Automatic control valve of butterfly centrifugal pump and control method

Abstract

The invention discloses a butterfly centrifugal pump self-control valve and a control method, and aims to solve the problem that an existing water pump control valve fails due to blockage of liquid impurities in a pipe network. The self-control valve comprises a valve body, a butterfly plate, a valve rod, a hydraulic cylinder and the like, the hydraulic cylinder comprises a piston cylinder, a piston and a cylinder seat with a quick / adjusting channel, and the adjusting channel is matched with an adjusting screw; purified water or oil is adopted as an independent hydraulic driving medium, and impurity blockage is avoided. When the valve is opened, water pressure of the water pump pushes the butterfly plate to rotate, and the piston firstly cuts off the quick channel to realize light-load pump starting and then communicates with the channel to fully open the butterfly plate; when the valve is closed, backflow water and gravitational torque of the butterfly plate drive the piston to move downwards, a rapid channel is cut off in the later period to reduce water hammers, and backflow is prevented after full closing. The device is simple in structure, low in cost, high in reliability, adaptive to an outlet of the centrifugal pump and capable of avoiding pump starting tripping and water hammer accidents.

Description

Technical Field

[0001] This invention relates to a valve device, and more particularly to a self-control valve and control method for a butterfly centrifugal pump outlet, which has functions of preventing backflow, light-load pump start-up, reducing water hammer, and automatic control. Background Technology

[0002] In centrifugal pump delivery systems, the pump control valve is a core component for regulating flow and ensuring system safety; its operational reliability directly determines the stability of the entire delivery system. Currently, existing pump control valves generally use the liquid transported by the pipeline network itself as the driving medium, relying on the water pressure difference in the pipeline network to open and close the valve. While this design simplifies the drive structure, it faces serious clogging and failure problems in practical applications, becoming a key bottleneck restricting the long-term stable operation of the system.

[0003] Specifically, the liquids transported in pipelines often contain large solid impurities such as silt, fibers, and algae, as well as scaling components such as calcium and magnesium ions and microorganisms. On the one hand, large impurities tend to accumulate in valve control pipelines (especially small-diameter control pipelines), gradually reducing the flow cross-section until complete blockage, preventing the transmission of driving pressure and causing the valve to lose its regulating ability. On the other hand, scaling components form a hard scale layer on the inner wall of the piston cylinder and the surface of the seals, which not only increases the resistance of piston movement but also damages the sealing performance, causing hydraulic leakage and further exacerbating the risk of valve failure. For example, in complex water quality scenarios such as municipal water supply and farmland irrigation, centrifugal pump systems using traditional control valves need to be shut down every 3-6 months on average to clean blocked components, which not only increases operation and maintenance costs but also causes water supply / irrigation interruptions due to downtime, resulting in economic losses.

[0004] To alleviate clogging issues, some existing technologies attempt to add filters to remove impurities or use anti-scaling coatings to treat the piston cylinder inner wall. However, significant drawbacks remain: filters require regular disassembly and cleaning; otherwise, clogging will increase pipeline pressure loss, negatively impacting centrifugal pump efficiency. While anti-scaling coatings can slow down scaling, they cannot completely prevent it, and the coating must be reapplied after wear, resulting in high maintenance costs. Furthermore, existing valves have shortcomings in their design regarding pump start-up overload and water hammer protection—traditional valves have uncontrollable opening speeds, making them prone to motor overload and tripping due to instantaneous flow surges during pump start-up; excessively fast valve closing can cause violent fluctuations in water flow within the pipe, generating a water hammer effect that impacts the pipes and pump body, potentially leading to pipe rupture, pump damage, and other safety accidents.

[0005] In summary, existing pump control valves have room for improvement in terms of adaptability to complex water quality, operational reliability, and safety protection capabilities. There is an urgent need for a new type of automatic control valve design that can fundamentally solve the clogging problem, while also taking into account the functions of light-load pump start-up and water hammer reduction, and is simple in structure and low in cost, in order to meet the needs of efficient, stable, and long-term operation of centrifugal pump systems. Summary of the Invention

[0006] The main technical problem solved by this invention is that existing water pump control valves, which rely on pipelines to transport liquid as the driving medium, are easily clogged by impurities in the water, leading to valve failure and safety accidents. This invention provides a butterfly centrifugal pump self-control valve that has any of the following characteristics: simple structure, low cost, and high reliability.

