GB2218697A

GB2218697A - Stud bolt handling equipment for reactor vessel

Info

Publication number: GB2218697A
Application number: GB8808610A
Authority: GB
Inventors: Thomas Walter Bunyan
Original assignee: Pilgrim Engineering Developments Ltd
Current assignee: Pilgrim Engineering Developments Ltd
Priority date: 1988-04-12
Filing date: 1988-04-12
Publication date: 1989-11-22
Anticipated expiration: 2008-04-12
Also published as: GB8808610D0; GB2218697B

Abstract

Reactor vessel stud bolt handling equipment includes means for transferring a stud bolt (20) to a carrier from a parking station, (e.g. I5) or vice versa. Preferably a number of stud bolts are handled simultaneously. The transfer means may include cross arms (21) rotatable about extendable columns (15), and the equipment is mounted on a mobile base for movement into and out of position. Each carrier comprises a tubular socket and an expandable sleeve to grip a stud bolt. <IMAGE>

Description

Mechanical handling equipment This invention relates to mechanical handling equipment.

More particularly it is concerned with apparatus for use in conjunction with reactor vessel closure removal and/or installation equipment as for example described in EP-A-9973.

Large reactor vessels have a cylindrical closure which is secured by a number of stud bolts and co-operating retaining nuts. Where the contents of the reactor vessel are aggressive and/or potentially hazardous, it is desirable to remove the closure of the vessel with the minimum of manual intervention. To this end, it is known to use multiple stud tensioning equipment to remove all, or more usually, half of the stud bolts in one, or two passes as appropriate. To this end, the multiple stud tensioning equipment is lifted into place on top of the reactor vessel with its individual stud tensioning tools located on the stud bolts securing the closure. The equipment is then operated to tension the studs so that the securing nuts can be released, by unscrewing them a few turns. The equipment can then be operated to unscrew the stud bolts themselves.However, it has then to be lifted clear of the reactor vessel so that the stud bolts can be retrieved from the equipment before carrying out a second pass, to remove the remaining stud bolts. Only when all of the stud bolts have been removed can the closure be lifted of the reactor vessel.

Because the stud bolts are extremely large, typically over 1.5 metres in length and 150 mm in diameter, they are not easy to handle. Removal of the individual stud bolts from the multiple stud tensioning equipment is accordingly a time consuming operation. Depending on the nature of the reactor vessel it may also be hazardous to personnel involved. It is an object of the present invention to minimise manual handling operations.

According to this present invention, stud bolt handling apparatus comprises a base provided with a stud bolt carrier and a stud bolt parking station, together with transfer means operable to grip an end of a stud bolt, lift it and then transfer it from the carrier to the parking station, or vice versa.

Preferably, the apparatus includes a plurality of transfer means, each associated with a different stud bolt carrier and at least one parking station, the transfer means being simultaneously operable to transfer a plurality of stud bolts in a single operation.

Advantageously the stud bolt carriers are provided with means for gripping stud bolts to prevent their rotation. This facilitates unscrewing the stud bolt pullers of the multiple stud tensioner from the free ends of the bolts. For example, inflatable collars may be provided inside the stud bolt carriers.

