GB2109461A - Apparatus for withdrawing and reassembling compressor rotors - Google Patents

Abstract

A frame 1 for withdrawing the rotor of a centrifugal gas compressor comprises lower end plates 2, 3 connected by struts 4, 5 and upper end plates 12, 13 joined by struts 14. The plates 2, 12 are secured to the compressor casing and the plates 3, 13 are provided with a total of three jacking points axially aligned with pulling points on the rotor. Each jacking point receives an hydraulic jacking unit which is connected to the pulling point of the rotor by a wire rope or chain or by a pushing device. The frame also has a slide rail 22 to support the rotor during withdrawal and replacement and is provided with jacking screws 25 to adjust the height of the rail. When the rotor has been pulled from its casing by the jacking units, it is levered on to the rail 22 by a suitable lever against lugs 4a on the strut 4. After servicing, the rotor is reinserted in the casing by attaching pushing units to the jacking units. In a modification, the pulling frame enables partial withdrawal of the rotor whilst the diffuser ring assembly is attached, followed by removal of this assembly and total withdrawal of the rotor. <IMAGE>

Description

SPECIFICATION A gas compressor pulling frame This invention is concerned with the removal of the rotor bundle (the rotor/diaphragm assembly) from a centrifugal gas compressor. More particularly the invention is concerned with the in situ removal of rotor bundles from compact, high and low pressure, centrifugal gas compressors as used on off-shore driliing platforms. In such environments compressors are often operated for periods of several thousands of hours without major maintenance. However, after such an extended period of operation it is often extremely difficult to remove the rotor bundle from the casing, for maintenance or replacement of the rotor assembly, without damaging delicate internal components.The aim of the present invention is to provide a means for extracting the rotor bundle from a centrifugal gas compressor, by an even and controlled application of force to the rotor bundle so as to withdraw the bundle from the outer casing of the compressor without causing any unnecessary damage to the rotor components.

A further objective is to provide a means as aforesaid that also facilitates reinstalling the rotor bundle, or installing a replacement rotor bundle, in the outer casing. Yet another objective is to provide a means as aforesaid that may conveniently be utilised to support the withdrawn rotor bundle in a manner facilitating the performance of servicing and maintenance operations thereon.

Accordingly the invention provides a pulling frame for attachment to a centrifugai gas compressor, comprising a compressor-end plate adapted to fit on to the outer casing of said compressor and a rear-end plate, said end plates being joined by struts to form a rigid frame; said rear-end plate having jacking means associated therewith for connection to the rotor bundle and positioned to apply jacking forces axially to the rotor bundle; and a profiled bottom slide rail to engage and support the rotor bundle during withdrawal from and replacement into the casing.

So that the invention may be more readily understood, the invention will now be described, by way of example and with reference to the accompanying drawings, in which: FIGURE 1 is an elevation of a pulling frame constituting one embodiment of the invention; FIGURE 2 is a plan of the pulling frame of Figure 1; FIGURE 3 is an end elevation of the pulling frame of Figure 1; FIGURE 4 is a cross-section taken on the line lV-IV of Figure 1; FIGURES 5 to 10 illustrate stages in the procedure for removing the rotor bundle from a centrifugal gas compressor using the pulling frame of Figures 1 to 4; FIGURE 11 is an elevation of a pulling frame constituting a further embodiment of the invention; FIGURE 12 is a plan of the pulling frame of Figure 11; FIGURE 13 is an end elevation of the pulling frame of Figure 11;; FIGURE 14 is a cross-section taken on the line of XIV--XIV of Figure 11; and FIGURES 1 5 to 1 9 illustrate stages in procedure for removing the rotor bundle from a centrifugal gas compressor using the pulling frame of Figures 11 to 14.

While the pulling frame of the invention may be adapted and utilised for withdrawing, working on, and reinstalling the rotor bundle of any centrifugal gas compressor of the type having a non-splittable casing, the embodiments herein described are particularly adapted for use with Ingersoll-Rand gas compressors, Type MTGB 524 and MTGB 733.

