Integrated double-mixing device suitable for high-consistency large-particle leaking stoppage slurry

Abstract

The utility model relates to the field of petroleum and natural gas well drilling plugging equipment, in particular to an integrated double-mixing device suitable for a high-consistency large-particle plugging paddle. The integrated skid-mounted stirring device comprises the pneumatic stirring mechanism and the mechanical stirring mechanism which are connected with the slurry preparation tank, the pneumatic stirring mechanism and the mechanical stirring mechanism are combined into an integrated structure, integrated skid-mounted combination is achieved, and the pneumatic stirring mechanism can work independently and can also work with the mechanical stirring mechanism at the same time; according to the device, an original double-layer double-blade paddle is innovatively designed into a three-layer four-blade paddle, so that the stirring capacity is enhanced, and the stability of mechanical stirring is ensured by increasing the load and the transmission ratio of the motor; a limiting device for mechanical stirring is additionally arranged, so that the stability of equipment under a dynamic condition is ensured, and the service life of the equipment is prolonged; due to the introduction of a pneumatic stirring function, the device can realize the dynamic rolling of the leaking stoppage material under the condition of continuous ventilation, so that the precipitation of the leaking stoppage material is avoided, and the uniform mixing of the paddle body is realized.

Description

Technical Field

[0001] The utility model relates to the field of oil and natural gas drilling plugging equipment, in particular to an integrated double-mixing device suitable for high-viscosity and large-particle plugging paddles. Background Art

[0002] During the drilling exploration and development process, well leakage is an unavoidable complex situation underground. If a weak pressure-bearing layer or a layer containing cracks is encountered, leakage will inevitably occur. If a layer with large cracks is encountered, conventional fine-grained plugging materials are difficult to seal the cracks. It is necessary to prepare a high-viscosity large-particle plugging slurry and use large particles and high solid phase for special plugging, so as to achieve the plugging of fractured layers.

[0003] Currently, the high-solids, large-particle plugging paddle is prepared in the circulation tank of the drilling circulation system. The single circulation tank adopts a rectangular design, which has a dead zone for mixing. To prevent the large particles from settling, two or three mechanical agitators are generally configured for stirring. However, in field applications, it is difficult to avoid the settling of plugging materials, resulting in the accumulation of large particles at the bottom of the circulation tank, resulting in poor plugging effect.

[0004] For example, the patent with publication number CN113019215A discloses a liquid dispensing device, comprising a tank for dispensing liquid and a mechanical stirring assembly and a pneumatic stirring assembly for stirring the liquid in the tank; the mechanical stirring assembly comprises a driving member and a stirring member connected to the driving member, the stirring member extends into the tank, and the driving member is used to drive the stirring member so that the stirring member stirs the liquid in the tank; the pneumatic stirring assembly comprises an air source and an air pipeline, one end of the air pipeline is connected to the air source, and the other end of the air pipeline is located in the tank, and the air source is used to provide gas to the air pipeline so that the gas is sprayed into the tank to stir the liquid in the tank. However, this invention has two independent stirring systems and a complex structure. Not only is it inconvenient to install and the on-site operation is cumbersome, but the pneumatic stirring assembly is prone to clogging during use, thereby losing its effectiveness. Utility Model Content

[0005] The utility model provides an integrated double-mixing device suitable for high-viscosity large-particle plugging paddles, aiming to solve technical problems such as the easy occurrence of plugging material precipitation and uneven plugging paddles during the preparation of high-solid phase large-particle plugging paddles, resulting in poor plugging effects.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0007] An integrated double-mixing device suitable for high-viscosity large-particle plugging paddles, comprising at least a paddle tank, and also comprising a pneumatic stirring mechanism and a mechanical stirring mechanism connected to the paddle tank; the pneumatic stirring mechanism and the mechanical stirring mechanism are an integrated structure; the mechanical stirring mechanism comprises a driving part, a transmission part and a stirring part, the driving part is connected to the outside of the paddle tank, and the stirring part is placed in the paddle tank, and the driving part is connected to the stirring part through the transmission part; the pneumatic stirring mechanism comprises an air input part and an air output part, the air input part is connected to the transmission part of the mechanical stirring mechanism, the air output part is connected to the stirring part, the air input part is connected to the inner cavity of the paddle tank through the transmission part of the mechanical stirring mechanism and the air output part; the pneumatic stirring mechanism can work independently or simultaneously with the mechanical stirring mechanism.

