Clamp and Method of Clamping a Flange

The present invention relates to clamps for use on a flange, a method of clamping a flange and a method for removing bolts on a pipeline flange. In particular, the invention provides a method for changing bolts used to secure adjacent pipeline flanges by application of a clamping force to maintain adjacent flanges in position, enabling bolts to be removed and replaced.

Pipelines are widely used throughout the world for transporting fluids. For example, the oil and gas industry use pipelines for transporting fluids which may be at high pressures and temperatures. For ease of transportation and maintenance, pipelines are assembled by bolting a series of shorter lengths of pipeline together. Each length of pipeline is typically provided with a flange at each end, which is positioned adjacent the flange of the next length of pipeline and bolted thereto to form a continuous pipeline.

It is often necessary to replace the bolts holding flanges together during the lifetime of the pipeline. Bolt changes may be required for routine maintenance, if the bolt has worked loose or because the quality of the bolt has deteriorated, for example, due to corrosion. In large pipelines having flanges connected by eight or more bolts, it is generally recognised that one bolt at a time can be changed while the pipeline is "live" i.e. when fluid is flowing in the pipeline. Removing and replacing bolts while the pipeline is live is referred to as "hot bolting".

Hot bolting of any flange with fewer than eight bolts is not recognised as safe practice within the engineering industry. Current practise therefore dictates that if bolts need to be changed in a flange having fewer than eight bolts, the relevant portion of pipeline needs to be isolated and relieved of its internal pressure. This process and resulting downtime of the portion of pipeline is expensive.

According to a first aspect of the present invention there is provided a clamp for use on a flange comprising a first jaw, a second jaw, a first displacement means and a second displacement means, wherein the first and second displacement means are arranged to allow relative movement of the first and second jaws.

The first displacement means can be actuable to allow a greater proportion of relative movement of the first and second jaws than the second displacement means. The first displacement means can therefore allow long range relative travel of the first and second jaws and the second displacement means can allow short range relative travel of the first and second jaws.

Therefore, the first displacement means can allow the grip length of the clamp between the first and second jaws to be significantly altered allowing for variations in the size of the apparatus or flange to be clamped. The first displacement means can be arranged to advance at least one of the first and second jaws so that the jaws are positioned adjacent a flange and the second displacement means can be actuable to apply the final clamping force.

The first and second jaws can be movable relative to one another along a common axis. This axis can be defined as the clamping axis.

The first jaw can be mounted on an arm portion, and the second jaw can be mounted on a body portion. The arm portion can be detachable from the body portion.

"First and second jaws" as used herein refer to a pair of components moveable with respect to each other in order to grip an object therebetween.

The first displacement means can comprise a housing slidably coupled to an arm portion. The first displacement means can also comprise a movable stop member. The movable stop member may be arranged to move the housing and substantially restrict sliding of the housing in at least one direction once the housing is assembled in the desired position. The movable stop member can be connected to the clamp by means of a screw thread. The housing and the moveable stop member can be rotatably coupled to one another. The moveable stop member can be rotatable relative to the housing. Adjacent ends of the housing and the stop member can each be provided with a recess and a protrusion, such that the protrusion of the housing is arranged to be accommodated and retained in the recess of the moveable stop member. The housing can accommodate the second displacement means.

The second displacement means can be hydraulically operated. In the case where the second displacement means is used for short range travel, this has the advantage that a pressure applied by the clamp can be accurately monitored as only small amounts of hydraulic fluid are required to apply the pressure via one of the first and second jaws. The second displacement means can comprise a ram hydraulically moveable within a chamber.

In the event that several clamps are used together on a single flange the hydraulic ports of each clamp can each be connected by a hose to a manifold and a

hydraulic pump with a pressure gauge. Thus, substantially the same pressure can be applied by each clamp.

The hydraulic cylinder can be provided with an inlet/outlet port in selective fluid communication with the chamber and wherein the port is movable relative to the remainder of the clamp. The housing can be provided with holes spaced circumferentially around the exterior thereof. A pin can be provided to connect the housing and arm portion. This pin can be selectively positioned in any of the holes in the exterior of the housing to locate the hydraulic port in its desired position. The selective positioning of the hydraulic port enables improved accessibility for easier attachment of the hydraulic hose to the clamps.

The housing or hydraulic cylinder can be detachable from the remainder of the clamp. This allows easy removal of the hydraulic system in case any part thereof needs to be serviced or replaced.

The first and second displacement means can both be provided in the body portion. The arm portion may be detachable from the body portion of the clamp. This increases the versatility of the clamp as different lengths of arm can be provided giving an additional means for altering the grip length of the clamp.

