GB2439447A

GB2439447A - Bearing Seal

Info

Publication number: GB2439447A
Application number: GB0711906A
Authority: GB
Inventors: Alan James Roddis
Original assignee: AES Engineering Ltd
Current assignee: AES Engineering Ltd
Priority date: 2006-06-21
Filing date: 2007-06-20
Publication date: 2007-12-27
Anticipated expiration: 2027-06-20
Also published as: GB2439447B; US20070296157A1; GB0612304D0; US7748715B2; GB0711906D0

Abstract

A bearing seal consist of a labyrinth seal with a radially split stator 5 and a rotor 7. The rotor 7 is enclosed within the stator 5 along the internal length of the rotor 7.

Description

P0159GB

BEARING SEAL

Field of the Invention

This invention relates to bearing protectors, especially, but not exclusively, of the non-contacting labyrinth seal type, and their use in rotating equipment, especially equipment which has a particularly large shaft or is difficult to disassemble/strip down.

Background to the Invention

An example of a piece of rotating equipment which is difficult to disassemble is a centrifugal pump with bearing assemblies supporting the rotating shaft.

In such equipment, each bearing arrangement typically consists of at least one bearing housed in a bearing chamber. The bearing is lubricated and sealed between the rotor to stator interface to prevent the ingress or egress of a fluid or solid to or from the bearing cavity, since such unwanted material results in the deterioration of equipment life.

Bearing protectors are often also referred to as bearing seals or bearing isolators. Such seals have applications beyond the protection of a bearing in rotating equipment. Accordingly, while reference will be made below to bearing protectors, it should be understood that this term is used, as far as this invention is concerned, in connection with such wider applications.

During pump operation, bearing seal components may deteriorate to such an extent that they must be repaired. Often, it is not economically feasible to take a pump out of production, disassemble it and remove the interference fitted bearings in order to fit new bearing seals. This therefore creates a dilemma for the pump operator, since the deteriorated seals will accelerate the probability that debris and moisture enter the bearings and cause major failure/cost.

P0159GB The purpose of a bearing protector is to prevent the ingress of fluid, solids and/or debris from entering a bearing chamber. Equally, bearing protectors are employed to prevent the egress of fluid or solids from a bearing chamber. Essentially, their purpose is to prevent the premature failure of the bearing.

Non-contacting bearing protectors can be of repeller or labyrinth configuration. Reference is made to our co-pending labyrinth seal bearing protection application GB0415548.7 which defines a substantially non-contacting bearing protector with a static shut-off device.

In a non-contacting bearing protector, the rotating component typically has a complex outer profile which is located adjacent and in close radial and longitudinal proximity to a complex inner profile of the stationary component.

Together these complex profiles, in theory, provide a tortuous path preventing the passage of the unwanted materials or fluids.

Split seals are used in applications where the rotating equipment is difficult to disassemble. Such seals comprise two parts, a stator and a rotor, both of which are radially split about their central axis, so that they can be radially mounted over a shaft compared to the more traditional longitudinal mounting on the shaft of a conventional non-split seal design.

Conventional labyrinth seal technology indicates that the closely positioned longitudinal counter rotational members are substantially parallel to each other and run perpendicular to the centreline of the shaft. As labyrinth seals are non-contacting designs there is a natural leak path through the rotor to stator interface. A radially split labyrinth thus has further leak points, given the nature of the design. In order to reduce leakage potential, radial, substantially male elements of the rotor can protrude longitudinally and P0159GB mesh into substantially female radial recesses of the stator, thereby creating a tortuous path for fluid to pass. Unfortunately, a radially split labyrinth seal has to have radial access so that the stator can be assembled over the rotor whilst in situ on the shaft. lntermeshing longitudinal protrusions between the rotor and stator render impractical radial assembly unless there is sufficient longitudinal space available in the equipment for this operation to be done in a longitudinally spaced position, i.e. with the rotor and stator separated. At least one longitudinal end of the stator and/or rotor assembly must be open and this creates a potential leak path for contaminants to enter.

Statement of the Invention

According to the present invention there is provided a bearing seal comprising a radially split stator and a rotor, said rotor being enclosed within the stator along the entire length of the rotor.

Preferably a tortuous path is defined between the stator and the rotor.

Preferably the rotor is also radially split.

Preferably the seal includes a static shut-off device. More preferably, the static shut-off device includes an annular sealing member located in a recess in one of said stator and said rotor, said sealing member bearing against an integral ring of the other member which extends into said recess.

Preferably the sealing member is moveable from a first position engaging said integral ring and a second position spaced from said integral ring.

Preferably a further annular member is located in the recess, the member being radially expandable when the rotor is rotated to allow movement of the sealing member to said second position.

P0159GB Preferably the tortuous path extends past said sealing member, when it is in its second position, and around a radial, integral protuberance forming part of said rotor. More preferably, the separate components of the rotor are connectable together by fastening means extending through said protuberance.

Accordingly, the present invention provides, in one embodiment, a split, non-contacting labyrinth seal which can be radially assembled onto an item of rotating equipment, the rotor and/or stator having a longitudinal extending protrusion which engages in a corresponding recess in the other of the rotor and/or stator.

The stator longitudinally encloses the rotor so that both longitudinal ends of the rotor are, when the seal is assembled, shrouded by radially extending portions of the stator. This makes it possible to create a tortuous, intermeshing fluid flow prevention path which is created by radially extending portions of the stator and/or rotor engaging in radially extending recesses of the rotor and/or stator.