More preferably, the base is configured to correspond to the layout of a reactor vessel cover with the stud bolt carriers disposed on the pitch circle diameter of the latter. For example, the base may be in the form of an annulus, optionally separable into at least two portions for ease of handling and/or storage. Advantageously in such a case, there are sufficient parking stations to accommodate all of the stud bolts from the reactor vessel cover. Where the apparatus is used in conjunction with multiple stud tensioning apparatus such as described in EP-A-9973 the apparatus preferably includes sufficient, equally spaced apart stud bolt carriers with associated transfer means to receive one half of the stud bolts from the reactor vessel cover.This is because it is a normal constraint to have to operate the multiple stud tensioner in two passes, alternate stud bolts being removed on the first pass and the remainder on the second pass. In between these passes, the multiple stud tensioner is presented to the stud bolt handling apparatus and half of the stud bolts are lowered into the respective stud bolt carriers. The gripper means are operated to firmly grip the stud bolts; the tensioning equipment is operated to release the stud pullers by unscrewing them from the stud bolt ends. The multiple stud tensioner is then lifted clear prior to operation of the handling apparatus to transfer the stud bolts directly into parking stations. The multiple stud tensioning equipment is then returned to the reactor vessel cover and used to remove the remainder of the stud bolts.After removal, they too are lowered into the carriers and transfered to parking stations. Preferably, the stud bolt handling apparatus is mobile, for example along rails, so that it can be used to carry the complete set of stud bolts away for servicing and/or storage. It may also be used to carry the multiple stud tensioning equipment itself to and from the vicinity of a reactor vessel which is to be opened or closed.

Where two parking stations are provided for each transfer means they are conveniently located at opposite sides of the base, the transfer means comprising an extendable, rotatable column supporting a cross arm carrying at each end a stud bolt lifting tool, so that two stud bolts can be lifted from adjacent carriers at once, prior to rotating the column to locate the bolts above their respective parking stations, followed by lowering the bolts into the latter, simultaneously.

The lifting tools are conveniently in the form of hooks which can be engaged with adjustments fixed to the free ends of the stud bolts.

In this embodiment, four generally diagonally opposed parking stations are preferably associated with each transfer means, so that only one of the latter is needed for every four stud bolts, allowing for a 2-pass removal procedure with the multiple stud tensioning equipment.

In order that the invention be better understood a preferred embodiment of it will now be described with reference with the accompanying figures in which: Figure 1 is an end view in section along line A-A of Figure 2a showing one stud bolt handling apparatus according to the invention.

Figure 2 is a composite illustration of a 1200 segment of a complete stud bolt handling system for a large reactor vessel. Figure 2a is a plan view; Figure 2b is a partial side view of the same segment, showing the disposition of support wheels for the apparatus.

In the interests of convienience like parts their like reference numerals in all figures. Referring now to all figures, a generally circular (at least in plan) base 11 is in this case comprised of three 1200 segments secured together by flanged connections 30,31. Six sub-frames 12 (only two of which are visible in Figure 2a) are provided in order that the apparatus can be moved to and from the vicinity of a reactor vessel. To this end, the sub-frames 12 have wheels 13 which run along tracks 14. The latter are only shown in Figure 1 and will be appreciated that they are themselves supported by the associated plant floor. The base 11 has a plurality of equally-spaced stud bolt carriers numbered 1 to 8. These are spaced apart at intervals corresponding to the pitch circle spacing between the stud bolts which retain the reactor vessel cover. Each stud bolt carrier consists of a tubular socket and as discussed earlier, includes an expandable sleeve (not shown) in order to enable a stud bolt to be gripped whilst in the carrier. In between adjacent pairs of stud bolt carriers there are transfer means comprising an extendable rotatable column 15 carrying at its upper end, a cross bar 21. The individual columns are locked to the supporting base by means of the conventional seismic locks (anti-vibration devices) 36. The purpose of these is simply to prevent the columns being accidentally released from the base, for example, impact/shock. The cross arm 21 carries at each end a stud bolt lifting hook 40,41 as best seen in Figure 1.

Located around the inner and outer periphery of the base, are a number of parking stations designated 11 to I8 and 111 to 118.

The operation of the apparatus is generally as described earlier. Firstly, the multiple stud tensioning apparatus (not shown) is transferred to the top of the reactor vessel and operated to remove half of the stud bolts.