[0008] The air input part includes an air source, an air intake pipeline and a rotating sealing component; the air source, the air intake pipeline and the rotating sealing component are connected to the upper surface of the propeller tank; one end of the air intake pipeline is connected to the air source, and the other end of the air intake pipeline is connected to the transmission part of the mechanical stirring mechanism through the rotating sealing component; the air output part includes a hollow tube and a one-way valve; the hollow tube is connected to the inside of the stirring part of the mechanical stirring mechanism and is connected to the inner cavity of the propeller tank; the one-way valve is installed at the end of the hollow tube to prevent other media in the inner cavity of the propeller tank from entering the hollow tube.

[0009] The driving part of the mechanical stirring mechanism includes a reduction gear box, a connecting rod and a motor, and the reduction gear box, the connecting rod and the motor are installed on the upper surface of the paddle tank, and the motor is connected to the reduction gear box through the connecting rod; the transmission part includes a central hollow tube and a positioning ring, the central hollow tube is vertically arranged, and its upper part is vertically connected to the inside of the reduction gear box, the upper end face of the central hollow tube is rotatably sealed and connected to the pneumatic stirring mechanism, and the lower end face of the central hollow tube is rotatably connected to the bottom of the paddle tank through the positioning ring; the stirring part is a blade, and the blade is a hollow structure, in which the air output part of the pneumatic stirring mechanism is connected, one end of the air output part is connected to the inner cavity of the paddle tank, and the other end of the air output part is connected to the central hollow tube.

[0010] The bottom end of the central hollow tube is 5-8 cm away from the bottom of the paddle tank, and the upper end is open and the lower end is sealed.

[0011] The mechanical stirring mechanism is driven to rotate by a motor through a reduction gearbox, and the reduction gearbox speed is 80 rpm; the motor power is 15 kW, and the transmission ratio is 2.5; the power supply method is a three-phase four-wire method.

[0012] There are multiple blades; each blade is a hollow structure, and its cavity is used to accommodate the air output part of the pneumatic stirring mechanism; the multiple blades are evenly connected to the outer wall of the central hollow tube, and their two ends are respectively connected to the central hollow tube and the inner cavity of the blade tank.

[0013] There are 12 blades in total; the 12 blades are evenly divided into three layers and spaced apart.

[0014] The lengths of the blades in the three layers are different, the length of the blades in the upper layer is the largest, and the length of the blades in the lower layer is the smallest.

[0015] The axis of the blade is parallel to the bottom of the propeller tank; and the upper surface of the blade is set at 45 degrees to the axis of the central hollow tube.

[0016] The width and height of each layer of blades are the same, 13-17 cm wide and 1-3 cm high; the lengths of the upper, middle and lower blades are set in a ratio of 14:10:5; the distance between the outermost end of the upper blade and the inner wall of the paddle tank is 800-1200 cm.

[0017] Beneficial effects:

[0018] (1) The utility model innovatively designs the original double-layer two-blade paddle into a three-layer four-blade paddle, thereby enhancing its stirring capacity and ensuring stable and steady mechanical stirring by increasing the motor load and transmission ratio.

[0019] (2) The utility model adds a limit device for mechanical stirring, thereby ensuring the stability of the equipment under dynamic conditions and extending the service life of the equipment.

[0020] (3) The utility model introduces a pneumatic stirring function, which enables the plugging material to tumble dynamically under the condition of continuous ventilation, thereby preventing the plugging material from settling and achieving uniform mixing of the paddle body.