The second displacement means can be provided with a locking member. The locking member can be operable to restrict movement of the second displacement means in at least one direction. The locking member and the first displacement means can be joined by means of a threaded connection therebetween. In the case where the second displacement means is a hydraulic system, the locking member provides a mechanical stop behind the hydraulic ram so that after the pressure is applied hydraulically, the locking member provides a mechanical failsafe.

The arm portion is provided with at least one aperture extending therethrough for receiving a strap. If more than one clamp is used at a time the at least two clamps can be shored together by passing straps through the holes to thereby fasten the clamps together. The arm portion can be provided with a plurality of apertures extending therethrough each aperture arranged to receive a strap. This allows an operator to select one or more appropriate apertures in each clamp through which straps can be fed depending on the physical constraints of the environment in which the clamp is used

The first and second jaws can each be provided with a contact point which is typically a substantially planar contact surface. Each of the surfaces can be arranged to engage a face of a flange. At least one of the contact surfaces on the first and second jaws can be pivotally mounted on the clamp. This

provides a tolerance in case there is dimensional variation in the surface of the apparatus or flange to be clamped.

A swivel device can be incorporated on at least one of the jaws, typically at the contact point between the jaw and the flange, to relieve stresses applied by the displacement means .

According to a second aspect of the present invention, there is provided a method for clamping a flange, the method comprising the steps of: providing a clamp having a first jaw and a second jaw, and a first and a second displacement means for moving the jaws relative to one another; and sequentially actuating the first displacement means and second displacement means to move the first and second jaws towards one another; and clamping the flange.

The method can include moving the first and second jaws along a common axis, which may be defined as a clamping axis.

Actuating the first displacement means typically enables a greater proportional convergence between the first and the second jaws along the clamping axis than actuating the second displacement means. The method can include actuating the first displacement means for relative long range travel of the first and second jaws and actuating the second displacement means to apply a clamping force.

The method can include accommodating the second displacement means within a housing; slidably coupling the housing to an arm portion of the clamp; actuating the first displacement means; and sliding the housing relative to the arm portion.

The method can include hydraulically actuating the second displacement means to apply the clamping force. The method may further include moving the hydraulic port of the second displacement means relative to the remainder of the clamp.

The method can include detachably mounting at least one of the first and second displacement means on the clamp.

The method can include providing the first and second jaws with first and second contact points respectively and pivotally mounting at least one of the first and second contact points.

The method can include monitoring the pressure applied y the or each clamp to the flange.

According to a third aspect of the present invention, there is provided a method for removing bolts associated with a pipeline flange joint including providing a clamp according to the first aspect of the invention, positioning the first and second jaws on opposite sides of a flange joint;

actuating the first displacement means to move at least one of the first and second jaws towards opposing sides of the flange joint; actuating the second displacement means to engage the first and second jaws with opposing sides of the flange joint; and removing one or more bolts associated with the flange joint while the clamp applies pressure to the flange joint.

The method can include increasing the force applied to the flange joint by providing and actuating two or more clamps spaced around the flange. Several clamps can be provided substantially circumferentially equispaced around the flange, typically between adjacent bolts. For example, the method for removing and replacing bolts on a four bolt flange may require the use of four clamps provided in between adjacent bolts. However, fewer than four clamps can be used with a four bolt flange, which may be necessary where portions of the flange joint are inaccessible.

The or each clamp can be used to apply a force to the flange joint greater than the force exerted by the or each bolt of the flange joint to thereby facilitate change out of bolts.

Alternatively, the or each clamp can be provided as an additional safety feature by exerting a similar pressure to a typical flange bolt. For example, one clamp can be used on an eight bolt flange in the

method for removing and replacing a flange bolt described above. This clamp could be arranged in the region of the bolt to be removed and replaced and apply a pressure to the flange similar to the remaining bolts. It will be appreciated by a person skilled in the art that this has the advantage of reducing the risks associated with conventional methods of changing out bolts which rely solely on the existing bolts to retain the flange joint. Several clamps can be used for this purpose.

The method can include providing the hydraulic ports of each of the clamps with a hose, connecting each hose, optionally via a manifold to a hydraulic pump and maintaining each clamp at the same pressure.

According to a fourth aspect of the invention, there is provided a method of removing bolts from a pipeline flange joint, wherein the joint provides a fluid tight seal and is connected with eight or fewer bolts and wherein the pipeline is carrying a pressurised fluid, the method including the steps of:- applying a clamping force across the flange joint using at least one clamp; maintaining the clamping force to retain a fluid tight seal across the flange joint using a retaining means associated with the or each clamp; and removing one or more bolts from the pipeline flange.

