WO2015112084A1

WO2015112084A1 - Sealing arrangement

Info

Publication number: WO2015112084A1
Application number: PCT/SE2015/050069
Authority: WO
Inventors: Jonas VASARA; Jimmy RIDHULT; Kent FORS
Original assignee: Foriwa Ab
Priority date: 2014-01-24
Filing date: 2015-01-23
Publication date: 2015-07-30
Also published as: SE1450072A1; SE537834C2

Abstract

The invention concerns a seal arrangement (1; 100) for a shaft (2) comprising a cover (3; 103) with a circular opening for the reception of the shaft, and a first and a second lamellar ring (12, 13; 112, 113) with a circular opening (6; 106) for the reception of the shaft, where each lamellar ring has a ring part (35) and lamellae arranged around the opening, where each lamella (17) has a coupling end (40) and a free end (41), whereby the lamellae (17.1, 17.2) are arranged overlapping around the external circumference (23) of the ring part, and the free ends (41) of the lamellae together form a continuous sealing surface (34.1, 34.2) that is designed to be in contact with a surface part (15.1, 15.2) at the shaft, where the cover (3, 103) has mounting assemblies (11.1, 11.2; 111.1, 111.2) for the mounting of the lamellar rings (12, 13; 112, 113) in a manner that allows them to be removed, and that the first and second lamellar rings (12, 13; 112, 113) can be mounted next to each other, and that a compartment (18) is formed in the axial direction between the lamellar rings, and where the cover (3, 103) has an inlet (8, 108) that is connected to the compartment between the lamellar rings, and that a medium (27) is supplied to the compartment (18) through the inlet during operation.

Description

Seal Arrangement

TECHNICAL AREA

The invention concerns a seal arrangement for the sealing of a shaft. BACKGROUND During the pelletization of iron ore in pelletizers, large amounts of particles and material is formed in the process plant, particularly at the grates on which the iron ore is dried and preheated. These particles and material are accompanied by leaking process gases: they worsen the work environment for the operator and lead to heavy wear on machine parts and high maintenance costs. The operating environment is very demanding with high temperatures and varying pressure ratios, and the load on shaft bearings and seals is high, as a consequence of the material that escapes from the process plant. It is, therefore, important to reduce the leakage of process gases and in this way reduce the amount of particles in the surrounding environment. Various seals have been tested in association with the grates, but these have not satisfied the requirements of the currently used operating conditions.

One purpose of the present invention is to reduce or overcome the deficiencies that arise within the prior art technology and to achieve a seal arrangement that reduces the leakage of gas and the spread of particles from the process plant in an efficient manner. The invention is intended also to offer a seal arrangement that is self-cleaning with improved operating times and a lower need for maintenance.

This purpose is achieved with a seal arrangement that demonstrates the distinctive feature specified in claim 1.

The idea of the present invention is to achieve a seal arrangement with double lamellar rings with for the sealing of shafts in a dryer facility, special at the grate in a pelletizer, where different pressure ratios are present along the shaft, which pressure ratios deviate from atmospheric pressure. A medium, preferably a medium under pressure, is supplied between the lamellar rings, which prevents the leakage of gas from the dusty environment along the shaft, whereby also the sealing surface of one of the lamellar rings is pressed against a surface part of the shaft. In addition to this, the medium escapes along the sealing surface of the second lamellar ring, which surface is in contact with the surface part of the shaft, which reduces deposits of particles along the sealing surface. The seal arrangement according to the invention is in this way self-cleaning, subject to less wear, and has a higher durability. The seal arrangement leads also to an improved work environment due to reduced spread of dust. Furthermore, the maintenance costs for the shaft bearings become lower. Further distinctive features and advantages of the invention and its embodiments will be made clear by the non-independent claims and the following detailed description of preferred embodiments of the invention.

DESCRIPTION OF DRAWINGS

The invention is described in more detail below with reference to the attached drawings, of which:

Figure 1A shows a perspective of a seal arrangement according to a first embodiment of the invention.

Figure IB shows a cross-sectional view of a seal arrangement according to Figure 1A. Figure 1C shows a cross-sectional view of a seal arrangement according to Figure 1A.

Figure ID shows an exploded view of the seal arrangement according to Figure 1A.

Figure 2 shows a second embodiment of the seal arrangement.

Figure 3 shows a ring part of a lamellar ring.

Figures 4A-C show a lamella. Figures 5A-D show a further embodiment of the seal arrangement according to the invention.

Figures 6A-B show a wear surface for a shaft.

