WO2014014426A2

WO2014014426A2 - Brush seal for high pressure applications

Info

Publication number: WO2014014426A2
Application number: PCT/TR2013/000201
Authority: WO
Inventors: Mahmut Faruk AKŞİT
Original assignee: Sdm Siradişi Arge Ve Mühendi̇sli̇k Sanayi̇ Ti̇caret Li̇mi̇ted Şi̇rketi̇
Priority date: 2012-06-28
Filing date: 2013-06-27
Publication date: 2014-01-23
Also published as: WO2014014426A3

Abstract

As the invention, the multilayer seal, can primarily be used in the energy industry in gas turbines and steam turbines, and aircraft engines; shortly to provide sealing between low and high pressure regions around a fast rotating shafts; it can also be applied to increase performance of existing brush seals, and it relates to fabrication methods for such seals.

Description

DESCRIPTION

BRUSH SEAL FOR HIGH PRESSURE APPLICATIONS TECHNICAL FIELD

As the invention, the multilayer seal can primarily be used in the energy industry in gas turbines and steam turbines, and aircraft engines; shortly to provide sealing between low and high pressure regions around a fast rotating shafts; it can also be applied to increase performance of existing brush seals, and it relates to a new fabrication method for such seals.

The mentioned method of fabrication can be utilized for the production of all types of brush seals, and it enables mass production of such seals. STATE OF THE ART

Thin-bristled standard brush seals cannot perform in high pressure environments. In standard thin-bristled brush seals, during the flow from a high pressure region to a low pressure region, the bristles between the rotor surface and the edge of the backing plate are exposed to a pressure load and bend towards the low pressure side, and this increases the level of stress at the bristles and the porosity of the seal, thereby negatively affecting sealing performance.

It is necessary to increase the diameter of brush seal wire to enable them to work in high pressure_enviroments. However, the use of a standard thick-bristled brush seal increases contact pressure on rotor, and an increase in wear and heat generation are observed as a result of this. The increase in wear results in higher brush seal working clearance, and it negatively affects sealing performance. The heat generated by friction causes a localized temperature rise in the rotor. This temperature increase may change rotor modal/frequency characteristics due to resulting partial rotor deformation, and it may also cause instability in the static and dynamic equilibrium of the rotor. On the other hand, in cases where the fluid medium is liquid, the heat due to friction causes an increase in fluid temperature and a subsequent decrease in the fluid viscosity. As a result of decreasing viscosity, the lifting force of the fluid decreases and the brush seal leakage performance is negatively affected.

Even though it is possible to increase the thickness of the seal to raise the pressure limit of thin-bristled brush seals, this thickness increase is limited by current manufacturing techniques since the uniform lay of wires is critical for sealing performance. In addition, the bristles in thick brush packs mix with each other, which prevents flexible motion of the brush and leads to an increase in seal porosity. To enable use of brush seals at high pressure, multistage brush seal applications have been tried (US5192084A). However, in multistage brush seals, field applications have shown that the required results cannot be achieved due to the fact that the pressure downstream of the last seal is the lowest and the pressure drop does not change linearly along the stages. A higher portion of the pressure load is carried by the last brush seal, which leads to damage of the seal and limits the maximum pressure load that can be carried by the seal. After the last brush seal is damaged, the brush seal upstream of the last brush seal begins to take a higher portion of the pressure load, which leads to damage of this seal. To overcome the existing problem in multistage brush seals, it is tried to increase pressure load capacity by installing brush seals next to each other (EP2305956A2, WO2010076636A1 , US2011072831 A1). It was observed that the problem which is faced in traditional multistage brush seals still has not been resolved due to the air gap in this arrangement. In short, in multistage brush seal applications, a proportional increase of pressure capacity to number of seals cannot be achieved. Using several brush packs together in a seal is another method proposed to increase the pressure \oad.(US5201530A, CN201671661U). In these seals, brush packs with varying wire diameter and length, are stacked next to each other and supported by a single backing plate. However, the data obtained from field applications showed that a seal locking problem was encountered as a result of the wire mixing with each other in these brush seals. As a result of seal locking, the seal leakage performance drops and the first brush pack which is designed to have a soft contact with the rotor causes higher rotor contact pressures than expected by behaving stiffer than intended. Increased contact pressure causes extensive wear and heat generation leading to the problems described earlier. In existing brush seal applications, the wires move towards the center of the rotor due to a pressure difference forming within the brush pack in the radial direction from outside to inside, in the steady-state region, this affects seal clearance and sealing performace, and extensive contact may occur in the transient region. In literature, it is reported that circular groove features concentric and parallel to the rotor surface on the backing plate are machined to prevent the bending of the brush by reducing the pressure difference in the radial direction (US2007216106A 1). However, these backing plate grooves may have different results at different operating pressures, and therefore it may not be possible to fine tune the level of rotor contact in some cases. In some field applications when the brush seal is installed with a gap, the targeted flow gap values with increasing pressure are not achievable due to a lack of control of the flow in the existing groove applications.

