APPARATUS FOR TENSIONING BOLTS AND STUDS

Abstract: A hydraulically-operable tensioning device is disclosed for tensioning studs and bolts for a flanged connection. The device has a bayonet-type connection to the bolt or stud and is pro­ vided with means which prevent operation of the tensioning device unless it is correctly located on the bolt or stud.

Description: Apparatus fortensioning bolts and studs The present invention relates to a hydraulically operable device for applying tension to solid bolts and studs in bolted flange joints, such as for example in joints employed in off-shore structures. Torque tightening of solid bolts or studs is time consuming and leads, frequently, to galling problems between mating surfaces. There is also a lack of predictability of the load in the torque-tightened bolt. Hydraulically operable devices have been used to tension solid bolts or studs in flanged joints, for example in steam turbine casings These comprise a device having a body portion which includes an annular piston surrounding the bolt or stud extending through the flange, and a puller member which is screwed onto a threaded extension of the bolt or stud. The annular piston is urged against the flange by hydraulic fluid under pressure in order to tension the bolt or stud. A radial slot in the piston enables the nut on the bolt or stud to be screwed down against the flange in order to maintain the tension when the hydraulic pressure is removed. It has also been proposed in UK patent 1 467 234 to use a beam member in which spaced cylindrical pistons and cylinders are used in order to tension a bolt or stud. US patents 3 917 224 and 4 012 826 also relate to tensioning devices for screwthreaded fasteners. Whilst all such tensioning devices involve the "pulling" of the bolt or stud in order to tension it, and do not involve lifting", they are frequently known in the industry as jacks or jacking devices. It has been found that the location of such devices on to the thread is time consuming, and it is not possible to readily ascertain whether sufficient thread engagement has been achieved. The present invention provides a means for quick and precise location of the tensioner on to the stud of bolt, and provides simultaneously interlocking safety features. According to the present invention there is provided apparatus for tensioning a bolt or stud for a flanged connnection comprising a body portion and a puller member for connection, in use, to the bolt or stud to be tensioned, the body member including at least one annular recess in which a sealing member is located and means for admitting hydraulic fluid into the annular recess or recesses, and a piston member of generally annular shape surrounding the bolt or stud and abutting the reaction face of the flange, characterised in that the puller member has a bayonet type connecting means and a springbiassed keying member for attachment in use to the head of the bolt or stud, the keying member and head each shaped such that they will mate only when the apparatus is correctly positioned. In accordance with an important feature of the device the keying member interlocks with an air valve which controls the supply of compressed air to an airdriven hydraulic pump such that the air valve can only be opened when the tensioner is correctly located on the head of the stud or bolt. The bayonet-type connection may be of the conventional type in which radially extending lugs on the bolt or stud engage with cooperating lugs on the puller member. However preferably the bolt or stud has a plurality of intermittent circumferential buttressed teeth which engage with a plurality of buttressed intermittent grooves within the puller member. The buttressed connection will withstand heavy axial thrust. In one embodiment the back (top) of the teeth have a slope of about 450 whilst the front (bottom) of the teeth are perpendicular to the axis of the puller member and of the bolt or stud. Alternatively both back and front teeth may be set at an angle, for example about 300, to the horizontal. The buttressed grooves are shaped to mate with the teeth. The keying member may, for example, have an elongated rectangular projection which mates with a mating keyway or recess in the bolt or stud, or may comprise a square or cruciform projection for use with a matching recess in the head of the bolt or stud. Alternatively the keying member may be recessed to mate with a projection on the head of the bolt or stud. The body portion of the tensioner of the invention may comprise a plurality of coacting components which together define the annular recess and form the piston member. However the body portion may be integral and shaped to define an annular recess between the puller member and itself. The puller member is provided with means for attachment to, or support by, the body member at the end distant from the bolt or stud. Preferably a solid annular seal of a plastics material such as polyurethane is located at the bottom of the or each annular recess, and serves to prevent the leakage of hydraulic fluid via the piston. An annular tyre into which hydraulic fluid is admitted to effect pressurisation may also be used but in general has insufficient strength for tensioning large studs or bolts. The invention will now be described by reference to the accompanying drawings in which: Figure 1 is a view in section of apparatus of the present invention for tensioning a stud shown as a fastener for a flanged connection. Figure 2 is a view of the stud used in Figure 1. Figure 3 is a section of one embodiment of the invention incorporating an air valve system. Figure 4 is a section of an alternative embodiment and Figure 5 is a cross-section on AA of Figure 4. Figure 6 is a section of a further alternative embodiment. Figure l shows a flanged connection 1 provided with a stud 2 to be tensioned therethrough. The stud 2 is anchored at its lower end by a nut 3 or other suitable means. A further nut 4 is located adjacent the head end for transmitting the clamp load on the flanges. Figure 2 shows in more detail the head 5 of the stud 2 which is of the bayonet type. The head is shown with two lugs 6, although more may prove desirable. A transverse keyway 7 is located in the head 5. The jacking device 10 has a body portion 11 having an