GB2438022A

GB2438022A - A bearing protector

Info

Publication number: GB2438022A
Application number: GB0609244A
Authority: GB
Inventors: Alan James Roddis
Original assignee: AES Engineering Ltd
Current assignee: AES Engineering Ltd
Priority date: 2006-05-10
Filing date: 2006-05-10
Publication date: 2007-11-14
Anticipated expiration: 2026-05-10
Also published as: GB2438022B; GB0609244D0

Abstract

A sealing device or bearing protector comprises a stator 16 which locates into a housing of a piece of rotating equipment 11. A rotor 14 locates on a shaft 12 of the equipment. A non-sparking member 31 is positioned between the rotor 14 and the stator 16 and has a substantially smaller radial and/or axial clearance between it and the stator 16 and/or rotor 14 compared to any other radial and/or axial distance between the stator 16 and the rotor 14 in the assembly.

Description

BEARING PROTECTORS

Field of the Invention

This invention relates to bearing protectors, specifically of the non-contacting labyrinth seal type and their use in rotating equipment, especially equipment which is used in pharametrical industry or sensitive areas of plant where traditional labyrinth seals manufactured from bronze and brass metallurgy's are not accepted.

An example of a piece of rotating equipment which requires stainless steel bearing protectors is a blower/fan in the chemical industry used to move air and prevent emissions escaping. In the pharmaceutical and food industries, bass and bronze materials are often avoided on centrifugal pumps because of potential contamination issues.

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 interface 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 GBO41 5548.7 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 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.

Conventional labyrinth seal technology indicates the said close longitudinal counter rotational members are substantially parallel to each other and run perpendicular to the centreline of the shaft. Because of the close running clearances between the labyrinth stator and rotor, together with the size and weight of the equipment the labyrinth is installed on, the running clearances of the rotor and stator are such that counter rotational contact may occur.

For this reason, labyrinth seals are manufactured from materials of construction that will not spark if they contact.

Typical materials employed include Bronze and plastics. The problem with plastic bearing protectors is that they can physically distort under thermal conditions. Metallic bearing protectors are far less likely to distort and therefore their use is common.

However, industrial applications preclude the use of popular materials of construction such as brass and bronze, preferring instead stainless steel grades. The issue for bearing protection suppliers is the fact that given equipment misalignment conditions, two counter rotating components, manufactured from stainless steel, will create a spark if they contact.

For this reason, bearing protector suppliers elect to increase the radial and axial clearances to reduce the likelihood of a spark being generated.

Unfortunately, this comprises the effectiveness of the bearing protector at discouraging contaminant entry and/or oil egress from the bearing chamber of the rotating equipment.

Statements of the Invention

According to the present invention there is provided a bearing seal having non-sparking member between the rotor and stator. The non-sparking member is either positively secured to at least one of the rotor or stator members or is not attached to either member, thereby allowing it to rotate with the rotor or be stationary with the stator, or run at an intermittent speed somewhere between the stator and rotor.

Preferably, said non-sparking member is manufactured in a substantially rigid material that is not susceptible to thermally distorting, for example, carbon.

Preferably, the bearing seal incorporates a device which positively sealingly engages the rotor and stator when the rotating equipment is idle, and non-sealingly engages either the rotor and/or stator when the equipment is operational. Preferably, said non-sparking member is positioned on the atmospheric side of said sealing device, thus minimising the possibility that wear from said device can enter the bearing lubrication media.

Preferably, said stator has a radially extending cavity, on its innermost 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 outermost 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.

Description of the drawings

The accompanying drawings are as follows: Figure 1 is a longitudinal cross section view of a labyrinth seal bearing protector of the invention.

Figure 2 is a longitudinal cross section view of an alternate 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 present invention may be used in rotary seals 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 1 of the accompanying drawings, a bearing protector 10 of the invention is mounted in an item of rotating equipment 11, which includes a rotating shaft 12 and stationary equipment housing 13.

Equipment housing 13 typically contains a bearing (not shown), mounted in the radial space between the shaft 12 and housing 13.

Area "X", adjacent to the bearing (not shown) and at one axial end of the bearing protector assembly 10, typically contains bearing lubrication fluid, yet could also contain solid and/or foreign debris and/or atmosphere. For clarity it will be termed "product substance", being used to describe a 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. Again 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 16.

The stator member 16 is preferable rotationally attached to the equipment housing 13, in sealing engagement using elastomer member 17.