Several limitations exist in the traditional fabrication methods of brush seals. The requirement of designing a new fixture for each seal size is one of the major limitations. This requirement prevents mass production of the brush seal, and increases the cost of brush seal fabrication. Even though in literature some methods proposed for the fabrication of brush seals (US2009/0218771 , US6062463, US7181843 B1) made it easier to automate the manufacturing process, these methods did not dismiss the need for a new fabrication fixture for every different brush seal inner diameter. In a study (US 4839997) where the use of a roller is suggested, the machining of the final diameter of ihe brush seal is the only automated step. Another study makes for easier production of different sized brush seals, but (US7454822 B2) it does not propose any method for automating any stages of fabrication. Also, it is observed that a significant amount of the brush seal's most expensive component, the super-alloy brush wire, is wasted in these fabrication methods.

In view of the existing state of the art, it is obvious that proposal of a new brush seal structure is necessary to solve the problems mentioned earlier.

BRIEF DESCRIPTION OF THE INVENTION

The purpose of the invention is to develop a multilayer brush to be used as a sealing element primarily in the energy industry in gas and steam turbines, and in aircraft engines, shortly between low and high pressure regions around fast rotating shafts, and to increase the performance of existing brush seals.

In order to solve the aforementioned problems, a metal sheet or woven metal is placed between each brush pack to make each brush pack in the same seal work properly. In Figure 1 , different types of woven metal are shown. These woven metals have a flexible structure in the radial and axial direction of the rotor as opposed to metal plates that have isotropic material properties. In this new technique, seal locking is mitigated by preventing brush wires from mixing with each other, as a result of this, the sealing performance of the seal at high pressure is increased. The extensive heat generation and wear problems resulting from high contact pressure in existing applications is also prevented. It is planned that the woven metals will be made of a metallic or non-metalic cloths woven by high temperature cobalt or similar fibers. As opposed to the standard backing plate grooves used in existing brush seal applications, in this new technique, the angle, length, width and thickness of the blowing grooves on the backing plate are designed to keep the flow at an optimized level. The shape and dimensions (width, depth, angle, etc) of these blowing grooves are also optimized to obtain the required rotor contact pressure. The aim of the new method is to develop specially designed grooves to control the blow-down of the brush by directing radial flow. When necessary, it is possible to connect these grooves to each other via connection grooves to enable pressure communication between them.

Another method proposed to control the pressure distribution within the brush is as follows. The pressure change on the backing plate can be adjusted as required by using woven metal (or non-metal) cloth placed on the grooves in a continues circular form opened on the brush side of the backing plate face. The same result can also be achieved by placing sponge or porous "felt metal" on these grooves. The proposed invention also includes a special design to protect the seal from vortex flow and outside effects. In this design, labyrinth knives are integrated into the front and rear backing plates to protect the brush and maintain the effectiveness of sealing in case of any abnormal conditions that result in the loss of all wires. This new seal can be installed or used as a stand alone sealing system due to the added knives on the front and rear plates, instead of placing it into the existing labyrinth seals.

A new method of fabrication is also proposed to keep the increased cost of the proposed multilayer brush seal under control. This new method enables automation of the brush seal fabrication process, and it eliminates the necessity of manufacturing a new fabrication fixture for seals with different inner diameters. Therefore, brush seal manufacturing time will decrease, reducing manufacturing cost.

