GB2575987A

GB2575987A - Seal assembly

Info

Publication number: GB2575987A
Application number: GB1812396.8A
Authority: GB
Inventors: Kailasam Sivabalan; Ernest Kinnaird Holbrook Alan
Original assignee: Edwards Ltd
Current assignee: Edwards Ltd
Priority date: 2018-07-30
Filing date: 2018-07-30
Publication date: 2020-02-05
Also published as: JP2021532316A; CN112654767A; GB201812396D0; TWI803674B; CN112654767B; EP3830394A1; TW202012789A; WO2020025924A1

Abstract

A seal assembly for a rotating machine, a rotating machine and corresponding method are provided. The seal assembly 20 is for a rotating machine (10 in Figure 1) comprising shell stators (12, 14 in Figure 1) defining at least one pumping chamber and end pieces (16, 18 in figure 1) mountable at either end of the shell stators 12,14. The seal assembly 20 comprises: at least one annular seal 26, 28; and at least one longitudinal seal 22,24, the annular seal defining an aperture 26C, 28C, 26D, 28D for receiving the longitudinal seal 22, 24. The annular seal 26, 28 is configured to reduce a size of the aperture26C, 28C, 26D, 28D upon compression of the annular seal 26, 28. In this way, a multi‑component seal assembly is provided which benefits from simplicity of manufacture and ease of assembly, but which also provides for the sealing effectiveness of a one-piece seal due to the improved sealing between the annular seal 26, 28 and the longitudinal seal 22, 24 the aperture which receives the longitudinal seal reduces in size to improve the effectiveness of the seal when the annular seal is compressed.

Description

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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- 1 SEAL ASSEMBLY

FIELD OF THE INVENTION

The field of the invention relates to a seal assembly for a rotating machine, a rotating machine and method.

BACKGROUND

Rotating machines, such as compressors or pumps, need to be carefully designed and manufactured in order for the moving parts to cooperate with each other accurately. Providing effective seals to seal the machine is problematic, particularly when fluid flow is encouraged by a pressure difference between the machine and ambient environment. Although existing approaches can assist, they have undesired consequences. Accordingly, it is desired to provide an improved seal.

SUMMARY

According to a first aspect, there is provided a seal assembly for a rotating machine comprising shell stators defining at least one pumping chamber and end pieces mountable at either end of the shell stators, the seal assembly comprising: at least one annular seal; and at least one longitudinal seal, the annular seal defining an aperture for receiving the longitudinal seal therewithin, the annular seal being configured to reduce a size of the aperture upon compression of the annular seal. The first aspect recognises that some rotating machine configurations have a stator arrangement which have an axial split-line along the stator which is formed from, typically, a pair of shell stators (stator halves), and these shell stators are then received between a pair of end plates. This configuration provides a rotating machine which is more conveniently assembled and requires a seal along the axial split-line of the shell stators, as well as an annular seal between the stator and the end plates. The interface between the longitudinal seal and the annular seal is sometimes referred to as a T-joint. Although a one-piece seal can be used to seal both the shell stator to shell stator

-2interface and between the stator and the end plates, such a seal is complex and difficult to mould.

Accordingly, a seal is provided. The seal may be for a rotating machine. The rotating machine may comprise shell stators which define or provide one or more pumping chambers. The rotating machine may comprise end pieces which may be mountable at either end of the shell stators. The seal may comprise one or more annular seals. The seal may comprise one or more longitudinal seals. The annular seal may define or provide an aperture or opening. The aperture may receive or retain the longitudinal seal. The annular seal may be configured or arranged to reduce or shrink the aperture when the annular seal is compressed. In this way, a multi-component seal assembly is provided which benefits from simplicity of manufacture and ease of assembly, but which also provides for the sealing effectiveness of a one-piece seal due to the improved sealing between the annular seal and the longitudinal seal as the aperture which receives the longitudinal seal reduces in size to improve the effectiveness of the seal when the annular seal is compressed.

In one embodiment, the annular seal is configured to reduce the size of the aperture upon compression of the annular seal between the shell stators and the end piece. Accordingly, the size or dimension of the aperture may be reduced in response to compression of the annular seal by the shell stators and the end piece.

In one embodiment, the annular seal is configured, upon compression of the annular seal between the shell stators and the end piece in a longitudinal direction, to extend in a radial direction to reduce the size of the aperture. Accordingly, when the annular seal is compressed in the direction along which the longitudinal seals extend, the annular seal extends or expands in a radial direction which is generally transverse to the longitudinal direction which reduces the size of the aperture.