Figures 1 to 4 of the drawings show a pulling frame, generally indicated 1, intended for use with a Type MTGB 524 (5stage) compressor. The frame 1 comprises a lower frame component, or cradle, and an upper frame component. The cradle consists of two shaped end plates, namely a lower compressor-end plate 2 and a lower rear-end plate 3, these end plates being separated by two pairs of struts 4 and 5. Preferably these struts 4, 5 project perpendicularly of the end plates and are so fixed that the end plates 2, 3 are held in parallel alignment. Preferably the struts 5 have a square cross section whilst the struts 4 may have a circular cross section. One end of each strut is welded to the compressor-end plate 2, the other end being welded to the rear-end plate 3 so as to form a rigid structure.One of the struts 4 is provided with upwardly projecting lugs 4a, for purposes that will be described below.

As is best seen in Figure 4, the lower compressor-end plate 2 is shaped to fit on to the casing of a centrifugal gas compressor (not shown), the inner surface 6 of the plate being so radiused that the gas compressor rotor bundle can be withdrawn from the compressor casing between the projecting struts 4 and 5. A plurality of holes 7 are positioned in non-load-bearing areas of the material of the compressor end plate 2 so as to restrict the weight of the latter. The plate 2 is adapted to fit on to the casing of a compressor, that has been stripped down for maintenance purposes, attachment of the lower frame component preferably being by means of the existing studs in the compressor casing that would normally retain the front end-cover of the compressor casing.

The lower rear-end plate 3 is formed from suitably stiffened metai plate and is provided with a jacking point 8 to receive a jacking unit (not shown). The jacking point 8 is so positioned that when the pulling frame is attached to a centrifugal gas compressor the jacking point is axially aligned with a pulling point provided on the exposed surface of the rotor bundle. The jacking unit is secured on this plate at four retaining points 1 0.

The jacking unit is adapted to be connected to the pulling point on the rotor bundle by means of a wire rope or chain, or by means of a suitable pushing device. Such rope, chain or pushing device is attached to the rotor bundle and jacking unit by adaptors (not shown). The rope or chain, used for pulling the bundle, preferably has a shortening clutch mechanism, for shortening the length of the rope or chain between successive pulling strokes of the jacking unit, while the length of the pushing device, used for pushing the rotor bundle in replacement thereof, is preferably telescopically adjustable.

As with the lower compressor-end plate 2, the lower rear-end plate 3 has a plurality of holes to minimise the weight of the plate.

The upper frame component comprises a pair of upper compressor-end plates 12, a rear-end plate 13 and a pair of struts 14, each strut being welded at one end to one of the compressor-end plates 12 and at the other end to the rear-end plate 13, to form a rigid structure.

The upper compressor-end plates 12 are so shaped that they fit on to the compressor casing without impeding the withdrawal of the rotor bundle. Each of these plates is adapted to be attached to the compressor casing using the front end cover retaining studs of the latter.

As is best seen in Figure 3, the upper rear-end plate 1 3 is a single rigid plate having an upper crossbar portion 1 5 and two side portions 1 6 and 1 7 that project perpendicularly downwards from the crossbar portion. The side portions are adapted to be secured to the lower end plate 3 so that the plates 3, 13 together form a rigid jacking plate. The upper crossbar portion 15 of the plate 13 has two further jacking points 18 and 1 9, having retaining points 20, 21 for receiving and securing jacking units (not shown). Each of these jacking points is positioned so as to be axially aligned with a pulling point on the rotor bundle.

The three jacking units are linked in a manner to provide synchronised operation to produce an even and in-line pulling force to three pulling points on the compressor bundle.

Preferably the jacking units are hydraulically actuated push/pull cylinders.

The pulling frame also has a bottom slide rail 22 that provides support for the rotor bundle during extraction, maintenance and replacement procedures. As best seen in Figures 1 and 3, the slide rail 22 is curved about its longitudinal axis to match the internal curvature of the compressor casing. This slide rail 22 has downwardly projecting members 23 that facilitate the support of the slide rail 22 on the lower frame struts 5. The members 23 coact with retaining adaptors 24 that are provided on the lower frame struts 5. Jacking screws 25 are associated with the retaining adaptors 24 so that the vertical height of the slide rail can be adjusted. The compressor end of the slide rail 22 is machined to fit into the compressor casing and provide a support for the withdrawal of the rotor bundle.