In order to achieve the mentioned goals; it can be used as a sealing element primarily in energy sector in gas turbines, steam turbines and aircraft engines, in short in between high pressure and low pressure regions around high speed rotating shafts; it can also be used to increase performance of the currently used brush seals; it is also a multiple brush production technique comprised of at least one front plate and a backing plate that are joined through a weld; as a feature of this production method, it is comprised of joining of brush seal front bars in the form a rectangular frame, and winding of wires around this frame in desired wire diameter and density, and depending on the type of the wire brush one, two, three or more brush stages can be wound around the formed frame; for windings with two or more stages, thin sheet or woven cloth (metal or nonmetal) can be placed between stages; once winding process is completed back bars are pressed on wound wires to hold tight between front and back bars; the wire brush pack that is secured between front and back bars can be brought to desired angle by relatively sliding front and back bars through a part allowing adjusting angle; once the wires are at desired angle front and back plates are welded together at the outer side from one end to other end (clamped or glued in nonmetallic brushes); this welding process is performed for both sides; once the welding process is completed wire brush groups formed across at each side that are attached by wire brush are separated by cutting the brush in between to split in two, and this way four linear brush strips are obtained; depending on the type of the brush that is to be manufactured front and back plates that are straight or with laby knife are welded to these brush strips (for non metallic brushes clamped or glued); blowing groves can be opened or woven/porous metal can be fitted on the back support plate before welding; the obtained brush pack can be curved to desired diameter.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 , The view of different types of woven metal.

Figure 2, Cross-section view of multilayer brush seal with gooves and flat backing and front plate. Figure 3, Cross-section view of multilayer brush seal with grooves and knife type backing and front plate.

Figure 4, The view of the grooves on backing plate.

Figure 5, Detailed view of brush seal design from upstream side.

Figure 6, Cross-section view of brush seal with complete woven metal or porous metal on a flat backing plate.

Figure 7, Cross-section view of brush seal with complete woven metal or porous metal on a backing plate with knife.

Figure 8, Cross-section view of brush seal with partial woven metal or porous metal on a flat backing plate. Figure 9, Cross-section view of brush seal with partial woven metal or porous metal on abacking plate with knife.

Figure 10a, 3D view of metal frame used for bristle winding in new fabrication technique. Figure 10b, Top view of metal frame used for bristle winding in new fabrication technique.

Figure 10c, Side view of metal frame used for bristle winding in new fabrication technique.

Figure 11a, 3D view of metal frame with wound bristle wire at required density in new fabrication technique. Figure 11b, Top view of metal frame with wound wires at required density in new fabrication technique.

Figure 11c, Top view of metal frame with wound wires at required density in new fabrication technique. Figure 12a, In new fabrication technique, 3D view of metal frame with wound wire at required density and front and rear holder plates attached.

Figure 12b, In new fabrication technique, top view of metal frame with wound wire at required density and front and rear holder plates attached.

Figure 12c, In new fabrication technique, side view of metal frame with wound wire at required density and front and rear holder plates attached.

Figure 13a, In new fabrication technique, 3D view of metal frame with wound wires at required density shifted against each other to adjust required wire brush angle.

Figure 13b, In new fabrication technique, top view of metal frame with wound wires at required density shifted against each other to adjust required wire brush angle.

Figure 14, Top view of straight wire brush seal segment obtained by welding and cutting the wire brush held between two flat plates. after setting the required angle. Figure 15, Locations of brush seals in a gas turbine where the brush seal, subject of the invention, can be used.

REFERANCE NUMBERS

1. Front plate 2. Backing plate 3. Weld 4. Sheet metal or woven metal

5. Sheet metal or woven metal

6. The first bristle pack

7. The second bristle pack 8. The third bristle pack

9. Support plate blowing grooves

10. Front plate sealing knives

11. Backing plate sealing knives

12. Full thick woven cloth metal or porous metal (Felt). 13. Partial thick woven cloth metal or porous metal (Felt).

14. Wire brush front bars

15. Front and rear bars fixing mechanism

16. Front and rear fixing mechanism

17. Front and rear bars connection holes 18. Wire bundle

19. Wire brush rear bars

20. Angle adjustment piece

21. Rotor

22. High pressure 23. Low pressure

24. Back support plate

DETAILED DESCRIPTION OF THE INVENTION

As the invention, the multilayer seal can primarily be used in the energy industry in gas turbines and steam turbines, and aircraft engines; shortly to provide sealing between high pressure regions (22) and low pressure regions (23) around a fast rotating shafts (21); it can also be applied to increase performance of existing brush seals, and it relates to a new fabrication method for such seals.

