WO2010020364A1

WO2010020364A1 - Slide ring seal arrangement having an improved secondary seal

Info

Publication number: WO2010020364A1
Application number: PCT/EP2009/005834
Authority: WO
Inventors: Andreas Schrüfer; Joachim Otschik; Günther Lederer; Petia Philippi; Peter Dröscher; Andreas Fesl; Berthold Vogel
Original assignee: Burgmann Industries Gmbh & Co. Kg
Priority date: 2008-08-19
Filing date: 2009-08-11
Publication date: 2010-02-25
Also published as: DE202008011032U1

Abstract

The invention relates to a slide ring seal arrangement comprising a stationary slide ring (2) having a first slide surface (2a), and a rotating slide ring (3) having a second slide surface (3a), wherein the rotating slide ring (3) mutually rotates together with a rotating component (10), wherein the slide surfaces (2a, 3a) of the slide rings (2, 3) are positioned opposite each other and define a seal gap (4) between each other, and a secondary seal (13), which provides a seal at a secondary seal gap (16) on one of the slide rings (2, 3) between the slide ring and a further component (11), wherein the secondary seal (13) is configured in an annular manner, and wherein the secondary seal (13) is made from a material having regions of varying degrees of stiffness in the axial direction (X-X).

Description

Mechanical seal assembly with improved secondary seal

description

The present invention relates to a mechanical seal assembly having a pair of sliding rings with an improved secondary seal which provides sealing at one of the slip rings at a secondary sealing gap.

Mechanical seal assemblies are known in the prior art in various configurations. In this case, mechanical seal assemblies are used in various fields of application. An example of this is gas-lubricated mechanical seal assemblies, which are used, for example, in compressors that compress a gas, such as natural gas. However, such natural gas compressors are operated in part to generate very high pressures of 800 x 10 ⁵ Pa or more. It has been found that in the previously used secondary seals, which provide a seal at a secondary sealing gap between a sliding ring and another component (eg housing), extrusion phenomena occur, whereby the material of the secondary seal in the secondary sealing gap between the sliding ring and the component is involved. In extreme cases, so thin-walled, tubular approaches can arise, which are pulled through the entire secondary sealing gap and can lead to impairment of the function of the mechanical seal assembly.

It is therefore an object of the present invention to provide a mechanical seal assembly with a secondary seal, which is easy to use even with media with very high pressures with a simple design and simple, cost manufacturability.

The mechanical seal assembly according to the invention with the features of claim 1 has the advantage that it can be used even at the highest pressures. This is u.a. is achieved by using an improved secondary seal, which provides a seal at a secondary sealing gap between one of the sliding rings of the mechanical seal assembly and another component, e.g. a housing component, provides. The secondary seal is annular and is made of a material which has areas of different stiffness in the axial direction of the secondary seal. Thus, according to the invention a secondary seal is proposed, which has different resistance to the forces acting on it at different areas. In this way, an undesired plastic deformation can be prevented at selected regions of the secondary seal and in particular an extrusion of the secondary seal can be avoided by the secondary sealing gap between the seal ring and another component. According to the invention, the secondary seal can thus have a very good resistance to deformation, which can occur in particular due to use of the mechanical seal arrangement at very high pressures of the medium. Thus, according to the invention, a secondary seal can be provided which has an area of high rigidity which is resistant to extrusion and prevents undesired deformation of the secondary seal, in particular pulling it into the secondary sealing gap.

Preferably, a region with the highest rigidity of the secondary seal is arranged at a first end of the secondary seal. The first end of the secondary seal is arranged at the secondary sealing gap. Thus, it can be prevented that Material of the secondary seal is extruded into the secondary sealing gap between the sliding ring and further component.

More preferably, the secondary seal at a second end on a first leg portion and a second leg portion, which form a U-shaped recess or a V-shaped recess in section. By the U- or V-shaped recess, the second end of the secondary seal on an enlarged surface, which comes into contact with a pressurized medium, so that in particular an improved sealing behavior in the radial direction of the secondary seal is achieved.

Particularly preferably, a rigidity of the secondary seal changes continuously in the axial direction. Preferably, a continuous change in rigidity is achieved by using at least two different materials whose mixing ratio varies continuously in the axial direction. The secondary seal preferably comprises polytetrafluoroethylene (PTFE) and polyetheretherketone (PEEK), with a proportion of PEEK continuously increasing in the direction of the first end of the secondary seal in order to continuously increase the rigidity of the secondary seal in the direction of the first end. The secondary seal preferably has a proportion of 100% of PEEK at the first end and a proportion of 100% of PTFE at the opposite second end. Thus, the secondary seal is preferably made of a penetration composite of at least two different materials having different properties.