DESCRIPTION OF EMBODIMENTS

Figures 1A-D show a first embodiment of the seal arrangement 1 for a shaft 2 (see Figure 1C) according to the invention, intended to be used in a dryer facility. The invention can be applied also in other types of device or facility that comprise a non-rotating part and a rotating part that has at least one longitudinally extended shaft.

In this description it is referred to that the fixed non-rotating part is constituted by a machine housing in a dryer facility that has several bearing housings. The rotating part is constituted by a longitudinally extended shaft 2 that extends from a bearing housing in a direction inwards into the machine. The pressure ratio can vary along the shaft. Figure 1A shows an embodiment of the invention in which the pressure P_H is higher on the inner surface of the machine cover than the surrounding atmospheric pressure P_L. Figure IB shows a cross-sectional view of a seal arrangement 1. The seal arrangement has a cover 3 comprising a fastening plate 4 and a cylindrical holder 5 arranged at one side of the fastening plate, with a circular opening 6 for the reception of a shaft 2 (not shown in the drawings). The fastening plate 4 and the holder 5 are integrated into one piece, but may be also separate parts. The cylindrical holder 5 has a circular opening 8 or inlet that penetrates radially through the holder wall 7, see also Figure 1A. The inlet 8 is intended to be connected to a source of medium (not shown in the drawings).

The cover 3 of the seal arrangement comprises also a cover 9 that is attached in a manner that allows it to be removed at the forward end 10 of the holder in order to close the seal arrangement.

The seal arrangement 1 has mounting assemblies 11 for the mounting of a first lamellar ring 12 and a second lamellar ring 13. The mounting assembly 11 is cylindrical and is designed to receive and surround the shaft 2. The lamellar rings 12, 13 are mounted in the mounting assembly 11 such that the lamellae are directed in the same direction and at a distance from each other. It is advantageous to design the mounting assembly 11 in at least two parts consisting of a first and a second mounting assembly 11.1, 11.2 in order to facilitate the mounting. Figure 1C shows the seal arrangement 1 with the lamellar rings 12, 13 that are components of it interacts in a sealing manner in the seal areas 14.1 and 14.2 with the surface parts 15.1, 15.2 on the rotating shaft 2 or a wear surface 16 arranged on the shaft, and prevents particles from escaping from the process compartment.

The first lamellar ring 12 is mounted closer to the side that has the higher pressure P_H. The lamellae 17.1, 17.2 are directed towards the side of the seal arrangement 1 at which the higher pressure P_H is prevalent, whereby the degree of leakage is minimised. The second lamellar ring 13 is in this way mounted such that the lamellae 17.2 are directed in towards the compartment 18.

Figure IB shows that the fastening plate 4 of the cover has an edge flange 19 with a support surface 20, where the edge flange extends in the radial direction towards the shaft around the circular opening in the fastening plate.

The first mounting assembly 11.1 has an internal contact surface 21 arranged to receive the first lamellar ring 12. The mounting assembly has a contact 22 direct radially inwards. The first lamellar ring, with lamellae 17.1 arranged on the external circumference 23 of the lamellar ring part, is mounted against the internal contact surface 21 between the edge flange 19 and the contact 22. The lamellae 17.1 are in this way clamped between the circumference 23 of the ring part and the contact surface 21. Also the lamellar ring is held in the correct position, and displacements along the shaft or in the holder are avoided.

The first mounting assembly 11.1 has a spacer element 24, an extension of the wall surface of the mounting assembly 11.1, that is directed towards the second mounting assembly 11.2. The spacer element 24 is equipped with at least one opening 25 directed transversely towards the axial direction through the wall surface 26 of the mounting assembly, where the opening corresponds in magnitude and form to the inlet 8 in the cover 3, in order to receive a medium 27, such as pressurised air. Since there is only one opening 25 in the compartment 18 that is formed between the lamellar rings and the shaft, pressure can be built up in the compartment 18. The first mounting assembly 11.1 has an edge surface 28 that comes directly into contact with an opposing edge surface 29 at the second mounting assembly 11.2, and in this way reduces the risk of pressure losses. The first lamellar ring 12 and the second lamellar ring 13 are in this way mounted next to each other and at an axial distance from each other, in the holder.