[0021] (4) The utility model combines pneumatic stirring with mechanical stirring to realize an integrated skid-mounted combination. The pneumatic stirring and mechanical stirring can work independently or simultaneously.

[0022] (5) The utility model is easy and efficient to install, and the air inlet pipeline adopts a quick connector to connect the pneumatic stirring component with the mechanical stirring component.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a schematic structural diagram of the utility model.

[0026] In the figure: 1. Air source; 2. Air inlet pipeline; 3. Rotating sealing component; 4. Reducer; 5. Connecting rod; 6. Motor; 7. Tank surface; 8. Center hollow pipe; 9. Propeller; 10. Hollow pipe; 11. One-way valve; 12. Positioning ring; 13. Tank bottom. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] Example 1: Figure 1 The device is an integrated double-mixing device suitable for high-viscosity large-particle plugging paddles. The device includes two stirring systems: mechanical stirring and pneumatic stirring. A pneumatic stirring mechanism and a mechanical stirring mechanism are connected to the paddle tank. The pneumatic stirring mechanism and the mechanical stirring mechanism are an integrated structure. The mechanical stirring mechanism includes a driving part, a transmission part and a stirring part. The driving part is connected to the outside of the paddle tank, and the stirring part is placed inside the paddle tank. The driving part is connected to the stirring part through the transmission part. The pneumatic stirring mechanism includes an air input part and an air output part. The air input part is connected to the transmission part of the mechanical stirring mechanism, and the air output part is connected to the stirring part. The air input part is connected to the inner cavity of the paddle tank through the transmission part of the mechanical stirring mechanism and the air output part. The pneumatic stirring mechanism can work independently or simultaneously with the mechanical stirring mechanism.

[0029] The driving part of the mechanical stirring mechanism includes a reduction gear box 4, a connecting rod 5 and a motor 6, and the reduction gear box 4, the connecting rod 5 and the motor 6 are installed on the upper surface of the paddle tank, and the motor 6 is connected to the reduction gear box 4 through the connecting rod 5; the transmission part includes a central hollow tube 8 and a positioning ring 12, the central hollow tube 8 is vertically arranged, and its upper part is vertically connected to the inside of the reduction gear box 4, the upper end face of the central hollow tube 8 is rotatably sealed and connected to the pneumatic stirring mechanism, and the lower end face of the central hollow tube 8 is rotatably connected to the bottom 13 of the paddle tank through the positioning ring 12; the stirring part is a blade 9, and the blade 9 is a hollow structure, and the air output part of the pneumatic stirring mechanism is connected thereto, one end of the air output part is connected to the inner cavity of the paddle tank, and the other end of the air output part is connected to the central hollow tube 8.

[0030] Furthermore, the bottom end of the central hollow tube 8 is 5-8 cm away from the bottom of the paddle tank, and the upper end is open and the lower end is sealed.

[0031] The pneumatic stirring mechanism and the mechanical stirring mechanism share a central hollow pipe 8 and a blade 9 to complete the pneumatic stirring;

[0032] The rotary sealing component 3 in this embodiment adopts a rotary joint in the prior art.

[0033] In some embodiments, the central hollow pipe 8 is vertically arranged in the propeller distribution tank, and the central hollow pipe 8 is vertically connected to the hollow pipe 10; the hollow pipe 10 is a through pipe opened in the blade 9, and a one-way valve 11 is installed at the end of the hollow pipe 10 to prevent other media in the propeller distribution tank from entering the hollow pipe 10. The central hollow pipe 8 is vertically arranged in the propeller distribution tank, and the central hollow pipe 8 is vertically connected to the hollow pipe 10.

[0034] In specific applications, the mechanical stirring mechanism drives the motor 6 to rotate through the reduction box 4, and the speed of the reduction box 4 is 80rmp / min; the power of the motor 6 is 15KW, and the transmission ratio is 2.5; the power supply method is the three-phase four-wire method to ensure the normal operation of the device.