According to an alternative embodiment of the present invention, the secondary seal is made of at least three separate components, wherein the at least three separate components form a one-piece secondary seal. The at least three components form an integral secondary seal in the form of a layered composite material, wherein each of the components provides a layer. Preferably, a first component is made of a material having a first elasticity, a second component is a fabric, and a third component is made of a material having an elasticity which is greater than the elasticity of the first component. For example, the first component is PEEK and the third component PTFE. Since the secondary seal must provide certain sealing properties, in particular, the first component must also have a certain elasticity in order to provide sufficient sealing of the secondary sealing gap between a sliding ring and another component. Preferably, the second component of the secondary seal formed as a layer composite material is a glass fabric or a carbon fiber fabric or a glass-carbon fiber blended fabric. Alternatively, graphite or another carbon-based fabric with further additives can be used as a second component.

In order to have particularly good sealing properties, the secondary seal further comprises a circumferential recess formed on a radially inner peripheral region of the secondary seal. The circumferential recess is preferably concave.

In order to have even better resistance to undesirable deformation of the secondary seal, the secondary seal further comprises a stiffening element. Preferably, the stiffening element is arranged in the U- or V-shaped recess of the secondary seal. As a stiffening element, a U-shaped or V-shaped metallic element can be used. In order to prevent undesired loosening of the stiffening element from the secondary seal, the secondary seal preferably has a radially outwardly directed shoulder on its first leg. This can prevent it from moving out of the stiffening element from the secondary seal.

Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing is:

1 is a schematic sectional view of a mechanical seal assembly with secondary seal according to a first embodiment of the invention,

2 shows a schematic sectional view of the secondary seal of the first exemplary embodiment, 3 is a schematic sectional view of a secondary seal according to a second embodiment of the invention,

4 shows a schematic sectional view of a secondary seal according to a third exemplary embodiment of the invention,

Fig. 5 is a schematic sectional view of a secondary seal according to a fourth embodiment of the invention, and

Fig. 6 is a schematic sectional view of a secondary seal according to a fifth embodiment of the invention.

Hereinafter, with reference to FIGS. 1 and 2, a mechanical seal assembly 1 with a secondary seal 13 according to a first embodiment of the invention will be described in detail.

As can be seen from Fig. 1, the mechanical seal assembly 1 comprises a first stationary seal ring 2 and a second rotating seal ring 3. The rotary seal ring 3 is fixed in a sleeve 12 which is fixed to a rotating shaft 10. Thus, the rotating seal ring 3 rotates together with the shaft 10. The two slip rings 2, 3 have opposing sliding surfaces 2a, 3a, which define a sealing gap 4 between them. The mechanical seal assembly 1 seals between a first space 5 and a second space 6. In this embodiment, the mechanical seal assembly is a gas-lubricated mechanical seal assembly used in a compressor which generates very high pressures. The pressures are here between 500 x 10 ⁵ Pa and 800 x 10 ⁵ Pa and the compressor is used in a compression of natural gas, which is conveyed into underground caverns for storage.

The mechanical seal assembly 1 further includes a biasing means 7 biasing the stationary seal ring 2 against the rotary seal ring 3, and the biasing means 7 comprises a pressure transmitting ring 8 and a plurality of biasing springs 9 distributed along the circumference. The Biasing device 7 allows the stationary seal ring in the axial direction X-X perform certain compensating movements and in particular ensures that the sealing gap 4 between the two slip rings 2, 3 is minimized.

As can also be seen from Fig. 1, the rear side, i.e. the side facing away from the sliding surface 2a of the stationary sliding ring 2, is also connected via the pressure ring 8 to the space 5, which comprises the pressurized medium. As a result, however, a secondary sealing gap 16, which is present between the stationary seal ring 2 and a bearing surface 11a on the housing 11, must be sealed. For this purpose, a secondary seal 13 is provided, which is arranged radially within the pressure ring 8.

The secondary seal 13 is annular and provides a seal at the beginning of the secondary sealing gap 16 ready. The secondary seal 13 is shown in detail in FIG. 2. The secondary seal 13 is a one-piece component, but made of different materials. In other words, the secondary seal 13 is a one-piece composite component.

