GB2449289A - Shaft with seal for accommodating axial shaft movement - Google Patents

Abstract

A seal device 20 accommodates axial displacement between a housing 23 and a shaft 22 of an item of rotating equipment 21. The device 20 has a bearing 31 positioned between a rotor 24 located on the shaft 22 and a stator 25 connected to the housing 23. Contact between the stator 25 and bearing 31, and the bearing 31 and the rotor 24 is made via shoulders (at 30) which act to limit the amount by which the rotor 24 may move along the shaft 22, which allows the shaft 22 to sealingly move through the rotor 24 and so the device 20 provides sealing integrity when the shaft 22 is both idle and operational. The sealing device 20 may be used, for example, in a refiner where a large amount shaft displacement occurs when impeller clearances are set.

Description

BEARING PROTECTOR FOR EXTENDED AXIAL SHAFT MOVEMENT

Field of the Invention

This invention relates to bearing protectors, specifically non-contacting labyrinth seal type and their use in rotating equipment, especially equipment, which has axial movement between the rotor and stator.

An example of a piece of rotating equipment which has axial movement between the rotating shaft and stationary housing, is a Double Ended Centrifugal Pump with bearing assemblies supporting the rotating shaft, at either end of said shaft. During operation, thermal growth of the shaft often occurs thus the pump design typically accommodates this by providing an axially fixed shaft end and an axially floating shaft end.

Furthermore, some types of equipment necessitate axial movement between the rotating shaft and stationary housing because of the impeller clearance, replacement and adjustment. Refiners, used in the Pulp and Paper industry can have longitudinal adjustment requirements in excess of 2.000" (50mm).

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

Bearing seals are often also referred to as bearing protectors or bearing : isolators, however, the use of such seals extends well 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 the invention is concerned, in connection with such having wider uses.

Background to the Invention

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 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 axial 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.

Conventional labyrinth seal technology indicates the said close axial counter rotational members are substantially parallel to each other and run perpendicular to the centreline of the shaft. Unfortunately, labyrinth seal technology has limited effectiveness at discouraging fluid, specifically in S...

applications such as double-ended centrifugal pumps where axial :. displacement is expected between the shaft and the housing.

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Axial movement of a rotor to a stator with a close axial relationship can lead * : to contact and frictional heat generation.

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It is therefore deemed advantageous if a mechanism is created which accommodates axial shaft movement of rotating equipment comprising of a non-contacting bearing protector whilst permitting the effective sealing of the bearing lubricant fluid at all times.

Several attempts have made to satisfy this basic sealing requirement, including Orlowski, US 5,498,006.

Orlowski US 5,498,006, teaches a plurality of radial pins projecting from the stator into a corresponding groove in the rotor. Orlowski relies on the clearances between the walls of the pins and the width of the rotor groove, to accommodate axial movement between rotor and stator The experience reader should note several technical drawbacks with Orlowski US 5,498,006, as follows; -the radial pins do not form a continuous annular surface, adjacent to the corresponding annular surface of the rotor groove. This leads to accelerated wear of the pins. The worn particles from the pins are dispersed adjacent and into the sealed bearing lubrication fluid. Said contaminates deteriorate the lubrication media leading to premature bearing failure.

*:,:* -as the bearing seal in Orlowski US 5,498,006 is installed into the equipment housing, the seal stator is pushed into the equipment housing :. stator via a suitable hydraulic press or pressing action. Given this action, * 25 the axial forces the transmitted from the rotor to the stator through the *** brittle pins, which can create irreversible damage, including pin **** : breakage. * *** *

-the axial clearance between the pins and the rotor groove, must be replicated at each axial location between the rotor and stator, otherwise rotor to stator contact will result. As axial movement of a refiner can be typically +/-25mm (+1-1.000"), such axial clearances at all locations between the rotor and stator, of US 5,498,006, compromise the sealing integrity of the teaching.

-Both Orlowskj US 5,378,000 and our co-pending application GB0415548.7 describe the importance of a sealing device, which provides sealing between the rotor and stator when the equipment is not in operation. Clearly, despite a requirement for such a device in bearing seals, the teaching described in Orlowski US 5,498,006 is unable to accommodate said beneficial feature due to the way in which the large amount of axial movement accommodated within the device.