A back support leg (not shown) is provided to support the rear of the frame during removal and maintenance of a rotor bundle.

Figures 5 to 10 illustrate a procedure for using this pulling frame to remove and replace the rotor bundle from a centrifugal gas compressor.

As shown in Figure 5, a gas compressor 26 has been stripped of all power sources and pipework connections, and the front end-cover (not shown) of its casing has been removed. To allow access to the rotor bundle the diffusing ring assembly is removed using a known technique.

As seen in Figure 6, the pulling frame 1 is rigidly attached to the casing of the compressor 26. In this Figure, the lower frame component is generally indicated at 28, the upper frame component at 29, and the bottom slide rail at 22.

The frame is supported by a back-end support member 30. The frame is aligned so as to ensure that the jacking points are correctly aligned with their corresponding pulling points on the rotor bundle surface, i.e. so that the jacking forces are directed perpendicularly to the vertical face 31 of the rotor bundle 32. Hydraulic jacking units 33 are then installed at the jacking points.

As shown in Figure 7, the hydraulic jacking units 33 are then connected by wire ropes 34, via suitable adapters (not shown), to the pulling points on the vertical face 31 of the rotor bundle 32.

Operation of the jacking units 33 (in the "puli" mode) produces a pulling force that withdraws the rotor bundle from the compressor casing by a distance equal to the full extent of one hydraulic stroke of the jacking units. At this stage the rotor bundle is supported on the bottom of the compressor casing. The bottom slide rail 22 is adjusted so as to provide support for the bundle as it is extracted. The wire ropes are then replaced with chains (not shown) that incorporate a shortening clutch, the length of the chain being adjusted, using the shortening clutch, to allow successive hydraulic strokes to further withdraw the rotor bundle from the casing. As the pulling forces are controlled and evenly distributed this removal operation causes no undue damage to the rotor bundle components. The hydraulic extraction procedure is continued until the diaphragm is clear of the casing. Having freed the rotor bundle from the casing it can be easily levered fully on to the bottom slide rail 22, using a suitable lever against lugs 4a on the strut 4 of the lower frame component 28, to enable access for maintenance work.

As illustrated in Figure 8, the upper frame component 29 can be removed at this stage to allow disassembly of the rotor bundle 31 and removal/replacement of the inner rotor assembly 35.

With the upper frame component 29 removed, the remainder of the pulling frame constitutes a convenient and stable support for the rotor bundle while servicing operations are performed thereon.

When the rotor bundle has been reassembled, e.g. after servicing, the upper frame component 29 is replaced. Using a suitable lever against the lugs 4a on the strut 4 of the lower frame component 28, the rotor bundle can be levered partly back into the casing, the bottom slide rail 22 being adjusted up and down as required to cater for variations in the internal diameter of the casing. As shown in Figure 9, after correct alignment of the rotor bundle with the casing, and partial insertion, has been effected, pushing devices 36 are attached to the hydraulic jacking units and are so arranged that one end of each pushing device contacts the vertical face 31 of the rotor bundle. The length of each pushing device 36 is adjustable. By operating the hydraulic units, in the "push" mode, the rotor bundle can be fully reinserted into the casing.When the rotor bundle is almost completely retained within the casing the bottom slide rail 22 can be removed, as the rotor bundle is now supported by the bottom of the casing. The pushing devices 36 are readjusted and hydraulic pressure is applied by the jacking units 33 to ensure that the rotor bundle is correctly aligned, on its bearing surfaces, and that the seals are intact.

As shown in Figure 10 the gas compressor pulling frame 1 is then removed, and the diffuser ring assembly 27 is replaced on the compressor 26. The compressor is then reassembled and is thereafter ready for operation.