[0007] To address the aforementioned technical problems, this application provides the following technical solution: A self-regulating valve for a butterfly centrifugal pump includes a valve body, a butterfly plate, a valve stem, a hydraulic cylinder, a crank, bearings, and a connecting pin. The hydraulic cylinder consists of a piston cylinder, a piston, a piston rod, a piston cylinder head, a piston cylinder seat, and a connecting pipe. The piston cylinder head has a fluid channel and is connected to the piston cylinder seat via the connecting pipe. The piston cylinder seat has a quick-access channel and an adjustment channel, with an adjustment screw at the adjustment channel. The piston cylinder head, piston cylinder, and piston cylinder seat are connected as a whole by a screw assembly. The upper end of the piston rod is connected to the piston by a nut, and the lower end of the piston rod is connected to the crank via a pin, allowing them to rotate relative to each other. The crank is fixedly connected to the valve stem. The butterfly plate has a lug, which is connected to the valve stem. Both ends of the valve stem are suspended from the valve body by bearings, allowing the butterfly plate and valve stem to rotate within the bearings. The self-regulating valve uses pure water or oil as the hydraulic drive medium, rather than the liquid transported in the pipeline network.

[0008] The present invention provides a self-control valve for a butterfly centrifugal pump, comprising a valve body (1), a butterfly plate (2), a valve stem (3), a hydraulic cylinder (4), a crank (5), a bearing (6), and a connecting pin (7). The hydraulic cylinder (4) is composed of a piston cylinder (41), a piston (42), a piston rod (43), a piston cylinder cover (44), a piston cylinder seat (45), and a connecting pipe (46). The piston cylinder cover (44) is provided with a fluid channel (47) and is connected to the piston cylinder seat (45) through the connecting pipe (46). The piston cylinder seat (45) is provided with a quick channel (48) and an adjustment channel (49). An adjustment screw (410) is provided at the adjustment channel (49).

[0009] The present invention provides a self-control valve for a butterfly centrifugal pump, wherein the piston cylinder head (44), piston cylinder (41), and piston cylinder seat (45) are connected as a whole by a screw assembly (411), the upper end of the piston rod (43) is connected to the piston (42) by means of a nut (9), and the lower end of the piston rod (43) is rotatably connected to the crank (5) by means of a pin (10).

[0010] Preferably, the crank (5) is fixedly connected to the valve stem (3). When the valve stem (3) rotates, it drives the crank (5) to rotate, thereby driving the piston (42) to perform lifting and lowering movements.

[0011] Preferably, the butterfly plate (2) is provided with a hanging lug (8) and is connected to the valve stem (3) as a whole through the hanging lug (8). The two ends of the valve stem (3) are suspended on the valve body (1) through bearings (6), and the butterfly plate (2) and the valve stem (3) can rotate in the bearings (6).

[0012] Preferably, pure water or oil is used as the hydraulic drive medium, which is independent of the liquid transported in the pipeline network.

[0013] Preferably, when the water pump starts, the water pressure at the valve inlet increases and pushes the butterfly plate (2) to rotate clockwise. This drives the piston rod (43) and piston (42) to rise through the valve stem (3) and crank (5). The hydraulic driving medium in the upper chamber of the piston (42) flows into the lower chamber of the piston (42) through the fluid channel (47) and the connecting pipe (46).

[0014] Preferably, when the piston (42) is located at the bottom of the piston cylinder (41), the fast channel (48) is interrupted, and the hydraulic drive medium can only enter the lower chamber of the piston (42) through the regulating channel (49), so that the disc (2) opens slowly to achieve light-load pump start-up.

[0015] Preferably, as the piston (42) rises, it gradually connects to the rapid channel (48), and the hydraulic driving medium flows rapidly into the lower chamber of the piston (42), causing the butterfly plate (2) to open rapidly to the fully open state.

[0016] Preferably, when the pump stops, the inlet pressure drops to zero, the water flows back, and the butterfly plate (2) rotates counterclockwise under its own gravity and the action of the backflow water. Through the valve stem (3) and crank (5), it drives the piston rod (43) and piston (42) to move downward. The hydraulic drive medium in the lower chamber of the piston cylinder (41) flows into the upper chamber of the piston (42) through the fast channel (48) and the regulating channel (49).

