WO2010020394A1

WO2010020394A1 - Sliding ring for a sliding ring seal

Info

Publication number: WO2010020394A1
Application number: PCT/EP2009/005968
Authority: WO
Inventors: Oliver Nöll
Original assignee: Surcoatec International Ag
Priority date: 2008-08-19
Filing date: 2009-08-18
Publication date: 2010-02-25
Also published as: DE102008038396A1; EP2350504A1

Abstract

The invention relates to a sliding ring (2) for a sliding ring seal, having at least one groove (1) being disposed on an upper side of the sliding ring (2), wherein the groove (1) comprises a feed region (3) leading toward the circumferential side of the sliding ring (2), wherein the feed region (3) of the groove (1) comprises a cross-sectional narrowing. In this manner the lift-off effect caused by a groove is further improved, and the friction of a sliding ring seal is substantially reduced. Furthermore, the lifespan of such seals is increased significantly.

Description

LOW RING FOR A SEAL SEAL -

The invention relates to a sliding ring for a mechanical seal, with at least one groove arranged on an upper side of the sliding ring.

Slip rings and counter rings are the two main components of a mechanical seal. As a sliding ring, the axially movable sealing ring of a mechanical seal is called. He is usually pressed by a spring to the mating ring. The counter ring usually sits rigidly in the stationary part or in the housing, the sliding ring, however, is usually mounted on the rotating shaft. Sliding ring and counter ring are constantly in contact in many cases. One calls them also as Gegenlaufpaare. They can be made of the same material, but often also form different materials, the mating pairs.

As slip ring or mating ring, a number of different materials come into question, which can be divided into four main groups: carbon materials, ceramic materials, metallic materials and plastic. The group of carbon materials includes carbon graphite, electrographite and resin-bonded carbon. The second group, the group of ceramic materials, includes silicon carbide, aluminum oxide and tungsten carbide. The third group, the group of metallic materials, includes steel, cast iron and chrome casting. For example, polytetrafluoroethylene (PTFE) belongs to the last group, the fourth group. In the following, the main focus will be on the ceramic materials. Due to their good tribological properties, they have replaced the metallic materials such as chrome casting, chrome molybdenum nut and chromium-nickel molybdenum steel as hard partners in mechanical seals. In addition to aluminum oxide and tungsten carbide, silicon carbide has acquired the greatest importance here because of its excellent properties. Silicon carbide is light (density: 3 g / cm ³ ) and extremely hard (Vickers hardness: 1500 to 3000 HV). This silicon carbide is very wear-resistant, very good thermal conductivity and has about twice as large elastic modulus as chrome steel. Furthermore, silicon carbide has a very good chemical resistance and corrosion resistance. Due to the importance of silicon carbide, a number of other specialty ceramics based on silicon carbide have been developed.

Important in the design of mechanical seals is the choice of materials. The type of mating depends heavily on the conditions of use. For sealing gaseous media, for example, hard-soft pairings are recommended. In abrasive media, more wear-resistant hard-hard pairings are required. The selection of the suitable material combination for the mechanical seal must be done very carefully.

Mechanical seals are also called dynamic seals and take over the sealing of rotating waves against a wall, for example, to a

Machine housing belongs. Main components are the already mentioned successive sliding components, the mostly feathered sliding ring and a counter ring. One of the two rings sits rigidly in the stationary part, i. in the case, the other is with the help of

Anti-rotation pins mounted on the rotating shaft. The surfaces between these two parts are usually flat depending on the type of mechanical seal and are usually made of carbon-graphite materials, metal, ceramic, plastic or resin-bonded carbon. Two groups of mechanical seals can be distinguished: the axial and the radial mechanical seal. As special forms of the axial mechanical seal apply the feed head gaskets, which are also called steam head gaskets, and ball valve seals. The radial seals can be subdivided into gap seals and contact seals.

The opposing axial or radial sealing surfaces rotate relative to each other and form a primary sealing gap. Depending on the state of matter, the surrounding medium creates a liquid or gaseous lubricating film between the sealing surfaces. The sealing of the mechanical seal parts with respect to the shaft or housing is generally carried out with secondary seals in the form of additional O-rings or sleeves. In this respect, mechanical seals basically consist of five components: the sliding ring, the mating ring, the feathering and one secondary seal each. Depending on the design of the seals, the number of components can be reduced or significantly increased.

Hard-soft pairing refers to a combination of sliding parts in which one of the sliding partners is significantly softer than the other, thus more easily worn, but also has better emergency running properties under unfavorable lubrication conditions. In Hart-Hart pairings, both sliding rings are made of hard and wear-resistant material. This pairing is mainly used in abrasive products, but has poor emergency running properties. In addition to the material pairing, the absolutely flat design of the sliding surfaces and the roughness depth are of crucial importance for the tightness and wear. They are therefore usually u.a. lapped and polished.