annular recess 12 with parallel axially directed side walls t3. An annular seal 14 is located in the recess 12 between the bottom thereof and a piston member 15 which is a sliding fit in the recess 12. A passage 16 extends through the body 11 for the introduction of pressure liquid from the exterior into the recess. The piston member 15 is of sufficient length so that it abuts the top face of the flange 1 in use, and its inner diameter is of such size as to allow free axial movement of the nut 4. A radial slot, not shown, through the wall of the annular piston member 15 allows access to the nut 4 for turning it. A puller member 17 having an internal bayonet type connecting means 18, is attached to the body member 11 by screw thread 19. The puller member 17 is shown with two lugs 20 which engage with the lugs 6 on the stud head 5. The puller member 17 also incorporates a spring-biassed keying member 21, shown in more detail in Figure 3. The keying member 21 engages, in use, with the keyway 7 in the stud head 5 only when the jacking device 10 is correctly positioned on the stud head 5. The screwed end 19 of the puller member 17 houses the upwardly extending rod 22 of the keying member 21, at the top end of which is located an air valve 23. The air valve 23 is fitted with a slotted flanged bush 24. The slot extends generally in the axial direction but includes a local circumferential slot as shown at 25. The rod 22 has a cross key 26 located to slide in the slot of the bush 24. An operating handle 27 is attached to the upper end of the flanged bush 24. In use the handle 27 can only be moved in the horizontal plane when the cross key 26 can slide in the circumferential slot 25. This can only occur when the keying member 21 is correctly engaged in the keyway 7 of the stud head 5. Also shown in Figure 3 are piston return springs 30 which serve to retract the piston member 15 when the hydraulic operating pressure is released. In operation the puller member 17 of the jacking device 1 is engaged with the lugs 6 of the stud head 5 of the stud to be tensioned. The keying member 21 in the stud puller 17 engages with the slot 7 in the stud head 5 only when correct engagement has been achieved. This allows the handle 27 to be operated to open the air valve 23 and thereby start the air operated hydraulic pump (not shown) . Hydraulic fluid at high pressure is admitted to the recess 12 of the body 11 via passage 16. The seal 14 serves to prevent leakage of oil from the annular recess 12. The pressure urges the piston member 15 axially out of the recess 12 and against the flange 1, the load generated being reacted by the stud 2 through the lugs 6 on the stud head 5 via the lugs 20 in the puller member 17, thereby stretching the stud 2 within its elastic limit. With the stud 2 in its stretched state, the nut 4 is turned and nipped tight by means of a tommy bar, not shown, inserted through the slot in the wall of the annular piston member 15. The operating handle 27 is then returned to its original position shutting off the air and automatically releasing the hydraulic pressure. The piston member 15 retracts into the body member 11 under the action of the spring 30. The jacking device 1 may then be removed from the stud 2 and is ready for use on further studs. Referring to Figure 4, the body portion 40 consists of a piston 41a,41b joined by keep-plate 42, and an inner ring defining tWD annular recesses 44, 45, each recess having an annular seal 46, 47 located at the bottom. A nut 48 retains the body portion in place and is fastened by screw threads 49 to the puller member 50. Means for supply of pressure liquid are provided as for the embodiment shown in Figure 3. The puller member 50 has an internal bayonet type connecting means 51 which consists of intermittent circumferential buttressed grooves 52 which mate with buttress teeth 53 on the stud 54. It will be seen that the teeth are perpendicular to the axis of the stud at their front end and have a 450 slope at the back. The arrangement of the buttressed teeth and grooves are shown more clearly in Figure 5. The puller member 50 also incorporates a spring-biassed keying member 55. This has a square ended key extension 56 which engages with a matching square recess 57 in the stud head 54. The distant end of the keying member operates an air valve, not shown, as described with reference to the embodiment shown in Figure 3. This tensioning device operates in the same way as for the previous embodiment. The grooves 52 of the puller member 50 engage with the teeth 53 of the stud, and it is only when this engagement is correctly achieved that the key extension 56 on the keying member 55 engages with the key way 57 in the stud head 54. This allows the air valve to be opened as in the previous embodiment. Hydraulic fluid is admitted at high pressure to the recesses 44, 45 and urges the piston 41b against the flange l. The reacting forces lead to stretching of the stud which is tightened as before. Referring to Figure 6, there is shown an alternative embodiment of a tensioner 60 in which the body portion 61 is integral and defines two annular recesses 62, 63 between itself and the puller member 64. The puller member 64 is shown with a shoulder 65 which abuts the body portion 61. Dished disc springs 66 are located above the shoulder 65 by retaining ring 67. Engagement between the puller member and stud are as shown in the previous embodiment and described in reference to Figures 4 and 5. In operation hydraulic fluid is admitted to the recesses 62, 63 via inlet means 68 after engagement of the buttress teeth of the stud in the grooves of the puller member, and engagement of the key extension in the stud head recess. The pressure in the recesses 62, 63 urges the body portion 61, with its integral piston, against the flange and the reaction through the puller member stretches the stud which is tightened as in the first embodiment described with reference to Figure 3. Tensioning devices, and "jacking systems" of the present invention are particularly useful for tensioning solid bolts in flanged connections in off-shore structures. Thus, they are particularly useful in oil-well riser pipe connections and in tension legs. Other applications include flanged connections in turbine generators and nuclear power plant.