The second mounting assembly 11.2 has also an internal contact area 30 and an edge flange 31 directed radially inwards towards the shaft 2 next to the forward end 10 of the holder. The second lamellar ring 13, with lamellae 17.2 arranged on the external circumference 32 of the ring part, is mounted against the contact surface 30 and the edge flange 31, whereby the lamellae are clamped between the ring part 32 and the contact surface 30 of the mounting assembly, and are held securely fixed in the correct position. The lamellar rings and the mounting assembly can be mounted in the seal arrangement in a manner that allows them to be removed in order to facilitate maintenance work. During the mounting of the seal arrangement 1 on the shaft 2 the flexible pliable lamellae 17.1, 17.2 are prestressed with a prestress force F against the surface part 15.1, 15.2 at the shaft. This leads to a sealing interaction in the region 14.1, 14.2 of the seals along the sealing surfaces 34.1, 34.2 of the seal arrangement and the relevant surface parts 15.1, 15.2 at the shaft. The sealing surfaces 34.1, 34.2 are in contact with and slide against the relevant surface part 15.1, 15.2 at the shaft, when the shaft rotates. A good sealing effect is obtained since the lamellae are flexible and prestressed.

The lamellae have a cross-section shaped as an arc and are flexible, which leads to the pressure P_H contributing to the sealing effect in that the lamellae in the first lamellar ring are pressed against the shaft. During the mounting of the lamellar rings 12, 13 in the holder and against the shaft, a compartment 18 is formed in the axial direction between the lamellar rings and the shaft. During operation, pressurised air or another gas is supplied to the compartment through the inlet 8 and the opening 25 of the mounting assembly. The medium 27 that is supplied may be water. The air may be supplied from, for example, a fan system, whereby air pressure is built up in the compartment between the lamellar rings. A second alternative is to supply pressurised air from a compressor.

Figure ID shows an exploded view of the seal arrangement according to Figures 1A-C. It is shown here in particular how the mounting assemblies 11.1, 11.2 and the lamellar rings 12, 13 are united with the holder 5. By creating an excess pressure in the compartment between the lamellar rings 12, 13, a considerable improvement of the sealing effect is obtained. In order to maintain the seal around the shaft, it is necessary that the air pressure P_M in the compartment 18 in the seal arrangement is higher than the pressure P_H inside the process compartment (to the right of the seal arrangement in Figure IB). It is preferable that the pressure P_M of the medium in the compartment 18 be higher than the pressure ratios on the outer surfaces of the seal arrangement. P_M in the compartment 18 is in this case higher than the pressure P_H (PH>PL) that is present inside the process compartment. It is conceivable also that the pressure P_M is equal to the pressure P_H.

The first lamellar ring 12 is mounted closer to the outer surface of the seal arrangement where a higher pressure P_H is prevalent, to the right in the drawing. The second lamellar ring 13 is arranged closer to the side with lower pressure P_L, to the left.

The pressurised air 27 that is supplied to the compartment 18 exerts a force onto the lamellae 17.2 in the second lamellar ring 13, which are in this way pressed against the surface part 15.2 at the shaft or the wear surface 16, and this leads to better sealing.

In the seal arrangement that is shown in Figure 1C, the pressure P_M in the compartment 18 is higher than the pressure P_H in the process compartment on the right, outer surface of the seal arrangement. The design of the seal arrangement has the advantageous effect that the pressurised air 27 in the compartment 18 not only presses the lamellae 17.2 of the second lamellar ring 13 against the surface part 15.2 at the shaft, but also is pressed out under the sealing surface 34.1 of the lamellae. At the same time, the pressurised medium 27 removes particle coating in the seal arrangement, and removes particles and dust that have collected next to and under the sealing surface 34.1. Surface wear on the shaft and lamellae is in this way reduced. Thus, the seal arrangement has a self-cleaning effect. Figure 2 shows a second embodiment of the invention. The seal arrangement 1 is in this case of similar type as that shown in Figure 1, but it has been adapted to the inverse pressure relationship. Similar features have the same reference number as in the previous embodiment. In this case, negative pressure P_L is prevalent in the process compartment, the machine housing to the right of the seal arrangement, relative to the atmospheric pressure P_atm that is prevalent on the outer surface of the seal arrangement. The seal arrangement according to the invention is very advantageous in this situation, since it prevents dust particles escaping from the process compartment. A second advantage in this case is a reduced load on process fans, and the savings in energy that follow. Also cooling of the process gases can be avoided in some cases. Each lamellar ring 12, 13 has a ring part 35 for its mounting into the mounting assembly 11.1, 11.2 and a lamellar part 36 in which separate thin flexible lamellae 17.1, 17.2 are arranged around the complete circumference of the lamellar ring and along the ring opening 37.

Figure 3 shows the ring part 35 with an external circumference 23 that is directed towards the contact surface of the mounting assembly 11.1, 11.2. The ring part 35 is equipped with a large number of ridges 39 around the complete circumference. The ridges 39 are arranged to separate, control and hold the coupling parts 40 of the lamellae in the desired position of the ring part. The ridges 39 are arranged at a distance from each other, whereby a depression 46 is formed at the circumference of the ring part that is shaped to receive the coupling end 40 of the lamellae.