[0017] Preferably, when the piston (42) descends to the lower part of the piston cylinder (41), the rapid channel (48) is blocked, and the hydraulic drive medium can only flow into the upper chamber of the piston (42) through the regulating channel (49), so that the butterfly plate (2) closes slowly to reduce water hammer. After the valve is completely closed, the backflow prevention function is achieved.

[0018] The present invention also provides a control method for a self-regulating valve of a butterfly centrifugal pump, which includes the following steps: S1. Valve opening control: Start the water pump, the water pressure at the valve inlet increases and pushes the butterfly plate (2) to rotate clockwise. Through the valve stem (3) and crank (5), the piston rod (43) and piston (42) rise. The hydraulic drive medium in the upper chamber of piston (42) flows through the fluid channel. (47) and the connecting pipe (46) flow into the lower chamber of piston (42); in the initial stage, piston (42) blocks the fast channel (48), and the hydraulic drive medium flows into the lower chamber only through the regulating channel (49). The butterfly plate (2) slowly opens to achieve light-load pump start-up; after piston (42) rises, it connects to the fast channel (48), and the hydraulic drive medium flows into the lower chamber quickly. The butterfly plate (2) quickly opens to full opening. S2, Valve Closure Control: After the pump stops, the inlet pressure drops to zero, the water flows back, and the butterfly plate (2) rotates counterclockwise under its own gravity and the action of the backflow water. Through the valve stem (3) and crank (5), the piston rod (43) and piston (42) move downward. The hydraulic driving medium in the lower chamber of the piston cylinder (41) flows into the upper chamber of the piston (42) through the fast channel (48) and the regulating channel (49). When the piston (42) moves down to the lower part of the quick channel (48), the hydraulic driving medium flows into the upper chamber only through the regulating channel (49). The butterfly plate (2) closes slowly to reduce water hammer. After the valve is fully closed, backflow is prevented.

[0019] Compared with the prior art, the self-control valve for a butterfly centrifugal pump of the present invention has at least the following beneficial effects: 1. Excellent anti-clogging performance: Using pure water or oil as the hydraulic drive medium avoids the blockage of control pipes or piston cylinders by impurities such as mud, fibers, and easily scaled particles contained in the liquid transported in the pipeline, greatly improving the reliability of valve operation and effectively solving the problem of easy failure of traditional valves.

[0020] 2. Comprehensive and practical functions: It integrates functions such as backflow prevention, light-load pump start-up, water hammer reduction, and automatic control. It is specially adapted for use at the outlet of centrifugal pumps and can effectively avoid tripping and water hammer accidents caused by pump overload, ensuring the safe operation of the pump and system.

[0021] 3. Simple and compact structure: The components are reasonably connected, the overall design is simple, easy to manufacture and process, and easy to maintain, reducing production and subsequent operation and maintenance costs.

[0022] 4. Convenient and efficient operation: It is automatically driven by the water pressure difference in the pipeline network, with a high degree of automation. No additional manual intervention is required. It can realize the automatic opening and closing of valves and adapt to the operating conditions of water pumps.

[0023] The following description, in conjunction with the accompanying drawings, further illustrates the self-regulating valve for a butterfly centrifugal pump according to the present invention. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the self-control valve of a butterfly centrifugal pump in the closed state according to the present invention; Figure 2 This is a schematic diagram showing some structural details of the self-control valve for a butterfly centrifugal pump according to the present invention; Figure 3 This is a schematic diagram of the hydraulic cylinder structure of a butterfly centrifugal pump in the fully closed state of the self-control valve. Figure 4 This is a schematic diagram of the structure of a butterfly centrifugal pump self-control valve in a half-open state according to the present invention; Figure 5 This is a schematic diagram of the structure of a butterfly centrifugal pump with its self-control valve in the fully open state according to the present invention; Figure 6 This is a schematic diagram of the self-control valve of a butterfly centrifugal pump in a semi-open state from another perspective. Figure 7 This is a schematic diagram of the self-control valve of a butterfly centrifugal pump in the fully open state from another perspective. Figure 8 This is a schematic diagram of the self-control valve of a butterfly centrifugal pump in the fully closed state from another perspective.