A metal sheet or woven metal (4,5) is placed between each brush packs to allow several brush packs to be used in the same seal without any problems at high pressure. In figure 1 , several different types of woven metal (4,5) is shown. As opposed to plates that have isotropic material properties, the woven metal (4,5) has a flexible structure in the radial and axial direction of the rotor. In this new technique, the seal locking issue is avoided by preventing brush wires from mixing with each other, as a result of this the performance of the seal is improved at high pressure, and excessive heat generation and wear problems resulting from high contact pressure encountered in existing applications are prevented. It is planned that the woven metal (4,5) will be made of a metallic or non-metalic cloths woven by high temperature cobalt or similar fibers.

In figure 2, a cross-section view of a brush seal with blowing grooves and flat front and backing plates is shown. The brush seal consists of a front plate (1) which is a metal section used in standard brush seals to provide support from the front side and a backing plate (2).

In standard brush seals, the length of the backing plate (2) can be nearly the length of wires.

Therefore, support is provided by the backing plate, and the increase in the gap between the brush and the rotor is prevented. The backing plate (2) and front plate (1) are the same length because the task of providing support in a standard brush seal is done by the second brush pack (7) and the third brush pack if exists (8) in the proposed design.

The welding method (3) is used to combine the brush packs (6,7,8) together after placing sheet metal or woven metal (4,5) between them. The bristle packs (6, 7,8) held together by clamping from the outer sides are fixed together by welding (3), then the clamps are removed. Final assembly is completed after welding the front plate (1) and backing plate (2). During this welding process, the wire brush front and rear bars ( , 19) are combined together.

Because of the sheet or woven metal (4, 5) placed between the brush packs (6, 7, 8), each brush pack can be independently designed and optimized, and each brush can function as flexibly as intended. Also, the downstream brush packs with these metals (4,5) provide support to the upstream brush pack. Thickness, length and other specifications of the sheet or woven metal (4, 5) to be placed between each brush packs (6, 7, 8) are seperately optimized. While the sheet and woven metal (4) is placed between the first brush pack (6) and the second brush pack (7), the other sheet or woven metal (5) is placed between the second brush pack (7) and the third brush pack (8). The first brush pack (6) of the brush seal that consists of the thinnest, the most flexible and the most dense brush, it provides perfect sealing. The limitaion of the starting load carried by the thin wires is compansated by the support provided by the second and the third brush packs (7, 8), therefore both sealing and maximum pressure capability are achieved. While this brush pack (6), the closest brush pack to the shaft, (21) provides maximum sealing, it contacts the rotor (21) more frequently, but it has a long lifetime due to the fact that wear and heat generation is limted during possible rotor (21) rubs since this pack can be designed to be soft and flexible, independent of the other brush packs (7,8). The number of layers can be more than 3 if necessary. The second brush pack (7) of the brush seal prevents the deflection of the upstream brush pack while operating under high pressure resulting increased porosity, and exposing excessive stress by providing support for the first brush pack (6). The second brush pack (7) is shorter than the first brush pack (6), but it has longer and thinner wires than the third brush pack (8). The second brush pack (7) provides pressure load support to the first brush pack (6). The stiffness of the second brush pack (7) is between the first brush pack (6) and the third brush pack (8), while it is mounted closer to the rotor than the first brush pack (6) and larger gap than the third brush pack (8). It contacts the rotor more often compared to the third brush pack and less compared to the first brush pack. Therefore, it has longer lifetime with its intermediate level of stiffness by contacting the rotor less than the third brush pack (8).

The third brush pack (8) is the brush pack that exists in standard brush seals. It is a special brush that acts as a flexible support and backing for pressure by its thickness and stiffness being different than the standard brushes due to its higher stiffness. The third brush pack (8) is cut with a large gap between it and rotor (21) as a result, contact between the rotor and the third pack happens only in extra-ordinary situations, as such its wear life increases even though it is made stiffer to support the pressure load.

The first, second and third brush packs can be cut individualy in steps to get a staggered gap between them and the rotor as explained earlier, or they can be cut together at a required angle with woven cloth (metal or non-metal) or thin sheet placed between the brush packs. On the backing plate (24), the blowing grooves (9) are considered at varying angles to optimize the pressure distribution between the backing plate (24) and the brush. These grooves (9), which are arranged at an opposite angle to the angle that the brushes make with rotor (21) provide controlled blowing of the brush towards the rotor (blowdown) when necessary. Therefore, it is possible to close the rotor (21) gap by blow-down as the brush is worn out.

Front plate sealing knives (10) and rear plate sealing knives (11) are integrated to the front metal section where the standard brush seal is supported. It was observed that the brush wires fall out when the stability of the brush wires is at risk in a highly turbulated flow. These sealing knives ( 0, 11) as a spare sealing element are designed to act as a fail-safe system to meet an urgent/minimum sealing need in case of wire loss. According to mounting type, the front face may have a flat surface or a step acting like a hook feature or other optimized shapes depending on the application.