The free ends 41 of the separate lamellae together form an essentially continuous sealing surface 34.1, 34.2 that makes contact in the sealing area 14.1, 14.2 with a surface part at the shaft or at a wear surface 16 arranged at the shaft. The term "continuous" is here used to describe the situation in which the lamellae overlap so tightly that no interruption arises along the sealing surface, also when the lamellar rings in the seal arrangement are mounted and the lamellae are brought into contact with the shaft, whereby the lamellae are prestressed against the surface of the shaft by being pressed apart. In a further embodiment of the invention, the lamellar ring is designed such that it can be divided into at least two bowed segments (not shown in the drawings). This makes mounting and maintenance of the seal arrangement easier.

Figures 4A-C show a lamella 17 in detail. The lamella 17 has a coupling end 40 comprising a plane attachment edge 42 intended to be placed in contact between two ridges 39 on the external circumference 23 of the lamellar ring and a transverse flange 43 for the attachment onto the lamellar ring, a free end 41 that is directed forwards, and a bent surface 44 that unites the attachment edge 42 at the coupling end 40 with the free end 41.

The free end 41 of the lamella has a forward contact edge 45 that, together with the contact edges of other lamellae, forms the sealing surface 34. The free end of the lamella has a cross-section with the form of an arc of a circle from the bent surface to the forward edge, with a radius of curvature that is adapted to the diameter of the shaft such that the initial diameter Dt of the sealing surface is somewhat smaller than the diameter Da of the shaft.

Thus the lamellae are in this way prestressed during the mounting, and the contact diameter of the sealing surface will be essentially equal to the diameter Da of the shaft. The coupling end 40 of the lamella, with the flange 43 and the attachment edge 42, is more narrow than the free end 41. The free end is broader, preferably up to double as broad or broader, than the coupling end. The coupling end is fixed in the depression between two ridges on the circumference of the ring part during the mounting. Since the free end 41 of the lamella is broader than the coupling end 40, the free end overlaps in this way the neighbouring lamella. It is preferable that the lamellae be manufactured from, for example, thin spring steel, and that they have flexible properties. It is conceivable also that the lamellae be manufactured from a composite material or plastic that has corresponding properties. The direction of the lamellae can in this way be adjusted for optimal sealing. During the mounting of the seal arrangement 1, the lamellae are held fixed between the circumference of the ring part and the contact area of the mounting assembly. Figures 5A-D show a further embodiment of the seal arrangement according to the invention. The drawings show the component parts in their unmounted condition. This seal arrangement 100 seals in a similar manner a shaft (not shown in the drawings) that has varying pressure ratio along the shaft. The seal arrangement in this case has a cover 103 with a fastening plate 104 and a holder 105 that are joined by screw joints. The seal arrangement 100 is united with the fastening plate 104 at the machine housing (not shown in the drawings). The cover 103 with the holder 105 is rectangular and has a central circular opening 106 in order to receive and surround a shaft with an internal contact surface 107 for the reception of mounting assemblies 111 and lamellar rings 112, 113. The holder has a transverse channel with a penetrating opening 108, an inlet, for the connection of a media line. The passage extends from the central opening 106 where the shaft is located to an end region 121 on the outer surface of the holder. The holder has an edge flange 119 arranged along one edge 120 of the opening, where the edge flange is directed radially inwards towards the shaft. A first ring-shaped mounting assembly 111.1 with an external circumferential surface and an internal contact surface is arranged at the outer surface of a first lamellar ring 112 and is mounted to have its external circumferential surface in contact with the contact surface 107 of the holder. The first lamellar ring 112 with the mounting assembly 111.1 has a forward transverse edge 122 that is in contact with the edge flange 119. The first mounting assembly 111.1 has axially directed spacer elements 124 along the circumference that are intended to hold a second lamellar ring 113 with the second mounting assembly 111.2 at a predetermined distance from the first lamellar ring 112 in the holder. The second mounting assembly 111.2 is arranged on the outer surface of the second lamellar ring 113 and is mounted with its external circumferential surface in contact with the internal contact surface of the holder and in contact with the spacer element 124. The spacer element 124 leads to a compartment being formed between the lamellar rings and the shaft, when mounted in the holder 105. The spacer element is designed as protuberances along the edge of the mounting assembly, whereby an opening is formed between two spacer elements. During assembly, such an opening is placed in correspondence with the inlet 108 of the holder such that a pressurised medium can be supplied to the compartment between the lamellar rings. The inlet 108 of the holder opens out into this compartment such that a medium can be supplied between the lamellar rings 112, 113 and can improve the sealing of the shaft.