[0035] In some embodiments, multiple paddles 9 are provided; each paddle 9 is a hollow structure, and its cavity is used to accommodate the air output part of the pneumatic stirring mechanism; multiple paddles 9 are evenly connected to the outer wall of the central hollow tube 8, and their two ends are respectively connected to the central hollow tube 8 and the inner cavity of the paddle tank.

[0036] The mechanical stirring mechanism and the pneumatic stirring mechanism share the central hollow tube 8, which provides a connection for the blade 9 for mechanical stirring, drives the blade to rotate, and realizes mechanical stirring; at the same time, it provides a gas channel for pneumatic stirring. The gas enters the hollow tube 10 built into the blade 9, passes through the one-way valve 11, and enters the inner cavity of the paddle tank to realize pneumatic stirring.

[0037] Furthermore, the lengths of the blades 9 of the three layers are different, the length of the blades 9 of the upper layer is the largest, and the length of the blades 9 of the lower layer is the smallest.

[0038] Furthermore, the axis of the blade 9 is parallel to the tank bottom 13 of the propeller tank; and the upper surface of the blade 9 is set at 45 degrees to the axis of the central hollow tube 8.

[0039] The width and height of each layer of blades 9 are the same, 13-17 cm wide and 1-3 cm high; the lengths of the upper, middle and lower blades 9 are set in a ratio of 14:10:5; the distance between the outermost end of the upper blade 9 and the inner wall of the paddle tank is 800-1200 cm.

[0040] In specific applications, the lengths of the blades 9 of different layers are set according to the actual size of the paddle tank to meet the need for uniform stirring.

[0041] In actual use, first install the integrated dual mixing device. Follow the steps below:

[0042] 1. The air source 1 is connected to the air inlet pipeline 2, the air inlet pipeline 2 is connected to the rotating sealing component 3, and the rotating sealing component 3 is connected to the central hollow pipe 8.

[0043] 2. Assemble the reduction gearbox 4, connecting rod 5, and motor 6, place them horizontally on the tank surface 7 with the propeller, and fix them at the four corners.

[0044] 3. Connect the central hollow tube 8 to the reduction box 4 with bolts. The upper end of the central hollow tube 8 is connected to the rotating sealing component 3, and the lower end is sealed, 5-8 cm away from the bottom of the tank.

[0045] 4. Weld the blade 9 with the built-in hollow tube 10 to the central hollow tube 8. The hollow tube 10, the central hollow tube 8 and the air inlet line 2 are all connected.

[0046] 5. A one-way valve 11 is installed at the end of the hollow tube 10 to prevent other media from entering the hollow tube 10.

[0047] 6. Install a limiting ring 12 at the bottom end of the central hollow tube 8. The limiting ring 12 wraps and fixes the central hollow tube 8 and is rotatable.

[0048] The specific steps are as follows:

[0049] 1. Open the air source 1 with a pressure of 0.7 MPa, and let the air enter the mixing tank through the air inlet pipeline 2, the rotating sealing component 3, the central hollow pipe 8, the hollow pipe 10, and the one-way valve 11 to achieve pneumatic stirring.

[0050] 2. Turn on the power, start the motor 6, and transmit the force to the reduction box 4 through the connecting rod 5. The reduction box 4 drives the central hollow tube 8 to rotate, accompanied by the rotation of the blade 9 to achieve mechanical stirring.

[0051] 3. Pneumatic stirring and mechanical stirring can be operated simultaneously or separately. For example, if they are operated simultaneously and a power outage occurs, the pneumatic stirring will continue to work and the prepared materials will not easily settle.

[0052] Example 2:

[0053] 1. Assemble the reduction gearbox 4, connecting rod 5, and motor 6, place them horizontally on the tank surface 7, and fix them at the four corners. The occupied area should be less than 150mm*50mm; the overall weight should be less than 300kg.

