Water spray pipeline device for high-altitude alternating-current extra-high-voltage main transformer
By designing a water spray pipeline device suitable for high-altitude ultra-high voltage main transformers, the problem of inapplicability of the existing layout scheme is solved, and higher explosion resistance and fire resistance are achieved, ensuring efficient fire extinguishing effect.
Patent Information
- Application Number
- CN202420932242.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-30
- Publication Date
- 2025-03-11
- Estimated Expiration
- 2034-04-30
AI Technical Summary
The existing water spray pipeline layout scheme is not suitable for high-altitude ultra-high voltage 1000 kV main transformer, and cannot effectively ensure fire safety.
A water spray pipe device for high-altitude AC ultra-high voltage main transformer is designed, including a water spray main ring pipe and multiple risers. The main ring pipe is buried around the main transformer, and the riser is distributed around the body transformer and the adjusting and replenishing transformer. Each riser is equipped with a water mist spray head, and the nozzle outlet points to the transformer.
By rationally arranging water spray pipes, the device enhances explosion resistance and fire resistance, reduces the number of nozzle damage, ensures fire extinguishing effect, and improves the overall performance of the water spray fire extinguishing system.
Smart Images
Figure CN222585404U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of fire protection of ultra-high voltage substations, in particular to a water spray pipeline device for an AC ultra-high voltage main transformer at high altitudes. Background Art
[0002] The dimensions of the UHV 1000 kV AC transformer are larger than those of the UHV ±800 kV DC transformer. Due to the increase in air gaps and poor heat dissipation in high-altitude substations, the dimensions of the high-altitude 1000 kV AC transformer are further increased, the largest among all oil-immersed transformers currently. The increase in the dimensions of the equipment has many impacts on fire protection.
[0003] According to national standards, large oil-immersed transformers need to be equipped with water spray fire extinguishing systems. The typical layout of water spray pipes for transformers (04S206) shown in the current national building standard design atlas shows that the transformer capacity is only 50MVA, its external dimensions are relatively small, and it does not include a regulating transformer. The water spray pipe layout scheme therein has no reference value at all and is not applicable to fire protection of high-altitude ultra-high voltage 1000 kV main transformers containing main transformers and regulating transformers. The latest 20th edition of the atlas replaces the 04th edition, but the new edition of the atlas does not update the typical layout of water spray pipes, and there is no standard or atlas requirement or reference for the layout of water spray pipes. Utility Model Content
[0004] In view of the problems existing in the prior art, a water spray pipe device for a high-altitude AC ultra-high voltage main transformer is provided, which is used to protect a high-altitude AC ultra-high voltage 1000 kV main transformer comprising a main transformer and a regulating transformer.
[0005] The technical solution adopted by the utility model is as follows: a water spray pipeline device for a high-altitude AC ultra-high voltage main transformer, wherein the ultra-high voltage main transformer comprises a main transformer and a regulating transformer arranged adjacently; the water spray pipeline device comprises a water spray main ring pipe and a plurality of risers, wherein the water spray main ring pipe is buried under the ground around the ultra-high voltage main transformer; at the same time, the water spray main ring pipe is also buried under the ground at the gap between the main transformer and the regulating transformer; the plurality of risers are connected to the water spray main ring pipe and distributed around the main transformer and the regulating transformer, and a water mist nozzle is installed on each riser, and the outlet of the water mist nozzle points to the main transformer or the regulating transformer.
[0006] As a preferred solution, a plurality of water mist nozzles are installed at intervals on each riser.
[0007] As a preferred solution, a tee and a pipe pier are provided at the connection between the riser and the water spray main ring pipe. The pipes at the pipe piers are connected by flanges, and metal-wrapped graphite gaskets are used at the flange connections; pipes with a diameter of DN50 and below are connected by threads, and pipe connections at other locations are welded.
[0008] As a preferred solution, the water spray main ring pipe is installed below the oil pit grille.
[0009] As a preferred solution, the water spray main ring pipe and branch pipes are made of galvanized steel pipes, and the pipe walls are thickened.