-typically, bearing seals incorporate a sealing elastomer between the seal stator and the equipment housing, however the sealable of the device in US 5,498,006 has been compromised since said stator-housing seal has been omitted in preference of the plurality of radial pins. The reader will relate to the physical space constraints of the typical bearing seal installation and the limited alternate location of Orlowski plurality of radial pins, by design.

It is thus deemed to be further advantageous if said axial accommodating *."., mechanism, incorporates a stator to rotor sealing device, which prevents S...

vapour and/or moisture entry into the bearing chamber when the equipment is idle and not in operation.

* : 25 Furthermore, it is deemed to be advantageous to provide a continuous * * : annular surface between the rotor and stator given that the rotor may contact the stator, during installation or operation.

Lastly, an invention which maintains traditional labyrinth axial clearances, which are typically 0.2mm (0.010") between the stator and rotor yet accommodates any amount of axial movement, including 50mm (2.000"), is deemed advantageous given the dynamic sealing function is not compromised.

Statements of the Invention

According to the present invention there is provided a bearing seal device, with an integral axial movement mechanism. Said axial movement mechanism comprises of rotor member, connected to the equipment shaft and a stator member is connected to the equipment housing and a bearing member mounted between the rotor and stator members, whereby the bearing member longitudinally restricts any longitudinal movement between the rotor and stator members.

Preferably, the inner most surface of said bearing member is a radial interference fit with the rotor member and the outer most surface of the bearing member is a radial interference fit with the stator member.

Preferably the first rotor member is mounted in a frictional sealing engagement with the shaft by one or more elastomeric members. Said elastomeric member transmits the rotary motion from the shaft to the first * ** rotor member. * *

:. Preferably, the bearing member incorporates an integral seal, hence * . 25 designated, "sealed for life". *** * I...

* : Preferably, a circlip member is housed in the stator member, adjacent to the bearing member, thereby pre-setting the axial relationship between the aforementioned rotor and stator members.

Preferably, the stator is sealing connected to the equipment housing, by an elastomeric member. Preferably the stator is rotationally coupled to said equipment housing.

Preferably, said stator has a radially extending cavity, on its inner most radial surface adjacent to the rotor and/or shaft. At the approximate 6 o'clock position, said radial cavity is discontinued with an orifice that communicates with the bearing chamber of the rotating equipment.

Preferably, said stator has a radially extending cavity, on its outer most radial surface. At the approximate 6 o'clock position, said radial cavity is discontinued with an orifice that communicates with the atmospheric side of the bearing chamber of the rotating equipment.

Preferably the rotorand stator are sealed by an elastomeric member when the equipment is idle. Preferably, said elastomer member disengages from either the rotor or stator members when the equipment is operational.

Description of the drawings

The accompanying drawings are as follows: Figure IA is a longitudinal cross section view of a labyrinth seal bearing protector, in its axially nominal position.

1.ss, Figure lB corresponds to Figure IA, and is a longitudinal cross sectional view of a labyrinth seal bearing protector in an axially displaced :. 25 position.

Figure 2 is a longitudinal cross sectional view of a labyrinth seal . : bearing protector of the invention.

Figure 3 corresponds to Figure 2 and shows, by way of example only, a longitudinal cross sectional view of a flange-mounted labyrinth seal bearing protector of the invention.

Detailed description of the Invention

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

The general principle of rotary seals in accordance with the present invention may be used not only in the case where the shaft is a rotary member and the housing is a stationary member but also the reverse situation, that is to say, in which the shaft is stationary and the housing is rotary.

Furthermore, the invention may be embodied in both rotary and stationary arrangements, cartridge and component seals with metallic components as well as non-metallic components.

Referring to Figure IA of the accompanying drawings, there is illustrated, a cross sectional view of a bearing protector 10 mounted in an item of rotating equipment 11.

The rotating equipment assembly 11 includes a rotating shaft 12 and a stationary equipment housing 13. The equipment housing 13 typically contains a bearing (not shown), mounted in the radial space between the * ** shaft 12 and housing 13 and separate to the bearing protector 10. * S * S*5

Area "X", adjacent to the bearing (not shown) and at one axial end of the * *;: 25 bearing protector assembly 10 typically contains bearing lubrication fluid, yet could also contain solid and/or foreign debris and/or atmosphere. For clarity *S*S it will herewith be termed "product substance", being used to describe the single or mixed medium.