[0054] 2. The gas source 1 is connected to the air inlet pipeline 2, the air inlet pipeline 2 is connected to the rotating sealing component 3, and the rotating sealing component 3 is connected to the upper end of the central hollow tube 8. The gas source pressure is 0.7 MPa, the diameter of the air inlet pipeline is 10 mm, the inner diameter of the central hollow tube 8 is 80 mm, and the wall thickness is 20 mm.

[0055] 3. Connect the central hollow tube 8 to the reduction box 4 with bolts. The upper end of the central hollow tube 8 is connected to the rotating sealing component 3, and the lower end is sealed, 5 cm away from the bottom of the tank.

[0056] 4. Weld the blade 9 with the hollow tube 10 built in to the central hollow tube 8. The hollow tube 10, the central hollow tube 8 and the air inlet line 2 are all connected. The diameter of the hollow tube 10 is 3-5 mm.

[0057] 5. Install a one-way valve 11 at the end of the hollow tube 10 to prevent other media from entering the hollow tube 10. There are a total of 12 hollow tubes 10 and 12 one-way valves.

[0058] Example 3: Specific application example

[0059] 100 units of the utility model were assembled and applied on site. The equipment was stable during operation and no equipment damage occurred. When using the integrated double mixing device of the utility model, there was almost no residue in the slurry mixing tank after use, and no accumulation and precipitation occurred. Typical cases are as follows:

[0060] Every well drilled in the Su XX well area has leakage. After each plugging construction, 1 / 3 of the plugging material remains in the tank, which is very difficult to clean. The integrated double mixing device of the utility model is installed in the original tank.

[0061] 1. After the size is determined on site, a matching mechanical stirring skid bottom is customized. The reduction gearbox, connecting rod and motor are assembled on the skid, placed horizontally on the tank surface 7 and fixed at the four corners.

[0062] 2. Take the gas from the on-site gas source room, connect the air inlet pipeline, the air inlet pipeline and the rotating sealing component, and then connect the rotating sealing component to the upper end of the central empty pipe.

[0063] 3. Connect the central hollow pipe to the reduction gear box with bolts. Connect the upper end of the central hollow pipe to the rotating sealing component and seal the lower end, 5 cm away from the bottom of the tank;

[0064] 4. Weld the impeller with the built-in hollow tube to the central hollow tube in advance. The hollow tube, the central hollow tube and the air intake line are all connected. The diameter of the hollow tube is 3mm.

[0065] 5. Install 12 one-way valves at the ends of the 12 hollow tubes; the overall installation time of the device is 1.5 hours;

[0066] 6. Use a slurry mixing funnel to prepare the plugging slurry. Start pneumatic stirring and mechanical stirring at the same time. The plugging material content after preparation is 45%, the maximum particle size of the plugging slurry is 30mm, and the consistency is greater than 80BC.

[0067] 7. After the leak plugging work is completed, check whether there is any sediment in the tank. If there is almost no sediment in the tank, simply rinse it with clean water.

[0068] In the absence of conflicts, those skilled in the art may combine the relevant technical features in the above examples according to actual circumstances to achieve corresponding technical effects. Specific descriptions of various combinations are omitted here.

[0069] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0070] In addition, the terms "first," "second," etc., used in this utility model are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features.

[0071] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to these embodiments, but is intended to conform to the broadest scope consistent with the principles and novel features disclosed herein. Any simple modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An integrated dual-mixing device suitable for high-viscosity, large-particle plugging paddles, comprising at least a paddle mixing tank, characterized in that: It also includes a pneumatic stirring mechanism and a mechanical stirring mechanism connected to the paddle tank; the pneumatic stirring mechanism and the mechanical stirring mechanism are an integrated structure; the mechanical stirring mechanism includes a driving part, a transmission part and a stirring part, the driving part is connected to the outside of the paddle tank, and the stirring part is placed in the paddle tank, and the driving part is connected to the stirring part through the transmission part; the pneumatic stirring mechanism includes an air input part and an air output part, the air input part is connected to the transmission part of the mechanical stirring mechanism, the air output part is connected in the stirring part, the air input part is connected to the inner cavity of the paddle tank through the transmission part of the mechanical stirring mechanism and the air output part; the pneumatic stirring mechanism can work independently, and can also work simultaneously with the mechanical stirring mechanism.