Claims: Claims 1. Apparatus for tensioning a bolt or stud 2 for a flanged connection comprising a body portion 11 and a puller member 17 for connection in use to the bolt or stud 2 to be tensioned, the body member 11 including at least one annular recess 12 in which a sealing member 14 is located and means for admitting hydraulic fluid into the annular recess or recesses 14, and a piston member 15 of generally annular shape surrounding the bolt or stud 2 and abutting the reaction face of the flange 1, characterised in that the puller member 17 has a bayonet-type connection means 20 and a spring-biassed keying member 21 for attachment in use to the head of the bolt or stud 2,the keying member 21 and head each shaped such that they will mate only when the apparatus is correctly positioned. 2. Apparatus as claimed in claim l in which the keying member 21 also interlocks with an air valve 23 which controls the supply of compressed air to an air driven hydraulic pump such that the air valve 23 can only be opened when the apparatus is correctly positioned. 3. Apparatus as claimed in claim 1 or claim 2 in which the bayonet-type connection means comprises a plurality of intermittent buttressed grooves 52 located within the puller member 51, the grooves mating in use with intermittent buttressed teeth 53 located circumferentially on the head of the bolt or stud 54 to be tensioned. 4. Apparatus as claimed in any one of the preceding claims in which the keying member 55 has a square, cruciform or rectangular projection 56 which mates in use with a matching recess 57 in the head of the bolt or stud 54 to be tightened. 5. Apparatus as claimed in any preceding claim in which the body member 61 is integral and is shaped to define an annular recess or recesses 62, 63 between itself and the puller member 64. 6. Apparatus as claimed in any one of claims 2 to 5 in which the keying member 21 has a further key 26 which slides in a slotted bush 24 connected to the air valve 23, the location of the key 26 and the slot 24 being such that the air valve 23 may only be operated when the projection 21 on the keying member is mated with the keyway or recess 7 in the head of the stud or bolt. 7. Apparatus as claimed in any preceding claim when in combination with a stud or bolt 2 to be tensioned, the stud or bolt 2 having a head having circumferentially extending lugs 6 or buttressed teeth 53 for a bayonettype connection to the puller member 17, 51 of the apparatus and also having a keyway or recess7, 57 to mate with a projection 21 on the spring-biassed keying member. 8. A bolt or stud for fastening a flanged connection having a head with circumferentially extending lugs 6 or buttressed teeth 53 for a bayonettype connection with the puller member 17, 51 of apparatus for tensioning the bolt or stud 2 as claimed in any one of claims 1 to 6, and having a keyway or recess 7, 57 in the head to mate with a projection 21, 56 on the spring biassed keying member 55 of the apparatus. 9. A bolt or stud as claimed in claim 8 in which the head has a plurality of intermittent buttressed teeth 53 extending circumferentially therefrom to mate in a bayonet type connection with the puller member 51 of apparatus as claimed in any of claims 1 to 5, and has a square or rectangular recess 57 extending axially into the head to mate with a projection 55 extending axially from the keying member of the tensioning apparatus.

Inventors: FIRTH, GEOFFREY, PERCIVAL-SMITH, HARRY DAVID, RUSHBROOKE, ROY
Applicants: PILGRIM MOORSIDE LIMITED
Application year: 1984
Main classification: B25B29
IPC codes: B25B29