The method can include replacing the one or more bolts removed from the pipeline flange.

"Pressurised fluid" as used herein is intended to refer to a fluid having a pressure greater than the ambient pressure of the environment .

The clamp and the method of applying the clamping force can be in accordance with the first and second aspects of the inventions and optional features and steps described with reference thereto.

Maintaining the clamping force can be achieved by substantially restricting movement of the first and second jaws. The retaining means can comprise the locking member described with reference to the first aspect of the invention.

Optionally, the clamping force applied by the or each clamp is greater than or equal to the force exerted on the flange joint by the or each bolt.

Embodiments of the present invention will now be described with reference to and as shown in the accompanying drawings in which: -

Fig. 1 is a plan view of a clamp in accordance with the present invention; Fig. 2 is a sectional view of the clamp of Fig. 1 along the line A-A; Fig. 3 is a view of the underside of the clamp of Fig. 2 along the section B-B;

Fig. 4 is an end view of the clamp of Fig. 1; Fig. 5 is the other end view of the clamp of Fig. 1 with the hydraulic port in a different location with an attached nozzle; Fig. 6 is a sectional view of two clamps positioned diametrically opposite around a flange joint of a pipeline; Fig. 7 is the pipeline and flange joint of Fig. 6 with schematic arrows indicating the direction of the forces applied thereto; and Fig. 8 is a view of part of a reaction screw and a body according to an alternative embodiment .

A clamp according to the present invention is indicated generally at 12 as shown in the sectional view of Fig. 2. The clamp 12 comprises a frame 10, an arm 14, a reaction screw 60, a locking member 50, a body 70 and a ram 100.

The frame 10 is C-shaped and is attached to the arm 14 along an inner face 11 of the frame 10. A slot 34 is located centrally and between the frame 10 and attached arm 14. The slot 34 can receive straps, which can be used to secure several clamps together in use.

The arm 14 is generally C-shaped and has a first end 15 and a second end 13. An inwardly facing portion of the first end 15 of the arm 14 is provided with a concave seat 82. A pad 30 having one flat side 32f and one convex side 32s adapted to fit into the

concave seat 82 is pivotally mounted in the seat 82 by means of a loose-head screw 40.

The frame 10 and arm 14 are manufactured from forged steel and provide structural support for the clamp 12. The frame 10 and arm 14 should be sufficiently strong to prevent buckling when the clamp 12 is applying a force .

The arm 14 has a T-shaped slot 16 and a centrally positioned opening 94. The T-shaped slot 16 in the arm 14 extends towards the second end 13 and retains the head of a pin 44 therein so that the head of the pin 44 can slide within the slot 16. A screw 20 is inserted into the arm 14 opposite the opening 94 of T-shaped slot 16. The purpose of this screw 20 is to provide a stop to prevent pin 44 from sliding out of T-shaped slot 16 in the region of the opening 94.

The second end 13 of the arm 14 is formed as a partially cylindrical portion 26 as shown in the end view of Fig. 4. The partially cylindrical portion 26 is provided with a threaded throughbore 24 which accommodates a reaction screw 60 having corresponding threads on its outer surface 64. Thus the reaction screw 60 is axially movable within the throughbore 24 of the cylindrical portion 26 by virtue of the threaded connection 64.

The reaction screw 60 is a substantially cylindrical member, provided with a threaded throughbore 62. The reaction screw 62 has an outer knurled surface

65 to increase the purchase of an operator on the screw 62 in use. The locking member 50 has corresponding threads on its outer surface 52 such that the locking member 50 is axially movable in the throughbore 62 of the reaction screw 60 by virtue of the threaded connection.

The body portion 70 is a substantially cylindrical member and has an inner T-shaped bore 68 with a narrow end 68n at the base of the T-shape, and a wider end 68w at the head of the T-shape. A ram 100 is inserted into and sealed within the T-shaped bore 68. The ram 100 has a first end 105, a second end 103, and between them a relatively larger annular step 104, having a radially outer surface that is sealed against inner surface of the wider section 68w of the T-shaped bore 68. The second end of the ram 103 has a substantially smaller diameter than the reaction screw 60 and is arranged so that its end face 107 can bear against the locking member 50. The first end 105 extends out of the wider end 68w of the T-shaped bore beyond the body portion 70, and has an end face 102, which is substantially flat and arranged to contact a portion of the flange in use.

A hydraulic port 74 selectively allows hydraulic fluid to be applied to an annular surface 72 of the annular step 104. Application of hydraulic pressure to the annular surface 72 through the port 74 causes axial movement of the ram 100 through the bore 68 so that the first end 105 moves away from the body 70, towards the first end 15 of the arm 14.