Main applications for mechanical seals include pumps for service water, feed water, car radiators or air conditioners, agitators, centrifuges or water turbines. These are mechanical seals for shaft diameters of approx. 5 to 630 mm, pressures of approx. 0.01 to 300 bar, temperatures of about -200 to +450 ° C and sliding speeds of up to about 150 m / s known.

The gaskets are roughly divided into contact gaskets and non-contact gaskets, as well as the type of relative movement of the parts to be sealed against each other: static (no movement), translational (back and forth) and rotary (rotating). The seals have the task of preventing or limiting unwanted mass transfer from one room to another. For example, the unwanted leakage or the mixing of substances should be prevented, for example, to reduce pressure or temperature changes. But seals can also take on other functions, such as the function of an electrical insulator, or serve for heat conduction or heat dissipation or power transmission. A mechanical seal belongs to the group of rotary seals, since the relative movement of the sealing elements is of a rotary nature.

It is known that mechanical seals can have grooves, also called throats. The groove or throat is an elongated depression or groove. The groove may, for example, have a rectangular cross-section or be designed in a trapezoidal shape with an outwardly slanted wall or as a dovetail. For example, grooves serve to fix, guide or sink components. In mechanical engineering, grooves serve as "counterparts" to seals.

^■ i

In order to engrave such grooves in the slip rings with the help of a laser, such as a YAG laser, one uses the so-called "Venturi nozzle effect." Without such grooves, the sliding seals would break after a short time due to the great friction.

A Venturi nozzle, also called Venturi tube, consists of a smooth-walled pipe section with a narrowing of the cross-section, for example, by two oppositely directed Konen, which are united at the point of their smallest diameter. At this point a pick-up tube is placed next to it. If a gaseous or liquid medium flows through the Venturi nozzle, the dynamic pressure or the dynamic pressure at the narrowest point of the tube is maximal and the static pressure or the static pressure is minimal. The velocity of the flowing fluid, ie the flowing gas or the liquid, increases in proportion to the cross sections as it flows through the constricted part, because the same amount flows through everywhere. At the same time, the pressure in the pick-up tube, which sits exactly in the narrow part, decreases. This creates a differential pressure that is then used in a variety of measuring instruments or for the suction of liquids or gases. The pressure difference is given in ideal gases and liquids, ie in incompressible media and without friction, by the Bernoulli equation.

Venturi nozzles are today in the art in a variety of applications, because they work low maintenance and cost. The pressure is the least where the cross-section of the tube is closest or the flow velocity is highest.

The US 6,446,976 Bl describes mechanical seals with grooved seal locks. This document describes T-shaped grooves (T-grooves) and spiral-shaped grooves (spiral grooves) which are "lasered" into the slip ring by means of a laser, as will be further described in US 7,194,803 B2, for this purpose an excimer laser This is, for example, a krypton-fluoride laser.

WO 2006/005359 A1 discloses a mechanical seal assembly comprising at least one pair of sealingly cooperating seal rings, one of which is mountable on a rotating member for conjoint rotation therewith. The other slide ring is held non-rotating relative to a stationary component. Furthermore, the arrangement comprises a device for centering the rotating component relative to the stationary component. The engaging in the grooves centering element is in at least the taken in the rotating component groove with clearance in radial planes, so that a throttle gap is formed in the annular space and further the grooves are rotatable relative to each other. The throttle gap causes a seal of a quench fluoride space with respect to the outside atmosphere, also an emergency seal is thereby created.

In the prior art, the high frictional forces are problematic, even when using the grooves described, which adversely affect the so-called "lift-off effect." Such grooves, which basically support the lift-off effect, become "lift-off grooves " called. In the worst case, i. In the case of very high friction and / or in the absence of lift-off grooves, slip ring and counter ring collapse and the motor shaft stops. The described T-grooves and spiral grooves only reduce the friction somewhat, because the lift-off effect starts relatively late.

It is the object of the invention to provide a way to further reduce the friction in mechanical seals or almost extinguish the friction and thus to increase the lift-off effect. Thus, the life of such mechanical seals should be extended.

This object is achieved by a sliding ring for a mechanical seal, with at least one groove arranged on an upper side of the sliding ring, wherein the groove comprises a feed region leading to the peripheral side of the sliding ring, and wherein the feed region of the groove comprises a cross-sectional constriction.