It is not always possible easily to remove the diffuser ring prior to withdrawal of the rotor bundle, this being the case, for instance, with the Ingersoll-Rand 7-stage Type MTGB 733 compressor. The pulling frame embodiment illustrated in Figures 11 to 14 is therefore designed to enable partial withdrawal of the rotor bundle, e.g. of a Type MTGB 733 compressor, to be effected while the diffuser ring assembly is still attached to the rotor bundle. Removal of the diffuser ring assembly may thereafter be accomplished, followed by total withdrawal of the rotor bundle from the compressor casing.

In the case of a compressor intended to be dismantled in this way, the rotor bundle is provided with three pulling points, two being positioned in a lower portion of the bundle and a third in an upper portion of the bundle. Clearance holes are provided in the diffuser ring to allow attachment of adaptors directly into the rotor bundle without removal of the diffuser ring.

The pulling frame shown in Figures 11 to 14, and generally indicated 37, comprises a lower frame component and an upper frame component.

The lower frame component has a lower compressor-end plate 38, a lower rear-end plate 39 and three pairs of struts 40,41 and 42.

Preferably the lower struts 42 have a square cross section whilst the struts 40 and 41 may have a circular cross section. One end of each strut is welded to the compressor-end plate 38, the other end being welded to the rear-end plate 39 so as to form a rigid structure.

The lower compressor-end plate 38 is adapted to fit on to the casing of a centrifugal gas compressor and has an inner surface 43 that is so radiused as to allow withdrawal of the rotor bundle between the projecting struts 40, 41 and 42. The struts 40 are provided with upwardly projecting lugs 40a.

As is best seen in Figure 13, the lower rear-end plate 39 has two jacking points 45 and 46, to receive jacking units (not shown), that are aligned with pulling points on the rotor bundle. The jacking units are secured at retaining points 47 and 48.

The upper frame component comprises an upper compressor-end plate 49, an upper rear-end plate 50 and a single rectangular section, strut 51.

The upper compressor-end plate 49 has an internal profile that is so radiused to allow withdrawal of the rotor bundle diffuser ring assembly from the casing, and is adapted to be attached to the compressor casing, using the front end-cover retaining studs of the latter.

As is best seen in Figure 1 3 the upper rear-end plate 50 has a generally hexagonal shape, comprising an upper horizontal section 52, side bars 53 and 54 that, when viewed in end elevation, project downwards at an angle of 450 from each end of the horizontal section 52, and two vertical side bars 55, 56. The side bars 55, 56 are adapted to be secured to the rear-end plate 39 so that the plates 38, 39 form a rigid jacking plate.

This upper section is essentially a "strongback" and is formed from stiffened plate. The upper horizontal section 52 has a single jacking point 57 associated therewith, that is aligned with a pulling point on the rotor bundle, and retaining points 58 for securing a jacking unit (not shown).

The pulling frame also has a vertically adjustable profiled bottom slide rail 59 that is supported by means of suitable adaptors 61 and associated jacking screws 62 that are positioned on the lower struts 42, and a rear support leg (not shown).

Figures 1 5 to 19 illustrate a procedure for using the pulling frame of Figures 11 to 14 to remove and replace the rotor bundle 63, the diffuser ring assembly 64 from a centrifugal gas compressor.

To enable attachment of the pulling frame a compressor 65 is stripped of all power sources and pipework connections and the front end cover is removed.

As seen in Figure 1 5 the lower frame component 66 and upper frame component 67 are secured to the casing via suitable fixing studs in the end of the casing. (At this stage the bottom slide rail is excluded from the frame assembly.) The frame is supported by back-end support member 69. The frame 37 is aligned so as to ensure that the jacking points are correctly aligned with corresponding pulling points on the rotor bundle surface, i.e. so that the jacking forces are directed perpendicularly to the vertical face of the rotor bundle 63. Hydraulic jacking units 70 are then installed at the jacking points. The hydraulic jacking units 70 are then connected, by wire ropes 71, via suitable adaptors (not shown) to pulling points on the rotor bundle. These adaptors pass through clearance holes, provided in the end diffuser ring 64, that align with the pulling points on the rotor bundle 63.The hydraulic jacking units are then operated (in their "pull" mode) to withdraw the rotor bundle from the casing by an amount sufficient to pull the diffuser ring assembly clear of the casing. By uncoupling the wire ropes 71, removing the adaptors from the rotor bundle and dismantling the upper frame component 67 the diffuser ring can then be removed using suitable winching means attached to an eyebolt 72 attached to the diffuser ring 64.