-3ln one embodiment, the annular seal is configured to reduce the size of the aperture to compress the longitudinal seal. Accordingly, the reduction in size of the aperture compresses or squeezes the longitudinal seal therewithin.

In one embodiment, the annular seal is deformable. Accordingly, the material from which the annular seal is made may deform or flow from one configuration to another in response to a force.

In one embodiment, the annular seal is an elastomer.

In one embodiment, the aperture is shaped to fit the longitudinal seal.

Accordingly, the aperture may be dimensioned to match the external shape of the longitudinal seal.

In one embodiment, the annular seal is shaped to constrict the aperture upon compression of the annular seal. Accordingly, the annular seal may constrict, narrow, contract or tighten the aperture against the longitudinal seal when the annular seal is squeezed.

In one embodiment, a surface defining the aperture is shaped to compress the longitudinal seal uniformly. Accordingly, the aperture may be shaped to extend uniformly when the annular seal is squeezed to compress and apply a uniform pressure along the length of the longitudinal seal within the aperture.

In one embodiment, the surface defining the aperture is recessed or concave.

In one embodiment, each annular seal comprises a pair of the apertures. Accordingly, two or more apertures may be provided, each of which may receive a respective longitudinal seal.

In one embodiment, the annular seal comprises annular faces shaped to engage with the shell stators and the end piece. Accordingly, the seal may be shaped to

-4fit with the shell stators and end piece to facilitate compression of the annular seal.

In one embodiment, the annular faces are planar.

In one embodiment, the annular seal comprises opposing, planar annular faces.

In one embodiment, the annular seal has a generally rectangular cross-section.

In one embodiment, the longitudinal seal is deformable.

In one embodiment, the longitudinal seal comprises an elastic and/or a ductile material.

In one embodiment, the longitudinal seal comprises a metal and/or an elastomer.

In one embodiment, the longitudinal seal is configured to form radial protrusions upon compression. Accordingly, the longitudinal seal may form or create radial or annular protrusions on its external surface when compressed by the annular seal.

In one embodiment, the longitudinal seal is configured to form at least one radial protrusion within the aperture upon compression by the shell stators.

Accordingly, the longitudinal seal may form or create radial or annular protrusions on its external surface when compressed by the shell stators. This provides for enhanced sealing between the longitudinal seal and the annular seal.

In one embodiment, the longitudinal seal is configured to form at least one radial protrusion extending within the aperture upon compression by the shell stators. Accordingly, the longitudinal seal may extend to fill the aperture during compression of the longitudinal seal. Again, this helps to improve the sealing between the longitudinal seal and the annular seal.

-5ln one embodiment, the longitudinal seal is dimensioned to form the at least one radial protrusion within a void defined by the aperture upon compression by the shell stators.

In one embodiment, the longitudinal seal is configured to form at least one radial protrusion bearing against an external annular face of the annular seal upon compression by the annular seal. Accordingly, the longitudinal seal may form or create a radial or annular protrusion which bears or urges against an external face of the annular seal when compressed. This provides for further sealing between the longitudinal seal and the annular seal and also locks the longitudinal seal in place to prevent movement during thermal cycling.

According to a second aspect, there is provided a rotating machine, comprising: shell stators defining at least one pumping chamber; end pieces mountable at either end of the shell stator; and the seal assembly of the first aspect and its embodiments.

In one embodiment, at least one of the shell stators and the end pieces comprise a member configured to restrict outward radial deformation of the annular seal upon compression of the annular seal. This helps to prevent the material of the annular seal from flowing at this radially outermost surface and encourages the material to flow into the aperture to improve the sealing between the longitudinal seal and the annular seal.

According to a third aspect, there is provided a method, comprising: providing at least one annular seal; providing at least one longitudinal seal, the annular seal defining an aperture for receiving the longitudinal seal therewithin; and compressing the annular seal to reduce a size of the aperture.

In one embodiment, the method comprises compressing the annular seal between shell stators and an end piece to reduce the size of the aperture.

-6ln one embodiment, the method comprises compressing the annular seal between the shell stators and the end piece in a longitudinal direction to extend the annular seal in a radial direction to reduce the size of the aperture.

In one embodiment, the method comprises compressing the longitudinal seal by reducing the size of the aperture.

In one embodiment, the annular seal is deformable.

In one embodiment, the annular seal is an elastomer.

In one embodiment, the method comprises shaping the aperture to fit the longitudinal seal.

In one embodiment, the method comprises shaping the annular seal to constrict the aperture upon compression of the annular seal.

In one embodiment, the method comprises shaping a surface defining the aperture to compress the longitudinal seal uniformly upon compression of the annular seal.