[0010] As a preferred solution, for the multiple water mist nozzles on the riser in the gap between the main transformer and the regulating transformer, the multiple water mist nozzle outlets are alternately directed to the main transformer and the regulating transformer for two-way spraying; each water mist nozzle first connects the branch pipe in reverse, and then winds back to the direction of the protected surface through multiple elbows.
[0011] As a preferred solution, a flow regulating valve is provided on the riser near the high-voltage outlet bushing of the main transformer.
[0012] As a preferred solution, a special water mist nozzle is arranged on the top of the riser near the high-voltage outlet bushing of the main transformer, and the branch pipe of the special water mist nozzle extends into the upper surface of the main transformer, and the outlet points to the connection between the high-voltage outlet bushing and the main transformer.
[0013] As a preferred solution, the main ring pipe has a diameter of DN300 and a wall thickness of 7 mm.
[0014] As a preferred solution, the riser has a diameter of DN150 and a wall thickness of 6 mm.
[0015] Compared with the prior art, the beneficial effects of the utility model are:
[0016] 1. The utility model makes the pipeline system explosion-proof by rationally arranging the water distribution pipes for water spray. The main ring pipe adopts a ring-shaped water supply pipe and is buried underground so that it is not affected by the explosion of the oil-immersed transformer; the fire branch pipe above the ground in the protection area is arranged vertically, and the nozzles are arranged on the vertical pipes, so that the number of damaged nozzles is reduced to a minimum. The branch pipes of the special nozzles for the casing avoid the corresponding positions on the front of the casing, so that the number of branch pipes affected by the explosion of the transformer is reduced to a minimum.
[0017] 2. The utility model improves the fire resistance of water spray system components, making the pipes of the water spray fire extinguishing system more resistant to fire and reducing the possibility of accidents. The pipes are connected by flange connection, threaded connection and welding. Metal-wrapped graphite gaskets are used at the flange connection to avoid plastic rubber gaskets. Pipes with a diameter of DN50 or less are connected by threads to avoid clamp connections. Improve fire resistance.
[0018] 3. The utility model adopts thickened galvanized steel pipes for the water spray pipes above the ground in the protection area to increase the strength of the pipe structure. The risers near the 1000kV high-voltage outlet bushing are most likely to be damaged. Flow regulating valves are installed on the two nearby risers, and the flow rate Q≈25L / s. Even if the branch pipe is damaged, too much fire water will not be lost, ensuring the fire water supply for other protected areas and ensuring the fire extinguishing effect.
[0019] 4. The utility model also arranges branch pipes and nozzles in the narrow gap space between the main transformer and the adjustment transformer, the tear of the oil tank body near the hole of the 1000kV high-voltage outlet bushing riser, etc., to ensure that there are no dead angles in the water mist fire extinguishing.
[0020] 5. The utility model further optimizes the arrangement of the nozzles, clarifies the nozzle models and quantities of each protection surface, makes the envelope range of the water mist cone more complete, improves the fire extinguishing effect, and better protects the safety of equipment and property. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is an overall schematic diagram of the high-altitude AC ultra-high voltage main transformer water spray pipeline device proposed by the utility model.
[0022] Figure 2 This is a schematic diagram of the arrangement of the flow control valve in one embodiment of the utility model.
[0023] Figure 3 This is a schematic diagram of the arrangement of the tear nozzles of the main transformer in one embodiment of the utility model.
[0024] Figure 4 It is a schematic diagram of the arrangement of the gap space between the main transformer and the regulating transformer in one embodiment of the utility model.
[0025] Figure 5 It is a schematic diagram of the arrangement of nozzles on the upper surface of the main transformer and the upper surface of the first heat sink in one embodiment of the utility model.
[0026] Figure 6 It is a schematic diagram of the arrangement of nozzles on the long side of the main transformer in one embodiment of the utility model.
[0027] Figure 7 The figure is a schematic diagram of the arrangement of the nozzles on the short side of the transformer body in one embodiment of the utility model.
[0028] Figure 8 It is a schematic diagram of the arrangement of nozzles on the long side of the first radiator of the main transformer in one embodiment of the utility model.