The use of full thick woven metal or porous metal (Felt) (12) with varying porosity to control the pressure distribution on the backing plate in an inexpensive way (2) is considered an innovation. Because of the variable porosity, pressure change in the radial direction from outer to inner can be controlled as required. As an alternative to full thick woven metal or porous metal (Felt) (12), partial thick woven metal or porous metal (Felt) (13) can be partly applied to achieve a different pressure distribution when needed.

The brush wire front bars (14) are fixed to form a rectangular frame, then the brush wire is wrapped around this frame. The position of the front bars (14) with respect to each other is fixed and controled by a fixing mechanism of front and rear bars (15, 16).

Connecting the front bars (14) to each other firmly and determining their positions is done using connection holes (17). The brush wires wrapped around the bars which are connected to form rectangular frame are what make the wire bundle (18).

The brush wire rear bars (19) are additional bars used to fix the brush wire wrapped around the rectangular frame between the two plates.

As opposed to the traditional method, in this invention fabrication of the brush seal is done by mass production. First, a rectangular frame is formed by the front and rear bars (14, 19), (Figure 10). The required diameter of brush wires (18) is wrapped around the frame at a requested density (Figure 11). This wire can be wrapped in one, two, three or more stages. In multilayer brush packs (6, 7, 8), a layer of sheet metal or woven metal (4,5) is placed between wires. By placing the front and rear bars (14, 19) on the wrapped wire (Figure 12), the wrapped wire is squeezed between the bars (14, 19). Then, the front and rear bars (14, 19) facing each other are shifted with respect to each other to adjust the brush wire angle of the brush pack. (Figure 13). When the required angle is achieved, the wires are welded to the front and rear bars (14, 19). When the welding process is complete, the wire is cut in half and four similar straight brush packs are obtained (Figure 14). The length of the straight segment is adjusted depending on the required diameter of the brush seal. Using this method, a brush pack is obtained. The obtained brush pack is trimmed from its bottom to smooth the surface contacting the rotor and it is shaved from top to remove the grooves where the bristles are placed, this gives the final shape of the brush pack. The brush pack in segment form can be welded from both ends and turned into to a full circle. Or after bending it, it can be cut such that it becomes parts of a full circle (two 180 degree segments, four 90 degree segments, etc.). Multilayer brush seals can also be obtained by welding and fixing together two single layer brush packs with a metal sheet or woven metal placed between them. After cleaning the excess welding material, this process can be repeated by adding as many brush pack as required. The blowing grooves are opened on the backing plate in the opposite direction of the brush. The angle of the grooves can be adjusted as requested. The brush packs and woven metal between them are welded to the front and backing plates as needed, and the final shape of the assembly is formed.

Because of the sheet metal or woven metals (4, 5) placed between the brush packs (6, 7, 8), seal locking is avoided by preventing the interlocking of the brush wires during operation, as a result, heat generation and wear problems are minimized.

The angle, length, width and thickness(24) of the blowing grooves (9) on the backing plate (2) are determined by an optimization method to bring flow performance to an optimal level. When necessary, it is possible to connect these grooves (9) to create pressure communication between them.

As shown in Figure 14, the proposed brush is used to provide sealing between regions having pressure difference around a rotating shaft. In Figure 14, regions denoted by an "A", in a typical gas turbine on diaphragms under stationary nozzles, at seals next to bearings etc., it can be used.

The proposed design and fabrication techniques are mainly applicable to turbomachines at pressure regions around a rotating and/or linear sliding shaft or rotor are used to provide sealing at these shaft locations, which will increase efficiency and power output of these systems. The aforementioned method can also be applied to the design of currently used brush seals. Since the brush fabricated using this method is straight, it can be used to seal pressure regions or prevent entrance of any foreign object into the systems that have a linear sliding motion. Similarly, it can be used to compansate for any expansion difference between stationary parts. The proposed fabrication method can be utilized at production shops, plants and lines that currently make brush seals.