[0025] Figure reference numerals: 1-Valve body, 11-Counterweight, 12-Foot, 13-Bracket, 14-Lower end cap, 15-Bolt, 16-Pin hole; 17-Crank pin. 2-Butterfly plate, 3-Valve stem, 4-Hydraulic cylinder, 41-Piston cylinder, 42-Piston, 43-Piston rod, 44-Piston cylinder head, 45-Piston cylinder seat, 46-Connecting pipe, 47-Fluid passage, 48-Quick passage, 49-Adjusting passage, 410-Adjusting screw, 411-Screw assembly, 5-Crank, 6-Sliding bearing, 7-Connecting pin, 8-Hanging lug, 9-Nut, 10-Pin. Detailed Implementation

[0026] like Figure 1 , 2 As shown, the self-regulating valve for a butterfly centrifugal pump involved in this invention mainly consists of a valve body 1, a butterfly plate 2, a valve stem 3, a hydraulic cylinder 4, a crank 5, a bearing 6, and a connecting pin 7. This self-regulating valve has functions such as preventing backflow, light-load pump start-up, reducing water hammer, and automatic control. Specifically applied to the outlet of a centrifugal pump, it can effectively avoid tripping and water hammer accidents caused by pump overload, ensuring the safe operation of the pump and the system.

[0027] See Figure 1 , Figure 2The hydraulic cylinder 4 consists of a piston cylinder 41, a piston 42, a piston rod 43, a piston cylinder head 44, a piston cylinder seat 45, and a connecting pipe 46. The piston cylinder head 44 has a fluid passage 47, which connects to the piston cylinder seat 45 via the connecting pipe 46. The piston cylinder seat 45 has a quick-access passage 48 and an adjustment passage 49. (See details...) Figure 3 An adjusting screw 410 is provided at the adjusting channel 49. The piston cylinder head 44, piston cylinder 41, and piston cylinder seat 45 are connected as a whole by a screw assembly 411. The upper end of the piston rod 43 is connected to the piston 42 by a nut 9. The lower end of the piston rod 43 is connected to the crank 5 by a pin 10, and the two can rotate relative to each other. The crank 5 is fixedly connected to the valve stem 3; when the valve stem 3 rotates, it will drive the crank 5 to rotate, thereby causing the piston 42 to move up and down.

[0028] The butterfly plate 2 is provided with a hanging lug 8, which is connected to the valve stem 3 as a whole; the two ends of the valve stem 3 are suspended above the valve body 1 through bearings 6; the butterfly plate 2 and the valve stem 3 can rotate in the bearings 6.

[0029] The following are examples of usage: 1. Valve Opening Process: After the water pump starts, the water pressure at the valve inlet gradually increases, pushing the butterfly plate 2 to rotate clockwise. This, through the valve stem 3 and crank 5, drives the piston rod 43 and piston 42 to rise. The liquid in the upper chamber of piston 42 flows into the lower chamber of piston 42 through the fluid channel 47 and connecting pipe 46. At this time, piston 42 is at the bottom of piston cylinder 41, blocking the rapid passage 48. Liquid can only enter the lower chamber of piston 42 through the regulating channel 49. Under the restriction of piston cylinder 41, butterfly plate 2 can only open slowly, thus achieving the light-load pump start-up function. As piston 42 slowly rises, the blocked rapid passage 48 gradually connects, allowing the liquid in the upper chamber of piston 42 to quickly flow into the lower chamber of piston 42. The butterfly plate 2 quickly opens to the fully open state. For details, please refer to [link to documentation]. Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 .

[0030] in, Figure 3 The internal structure of the hydraulic cylinder is shown in magnification, clearly showing the position of the piston (42) in the fully closed state (bottom of the piston cylinder), the state that the rapid passage (48) is blocked, the hydraulic medium flows only through the regulating passage (49), and the assembly relationship of each hydraulic cylinder component.

[0031] Figure 4 The relative positions of the upper and lower chambers inside the hydraulic cylinder in the half-open state are shown, reflecting the change in the flow space of the hydraulic medium from the upper chamber of the hydraulic cylinder through the connecting pipe (46) into the lower chamber, and indirectly reflecting the half-open angle of the butterfly plate.