In one embodiment, the surface defining the aperture is recessed.

In one embodiment, the method comprises providing a pair of the apertures.

In one embodiment, the method comprises shaping annular faces of the annular seal to engage with the shell stators and the end piece.

In one embodiment, the annular faces are planar.

In one embodiment, the annular seal comprises opposing, planar annular faces.

-7ln one embodiment, the annular seal has a generally rectangular cross-section.

In one embodiment, the longitudinal seal is deformable.

In one embodiment, the longitudinal seal comprises at least one of an elastic and a ductile material.

In one embodiment, the longitudinal seal comprises at least one of a metal and an elastomer.

In one embodiment, the method comprises forming radial protrusions on the longitudinal seal upon compression.

In one embodiment, the method comprises forming at least one radial protrusion within the aperture upon compression by the shell stators.

In one embodiment, the method comprises forming at least one longitudinal protrusion extending within the aperture upon compression by the shell stators.

In one embodiment, the method comprises dimensioning the longitudinal seal to form the at least one longitudinal protrusion within a void defined by the aperture upon compression by the shell stators.

In one embodiment, the method comprises configuring the longitudinal seal to form at least one radial protrusion bearing against an external annular face of the annular seal upon compression by the annular seal.

In one embodiment, the method comprises restricting outward radial deformation of the annular seal upon compression of the annular seal.

-8Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

Figure 1 illustrates schematically a housing of a rotating machine according to one embodiment;

Figure 2 illustrates a seal assembly for sealing the housing according to one embodiment;

Figures 3A to 3C show schematically the steps for incorporating the seal assembly into the housing according to one embodiment; and Figure 4 illustrates an aperture profile according to one embodiment.

DESCRIPTION OF THE EMBODIMENTS

Before discussing the embodiments in any more detail, first an overview will be provided. Embodiments provide a sealing arrangement for a multi-component housing of a rotating machine such as a pump or a compressor. In order to facilitate ease of assembly, the housing or stator of a rotating machine may be formed from multiple component parts, shells or end plates which need to be sealed upon assembly. In one arrangement, the stator is formed by bringing together two or more stator housing parts or shells which are then retained between a pair of end plates. The stator housing parts typically require one or more longitudinal seals along their joining faces, with each end plate requiring an annular seal between that end plate and the stator housing parts. Providing effective sealing between the annular and longitudinal seals is problematic, and

-9so embodiments provide an arrangement where each annular seal has an aperture which receives each longitudinal seal. Compression of the annular seal between the end plate and the stator housing parts causes the apertures within which the longitudinal seals are received to contract, which provides for improved sealing between the longitudinal seal and the annular seal. In particular, when the annular seal is deformable, the compression of the annular seal causes it to deform, with the seal material flowing in response. The flow of the seal material causes the aperture to reduce in size, thereby compressing the longitudinal seal to improve sealing. When the longitudinal seal is also deformable, compression of the longitudinal seal by the stator housing parts causes the longitudinal seal material to flow, expanding into the aperture within the annular seal, which also improves sealing. The compression of the aperture during compression of the annular seal causes the material of the longitudinal seal to flow further to form an annular protrusion around an external face of the annular seal. This again improves the sealing and helps prevent movement of the seals during thermal cycling.

Rotating Machine

Figure 1 illustrates schematically a housing 10 of a rotating machine, according to one embodiment. The housing 10 comprises a pair of shell stators 12, 14 and a pair of end plates 16, 18. The shell stators 12, 14 define recesses which receive components of the rotating machine. The shell stators 12, 14 are brought together to retain the components in those recesses. The end plates 16, 18 are then brought to retain the shell stators 12, 14. This provides for particularly convenient assembly of the rotating machine.

However, as will be explained in more detail below, to adequately seal the shell stators 12, 14 together, a pair of longitudinal seals is required. Also, to ensure adequate sealing between the shell stators 12, 14 and the respective end plates 16, 18, a pair of annular seals is required.

- 10Sealinq Assembly

Figure 2 illustrates a seal assembly 20 for sealing the housing 10 according to one embodiment. The seal assembly 20 has a pair of longitudinal seals 22, 24 and a pair of annular seals 26, 28.

The longitudinal seals in this example are O-hng cords with a circular crosssection and are made of an elastomer material.