Claims

It can be used as a sealing element primarily in energy sector in gas turbines, steam turbines and aircraft engines, in short in between high pressure (22) and low pressure (23) regions around high speed rotating shafts (21); it can also be used to increase performance of the currently used brush seals; it is a multibrush seal comprised of at least on front plate (1) and at least on back plate (1) where front and back plates (1 ,2) are joined together characterized in that; in order to achieve both sealing and maximum pressure capacity; it features a first stage brush group (6) that is positioned closest to the shaft (21), a second stage brush group (7) that supports first stage brush group (6) by preventing front group brushes excessively deform during operation under high pressure and having increased gap with rotor, and a third stage brush group (8) that is positioned at far away point from shaft as compared to other brush groups (6,7) and contacts shaft (21) during only exceptional cases, and between each brush group (6,7,8) sheet or woven metals (4,5) are placed.

A brush seal according to Claim , characterized in that; weave that is used is made of metal weave (4,5); as high temperature durable alloys such as cobalt, nickel and the like or woven metal from ceramic fibers or cloth made of fibers or for low temperature applications nonmetal aramid, nylon, graphite, glass fiber and the like.

A brush seal according to claim 1 characterized in that; the length of backing plate (2) is the same as the length of the front plate (1), but in need, the front plate (1) is shorter than the backing plate (2).

A brush seal according to claim 1 characterized in that; brush packs (6, 7, 8) are connected by a welding process (3) by placing sheet metal or woven metals (4,

5) between them.

A brush seal according to claim 1 characterized in that; the first stage brush pack (6) has finer, more flexible and more dense wires compared to the other brush packs (7,8).

A brush seal according to claim 1 , characterized in that; the second brush pack (7) is shorter than the first brush pack (6) and has longer and finer wires than the third brush pack (8), and the stiffness of the second brush pack(7) is between the first brush pack

(6) and the third brush pack (8).

7. A brush seal according to claim 1 characterized in that; the second brush pack (7) is mounted at a rotor with a gap that is larger than the first brush pack (6) and smaller than the third brush pack (8), and it (7) contacts the rotor less than the first brush pack (6) and more than the third brush pack (8).

8. A brush seal according to claim 1 characterized in that; the third brush pack (8) is stiffer than the other brush packs (6, 7).

9. A brush seal according to claim 1 characterized in that; variable angle blowing grooves on the back support plate (24) are considered to optimize the pressure distribution between the back support plate (24) and brush, and these grooves (9) are placed at an opposite direction to the angle that brushes make with rotor (21) and they provide the blow down of the brush to rotor when needed.

10, A brush seal according to claim 1 characterized in that; variable porous woven cloth

(metal or non-metal) or porous felt metal (metal or non-metal) (12) is used to control the pressure distribution on the backing plate (2). 11. A brush seal according to claim 1 characterized in that; as opposed to full woven cloth (metal or non-metal) or porous felt material (12), partial woven cloth (metal or non-metal) or porous felt material (13) is intermittently applied to achieve different pressure distributions. 12. Primarily in energy sector, it can be used as a sealing element in gas turbines, steam turbines and aircraft engines, in short, in between high pressure (22) and low pressure regions (23) around high speed rotating shafts (21); it can also be used to increase performance of the currently used brush seals; it is also a multiple brush production technique comprised of at least one front plate (1) and at least one backing plate (2) that are joined together (1 ,2) through a weld (3) (or gluing or other techniques in nonmetallic seals); characterized in that, wire brush front bars (14) to be tied to form a rectangular frame, and winding of wires around this formed frame in desired wire diameter and density, and depending on the type of the wire brush; one, two, three or more brush stages to be wound around the formed frame; for windings with two or more stages, thin sheet or woven cloth (metal or nonmetal) (4,5) to be placed between stages; once winding process is completed wire brush back bars (19) to be pressed on wound wires to hold tight between front and back bars (14, 19); the wire brush pack that is secured between front and back bars (14, 19) to be brought to desired angle by relatively sliding front and back bars (14, 19) through a piece (20) allowing adjusting ingle; once fhe wir $ are at desired angle; front and back plates (1 ,2) to be welded together at the outer side from one end to other end (or glued etc in nonmetallic brushes); tHis welding process to be performed for both sides; once the welding process is completed wire brush groups formed across at each side that are attached by wire brush to be separated by cutting the brush in between brush groups to split in two, and this way four linear brush strips to be obtained; depending on the type of the brush that is to be manufactured front and back plates (10,11) that are straight or with knife to be welded to these brush strips (glued for non metallic brushes); blowing grooves (9) to be opened or woven or porous metal (12, 13) to be fitted on the back support plate (24) before welding; the obtained brush pack to be curved to desired diameter.