[0029] Fig. 9 It is a schematic diagram of the arrangement of nozzles on the short side of the first radiator of the main transformer in one embodiment of the utility model.
[0030] Fig.10 It is a schematic diagram of the arrangement of nozzles on the upper surface of the second heat sink of the main transformer in one embodiment of the utility model.
[0031] Fig.11 It is a schematic diagram of the arrangement of nozzles on the long side of the second radiator of the main transformer in one embodiment of the utility model.
[0032] Fig.12 It is a schematic diagram of the arrangement of nozzles on the short side of the second radiator of the main transformer in one embodiment of the utility model.
[0033] Fig.13 It is a schematic diagram of the arrangement of the nozzles on the side of the oil pillow of the main transformer in one embodiment of the utility model.
[0034] Fig.14 It is a schematic diagram of the arrangement of nozzles at both ends of the oil pillow of the main transformer in one embodiment of the utility model.
[0035] Fig.15 It is a schematic diagram of the arrangement of the oil pit nozzles of the main transformer in one embodiment of the utility model.
[0036] Fig.16 It is a schematic diagram of the arrangement of the nozzles of the elevated seat of the main transformer in one embodiment of the utility model.
[0037] Reference numerals:
[0038] 1- High voltage outlet bushing;
[0039] 2-body transformer;
[0040] 3-Adjusting transformer;
[0041] 4- Water spray main ring pipe;
[0042] 5- riser;
[0043] 6-Flow regulating valve;
[0044] 7-Special nozzle for tearing opening;
[0045] 8- Bidirectional nozzle arrangement in narrow gap space;
[0046] 9- Nozzle arrangement on the upper surface of the transformer and the upper surface of the first radiator;
[0047] 10-Layout of nozzles on the long side of the transformer body;
[0048] 11-Short side nozzle arrangement of the transformer body;
[0049] 12- Nozzle arrangement on the long side of the first radiator of the transformer;
[0050] 13- Arrangement of nozzles on the short side of the first radiator of the transformer;
[0051] 14- Nozzle arrangement on the upper surface of the second radiator of the transformer;
[0052] 15- Nozzle arrangement on the long side of the second radiator of the transformer;
[0053] 16- Nozzle arrangement on the short side of the second radiator of the transformer;
[0054] 17-Layout of nozzles on the side of the transformer oil pillow;
[0055] 18- Arrangement of nozzles at both ends of the transformer oil pillow;
[0056] 19-Oil pit nozzle arrangement of the main transformer;
[0057] 20- Arrangement of nozzles on the elevated seat of the main transformer. DETAILED DESCRIPTION
[0058] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar modules or modules with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be construed as limitations on the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.
[0059] Please refer to Figure 1 The utility model proposes a high-altitude AC UHV main transformer water spray pipeline device, which is mainly aimed at the adjacent arrangement of a main transformer 2 and a regulating transformer 3 in the UHV main transformer. The water spray pipeline device mainly includes a water spray main ring pipe 4 and a plurality of risers 5.
[0060] Among them, the water spray main ring pipe 4 is arranged around the UHV main transformer. In order to prevent the water spray main ring pipe 4 from being damaged by explosion in the event of a transformer accident, the water spray main ring pipe 4 is arranged underground. At the same time, in this embodiment, a water spray main ring pipe is also buried under the ground at the gap between the main transformer 2 and the regulating transformer 3. Multiple risers 5 are connected to the water spray main ring pipe 4 and distributed around the main transformer 2 and the regulating transformer 3. The outlet of the water mist nozzle points to the main transformer 2 or the regulating transformer 3. In order to ensure the fire extinguishing ability, each riser 5 is arranged from top to bottom with multiple water mist nozzles. This arrangement enables the pipeline system to have explosion-proof ability, wherein the main ring pipe adopts an annular water supply pipe and is arranged underground so that it is not affected by the explosion of the oil-immersed transformer; the fire branch pipe above the ground in the protection area adopts a vertical arrangement, and the nozzle is arranged on the riser, so that the number of damaged nozzles is reduced to a minimum. The branch pipe of the special nozzle for the casing avoids the corresponding position on the front of the casing, so that the number of branch pipes affected by the transformer explosion is reduced to a minimum.