2. The integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 1, characterized in that: The gas input portion comprises a gas source (1), an air intake pipeline (2) and a rotating sealing component (3); the gas source (1), the air intake pipeline (2) and the rotating sealing component (3) are connected to the upper surface of the propeller tank; one end of the air intake pipeline (2) is connected to the gas source (1), and the other end of the air intake pipeline (2) is connected to the transmission part of the mechanical stirring mechanism through the rotating sealing component (3); the gas output portion comprises a hollow tube (10) and a one-way valve (11); the hollow tube (10) is connected to the inside of the stirring part of the mechanical stirring mechanism and is communicated with the inner cavity of the propeller tank; the one-way valve (11) is installed at the end of the hollow tube (10) and is used to prevent other media in the inner cavity of the propeller tank from entering the hollow tube (10).

3. The integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 1, characterized in that: The driving part of the mechanical stirring mechanism comprises a reduction box (4), a connecting rod (5) and a motor (6), wherein the reduction box (4), the connecting rod (5) and the motor (6) are mounted on the upper surface of the paddle tank, and the motor (6) is connected to the reduction box (4) through the connecting rod (5); the transmission part comprises a central hollow tube (8) and a positioning ring (12), wherein the central hollow tube (8) is vertically arranged, and its upper part is vertically connected to the inside of the reduction box (4), the upper end surface of the central hollow tube (8) is rotatably sealed and connected to the pneumatic stirring mechanism, and the lower end surface of the central hollow tube (8) is rotatably connected to the tank bottom (13) of the paddle tank through the positioning ring (12); the stirring part is a blade (9), which is a hollow structure, and the air output part of the pneumatic stirring mechanism is connected therein, one end of the air output part is connected to the inner cavity of the paddle tank, and the other end of the air output part is connected to the central hollow tube (8).

4. The integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 3, characterized in that: The bottom end of the central hollow tube (8) is 5-8 cm away from the bottom of the paddle tank, and the upper end is open and the lower end is sealed.

5. The integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 3, characterized in that: The mechanical stirring mechanism drives the motor (6) to rotate via a reduction box (4), and the speed of the reduction box (4) is 80 rpm; the power of the motor (6) is 15 kW, and the transmission ratio is 2.5; and the power supply method is a three-phase four-wire method.

6. The integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 3, characterized in that: A plurality of blades (9) are provided; each blade (9) is a hollow structure, and its cavity is used to accommodate the gas output part of the pneumatic stirring mechanism; the plurality of blades (9) are evenly connected to the outer wall of the central hollow tube (8), and their two ends are respectively connected to the central hollow tube (8) and the inner cavity of the blade tank.

7. The integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 6, characterized in that: A total of 12 blades (9) are provided; the 12 blades (9) are evenly spaced and arranged in three layers.

8. The integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 7, characterized in that: The lengths of the blades (9) of the three layers are different, the blades (9) of the upper layer are the longest, and the blades (9) of the lower layer are the shortest.

9. An integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 7 or 8, characterized in that: The axis of the blade (9) is parallel to the tank bottom (13) of the blade tank; and the upper surface of the blade (9) is arranged at a 45° angle to the axis of the central hollow tube (8).

10. The integrated dual-mixing device suitable for high-viscosity large-particle plugging paddle according to claim 8, characterized in that: The width and height of each layer of blades (9) are the same, with a width of 13-17 cm and a height of 1-3 cm; the lengths of the upper, middle and lower blades (9) are arranged in a ratio of 14:10:5; the distance between the outermost end of the upper blade (9) and the inner wall of the paddle tank is 800-1200 cm.

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