The pin 44 attaches the body 70 to the arm 14 and is secured in a hole 78 in the outer surface of the body 70. Several such holes 78 are provided in the exterior of the body 70 to enable the hydraulic port 74 to occupy different radial positions in relation to the arm 14 and frame 10. One such alternative position is shown in Fig. 5 where the hydraulic port 74 is at an angle 45° from the vertically protruding frame 10.

Fig. 5 shows a port attachment 106 connected directly with the hydraulic port 74. The port attachment 106 is provided with a nozzle 110 that is able to pivot around a pivot axis 108. The nozzle 110 is provided for attachment to hoses for delivering hydraulic fluid in use. Pivotal movement of the nozzle 110 about the axis 108 enables the nozzle 110 to be positioned in a convenient location for attachment to the hose (not shown) .

Fig. 6. shows a flange joint 118 consisting of two flanges 118a, 118b and a sealing gasket 120 provided therebetween. The flanges are bolted together using stud bolts (not shown) to join two lengths of pipeline 116, 117. The total length of the flange joint 118 is in the region of 68mm.

According to this embodiment, the first displacement means comprises the body 70 slidably coupled to the arm 14 and the reaction screw 60. The second displacement means in the present embodiment

comprises the hydraulic ram 100, which is housed in the body 70.

In use, the clamp 12 is assembled in relation to the pair of bolted flanges 118a, 118b so that the first end 15 of arm 14 is placed on one side of the flange joint 118 adjacent the flange 118a and the second end 13 is positioned on the opposing side of the flange joint 118, adjacent the flange 118b such that flat face 32f of the pad 30 and the face 102 of the ram 100 are close to the faces of the flanges 118a, 118b respectively.

The flat face 32f of the pad 30 is brought into contact with the flange 118a. The body 70 and enclosed ram 100 is moved inwardly by sliding the pin 44 in the T-shaped slot 16. In this way the body 70 is moved close to the face of the flange 118b. When the body 70 is close enough to the flange 118b the reaction screw 60 is advanced through the bore 24 of the cylindrical portion 26 until it abuts the rear face of the body portion 70.

Thus, the first displacement means comprising the combination of the T-shaped slot 16 and reaction screw 60 is optimised for long travel bringing the contact ^' face 102 of the- ram 100 towards the flange 118b. This long travel mechanism enables the correct grip length to be achieved for different- sized flanges, since the position of the body 70 containing the hydraulics is adjustable according to the grip length required for each flange joint 118.

Additionally, the first displacement means does not need to exert high forces on the flange joint 118 when it is being activated because its function is to deliver the clamp faces to the correct positions for application of the clamping force by the second displacement mechanism, and so simple screw threads and other long travel components are quite suitable for the first displacement means. At this stage, in the present embodiment, the distance between the flat face 32f of the pad 30 and the face 102 of the ram 100 is slightly greater than 68mm.

When the ram 100 is near the flange 118b or just in contact with the flange 118b, hydraulic pressure can then be delivered via nozzle 110, port attachment 106 and port 74 from a pump via a hydraulic hose (not shown) . The hydraulic fluid acts on annular face 72 to push the ram 100 and contact face 102 towards the flange 118b.

The second displacement means comprising the hydraulic ram 100, the body 70 and the hydraulics therein are optimised for transmission of high forces (necessary for clamping) over short distances and apply the actual clamping force to the flange joint 118. The second displacement means does not need to exert forces over long distances and the amount of hydraulic fluid required to move the ram 100 into contact with the flange 118b is relatively small, so the hydraulic circuit and the seals etc can be fairly simple, and the pressure applied by the clamp 12 to the flanges 118a, 118b can be

accurately monitored by a pressure gauge attached to the pumps .

Therefore, the first and second displacement means can be simplified without engineering compromises affecting their primary functions.

The hydraulic system can be maintained at the required pressure for the change-out of stud bolts from the flange. However, the locking member 50 optionally provides a mechanical failsafe locking system when it is screwed up behind the hydraulic piston so that its end face 107 abuts the hydraulic ram 100. This mechanical failsafe allows the clamps 12 to be used on pipelines flange joints 118 having eight or fewer bolts. In the event that the hydraulic system fails, the mechanical backup maintains the clamping force.

The pad 30 can move within the seat 82, allowing a tolerance, such that the faces 32f and 102 remain parallel to the flanges 118a, 118b. In this way, it is possible to ensure that the same area is contacted by each face 32f, 102 such that application of a certain pressure results in substantially the same force being applied on each flange 118a, 118b, making up the flange joint 118.