[0061] In one embodiment, the water spray main loop pipe 4 has a diameter of DN300 and is installed below the transformer oil pit grid at an elevation of -0.75 meters underground.
[0062] In this embodiment, flange connection, threaded connection and welding are used for the connection of each pipeline. A tee and a pipeline support are set at the connection between the riser 5 and the water spray main ring pipe 4. The pipeline at the pipeline support is flange-connected for easy disassembly, and a metal-wrapped graphite gasket is used at the flange connection. Pipes with a diameter of DN50 or less are threaded to avoid the use of clamp connections to improve fire resistance. Pipe connections in other parts are welded. Through this setting, the fire resistance of the water spray pipeline device is improved, making the pipeline of the water spray fire extinguishing device more resistant to fire burning and reducing the possibility of accidents. In one embodiment, the diameter of the riser 5 is DN150.
[0063] Furthermore, in order to ensure the stability of the pipeline device, the water spray main ring pipe and branch pipe in this embodiment are made of galvanized steel pipes, and the pipe wall thickness is thickened to increase the pipe structure strength. In one embodiment, the water spray main ring pipe has an outer diameter of 324 mm and a wall thickness of 7 mm; the standpipe has an outer diameter of 168 mm and a wall thickness of 6 mm.
[0064] When the UHV 1000 kV AC main transformer is in operation, the main transformer and the regulating transformer are in operation at the same time. In the event of an accident, both of them may catch fire. However, the gap between the main transformer and the regulating transformer is narrow, making it difficult to extinguish the fire. In this embodiment, multiple risers 5 are set in the gap between the main transformer 2 and the regulating transformer 3. Multiple water mist nozzles are set on each riser 5. For each water mist nozzle on a riser, its outlet points alternately to the main transformer and the regulating transformer to achieve two-way spraying. In a narrow space, the distance between the nozzle and the protected surface is insufficient, and the effective range of the nozzle is short. In this embodiment, each water mist nozzle first connects the branch pipe in reverse, and then goes back to the direction of the protected surface through multiple elbows, which effectively increases the distance between the nozzle and the protected surface, fully utilizes the effective range of the nozzle, and makes the nozzle protection area larger.
[0065] Please refer to Figure 2 , and the riser near the 1000kV high-voltage outlet bushing of the main transformer is most likely to be damaged. Two risers near it are equipped with flow control valves 6, and the flow rate Q≈25L / s. Even if the branch pipe is damaged, too much fire water will not be lost, ensuring the fire water supply of other protected parts and ensuring the fire extinguishing effect.
[0066] At the same time, after a fire, the oil tank body near the opening of the 1000kV high-voltage outlet bushing riser seat may form a tear, which is difficult to extinguish. Therefore, in this embodiment, a tear nozzle 7 is set at the opening of the 1000kV high-voltage outlet bushing riser seat for protection, and the other openings of the bushing riser seat are protected by the top surface nozzle of the oil tank body. Please refer to Figure 3 The branch pipe of the special water mist nozzle extends into the upper surface of the main transformer 2, and the outlet points to the connection between the high-voltage outlet bushing 1 and the main transformer 2. Branch pipes and nozzles are also arranged in the narrow gap between the main transformer and the adjustment transformer, and the tear of the oil tank body near the hole of the 1000kV high-voltage outlet bushing riser, to ensure that there is no dead angle for water mist fire extinguishing.
[0067] Please refer to Figure 4 to Figure 16 , shows the specific arrangement of the water spray pipe device of the main transformer in an embodiment, which is described one by one below. Before the introduction, a brief description is given of the composition of the main transformer and the regulating transformer. The main transformer and the regulating transformer are both provided with a first radiator, a second radiator and an oil pillow.
[0068] Please refer to Figure 4 , showing a bidirectional nozzle arrangement 8 in the narrow gap space between the main transformer and the regulating transformer, including four risers, each of which first connects the branch pipe in reverse and then winds back to the protected surface through a plurality of elbows.