The secondary seal 13 has a first end 13a and a second end 13b, which are aligned opposite to each other in the axial direction X-X. The first end 13a is in this case with the stationary seal ring 2 in contact. The second end 13b is substantially free and in contact with the medium to be sealed, which is under high pressure. As can be seen in FIG. 2, the secondary seal 13 further comprises a first leg 13c and a second leg 13d, which are arranged at the second end 13b of the secondary seal. Between the two legs 13c, 13d, a V-shaped recess 13e is formed. The reference numeral 13f denotes an inner peripheral recess.

As can be seen further from FIG. 2, the secondary seal is produced as a composite component from two different materials. At the first end 13a of the secondary seal is provided as the material 14 PEEK and the second material 15, which forms the remaining part of the secondary seal 13 and in particular the two legs 13c and 13d, is PTFE. As can be seen from FIG. 2, the PEEK material 14 is in the form of a layer on the end of the PTFE tube facing the static sliding ring 2. Materials 15 arranged. Thus, the secondary seal 13 of the first embodiment consists of two different materials which have different stiffnesses in the axial direction XX. Here PEEK has a higher stiffness than PTFE, so that in particular it has an improved extrusion resistance to extrusion through the secondary sealing gap 16 as PTFE. In this way it can be prevented that despite the use of the mechanical seal assembly at extremely high pressures, the secondary seal is drawn into the secondary sealing gap 16 between the stationary seal ring 2 and the bearing surface 11a on the housing member 11. Nevertheless, the portion 13b of the sub-seal 13 in contact with the high-pressure medium has sufficient elasticity to allow excellent sealing by deformation of the PTFE. The seal is in this case supported in particular by the V-shaped recess 13e and the two legs 13c and 13d.

Thus, a secondary seal 13 can be provided, which are also used in high pressure applications and high temperature applications. In this case, in particular, the part made of PEEK of the secondary seal is protected by the PTFE, which has an excellent resistance to almost all media. Due to the integral nature of the secondary seal 13, a simple and cost-effective installation can furthermore be achieved, with the secondary seal, although comprising two different materials, nevertheless being able to be manufactured relatively simply and inexpensively.

Hereinafter, a secondary seal according to a second embodiment will be described with reference to FIG. 3, wherein identical or functionally identical parts are denoted by the same reference numerals as in the first embodiment.

As shown in FIG. 3, the sub-seal 13 of the second embodiment has substantially the same shape as the sub-seal of the first embodiment, but the sub-seal 13 of the second embodiment is made of three different materials. As can be seen from FIG. 3, the secondary seal 13 is made of a first component 14 of PEEK, of a second component 15 of PTFE and a third Component 17 made of a fabric. The fabric 17 is arranged between the other two components. Thus, the secondary seal 13 of the second embodiment is constructed similarly to a multilayer composite component, wherein the thickness of the fabric 17 is smaller than a thickness of the PEEK material and the PTFE material. The fabric 17 is, for example, glass fiber or carbon fiber or a mixture of these fibers. The arrangement of the tissue between the materials PEEK and PTFE allows a very good separation of the two materials. Otherwise, this embodiment corresponds to the first embodiment, so that reference may be made to the description given there.

Fig. 4 shows a secondary seal of a mechanical seal assembly according to a third embodiment of the invention, in turn, the same or functionally identical parts are designated as in the preceding embodiments.

As shown in FIG. 4, a shape of the sub-seal 13 of the third embodiment is substantially the same as that of the first and second embodiments. In contrast, in the side seal 13 of the third embodiment, there is no sharp separation between the various materials used. The secondary seal 13 of the third embodiment is made of the two materials PEEK and PTFE. Here, in particular, the two legs 13c, 13d made of PTFE and a share of PEEK increases continuously up to the first end 13a. In FIG. 4, the area made exclusively of PTFE is marked with the letter A, and the area in which the proportion of PEEK in PTFE increases continuously is indicated by the letter B. The arrow C is intended to illustrate the increasing proportions of PEEK in PTFE. At the end facing the stationary seal ring 2 end 13a of the secondary seal 13, a PEEK proportion should be 100%. Thus, a penetration of the secondary seal with PEEK, starting from a position at about 2/3 of the total length of the secondary seal 13 increases continuously, so that the secondary seal 13 may also be referred to as a partial-penetration composite workpiece. In this case, only the region B is penetrated by PEEK in order to obtain an improved rigidity of this end of the secondary seal 13. Otherwise, this embodiment corresponds to the previous embodiments, so that reference may be made to the description given there.