Area "Y" at the other axial end of the bearing protector assembly 10 could also partially contain fluid, typically sprayed moisture, and/or solids and/or foreign debris and/or atmosphere, however for clarity it will herewith be termed "atmospheric substance" being used to describe the single or mixed medium.

The bearing protector assembly 10 includes a rotor member 14, which is radially and axially adjacent to stator member 15.

The stator member 15 is typically rotationally attached to the equipment housing 13, in sealing engagement using elastomer member 16.

The rotor 14 is radially mounted in sealing engagement with shaft 12 by at least one elastomeric member 17. The frictional squeeze on said elastomer 18 is typically sufficient to transmit the rotational drive from the shaft 12 to the rotor 14.

An elastomer 18 is positioned between the rotor 14 and stator 15. Said elastomer 18 is designed to hold the rotor 14 to stator 15 which is deemed of benefit during assembly of the bearing protector 10 to the rotating equipment 13.

From Figure 18, when the bearing protector 10 is subjected to longitudinal movement of the equipment shaft 12, for example when the impeller of the *.

equipment is longitudinally adjusted by displacements of 50mm, the rotor 14 attempts to move longitudinally with the shaft 12, given said rotor 14 is * 25 couplingly attached via the elastomer 17. Unfortunately, this places S..

elastomer 18 under a shear force, which creates high friction between the I...

.. : rotor 14 and stator 15, acting to seize the rotor 14 to the stator 15.

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When the rotary shaft 12 starts to rotate, the high frictional force of the elastomer 18 acts to lock the rotor 14 to the stator 15. Thus instead of the rotor 14 rotating with the shaft 12, it remains static with the stator 15.

This means that the inner most surface of the rotor seal 17 in connection with the shaft 12 starts to slip on the shaft and rapidly deteriorates, wearing both the elastomer 17 and the shaft 12 and creating high heat generation which results in seal failure.

From Figure 2, a bearing protector 20 of the invention is herewith described.

The rotating equipment assembly 21 includes a rotating shaft 22 and a stationary equipment housing 23. The equipment housing 23 typically contains a bearing (not shown), mounted in the radial space between the shaft 22 and housing 23 and separate to the bearing protector 20.

Once again, area "X", adjacent to the bearing (not shown) and at one axial end of the bearing protector assembly 20 typically contains bearing lubrication fluid termed "product substance".

Area "Y" at the other axial end of the bearing protector assembly 10 is termed "atmospheric substance".

The bearing protector assembly 20 includes a rotor member 24, which is radially and axially adjacent to stator member 25. * IS * * * * S.

*::::* The stator member 25 is typically rotationally attached to the equipment housing 23, in sealing engagement using elastomer member 26.

The rotor 24 is radially mounted in sealing engagement with shaft 22 by at least one elastomeric member 27. The frictional squeeze on said elastomer 28 is typically sufficient to transmit the rotational drive from the shaft 22 to the rotor 24.

An elastomer 28 is positioned between the rotor 24 and stator 25. Said elastomer 28 is designed to provide a sealing means between the rotor 24 and stator 25 which is deemed of benefit to prevent moisture passing from the atmospheric side into to the product substance side, specifically when the equipment is idle.

When the bearing protector 20 is subjected to longitudinal movement of the equipment shaft 22, the rotor 24 attempts to move longitudinally with the shaft 22, given said rotor 24 is couplingly attached via one or more elastomers 27. This longitudinal movement acts to place the rotor shoulder to abut the bearing shoulder 32 of bearing 31.

As bearing 31 is longitudinally restrained to the stator 25, by frictional resistance and/or a circlip 33, the rotor is unable to longitudinally move with the shaft 22. Therefore the shaft 22 is allowed to slide through the elastomer 27 until it rests. This means that any amount of longitudinal shaft 22 movement can be accommodated by the bearing protector 20 of the invention without the bearing protector 10 longitudinal length "Q" having to be a size larger than the shaft movement.