[0069] Please refer to Figure 5, showing the nozzle arrangement 9 on the upper surface of the main transformer and the upper surface of the first radiator, the nozzle specification used is ZSTWB 79.2, the specific nozzle model is ZSTWB 79.2 / 90, and the number is 11.
[0070] Please refer to Figure 6 , showing the arrangement of nozzles 10 on the long side of the transformer body, the nozzle specification used is ZSTWB79.2, the specific nozzle model is ZSTWB 79.2 / 120, and the number is 10.
[0071] Please refer to Figure 7 , showing the arrangement of the nozzles 11 on the short side of the transformer body, the nozzle specification used is ZSTWB67, the specific nozzle model is ZSTWB 67 / 90, and the number is 6.
[0072] Please refer to Figure 8 , showing the nozzle arrangement 12 on the long side of the first radiator of the main transformer, the nozzle specification used is ZSTWB 67, and the total number is 15; specifically, the number of nozzles with the nozzle model ZSTWB 67 / 120 is 12; the number of nozzles with the nozzle model ZSTWB 67 / 90 is 3.
[0073] Please refer to Fig. 9 , showing the nozzle arrangement 13 on the short side of the first radiator of the main transformer, the nozzle specification used is ZSTWB 67, the specific nozzle model is ZSTWB 67 / 90, and the number is 2.
[0074] Please refer to Fig.10 , showing the nozzle arrangement 14 on the upper surface of the second heat sink of the main transformer, the nozzle specification used is ZSTWB 43, the specific nozzle model is ZSTWB 43 / 90, and the number is 4.
[0075] Please refer to Fig.11 , showing the nozzle arrangement 15 on the long side of the second heat sink of the main transformer, the nozzle specification used is ZSTWB 67, the specific nozzle model is ZSTWB 67 / 120, and the number is 12.
[0076] Please refer to Fig.12 , showing the nozzle arrangement 16 on the short side of the second radiator of the main transformer, the nozzle specification used is ZSTWB 67, the specific nozzle model is ZSTWB 67 / 90, and the number is 4.
[0077] Please refer to Fig.13 , showing the arrangement of the nozzles 17 on the side of the oil pillow of the transformer body, the nozzle specification used is ZSTWB100, the specific nozzle model is ZSTWB 100 / 120, and the number is 6.
[0078] Please refer to Fig.14 , showing the arrangement of nozzles 18 at both ends of the main transformer oil pillow, the nozzle specification used is ZSTWB40.3, the specific nozzle model is ZSTWB 40.3 / 90, and the number is 2.
[0079] Please refer to Fig.15 , showing the main transformer oil pit nozzle arrangement 19, the nozzle specification used is ZSTWB 40.3, the specific nozzle model is ZSTWB 40.3 / 120, and the number is 17.
[0080] Please refer to Fig.16 , showing the main body transformer riser nozzle arrangement 20, the nozzle specification used is ZSTWB 67, the total number is 5; among them, the number of nozzles with nozzle model ZSTWB 67 / 90 is 3; the number of nozzles with nozzle model ZSTWB 100 / 90 is 2.
[0081] In one embodiment, for the compensation transformer,
[0082] The upper surface of the regulating transformer + the upper surface of the first radiator include: the nozzle specification is ZSTWB 67, the specific nozzle model is ZSTWB 67 / 90, and the quantity is 8.
[0083] The long side of the transformer body includes: the nozzle specification is ZSTWB 54, the specific nozzle model is ZSTWB 54 / 120, and the quantity is 8.
[0084] The short side of the regulating transformer includes: the nozzle specification is ZSTWB 54, the total number is 8; among them, the number of nozzles with the nozzle model of ZSTWB 54 / 120 is 4; the number of nozzles with the nozzle model of ZSTWB 54 / 90 is 4.
[0085] The long side of the first radiator of the regulating transformer includes: the nozzle specification is ZSTWB 54, the specific nozzle model is ZSTWB 54 / 120, and the quantity is 8.
[0086] The short side of the first radiator of the regulating transformer includes: the nozzle specification is ZSTWB 54, the specific nozzle model is ZSTWB 54 / 90, and the quantity is 4.