[0032] Figure 5The final position of the upper and lower chambers inside the hydraulic cylinder is shown in the fully open state. The hydraulic medium flows quickly through the fast channel (48), corresponding to the hydraulic drive state when the butterfly plate is fully open. The medium flow direction arrow indicates the smooth flow direction of the medium.

[0033] Figure 6 From another perspective, it presents a half-open state, highlighting the direction of the medium flow through the valve body channel and the relative positional relationship between the butterfly plate and the valve body.

[0034] Figure 7 From another angle, the fully open state is clearly shown, illustrating the assembly relationship between the valve body and the butterfly plate under full flow conditions. The arrow indicating the flow direction of the medium at its maximum flow rate is displayed. 2. Valve Closing Process: When the pump stops, the valve inlet pressure rapidly drops to zero, and the water in the pipe quickly flows back. Under the combined action of its own gravity and the backflowing water, the eccentrically designed butterfly plate 2 rotates rapidly counterclockwise, driving the piston rod 43 and piston 42 downwards via the valve stem 3 and crank 5. The liquid in the lower chamber of piston cylinder 41 flows rapidly into the upper chamber of piston 42 through the fast channel 48 and regulating channel 49, and through the connecting pipe 46 and fluid channel 47. When piston 42 descends to the lower part of piston cylinder 41, the fast channel 48 is blocked, and the liquid can only enter the upper chamber of piston 42 through the regulating channel 49. Under the constraint of piston cylinder 41, butterfly plate 2 can only close slowly, achieving the function of reducing water hammer. When the valve is fully closed, it can achieve the function of preventing backflow.

[0035] Figure 8 Presented from another angle in the fully closed state, it clearly shows the assembly relationship between the valve body and the butterfly plate under the condition of medium backflow, and the medium flow direction arrow indicates the flow direction of the medium. Specific implementation examples: Butterfly board eccentric design: The butterfly plate (2) adopts a double eccentric structure with an upper and lower eccentric distance of 50-200mm and a left and right eccentric distance of 100 / 200mm. The eccentric direction is towards the valve inlet end; ② Adjusting screw: "Adjusting screw (410) pitch 1.5mm, adjustment stroke 0-10mm, suitable for centrifugal pumps with pipe diameter DN500-DN200"; ③ New component: The weight (11) is made of cast iron and weighs 5-50kg (the larger the pipe diameter, the greater the weight). It is fixed to the hydraulic cylinder (4) by welding through a Q235 steel bracket (13) (thickness 20-40mm); The foot (12) is made of carbon steel and is equipped with M16-M45 bolt holes with a bolt preload of 500-2000N・m.

[0037] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A self-regulating valve for a butterfly centrifugal pump, characterized in that, Includes valve body (1), butterfly plate (2), valve stem (3), hydraulic cylinder (4), crank (5), bearing (6) and connecting pin (7); The butterfly plate (2) is connected to the valve stem (3) as a whole through the lug (8). The two ends of the valve stem (3) are suspended in the valve body (1) through the bearing (6), which can drive the butterfly plate (2) to rotate around the axis of the valve stem (3). The hydraulic cylinder (4) consists of a piston cylinder (41), a piston (42), a piston rod (43), a piston cylinder head (44), a piston cylinder seat (45), and a connecting pipe (46). The piston cylinder head (44) is provided with a fluid passage (47) and is connected to the piston cylinder seat (45) through the connecting pipe (46). The piston cylinder seat (45) is provided with a quick passage (48) and an adjustment passage (49). An adjustment screw (410) is provided at the adjustment passage (49). One end of the crank (5) is fixedly connected to the valve stem (3), and the other end is rotatably connected to the lower end of the piston rod (43) via a pin (10). The upper end of the piston rod (43) is connected to the piston (42), and the piston (42) can move up and down in the piston cylinder (41).

2. The self-regulating valve for a butterfly centrifugal pump according to claim 1, characterized in that, The piston cylinder head (44), piston cylinder (41), and piston cylinder seat (45) are connected as a whole by a screw assembly (411). The upper end of the piston rod (43) is connected to the piston (42) by means of a nut (9). The lower end of the piston rod (43) is rotatably connected to the crank (5) by means of a pin (10).