When the rotary shaft 22 starts to rotate, the low frictional force of the * ** bearing 31 ensures that the rotor 24 rotates with the shaft and the stator 25 remains static with the equipment housing 23, and thereby works perfectly as a bearing protector sealing device. * 25 *.*

The reader will note that the bearing 31 is preferably frictionally mounted on its inner most surface to the rotor 24 and preferably frictionally mounted on its outer most surface to the stator 25.

Preferably, the bearing as integral sealing means 40 and 41.

The static shut off device 42, is allowed to seal the rotor to stator when the shaft is at rest/idle and provides a non-contact seal when the shaft is in operation, is defined in our co-pending labyrinth seal bearing protection application GBO41 5548.7 and thus will not be further described. Clearly, the present invention may be offered with or without such a static shut off feature or an equivalent.

Preferably stator 25 incorporates a radially extending groove 48 extending from the inner most circumference, and substantially adjacent to the rotor or shaft 22 as shown. Preferably said groove is positioned adjacent to area "X" and the sealed media in the equipment bearing chamber 21. Preferably said groove 48 is circumferentially discontinued at the 6 o'clock position by an orifice 49 which communicates between area "X" and the outer most radial surface of the groove 48.

Preferably stator 25 incorporates a groove 50 positioned adjacent to area "Y" and the atmospheric side of the equipment bearing chamber 21. Preferably said groove 50 is circumferentially discontinued at the 6 o'clock position by an orifice 51 which communicates between area "Y" and the inner most radial surface of the stator 25.

*:*::* The experienced reader will therefore see that the bearing protector 20 of the invention accommodates any given axial displacement of the shaft 22 to equipment housing 23, without compromising the sealability or integrity of : 25 the assembly.

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Clearly, the invention anticipates and thus may accommodate any and all possible axial displacement situations of the shaft 22 to equipment housing 23.

The reader will note that non-contacting labyrinth seals rely on a close radial and axial clearances between the rotor 24 and stator 25, and the invention provides the innovative step of setting such radial and axial clearances irrespective of shaft longitudinal displacement. Clearly a series of radially and axially extending castellations 60 may be incorporated in both of the counter rotational membcrs, to create a tortuous path of resistance for fluid to pass.

Figure 3 corresponds to Figure 2 and is a longitudinal cross section view of the bearing protector 70 of the invention, which has a radially extended stator member 71 with the provision to securely attach said stator 71 to the equipment housing 72 via one or more bolts 73.

The embodiments of the invention, described and shown, clearly show innovative step and considerable advantages, over the existing prior art sealing, of rotating equipment, such as refiners, which, by their nature, have large amounts of longitudinal shaft to housing displacement. * *. * * * * ** I... 20 ** * * * .1* * *.* * **** * * S ** S

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Claims (9)

1. A seal device comprising of; -a stator which locates into the housing of a piece of rotating equipment -a rotor which locates on the shaft of a piece of rotating equipment, -and a bearing mounted radially between said rotor and said stator whereby said rotor shoulder contact said bearing shoulder and said stator shoulder contacts said bearing shoulder.

2. A seal device, according to Claim 1, where the rotor is in sealing engagement with the equipment shaft, via at least one solid deformable toroid member

3. A seal device, according to Claim 1, where the stator is in sealing engagement with the equipment housing, via at least one solid deformable toroid member * **

4. A seal device according to any preceding claim, which comprises of at least one solid deformable toroid member positioned adjacent to the second rotor and stator, said toroid member sealingly engages the second rotor and stator when the shaft of the rotating equipment is idle and sealingly disengages at least one rotor/stator member when the shaft is operation. **..

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5. A seal device according to any preceding claim, whereby the seat device is that of a non-contacting labyrinth design with close radial and axial adjacent surfaces between the rotor and stator.

6. A seal device according to any preceding claim, which comprises of at least one radially extending cavity, substantially adjacent to the shaft and/or rotor member(s) and adjacent to the sealed media of the rotating equipment.

7. A seal device according to Claim 6, whereby said radially extending cavity is circumferentially discontinued by an orifice which communicates between the sealed media and the outer most radial surface of the cavity.

8. A seal device according to any preceding claim, where the outer most radial surface of the stator is circumferentially discontinued by an orifice which communicates between the atmospheric side of the equipment and an inner radial surface of the stator.

9. A seal device as defined in claim 1 and substantially detailed by Figures 2 and 3. * ** * * * * S. ***. *. * . * **.

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