The stud bolt handling apparatus is wheeled along the rails 14 to the proximity of the reactor vessel and all of the arms 21 are pivoted to the position indicated at 35 in Figure 2a; that is to say they are turned so that the lifting hooks 40,41 are not immediately above the stud bolt carriers 1 to 8 respectively. The multiple stud tensioning equipment is then presented to the top of the stud bolt handling apparatus and the stud bolts (half of them as explained earlier) are lowered into the respective stud bolt carriers. The upper ends of the stud bolts are then released from the multiple stud tensioning equipment by using the expandable sleeves to hold the stud bolts 20 whilst the pullers are unscrewed.

The equipment is returned to the top of the reactor vessel in order to remove the remaining stud bolts.

The cross arms 21 are then rotated about the column 15, which is previously extended so that lifting hooks 40 and 41 will clear the stud bolts. The column is rotated and the lifting hooks are engaged with abutments 23 fixed to the free ends of the bolts. To illustrate this, two bolts 20 are shown in Figure 1 each having its securing nut 22 still in place. When the bolts have been engaged by the lifting hooks, column 15 is extended, thereby lifting the stud bolts 20 out of the stud bolt carriers. The column is then rotated about its axis to locate the stud bolts directly above the parking stations. They are then lowered into the parking stations and the lifting hooks are disengaged by rotating the columns 15 back to the position 35 (Figure 2a).At this stage half of the stud bolts are safely parked in the parking station and the stud bolt carriers are available to receive the second set of stud bolts from the reactor vessel cover. The sequence can then be repeated until all of the stud bolts from a particular reactor vessel are in parking stations and can be wheeled away in a single operation for maintenance and/or storage purposes. If necessary, the multiple stud tensioning equipment can be lowered on top of the stud bolt handling apparatus for ease of transport/storage whilst the reactor vessel cover itself is being removed.

It will be appreciated that because of the simplicity of the apparatus it is relatively easy to automate substantially the whole of the operation so that it is not necessary to handle any of the stud bolts manually.

In fact, substantially, the whole of the operation of removal and storage of stud bolts and reactor vessel cover can be carried out with the minimum of manual intervention. The whole apparatus can be remote controlled from a safe distance.

Claims

1. Stud bolt handling apparatus comprising a base provided with a stud bolt carrier and a stud bolt parking station, together with transfer means operable to grip an end of a stud bolt, lift it and then transfer it from the carrier to the parking station, or vice versa.

2. Apparatus according to Claim l including a plurality of transfer means, each associated with a different stud bolt carrier and at least one parking station, the transfer means being simultaneously operable to transfer a plurality of stud bolts in a single operation.

3. Apparatus according to Claim 1 or Claim 2 wherein each stud bolt carrier is provided with means operable to grip a stud bolt located therein.

4. Apparatus according to Claim 3 wherein said gripping means are constituted by inflatable collars.

5. Apparatus according to any preceding claim wherein the base is configured to correspond to the layout of a reactor vessel cover.

6. Apparatus according to Claim 5 wherein the base is in the form of an annulus, optionally separable into at least two portions for ease of handling/storage.

7. Apparatus according to Claim 5 or Claim 6 wherein there are sufficient parking stations to accommodate all of the stud bolts from the cover of a particular reactor vessel.

8. Apparatus according to any preceding claim for us in conjunction with multiple stud tensioning equipment, the apparatus including sufficient, equally-spaced apart stud bolt carriers with associated transfer means to receive one half of the stud bolts from a reactor vessel cover.

9. Apparatus according to any preceding claim wherein the transfer means comprises an extendable, rotatable column supporting a cross arm carrying at each end a stud bolt engaging tool, so that two stud bolts can be lifted from adjacent stud bolt carriers at once, prior to rotating the column to locate the bolt above respective parking stations, followed by lowering the bolts into the latter substantially simultaneously.

10. Apparatus according to Claim 9 wherein four generally diagonally opposed parking stations are associated with each transfer means, so that only one transfer means is needed for every four stud bolts of a reactor cover.

11. Stud bolt handling apparatus substantially as hereinbefore described with reference 2 and as illustrated by the accompanying drawings.