[0087] The side of the oil pillow of the regulating transformer includes: the nozzle specification is ZSTWB 100, the specific nozzle model is ZSTWB 100 / 120, and the quantity is 3.
[0088] The two ends of the oil pillow of the regulating transformer include: the nozzle specification is ZSTWB 40.3, the specific nozzle model is ZSTWB 40.3 / 90, and the quantity is 2.
[0089] The transformer oil pit adjustment and compensation includes: nozzle specification is ZSTWB 40.3, specific nozzle model is ZSTWB 40.3 / 120, and the quantity is 16.
[0090] It should be noted that, in one embodiment, the orifice of the raised seat can be taken care of by the spray head on the top surface of the oil tank.
[0091] The utility model further optimizes the arrangement of the nozzles, clarifies the nozzle models and quantities of each protection surface, makes the envelope range of the water mist cone more complete, improves the fire extinguishing effect, and better protects the safety of equipment and property.
[0092] It should be noted that in the description of the embodiments of the present utility model, unless otherwise clearly specified and limited, the terms "setting" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances; the drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of the present utility model. Obviously, the described embodiments are part of the embodiments of the present utility model, not all of the embodiments. The components of the embodiments of the present utility model described and shown in the drawings here can be arranged and designed in various different configurations.
[0093] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.
Claims
1. A water spray pipeline device for high altitude AC UHV main transformer, characterized in that: The UHV main transformer comprises a main transformer and a regulating transformer which are arranged adjacent to each other; the water spray pipeline device comprises a water spray main ring pipe and a plurality of risers, the water spray main ring pipe is buried under the ground around the UHV main transformer; at the same time, the water spray main ring pipe is also buried under the ground at the gap between the main transformer and the regulating transformer; the plurality of risers are connected to the water spray main ring pipe and are distributed around the main transformer and the regulating transformer, each riser is equipped with a water mist nozzle, and the outlet of the water mist nozzle points to the main transformer or the regulating transformer.
2. The high altitude AC UHV main transformer water spray pipe device according to claim 1 is characterized in that: A plurality of water mist nozzles are installed at intervals on each riser.
3. The high altitude AC UHV main transformer water spray pipe device according to claim 1, characterized in that: A tee and a pipe pier are arranged at the connection between the riser and the water spray main ring pipe. The pipes at the pipe piers are connected by flanges, and metal-wrapped graphite gaskets are used at the flange connections; pipes with a diameter of DN50 and below are connected by threads, and pipe connections at other locations are welded.
4. The high altitude AC UHV main transformer water spray pipe device according to claim 1, characterized in that: The water spray main ring pipe is installed below the oil pit grille.
5. The high altitude AC UHV main transformer water spray pipe device according to claim 1, characterized in that: The water spray main ring pipe and branch pipes are made of galvanized steel pipes, and the pipe walls are thickened.
6. The high altitude AC UHV main transformer water spray pipe device according to claim 1, characterized in that: For the multiple water mist nozzles on the riser in the gap between the main transformer and the regulating transformer, the multiple water mist nozzle outlets are alternately directed to the main transformer and the regulating transformer for two-way spraying; each water mist nozzle first connects the branch pipe in reverse, and then winds back to the direction of the protected surface through multiple elbows.
7. The high altitude AC UHV main transformer water spray pipe device according to claim 1, characterized in that: A flow regulating valve is arranged on the riser near the high-voltage outlet bushing of the main transformer.
8. The high altitude AC UHV main transformer water spray pipe device according to claim 1, characterized in that: A special water mist nozzle is arranged on the top of the riser near the high-voltage outlet bushing of the main transformer, and the branch pipe of the special water mist nozzle extends into the upper surface of the main transformer, and the outlet points to the connection between the high-voltage outlet bushing and the main transformer.
9. The high altitude AC UHV main transformer water spray pipe device according to claim 1, characterized in that: The main ring pipe has a diameter of DN300 and a wall thickness of 7 mm.
10. The high altitude AC UHV main transformer water spray pipe device according to claim 1, characterized in that: The riser has a diameter of DN150 and a wall thickness of 6 mm.