The annular seals 26, 28 are ring-shaped. In this example, the annular seals 26, 28 are square ring-shaped with curved comers. Major faces 26A, 26B, 28A, 28B are provided which abut against major faces of the end plates 16, 18 and the adjacent faces of the shell stators 12, 14. In this example, the annular seals 26, 28 have planar faces, a constant thickness and are made of an elastomer. The annular seals 26, 28 have apertures 26C, 26D, 28C, 28D into which the longitudinal seals 22, 24 are received. In this example, the apertures 26C, 26D, 28C, 28D are shaped and dimensioned to fit the external surface of the longitudinal seals 22, 24.

Although in this example the longitudinal seals 22, 24 are of constant, circular cross-section, it will be appreciated that they may be provided with alternative cross-sections such as square, triangular, oval, etc, and they may be of nonuniform cross-section. Also, the longitudinal seals 22, 24 need not be made of an elastomer but may simply be deformable; for example, made of a metal.

Although in this example the annular seals 26, 28 are made of an elastomer, it will be appreciated that they may be made of any material which is deformable. Although the major faces 26A, 26B, 28A, 28B in this example are planar, it will be appreciated that they may be any shape which is suitable for engaging with the major faces of the end plates 16,18 and the adjacent faces of the shell stators 12, 14.

- 11 Seal Assembly

Figures 3A to 3C show schematically the steps for incorporating the seal assembly 20 into the housing 10 according to one embodiment. The shell stator 14 is provided, into which components (not shown) of the rotating machine are assembled. The longitudinal seals 22, 24 are placed, typically in seal grooves (not shown) extending along the joining face of shell stator 14. The shell stator 12 is brought into close contact with the longitudinal seals 22, 24. The annular seals 26, 28 are received by protruding portions of the longitudinal seals 22, 24 and these protruding portions pass through the apertures 26C, 26D, 28C, 28D. The end plates 16, 18 are positioned in proximity to the annular seals 26, 28.

As shown in Figure 3B, the shell stators 12, 14 are clamped together, which compresses the longitudinal seals 22, 24 radially. The longitudinal seals 22, 24 deform and material flows out of the constricting volume between the shell stators 12, 14 and creates annular protrusions 24A within the apertures 26C, 26D, 28C, 28D which improves sealing between the annular seals 26, 28 and the longitudinal seals 22, 24.

As shown in Figure 3C, the end plates 16, 18 are brought together to compress the annular seals 26, 28 in the longitudinal direction. This causes the annular seals 26, 28 to deform and for material to flow in the radial direction, which reduces the size of the apertures 26C, 26D, 28C, 28D and radially compresses the longitudinal seal 22, 24 which improves sealing between the annular seals 26, 28 and the longitudinal seals 22, 24. This compression of the longitudinal seal 22, 24 causes material to flow in the longitudinal direction, which causes radial protrusions 24B to form adjacent the major faces 26A, 28A of the annular seals 26, 28 which improves sealing between the annular seals 26, 28 and the longitudinal seals 22, 24.

Hence, it can be seen that a tight seal is created between the apertures 26C, 26D, 28C, 28D and the longitudinal seals 22, 24, due to the tightening of the

- 12apertures on the longitudinal seals 22, 24 and the presence of the radial protrusions 24B. This helps to prevent leakage.

Although in this example the apertures 26C, 26D, 28C, 28D are defined by a planar surface to provide a constant aperture diameter through the annular seals 26, 28, it will be appreciated that non-planar surfaces may be provided. In particular, a concave surface may be provided, as illustrated in Figure 4, in order to provide for more uniform compression of the longitudinal seals 22, 24 within the aperture.

Also, although in this example the end plates 16, 18 have voids 16A, 18A into which the longitudinal seals 22, 24 project, it will be appreciated that the longitudinal length of the longitudinal seals 22, 24 may be shorter such that they only extend part way through the apertures 26C, 26D, 28C, 28D, which would obviate the need for the voids 16A, 18A in the end plates 16, 18.

Accordingly, embodiments provide an elastomer gasket and O-ring cord combination to provide a T-joint sealing arrangement for metal, plated or coated clam pumps. The O-hng cord would clamped by gasket to provide required sealing at any contact surfaces. The clamping within the arrangement would be immune to the surface fiction coefficient of any clamp.

As mentioned above, pumps which have an axial split-line along the stators require a seal at each end of the split-line, which is referred to as a T joint. Whilst a one-piece seal can be used to seal both the stator to stator interface and between the stators and the end plates, such a seal is complex and would be difficult to mould.

Some pump surfaces are plated and have a lower friction co-efficient compared to existing materials. Existing sealing solutions have temperature and surface friction co-efficient limitations which results in leaking. As the process applications become more challenging, plated stators and rotors are required to

- 13overcome process condensation and corrosion. Embodiments clamp the O-ring cord within a gasket which would be immune to high temperature and surface friction.