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

Clearly, a separate drive mechanism could be employed to transmit said drive if so required.

The static shut off device 23, which seals the rotor to stator when the shaft is at rest/idle and provides a non-contact seal when the shaft is in operation, is described in our co-pending labyrinth seal bearing protection application GB0415548.7 and will not be further described. Clearly, the present invention may be offered with or without such a static shut off feature or an equivalent.

The rotor 14 is longitudinally restrained to the stator 16 by a first axial restraining member 24, which is longitudinally restrained and radially extends from a groove 25 in stator 16. Preferably said longitudinal restraining member 24 is provided in a material with low co-efficient of friction property.

PreferabJy, stator 16 incorporates a radially extending groove 28 extending from the inner most circumference, and substantially adjacent to the rotor or shaft 12 as shown. Preferably groove (28) is positioned adjacent to area "X" and the sealed media in the equipment bearing chamber 11. Preferably, groove 28 is circumferentially discontinued at the 6 o'clock position by an orifice 29 which communicates between area "X" and the outermost radial surface of the groove 28.

Preferably on the outermost radial surface of the stator 16, positioned adjacent to area "Y" and the atmospheric side of the equipment 11, said surface 30 is circumferentially discontinued at the 6 o'clock position by an orifice 31 which communicates between area "Y" and the innermost radial surface of the stator 16 adjacent to said surface 30.

A non-sparking member 31 is radially and axially positioned in the radial gap between the stator 16 and rotor 14. Said non-sparking member 31 is preferably rotationally secured to the stator 16 on the outermost surface of member 31 and innermost surface of stator 16.

Preferably, the radial distance between the inner most surface of member 31 and outer most surface of rotor 14 is smaller than any other radial distance between the rotor 14 and stator 16.

Preferably, the longitudinal distance between the longitudinal annular end surface of member 31 and the longitudinal annular end surface of rotor 14 is smaller than any other longitudinal distance between the rotor 14 and stator 16.

These longitudinal and radial clearances between the stator 16 and rotor 14 are termed running clearances.

The bearing protector 10 can accommodate longitudinal or radial counter rotational contact between the stator and rotor given and maintain close labyrinth running clearances given the inclusion of the integral non-sparking member. The sealability or integrity of the assembly is not compromised in a bearing protector of the invention.

The non-sparking member 31 is longitudinally positioned on the atmospheric side of the static shut-off valve 23, SO that any debris from the rotor 14 contacting member 31 is exhausted through orifice 31.

In alternative bearing assembly 50 shown in Figure 2 rotor 51 is radially wrapped over the outermost surface of the stator 52. The mechanics of the invention remain the same as described with reference to Figure 1 embodiment

Claims

CLAIMS

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; -a non-sparking member which is positioned between the rotor and stator, said member having substantially smaller radial and/or axial clearances between it and the stator and/or rotor, compared to any other radial and/or axial distance between the stator and rotor in the assembly.

2. A sealing device according to Claim 1, wherein the non-sparking member is longitudinally and radially restrained to the stator.

3. A seal device according to Claim 2, whereby the radial restraint of the non-sparking member and stator is between innermost radial surface of the stator and the outermost radial surface of the non-sparking member..

4. A sealing device, according to any of the preceding claims, wherein the rotor is in sealing engagement with the shaft of a piece of rotating equipment via at least one solid deformable toroid member 5. A sealing device according to any of the preceding claims, wherein the non-sparking member is non-rotatabily coupled to either the stator or the rotor.

6. A sealing device according to any of the preceding claims, the device comprises at least one solid deformable toroid member positioned adjacent to the rotor and stator, said toroid member sealingly engaging the 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.

7. A sealing device according to any of the preceding claims, wherein the non-sparking member is longitudinally positioned towards the atmospheric side of the toroid member.

8. A seal device according to any of the preceding claims, the device comprising of at least one solid deformable toroid member in sealing engagement between the seal stator and the equipment housing.

9. A sealing device according to any preceding claim, the device comprising 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.

10. A sealing device according to Claim 10, wherein said radially extending cavity is circumferentiatly discontinued by an orifice which communicates between the sealed media and the outer most radial surface of the cavity.

11. A seal device according to any preceding claims, wherein the outermost 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.

12. A sealing device substantially described with reference to Figure 1 ro Figure 2 of the accompanying drawings.