By "guiding the feeding area of the groove to the peripheral side of the sliding ring", it is meant that the feeding area of the groove is arranged to allow access of a certain depth to the groove not only from the top and bottom of the sliding ring but also from the bottom Peripheral side of the sliding ring is possible. By "cross-sectional constriction of the Zuführungsbe ^'realm of the groove" is meant that the cross section of the feed area of the groove, more specifically the Querschnittsfiäche is parallel to an upper side of the sliding ring, first close and then wider again. This means that the cross-sectional area until a constriction area, and then For this purpose, inserted special structures can be used, as described below, for example bevels or steps.

According to a preferred embodiment of the invention, the cross-sectional constriction of the feed region comprises a slope, such as a linear straight line, also called leveling or ramp, a double slope, a plurality of steps and / or a butterfly-shaped structure. Preferably, the double slope corresponds to two consecutive slopes with the same slope and opposite signs. In addition, stair steps are preferably designed on the slopes and / or double slopes, which are preferably designed in miniature.

According to another preferred embodiment of the invention, the butterfly-shaped structure is lasered into the feed area of the groove. This butterfly-shaped structure is also referred to as "butterfly lasering." Preferably, the butterfly-shaped structure corresponds to at least two double bevels opposite the groove of the groove All the structures mentioned above support the Venturi nozzle effect, thereby reducing friction in a mechanical seal it is also possible to arrange the structures at one end of the groove or to combine different structures at different regions of the groove.

According to another preferred embodiment of the invention, the cross-sectional constriction has a depth of <6 microns the peripheral side of the sliding ring, preferably a depth of <2 microns in the peripheral side of the sliding ring. According to a further preferred exemplary embodiment of the invention, at least one delimiting wall of the groove has a continuous gradient in the peripheral side of the sliding ring. Preferably, the continuous slope corresponds to a linear slope.

According to a further preferred embodiment of the invention, the bottom of the groove has stored waves for increasing the back pressure. These waves produce more and / or stronger eddies because they contain a constriction, or a subsequent elevation, causing a so-called "pressure / suction pattern." This further enhances the Venturi nozzle effect.

According to a further preferred embodiment of the invention, the groove T-shaped (T-slot), spiral (spiral groove), rectangular, curved and / or curved designed. Preferably, the slip ring comprises a material of silicon nitride (SiN), silicon carbide (SiC), hardened steel and / or a hard metal. The hard metal preferably comprises tungsten nitrite (WoN) and / or tungsten carbide (WoC). According to another preferred embodiment, the material comprises a multilayer layer. The multilayer layer preferably comprises a high-velocity oxygen fuel layer (HVOF layer) and / or a diamond-like carbon layer (DLC layer). The layers are preferably applied as multilayers.

According to a further preferred embodiment of the invention, the sliding ring is designed as a counter ring. Preferably, the mechanical seal is suitable for a fluid to flow through it. The flowing fluid preferably comprises a gaseous medium or a liquid medium. With the device according to the invention, the lift-off effect is fundamentally promoted and thus kept the friction in mechanical seals as low as possible. Thus, the life of such mechanical seals is increased.

The invention will be explained with reference to ^"preferred embodiments with reference to the drawings in further detail.

Fig. 1 shows a slide ring with a T-groove on a top according to a first preferred embodiment of the invention;

Fig. 2 is a plan view of the T-slot with butterfly laser according to a second preferred embodiment of the invention;

Fig. 3 shows the T-groove with a double slope at one end according to a third preferred embodiment of the invention; and

Fig. 4 shows stored waves on the bottom of the T-groove according to a fourth preferred embodiment of the invention.

According to a first preferred embodiment of the invention, in a mechanical seal consisting of a sliding ring 2 and a counter ring made of silicon nitride (SiN), lift-off grooves are "lasered out" or engraved into the slip ring by means of a laser. By "edge throw-up" is meant an uneven sloping surface on the slide ring in the vicinity of the groove.

Fig. 1 shows a T-slot 1 arranged in a sliding ring 2, wherein the T-slot 1 was lasered on the top of the sliding ring 2. According to this first embodiment of the invention, the sliding ring 2 comprises a groove 1 arranged on an upper side. According to others preferred exemplary embodiments, a plurality of grooves on an upper side of the sliding ring and / or arranged on the peripheral side of the sliding ring. According to yet other preferred embodiments, the grooves are arranged concentrically, radially and / or axially in the sliding ring. As can be seen in FIG. 1, the T-slot 1 comprises a feed area 3 leading to the peripheral side of the sliding ring 2, so that the T-slot 1 is accessible not only from the upper side of the sliding ring 2 but also from the peripheral side of the sliding ring 2 is.