In embodiments, the O-ring cord is the interlink between both gaskets. It will be appreciated that the cord and the gasket can have different shapes or thicknesses to suit the arrangement of the housing. The O-ring cord is placed between clamshells. The clamshells are spaced by a tool. Then gaskets are placed on both ends. An end plate is placed both ends but not torqued up. The clamshells are torqued in sequence so those clamshells are well aligned and the O-ring cord sandwiched to create the seal. The O-ring cord might fill the gasket hole (interconnection) due to compression. The end plates are torqued up in sequence. The interconnection hole will minimise in size and grip the O-ring cord, thus providing T-joint sealing. The O-ring cord is trapped within the gasket thus preventing T-joint sealing failure on low friction surfaces. Embodiments use 2 body elastomers to create a T-joint sealing with plated or coated surface clamshells which have a lower surface friction coefficient.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

- 14REFERENCE SIGNS

- Housing

12, 14-Shell Stator

16, 18 - End Plates

16A, 18A-Void

- Seal Assembly

22, 24 - Longitudinal Seal

24A, 24B - Radial Protrusion io 26, 28 - Annular Seal

26A, 26B, 28A, 28B - Major Faces

26C, 26D, 28C, 28D - Apertures

Claims

1. A seal assembly for a rotating machine comprising shell stators defining at least one pumping chamber and end pieces mountable at either end of the shell stators, said seal assembly comprising:

at least one annular seal; and at least one longitudinal seal, said annular seal defining an aperture for receiving said longitudinal seal therewithin, said annular seal being configured to reduce a size of said aperture upon compression of said annular seal.

2. The seal assembly of claim 1, wherein said annular seal is configured to reduce said size of said aperture upon compression of said annular seal between said shell stators and said end piece.

3. The seal assembly of claim 1 or 2, wherein said annular seal is configured, upon compression of said annular seal between said shell stators and said end piece in a longitudinal direction, to extend in a radial direction to reduce said size of said aperture.

4. The seal assembly of any preceding claim, wherein said annular seal is configured to reduce said size of said aperture to compress said longitudinal seal.

5. The seal assembly of any preceding claim, wherein said annular seal is deformable.

6. The seal assembly of any preceding claim, wherein said annular seal is an elastomer.

7. The seal assembly of any preceding claim, wherein said aperture is shaped to fit said longitudinal seal.

8. The seal assembly of any preceding claim, wherein said annular seal is shaped to constrict said aperture upon compression of said annular seal.

9. The seal assembly of any preceding claim, wherein a surface defining said aperture is shaped to compress said longitudinal seal uniformly.

10. The seal assembly of claim 9, wherein said surface defining said aperture is recessed.

11. The seal assembly of any preceding claim, comprising a pair of said apertures.

12. The seal assembly of any preceding claim, wherein said annular seal comprises annular faces shaped to engage with said shell stators and said end piece.

13. The seal assembly of claim 12, wherein said annular faces are planar.

14. The seal assembly of any preceding claim, wherein said annular seal comprises opposing, planar annular faces.

15. The seal assembly of any preceding claim, wherein said annular seal has a generally rectangular cross-section.

16. The seal assembly of any preceding claim, wherein said longitudinal seal is deformable.

17. The seal assembly of any preceding claim, wherein said longitudinal seal comprises at least one of an elastic and a ductile material.

18. The seal assembly of any preceding claim, wherein said longitudinal seal comprises at least one of a metal and an elastomer.

19. The seal assembly of any preceding claim, wherein said longitudinal seal is configured to form radial protrusions upon compression.

20. The seal assembly of any preceding claim, wherein said longitudinal seal is configured to form at least one radial protrusion within said aperture upon compression by said shell stators.

21. The seal assembly of any preceding claim, wherein said longitudinal seal is configured to form at least one radial protrusion extending within said aperture upon compression by said shell stators.

22. The seal assembly of any preceding claim, wherein said longitudinal seal is dimensioned to form said at least one radial protrusion within a void defined by said aperture upon compression by said shell stators.

23. The seal assembly of any preceding claim, wherein said longitudinal seal is configured to form at least one radial protrusion bearing against an external annular face of said annular seal upon compression by said annular seal.

24. A rotating machine, comprising:

shell stators defining at least one pumping chamber;

end pieces mountable at either end of the shell stator; and said seal assembly as claimed in any preceding claim.

25. A method, comprising: providing at least one annular seal;

providing at least one longitudinal seal, said annular seal defining an aperture for receiving said longitudinal seal therewithin; and compressing said annular seal to reduce a size of said aperture.