In one embodiment, the radially split assembly is installed as a cartridge, in which the rotor and stator are captured within one cartridge assembly. This allows the optimum axial relationship between the rotor and the stator to be maintained when the assembly is pushed into its final, in use position.

As indicated above, a preferred embodiment of the present invention incorporates a shut-off device which is a stator to rotor sealing arrangement and which prevents vapour and/or moisture entering into the bearing chamber when the equipment is idle, that is to say not in operation.

P0159GB

Brief Description of the Drawings

The accompanying drawings are as follows:-Figure 1 is a longitudinal section of one half of a bearing seal of the invention; and Figure 2 is a similar longitudinal section of the bearing seal of Figure 1 but with the components in their separated condition.

Detailed Description of the Invention

The invention will now be further described, by way of example only, with reference to the accompanying drawings.

Referring to Figures 1 and 2 of the accompanying drawings there is illustrated a bearing seal I mounted on a drive shaft 3 and comprising a stator 4, attached directly or indirectly to the bearing housing and a rotor 7 secured to drive shaft 3 for rotation therewith.

The seal I is in the form of a non-contacting labyrinth seal and, in the "in use" condition, shown in Figure 1, the rotor 7 lies wholly within the stator 5.

The stator 5 is sealed to the bearing housing, or another part connected to the bearing housing, by means of a sealing ring and the rotor 7 is attached and sealed to shaft 3 by means of sealing rings II and 13.

Rotor 7 includes a recess 15 which extends longitudinally from one end of rotor 7 about a third of the way longitudinally into said rotor. Mounted within recess 15 is a first sealing ring 17 which is located adjacent to the mouth of recess 15 and, between sealing ring 17 and the blind end of recess 15, a second smaller diameter sealing member 19 which bears against the end wall of recess 15 and also against the larger sealing ring 17.

P0159GB Sealing ring 17 also bears against a protuberance which extends from inner radial surface 23 into the mouth of recess 15. The end surface of protuberance 21 includes a radial portion and an inner inclined portion, at least the latter bearing against sealing ring 17 while the equipment is stationary. When the equipment is rotating, centrifugal force acting on ring 19 causes it to expand radially outwardly and allow sealing ring 17 to move longitudinally out of engagement with protuberance 21 of stator 5. This opens up a tortuous path which extends from the bearing cavity between the stator 5 and the drive shaft 3 and then all the way round the rotor and within the stator to the exterior (right hand side as seen in Figure 1) of the bearing seal 1. This tortuous path is defined at least partly by a radially extending protuberance 23 which forms an integral part of rotor 7 and which extends into and is accommodated by a large recess 25 formed within stator 5. The tortuous flow extends further around a flange-like member 27 which extends radially outwardly from a circumferential surface 29 of rotor 7 and is accommodated within a relatively small recess 31 of stator 5.

Both the stator 5 and the rotor 7 are radially split into two halves. In order to assemble the seal while on the drive shaft 3, the Iwo halves of the rotor 7 are first brought together round the drive shaft 3. They are fastened together by means of a nut and bolt arrangement 31 extending through the mating protuberances 23 of the rotor 7. Then the two halves of the stator 5 are brought together around drive shaft 3 at a position, relative to rotor 7, as illustrated in Figure 2. Accordingly the protuberance 21 lies, in this position, outside the mouth of recess 15. thereby enabling the two halves of stator to be brought together. They inter-connect by means of integral dowels in one or both halves engaging in corresponding recesses in the other half. Once this has been done, the seal may be pushed along the drive shaft until the stator 5 engages with the bearing housing as illustrated in Figure 1. The rotor 7 is in turn pushed from the position shown in Figure 2 to that shown in Figure 1 so that the sealing ring 17 engages the protuberance 21.

P0159GB The stator 5 may optionally be provided with location pegs and corresponding recesses, indicated at 33, which aid proper alignment of the stator halves during assembly. Alternatively or in addition, the stator may be provided with screw or bolt assemblies for fastening the two halves of the stator together

Claims

P0159GB

CLAIMS

1. A bearing seal comprising a radially split stator and a rotor, said rotor being enclosed within the stator along the entire length of the rotor.

2. A seal according to Claim 1 wherein a tortuous path is defined between the stator and the rotor.

3. A seal according to Claim 1 or 2 wherein the rotor is also radially split.

4. A seal according to any of the preceding Claims wherein the seal includes a stator shut-off device.

5. A seal according to Claim 4 wherein the stator shut-off device includes an annular sealing member located in a recess of one of said stator and said rotor and bearing against an integral ring on the other of said stator and said rotor, said ring extending into said recess.

6. A seal according to Claim 5 wherein said sealing member is moveable from a first position engaging said integral ring and a second position spaced from said integral ring.

7. A seal according to Claim 6 wherein a further annular member is located in the recess, said further annular member being radially expandable when the rotor is rotated to allow movement of the sealing member to said second position.

8. A seal according to any of the preceding Claims wherein said tortuous path extends past said sealing member, when it is in its second position, and around a radial, integral protuberance of said rotor.

P0159GB 9. A seal according to Claim 8 wherein the separate components are connectable together by fastening means extending through said protuberance.

10. A seal according to Claim I and substantially as herein described.

11. A bearing seal substantially as described herein with reference to the accompanying drawings.