Fig. 7 shows a typical "live" bolted flange. Arrows 126 indicate the force exerted by the pressurised fluid carried within the portions of pipe 116, 117. Arrows 128 indicate the forces tending to separate

the two flanges 118a, 118b. Schematic arrows 130 show opposing forces generated by the bolts on the flanges 118a, 118b. In order to maintain the flanges 118a, 118b in contact with one another and to provide a fluid tight seal between the gasket 120 and the flanges 118a, 118b, the forces opposing separation of the flanges 118a, 118b depicted by the arrows 130, must be greater than the forces acting to separate the flanges 118a, 118b shown by arrows 128.

In order to remove and replace stud bolts (not shown) holding the pipeline flanges 118a, 118b together, the clamps 12 are spaced around the flanges 118a, 118b and used to apply pressure thereto in the manner previously described.

In the case of four bolt flanges it is preferable to provide two pairs of diametrically opposing clamps 120. One clamp is therefore positioned between each set of adjacent bolts. All the clamps 12 are connected to a common source of pressurised fluid, such as a pump, by means of hydraulic hoses and a manifold (not shown) . The simultaneous load applied by the clamps 12 can be calculated from the pressure reading on an attached pressure gauge. Prior to pressurisation of the flanges, each flange joint 118 should have a pre-determined maximum pressure at which it can operate based on the materials of the flange joint, the gasket 120, its pressure ratings and temperatures.

In the present embodiment, the clamps 12 simultaneously apply pressure as required by means of a manually operated hand pump unit (not shown) . As the pressure is increased a spanner or other suitable device should be used to identify any bolts which may become loose on the flange 118a, 118b. In the event of a stud bolt (not shown) becoming loose the pressure should be held at a constant level and the clamps 12 can be locked in this position at the desired pressure by rotating and tightening the locking screw 50. Before removal of the stud bolts, the clamps 12 should apply a force to the flanges 118a, 118b which is greater than the force exerted on the flange joint 118 by the bolts. The stud bolts are then removed and can be replaced with new bolts. Ideally, bolts should be removed one at a time. Various methods of removal for the stud bolts would be known to a person skilled in the art.

The pressure applied by the clamp 12 should never exceed the pre-determined maximum pressure calculated. Preferably, the clamp described in the present embodiment is operable in the region of 1000 psi (6.89 MPa) . When all the stud bolts have been changed the clamps 12 can be de-pressurised and removed. Thus, the change out of bolts is achieved without taking the bolted flange 118 out of operating service.

Fig.8 is a part sectional view of a modified reaction screw 160 coupled to a modified body portion 170. Internal components, such as the ram

100 and the locking member 50 are housed within the body portion 170 and the reaction screw 160 but are not shown in Fig 8. The body portion 170 is slidably attached to the arm 14 by the pin 44 and the reaction screw 160 is rotatable within the threaded throughbore 24 of the cylindrical portion 26, as previously described. The body portion 170 has a neck 174 and an annular protrusion 172 surrounding a bore (not shown) that accommodates the end 103 of the ram 100 as described in connection with the first embodiment. The reaction screw 160 has a threaded bore 162 extending therethrough and has an annular recess 161 towards its leading end. The recess 161 is bounded by an annular step 163.

The annular protrusion 172 of the body portion 170 is accommodated in the annular recess 161 of the reaction screw 160 and retained therein by the annular step 163. This arrangement couples the body portion 170 to the reaction screw 160 such that linear movement of the body portion 170 results in corresponding linear movement of the reaction screw 160. However, this coupling also allows the reaction screw 160 to rotate relative to the body portion 170, since the body portion 170 is prevented from rotation by the pin 44. This rotatable coupling has the advantage that the contact face 102 of the ram 100 can be aligned perpendicular to a clamp axis 90 since the body portion 170 is supported by the reaction screw 160. This additional support for the body portion 170 means that the pin 44 that is less prone to failure.

Modifications and improvements may be made without departing from the scope of the invention, for example, the clamp 12 can be used on any size of flange and with any number of bolts. The size and shape of the jaws or contact points can be modified to increase the footprint area thereby spreading the load over a greater area and enabling the pressure applied to be reduced for a specific force. Optionally, two additional slots 34 can be provided towards opposing ends of the arm 14, thereby providing flexibility and enabling an operator to select an appropriate slot 34 for use with a strap depending on environmental constraints. Dimensions of the clamp can be tailored to the requirements of the flange 118 on which they are to be used. Optionally, the width of the frame 10 can be reduced to facilitate access to the bolts. Alternatively or additionally, the location of the contact surface can be modified by raising or lowering the contact faces 32f, 102 to improve access to the bolts to be removed by engaging the clamp 12 in different areas of the flange joint.