5 and 6 show secondary seals for a mechanical seal assembly according to a fourth and fifth embodiment of the invention, in turn, the same or functionally identical parts are designated as in the preceding embodiments.

As is apparent from Figs. 5 and 6, the secondary seals of the fourth and fifth embodiments are mirror-inverted to the secondary seals of the previous embodiments. Here, the secondary seal 13 of the fourth embodiment corresponds substantially to the secondary seal of the third embodiment. Furthermore, the secondary seal of the fifth exemplary embodiment in FIG. 6 essentially corresponds to the secondary seal of the second exemplary embodiment of FIG. 3. In contrast to the previous exemplary embodiments, the secondary seals of the fourth and fifth exemplary embodiments also have a stiffening element 18. The stiffening element 18 is made of a metallic material or a plastic material and has in section substantially a V-shaped configuration. As can be seen from FIGS. 5 and 6, the stiffening element 18 is arranged in a substantially U-shaped recess 13e. In order to prevent the stiffening element 18 from unintentionally releasing from the secondary seal 13, a circumferential, radially outwardly projecting shoulder 13g is also formed integrally with the first leg 13c on the first leg 13c. In particular, the stiffening element 18 has the task of spreading the two legs 13c, 13d in order to achieve an improved seal in the region of the radially inwardly or radially outwardly directed surfaces of the legs 13c, 13d. Otherwise, the fourth and fifth embodiments of the second and third embodiments, so that reference may be made to the description given there.

Claims

claims

A mechanical seal assembly comprising a stationary slip ring (2) having a first sliding surface (2a), a rotating slip ring (3) having a second sliding surface (3a), said rotating slip ring (3) being integral with a rotating member

(10) rotates, wherein the sliding surfaces (2a, 3a) of the sliding rings (2, 3) facing each other and define between them a sealing gap (4), and a secondary seal (13) which on one of the sliding rings (2, 3) a

Sealing at a secondary sealing gap (16) between the sliding ring and a further component (11), wherein the secondary seal (13) is annular, and wherein the secondary seal (13) is made of a material which in the axial direction (XX) regions of different Having stiffness.

Second mechanical seal assembly according to claim 1, characterized in that a stiffest portion of the secondary seal (13) at a first end (13 a) is arranged and the first end (13 a) at the secondary sealing gap (16) is arranged.

3. Mechanical seal arrangement according to claim 1 or 2, characterized in that at a second end (13b) of the secondary seal (13), a first leg (13c) and a second leg (13d) are formed, which between them a U-shaped in section Form recess or a cut V-shaped recess (13e).

4. Mechanical seal arrangement according to one of the preceding claims, characterized in that the rigidity of the secondary seal (13) in the axial direction (X-X) changes continuously.

5. Mechanical seal assembly according to claim 4, characterized in that the secondary seal (13) comprises PTFE and PEEK, wherein a proportion of PEEK in the direction of the first end (13a) of the secondary seal (13) continuously rises to continuously increase a rigidity of the sub-seal (13) toward the first end (13a).

6. mechanical seal assembly according to one of claims 1 to 3, characterized in that the secondary seal (13) is made of at least three separate components, wherein a first component (14) has a rigidity which is greater than a rigidity of a third components (15) and a second component (17) is a fabric disposed between the first and third components, and wherein the at least three separate components form an integral secondary seal.

7. The mechanical seal assembly according to claim 6, characterized in that the second component (17) is a glass fabric, or a carbon fiber fabric or a glass-carbon fiber blended fabric or graphite or a carbon-containing fabric.

8. The mechanical seal assembly according to one of the preceding claims, characterized in that the secondary seal (13) at a radially inner peripheral region has an inner circumferential recess (13f).

9. mechanical seal assembly according to one of claims 3 to 8, characterized in that the secondary seal (13) further comprises a stiffening element (18) which is arranged in the U- or V-shaped recess (13e).

10. mechanical seal assembly according to claim 9, characterized in that the secondary seal (13) on the first leg (13c) has a radially outwardly directed shoulder (13g) to prevent inadvertent release of the stiffening element (18) of the secondary seal (13) ,