The cover has also a cover 109 that can be opened and that is attached by a screw joint. In one embodiment of the seal arrangement according to the invention the shaft is provided with a wear surface 16. Figures 6A-B show such a wear surface.

The wear surface 16 comprises a sheath 47 that is attached on the shaft. The sealing surfaces 34.1, 34.2 of the lamellae are in contact with a contact 48 at the wear surface 16 and interact in a sealing manner with the contact surface (see also Figure 1C). The contact surface 48 of the wear surface may be provided with different types of pattern in order to obtain efficient sealing.

In one variant, the wear surface 16 is provided with an L-shaped peg 49 around the complete circumference of the wear surface on the side that has the higher pressure P_H. The L-shaped peg 49 is directed in the axial direction and forms a gap 50 next to the surface of the shaft. The peg 49 is arranged such that the lamellae 17.1 on the first lamellar ring 12 protrude into the gap under the peg (see also Figure 1C). The peg and the gap bring the advantage that air and particles from the process facility are prevented from being pressed in under the lamellae.—

Claims

1. A seal arrangement (1; 100) for a shaft (2) comprising a cover (3; 103) with a circular opening for the reception of the shaft characterised by a first and a second lamellar ring (12, 13; 112, 113) with a circular opening (6; 106) for the reception of the shaft, where each lamellar ring has a ring part (35) and lamellae arranged around the opening, where each lamella (17) has a coupling end (40) and a free end (41), whereby the lamellae (17.1, 17.2) are arranged overlapping around the external circumference (23) of the ring part (35), and the free ends (41) of the lamellae together form a continuous sealing surface (34.1, 34.2) that is designed to be in contact with a surface part (15.1, 15.2) at the shaft, where the cover (3, 103) has mounting assemblies (11.1, 11.2; 111.1, 111.2) for the mounting of the lamellar rings (12, 13; 112, 113) in a manner that allows them to be removed, and that the first and second lamellar rings (12, 13; 112, 113) can be mounted next to each other, and that a compartment (18) is formed in the axial direction between the lamellar rings, and where the cover (3, 103) has an inlet (8, 108) that is connected to the compartment between the lamellar rings, and that a medium (27) is supplied to the compartment (18) through the inlet during operation.

2. The seal arrangement according to claim 1, where the medium is pressurised air, another pressurised gas, or water.

3. The seal arrangement according to claim 1 or 2, where the lamellar rings (12, 13; 112, 113) are arranged such that the lamellae (17.1, 17.2) are directed in the same direction and towards the side on which a higher pressure P_H is prevalent.

4. The seal arrangement according to any one of the previous claims, where the first lamellar ring (12; 112) is arranged closer to the side with the higher pressure P_H.

5. The seal arrangement according to any one of the previous claims, where the second lamellar ring (13; 113) is arranged with the lamellae (17.2) directed in towards the compartment (18) and that the medium (27) exerts a force on the lamellae.

6. The seal arrangement according to any one of the previous claims, where the lamellar ring (12, 13; 112, 113) can be divided into at least two bowed segments.

7. The seal arrangement according to any one of the previous claims, where the medium (27) has a pressure P_M that is equal to or greater than the highest pressure P_H that is prevalent on the outer surface of the seal arrangement (1, 100).

8. The seal arrangement according to any one of the previous claims, where mounting assemblies (11.1, 11.2; 111.1, 111.2) are designed to be in contact against the inner surface of the cover (3; 103) and designed to arrange the lamellar rings (12, 13; 112, 113) at a distance from each other, and where the mounting assembly has an opening (25) that is connected to the inlet (8; 108) of the cover.

9. The seal arrangement according to any one of the previous claims, where the free end (41) of the lamella has a cross-section that is shaped as an arc and has a contact edge (45) arranged to be in contact with the surface part (15.1, 15.2) at the shaft.

10. The seal arrangement according to any one of the previous claims, where the lamella (17) has a coupling end (40) comprising a plane attachment edge (42) with a transverse flange (43) for arrangement at the lamellar ring, and a bent surface (44) that unites the coupling end (40) with the free end (41), which has the form of an arc of a circle.

11. The seal arrangement according to any one of the previous claims, where the lamellae are exerted a prestress force against the surface part at the shaft during the mounting of the lamellar ring in the cover.

12. The seal arrangement according to any one of the previous claims, where the surface part (15.1, 15.2) at the shaft is provided with a wear surface (16).

13. The seal arrangement according to claim 12, where the wear surface (16) comprises a peg (49) in the axial direction that forms a gap (48) next to the shaft.