3. The self-regulating valve for a butterfly centrifugal pump according to claim 2, characterized in that, The crank (5) is fixedly connected to the valve stem (3). When the valve stem (3) rotates, it drives the crank (5) to rotate, thereby driving the piston (42) to perform lifting and lowering movements.

4. The self-regulating valve for a butterfly centrifugal pump according to claim 3, characterized in that, The butterfly plate (2) is provided with a hanging lug (8), and is connected to the valve stem (3) as a whole through the hanging lug (8). The two ends of the valve stem (3) are suspended on the valve body (1) through bearings (6), and the butterfly plate (2) and the valve stem (3) can rotate in the bearings (6).

5. The self-regulating valve for a butterfly centrifugal pump according to claim 4, characterized in that, Pure water or oil is used as the hydraulic drive medium, which is independent of the liquid transported in the pipeline network. When the water pump starts, the water pressure at the valve inlet increases and pushes the butterfly plate (2) to rotate clockwise. Through the valve stem (3) and crank (5), the piston rod (43) and piston (42) are driven to rise. The hydraulic drive medium in the upper chamber of the piston (42) flows into the lower chamber of the piston (42) through the fluid channel (47) and the connecting pipe (46).

6. The self-regulating valve for a butterfly centrifugal pump according to claim 5, characterized in that, When the piston (42) is located at the bottom of the piston cylinder (41), the quick channel (48) is interrupted, and the hydraulic drive medium can only enter the lower chamber of the piston (42) through the regulating channel (49), so that the disc (2) opens slowly to achieve light-load pump start-up.

7. The self-regulating valve for a butterfly centrifugal pump according to claim 6, characterized in that, As the piston (42) rises, it gradually connects to the fast channel (48), and the hydraulic driving medium flows rapidly into the lower chamber of the piston (42), causing the butterfly plate (2) to open rapidly to the fully open state.

8. The self-regulating valve for a butterfly centrifugal pump according to claim 7, characterized in that, When the pump stops, the inlet pressure drops to zero, the water flows back, and the butterfly plate (2) rotates counterclockwise under its own gravity and the action of the backflow water. Through the valve stem (3) and crank (5), it drives the piston rod (43) and piston (42) to move downward. The hydraulic drive medium in the lower chamber of the piston cylinder (41) flows into the upper chamber of the piston (42) through the fast channel (48) and the regulating channel (49).

9. A self-regulating valve for a butterfly centrifugal pump according to claim 8, characterized in that, When the piston (42) descends to the lower part of the piston cylinder (41), the rapid channel (48) is blocked. The hydraulic drive medium can only flow into the upper chamber of the piston (42) through the regulating channel (49), so that the butterfly plate (2) closes slowly to reduce water hammer. After the valve is completely closed, the backflow prevention function is achieved.

10. A control method for an automatic control valve of a butterfly centrifugal pump, characterized in that, Includes the following steps: S1. Valve opening control: Start the water pump, the water pressure at the valve inlet increases and pushes the butterfly plate (2) to rotate clockwise. Through the valve stem (3) and crank (5), the piston rod (43) and piston (42) rise. The hydraulic drive medium in the upper chamber of piston (42) flows through the fluid channel. (47) and the connecting pipe (46) flow into the lower chamber of piston (42); in the initial stage, piston (42) blocks the fast channel (48), and the hydraulic drive medium flows into the lower chamber only through the regulating channel (49). The butterfly plate (2) slowly opens to achieve light-load pump start-up; after piston (42) rises, it connects to the fast channel (48), and the hydraulic drive medium flows into the lower chamber quickly. The butterfly plate (2) quickly opens to full opening. S2, Valve Closure Control: After the pump stops, the inlet pressure drops to zero, the water flows back, and the butterfly plate (2) rotates counterclockwise under its own gravity and the action of the backflow water. Through the valve stem (3) and crank (5), the piston rod (43) and piston (42) move downward. The hydraulic driving medium in the lower chamber of the piston cylinder (41) flows into the upper chamber of the piston (42) through the fast channel (48) and the regulating channel (49). When the piston (42) moves down to the lower part of the quick channel (48), the hydraulic driving medium flows into the upper chamber only through the regulating channel (49). The butterfly plate (2) closes slowly to reduce water hammer. After the valve is fully closed, backflow is prevented.

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