At this stage the bottom slide rail 73 is installed to provide a platform on to which the rotor bundle can be extracted. As shown in Figure 1 6 the adaptors are replaced in the pulling points on the rotor bundle and chains 74, incorporating a shortening clutch mechanism (not shown), are connected between these adaptors and the hydraulic jacking units 70. Replacement of the upper section 67 is optional at this stage, as the now freed bundle should slide evenly by pulling on the bottom two positions only.

As illustrated in Figures 16, 17 and 18 the rotor bundle can now be completely withdrawn from the casing, disassembled for maintenance work, reassembled and re-inserted in the casing.

Reinsertion is accomplished initially by using a suitable lever against the lugs 40a on the strut 40 at the lower frame component to lever the rotor bundle partly back into the casing, the bottom slide rail being adjusted as required, when correct alignment of the bundle has been achieved.

Thereafter insertion of the rotor bundle is continued using pushing devices 75 attached to the jacking units, which are now operated in their "push" mode. When the front face 76 of the rotor bundle is approximately 10-20 mm inside of the casing the bottom slide rail 73 can be dispensed with. The upper frame component 67 is then removed to allow the replacement of the diffuser ring assembly 64.

As shown in Figure 1 9 the upper frame component is then reassembled and the length of the pushing devices 75 adjusted so as to complete the replacement of the rotor bundle. The use of the hydraulic devices ensures that all bearing surfaces remain correctly aligned and that all sealing joints are correctly formed. The frame is then removed from the casing and the centrifugal gas compressor can be reassembled for operation.

Claims (13)

1. A pulling frame for attachment to a centrifugal gas compressor, comprising a compressor-end plate adapted to fit on to the outer casing of said compressor and a rear-end plate, said end plates being joined by struts to form a rigid frame; said rear-end plate having jacking means associated therewith for connection to the rotor bundle and positioned to apply jacking forces axially to the rotor bundle; and a profiled bottom slide rail to engage and support the rotor bundle during withdrawal from and replacement into the casing.

2. A pulling frame according to claim 1, including a lower frame component and an upper frame component that can be locked together to form a rigid structure.

3. A pulling frame according to claim 1 or claim 2, in which said jacking means can be actuated in a pulling or a pushing mode.

4. A pulling frame according to any one of claims 1 to 3, in which said jacking means is hydraulically actuated.

5. A pulling frame according to any one of claims 1 to 4, in which said jacking means is adapted for association with a wire rope or chain for attachment to the rotor bundle such that operation of the jacking means in a pulling mode provides a pulling force for removing the rotor bundle from the compressor casing.

6. A pulling frame according to claim 5, in which said wire rope or chain includes a shortening clutch.

7. A pulling frame according to any one of the preceding claims, in which said jacking means is adapted for association with a pushing device such that operation of the jacking means in a pushing mode provides a pushing force for replacing the rotor bundle within the compressor casing.

8. A pulling frame according to claim 7, in which the length of said pushing device is telescopically adjustable.

9. A pulling frame substantially as described with reference to and as shown in Figures 1 to 4 of the accompanying drawings.

1 0. A pulling frame substantially as described with reference to Figures 11 to 14.

11. A method for extracting and replacing the rotor bundle of a centrifugal gas compressor substantially as described with reference to Figures 5 to 10 of the accompanying drawings.

12. A method for extracting and replacing the rotor bundle of a centrifugal gas compressor substantially as described with reference to Figures 1 5 to 1 9 of the accompanying drawings.

13. Every novel feature and every novel combination of features disclosed herein.