge of the coupling flanges 36a, 36b than at the portion of the coupling flanges 36a, 36b adjacent the pipe 38. In this case the clamp parts 12a, 12b could be configured so the engagement portions become thicker moving along the engagement portions away from the body portion, or vice versa, so to that the clamp faces 20a, 20b are not perfectly perpendicular to the longitudinal axis A of the threaded clamping element 14.

Claims

CLAIMS1. A method of replacing a fastener in a pipe coupling, the pipe coupling comprising two pipes each having at their adjacent ends a radially outwardly extending flange, and a plurality of fasteners which connect the two flanges and urge the two flanges into sealing engagement with one another, the method including mounting a first clamp comprising two opposing clamp parts on the flanges in between two adjacent fasteners and next to the fastener to be replaced, tightening a clamp element of the first clamp to urge the clamp parts together so the flanges are clamped between the clamp parts, and mounting a second clamp comprising two opposing clamp parts on the flanges in between the two adjacent fasteners and next to the fastener to be replaced on the other side of the fastener to be replaced to the first clamp part, tightening a clamp element of the second clamp to urge the clamp parts together so the flanges are clamped between the clamp parts, wherein the first and second clamps are separate to the extent that their separation is not fixed, and they can be mounted on the flanges one after the other.The method of claim 1 further comprising, after mounting the clamps on the pipe coupling, fastening a strap or belt around the radially outwardly facing surfaces of one of the clamp parts of both the first and second clamps. The method of claim 2 further comprising, after mounting the clamps on the pipe coupling, fastening a further strap or belt around the radially outwardly facing surfaces of the other one of the clamp parts of both the first and second clamp.The method of claim 1 further comprising mounting the clamps on a strap or belt such that movement of the clamps along the strap or belt is permitted, before mounting the clamps on the pipe coupling, and, after clamping ing the clamps on the flanges of the pipe coupling, tightening the strap or belt around the radially outward facing surfaces of the clamps.The method of any preceding claim including mounting one clamp in every space between adjacent fasteners around the pipe coupling.The method of any preceding claim wherein each clamp includes only one clamp element. 2. 3. 4. 5. 6.7. The method of any preceding claim wherein the step of tightening the clamp element includes rotating the clamp element about its longitudinal axis.8. The method of any preceding claim further including, after tightening the clamp element, mounting a lock nut on an end of the clamp element to substantially prevent any further rotation of the clamp element about its longitudinal axis.9. The method of any of claims 7 or 8 wherein each clamp part has a body portion which contains an aperture through which the clamp element extends, and the clamp element has a longitudinal axis and is provided with two threaded portions, one of which carries a right-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of one of the clamp parts, and the other of which carries a left-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of the other of the clamp parts, wherein the step of tightening the clamp element includes rotating the threaded clamp element about its longitudinal axis.10. The method of any preceding claim wherein the step of tightening the clamp element may include engaging a tool with a tool engagement formation provided on an end of the clamp element, and using the tool to rotate the clamp element about its longitudinal axis.11.The method of any preceding claim further comprising inserting an elongate reaction element such as a rod or bar, into a socket provided on one of the clamp parts so that a longitudinal axis of the reaction element extends generally perpendicular to the longitudinal axis of the clamp element, and exerting a force on the reaction bar during tightening of the clamp element to prevent the clamp part from rotating with the clamp element.12.A system for replacing a fastener in a pipe coupling, the pipe coupling comprising two pipes each having at their adjacent ends a radially outwardly extending flange, and a plurality of fasteners which connect the two flanges and urge the two flanges into sealing engagement with one another, the system including a first clamp and a second clamp, each having two opposing clamp parts which are connected by a single clamp element having a longitudinal axis and which is operable to move the clamp parts to increase or decrease their separation, wherein the first and second clamps are separate to the extent that their separation is not fixed, and they can be mounted on the flanges one after the other.13.A system according to claim 12 wherein each clamp part has a body portion which contains an aperture through which the clamp element extends, and the clamp element is provided with two threaded portions, one of which carries a right-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of one of the clamp parts, and the other of which carries a left-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of the other of the clamp parts 14.A system according to claim 13 wherein the threaded portions of the clamp element are separated by an unthreaded portion.15.A system according to claim 13 or 14 wherein each clamp part further comprises a flange engagement portion which extends from the body portion and which provides a clamping face which is generally perpendicular to the longitudinal axis of the clamp element.16.A system according to claim 15 wherein each clamp further comprises a guide which maintains the clamp parts in an aligned position in which the clamp face of one clamp part is directly aligned with the clamping face of the other clamp part whilst the clamp element is operated to alter the separation of the clamp parts.17.A system according to any one of claims 12 to 16 wherein the clamp element may have a first end which is provided with a tool engagement formation which is adapted, in use, to be engaged with a tool to assist in rotating the threaded clamp element about its longitudinal axis.18.A system according to any one of claims 12 to 17 further comprising a retaining strap or belt which can be fastened around the radially outwardly facing surfaces of one of the clamp parts of both the first and second clamps. 19.A system according to claim 18 further comprising a further strap or belt which can be fastened around the radially outwardly facing surfaces of the other one of the clamp parts of both the first and second clamp.20.A system according to claims 18 or 19 wherein the clamp further comprises a strap or belt retainer whereby the clamps may be mounted on a strap or belt such that movement of the clamps along the strap or belt is permitted.21. A hot bolting clamp having two opposing clamp parts which are connected by a threaded clamp element which is operable to move the clamp parts to increase or decrease their separation, wherein each clamp part has a body portion which contains an aperture through which the threaded clamp element s extends, and the threaded clamp element is provided with two threaded portions, one of which carries a right-handed screw thread which engages with a corresponding screw thread provided around the aperture in the body portion of one of the clamp parts, and the other of which carries a left-handed screw thread which engages with a corresponding screw thread provided to around the aperture in the body portion of the other of the clamp parts.22.A hot bolting clamp according to claim 21 wherein the threaded portions of the threaded clamp element are separated by an unthreaded portion.23.A hot bolting clamp according to claim 21 or 22 wherein each clamp part further comprises a flange engagement portion which extends from the body portion and which provides a clamping face which is generally perpendicular to the longitudinal axis of the threaded clamp element.24.A hot bolting clamp according to any one of claims 21 to 23 further comprising a guide which maintains the clamp parts in an aligned position in which the clamp face of one clamp part is directly aligned with the clamping face of the other clamp part whilst the threaded clamp element is operated to alter the separation of the clamp parts.25.A hot bolting clamp according to claim any one of claims 21 to 24 wherein the threaded clamp element has a first end which is provided with a tool engagement formation which is adapted, in use, to be engaged with a tool to assist in rotating the threaded clamp element about its longitudinal axis.