Fig. 2 shows a plan view of the T-slot 1 according to a second preferred embodiment of the invention. The feed region 3 of the T-groove 1 has a butterfly-shaped structure or a butterfly laser. These are according to this second embodiment, two at the feed region 3 of the T-slot 1 opposite double slopes 4, wherein a double bevel 4 two consecutive

Sloping with the same slope and opposite sign corresponds. Thus, the feed region 3 of the T-groove 1 in Fig. 2 has a cross-sectional constriction. The

Cross-sectional area parallel to an upper surface of the sliding ring 2 of Fig. 1 becomes first narrower and then wider again, i. the cross-sectional area has a constriction area and a broadening area. According to other preferred embodiments can be lasered in addition to the double oblique 4 and / or on a slope miniature stairs, which further support the Venturi nozzle effect.

Fig. 3 shows a third preferred embodiment of the invention. The T-slot 1 comprises at one end two successive bevels, ie a double bevel 4. The double bevel 4 in Fig. 3 must therefore not necessarily be arranged on the feed section 3, but according to this third preferred embodiment also at one end to the wall the T-slot 1 can be arranged. According to this third preferred exemplary embodiment of the invention, the cross-sectional constriction has a depth of <6 μm in the peripheral side of the sliding ring 2. According to other preferred exemplary embodiments, the depth may have an even lower value, for example <2 μm. In addition, according to the third preferred embodiment of the invention, at least one bounding wall of the T-groove 1 has a continuous slope (not shown in FIG. 3) in the circumferential side of the sliding ring 2. According to this embodiment, the continuous slope corresponds to a linear slope. According to other preferred embodiments, any continuous slopes are used. It is emphasized that ramped slopes are not suitable because they cause the lift-off effect to begin very late.

Fig. 4 shows a fourth preferred embodiment of the invention. Again, a T-groove 1 is shown. The bottom of the T-slot 1 has embedded waves 6. Such embedded waves additionally increase the dynamic pressure and thus further promote the Venturi nozzle effect. According to the fourth embodiment of the invention, "slip edges" at the end of the T-groove 1 are not incorporated in a 90 ° edge, but in a ramp with 45 ° slope, which also has miniature steps (not shown in Fig. 4).

The grooves can have any shape, such as T-shaped (T-grooves), spiral (spiral), rectangular, curved and / or curved. The inserted structures in the groove lead to Liftwirbeln, which strongly support the lift-off effect of the counter-rotating sliding and counter rings. According to a further preferred embodiment of the invention, a plurality of grooves are arranged on a sliding ring, wherein forms a vortex behind each groove. As a result, even more air or gas is sucked in by the negative pressure, and thus the lift-off effect sets in very early due to the resulting pressure. Thus, the friction is almost extinguished or at least reduced.

Claims

claims

1. Sliding ring (2) for a mechanical seal, with at least one on an upper side of the sliding ring (2) arranged groove (1), wherein the groove (1) on the peripheral side of the sliding ring (2) leading

Feed region (3), and wherein the feed region (3) of the groove (1) comprises a cross-sectional constriction.

2. Sliding ring according to claim 1, wherein the cross-sectional constriction of the feed region (3) has a bevel, a double bevel (4), a plurality of

Stair steps and / or a butterfly-shaped structure comprises.

3. A sliding ring according to claim 2, wherein the double slope (4) corresponds to two consecutive slopes with the same slope and opposite signs.

4. Sliding ring according to claim 2, wherein the steps are designed miniaturized.

5. The sliding ring according to claim 2, wherein the butterfly-shaped structure corresponds to at least two double bevels (4) opposite the feed region (3) of the groove (1).

6. Sliding ring according to one of the preceding claims, wherein the cross-sectional constriction has a depth of <6 microns in the peripheral side of the sliding ring (2), preferably a depth of <2 microns in the peripheral side of the sliding ring (2).

7. Sliding ring according to one of the preceding claims, wherein at least one delimiting wall of the groove (1) has a continuous slope in the peripheral side of the sliding ring (2).

8. A sliding ring according to claim 7, wherein the continuous gradient corresponds to a linear slope.

9. Sliding ring according to one of the preceding claims, wherein the bottom of the groove (1) has embedded shafts (6) for increasing the back pressure.

10. Sliding ring according to one of the preceding claims, wherein the groove (1) T-shaped, spiral, rectangular, curved and / or curved is configured.

11. The sliding ring according to one of the preceding claims, wherein the sliding ring (2) comprises a material of silicon nitride, silicon carbide, hardened steel and a hard metal.

12. The sliding ring according to claim 11, wherein the hard metal comprises tungsten nitrite and / or tungsten carbide.

13. Sliding ring according to one of the preceding claims, wherein the sliding ring (2) is designed as a counter ring.

14. A sliding ring according to any one of the preceding claims, wherein the mechanical seal is adapted to a fluid flowing through it.

15. A sliding ring according to claim 14, wherein the flowing fluid comprises a gaseous medium or a liquid medium.