Gate valves and butterfly valves serve the purpose of opening, closing, and regulating flow in pipelines. However, there are considerations to be made during the selection process.
In water supply networks, larger diameter pipelines often opt for butterfly valves to minimize soil cover depth. For situations where soil depth isn't a significant concern, gate valves are preferred to minimize costs, although gate valves of the same specifications tend to be more expensive than butterfly valves. The specific division between the two valve types should be determined based on local conditions. Based on usage trends in the past decade, butterfly valves have experienced higher failure rates compared to gate valves. Therefore, expanding the use of gate valves where feasible warrants attention.
Regarding gate valves in recent years, many domestic valve manufacturers have developed or imitated soft-sealed gate valves. These valves offer the following characteristics compared to traditional wedge or parallel double-disc gate valves:
1. The valve body and bonnet of soft-sealed gate valves are precision cast in a single molding process, requiring minimal machining and eliminating the need for sealing copper rings, thereby saving non-ferrous metals.
2. The bottom of soft-sealed gate valves is free of recesses, preventing the accumulation of debris and reducing the failure rate during valve operation.
3. The standardized dimensions of soft-sealed rubber-lined valve discs enhance interchangeability.
Therefore, soft-sealed gate valves will be a preferred option in the water supply industry. Currently, domestically manufactured soft-sealed gate valves can reach diameters of up to 1500mm, although most manufacturers produce sizes ranging from 80mm to 300mm, and there are still many technical issues in domestic manufacturing processes. The critical component of soft-sealed gate valves is the rubber-lined valve disc, and the technical requirements for this component are high, not all foreign manufacturers can meet them, often requiring assembly from reliable sources.
In domestic soft-sealed gate valves, the copper nut block is embedded above the rubber-lined valve disc, similar to the structure of traditional gate valves. However, the movement friction of the nut block easily causes the rubber lining of the valve disc to peel off. In contrast, in a certain foreign company's soft-sealed gate valves, the copper nut block is embedded within the rubber-lined gate disc, forming an integral unit, overcoming the aforementioned drawbacks. However, this design requires higher concentricity between the valve bonnet and body.
When operating soft-sealed gate valves, it is essential not to close them too tightly. Achieving a water-tight seal is sufficient; otherwise, it may become challenging to reopen or cause the rubber lining to peel off. Some valve manufacturers use torque wrenches to control the degree of closure during valve pressure testing, and water utility personnel should follow this closing method when operating the valves.
What are the differences between butterfly valves and gate valves in their usage?
In terms of function and application, gate valves have low flow resistance and excellent sealing performance. However, if the gate valve is not fully closed, causing the medium to impact the gate and induce vibration, it can easily damage the sealing of the gate valve due to the perpendicular angle between the gate disc and the flow direction.
Butterfly valves, also known as flip-disc valves, are simple in structure and commonly used for regulating low-pressure pipeline media. The butterfly valve refers to a type of valve with a circular disc as the closing member (valve disc or butterfly plate), which rotates around the valve shaft to achieve opening and closing. These valves can control the flow of various types of fluids, such as air, water, steam, corrosive media, slurry, oil, liquid metal, and radioactive substances, mainly serving the purpose of cutting off and throttling in pipelines.
The butterfly disc is driven by the valve stem and completes one opening or closing cycle by rotating 90°. By changing the deflection angle of the disc, the flow rate of the medium can be controlled.
Usage Conditions and Medium: Butterfly valves are suitable for various engineering systems, such as blast furnaces, gas, natural gas, liquefied petroleum gas, urban gas, cold and hot air, chemical smelting, power generation environmental protection, and building water supply and drainage systems. They are used for regulating and cutting off the flow of corrosive and non-corrosive fluid media.
Gate valves consist of a gate disc as the closure element, and the movement direction of the gate disc is perpendicular to the fluid direction. Gate valves can only be fully opened or fully closed and are not suitable for throttling applications. The sealing surface angle of the gate valve is usually 5°, but it can vary depending on the valve parameters, typically 2°52' when the medium temperature is not high. To improve its manufacturability and compensate for deviations in sealing surface angles during processing, an elastic gate disc is used.
When a gate valve is closed, the sealing surface can rely solely on the pressure of the medium to seal, known as self-sealing. However, most gate valves use forced sealing, meaning that external force is required to press the gate disc against the valve seat to ensure sealing.
Movement Method: The gate disc of a gate valve moves linearly with the valve stem, also known as a rising stem gate valve. Typically, there is a trapezoidal thread on the rising stem, and the rotational motion is converted into linear motion through the nut on the top of the valve and the guide groove on the valve body. When the gate valve is fully open, the fluid passage is completely unobstructed when the lifting height of the gate disc equals the valve diameter at a 1:1 ratio. However, this position cannot be monitored during operation. In practical use, the vertex of the stem serves as a reference point, indicating the fully open position. To prevent jamming due to temperature changes, the valve is usually opened to the vertex position and then reversed by 1/2 to 1 turn, serving as the fully open position. Therefore, the fully open position of the valve is determined by the position of the gate disc (i.e., the stroke). Some gate valves have the stem nut located on the gate disc, where rotation of the handwheel drives the stem to lift the gate disc, known as a rotary stem gate valve or concealed stem gate valve.
In water supply networks, larger diameter pipelines often opt for butterfly valves to minimize soil cover depth. For situations where soil depth isn't a significant concern, gate valves are preferred to minimize costs, although gate valves of the same specifications tend to be more expensive than butterfly valves. The specific division between the two valve types should be determined based on local conditions. Based on usage trends in the past decade, butterfly valves have experienced higher failure rates compared to gate valves. Therefore, expanding the use of gate valves where feasible warrants attention.
Regarding gate valves in recent years, many domestic valve manufacturers have developed or imitated soft-sealed gate valves. These valves offer the following characteristics compared to traditional wedge or parallel double-disc gate valves:
1. The valve body and bonnet of soft-sealed gate valves are precision cast in a single molding process, requiring minimal machining and eliminating the need for sealing copper rings, thereby saving non-ferrous metals.
2. The bottom of soft-sealed gate valves is free of recesses, preventing the accumulation of debris and reducing the failure rate during valve operation.
3. The standardized dimensions of soft-sealed rubber-lined valve discs enhance interchangeability.
Therefore, soft-sealed gate valves will be a preferred option in the water supply industry. Currently, domestically manufactured soft-sealed gate valves can reach diameters of up to 1500mm, although most manufacturers produce sizes ranging from 80mm to 300mm, and there are still many technical issues in domestic manufacturing processes. The critical component of soft-sealed gate valves is the rubber-lined valve disc, and the technical requirements for this component are high, not all foreign manufacturers can meet them, often requiring assembly from reliable sources.
In domestic soft-sealed gate valves, the copper nut block is embedded above the rubber-lined valve disc, similar to the structure of traditional gate valves. However, the movement friction of the nut block easily causes the rubber lining of the valve disc to peel off. In contrast, in a certain foreign company's soft-sealed gate valves, the copper nut block is embedded within the rubber-lined gate disc, forming an integral unit, overcoming the aforementioned drawbacks. However, this design requires higher concentricity between the valve bonnet and body.
When operating soft-sealed gate valves, it is essential not to close them too tightly. Achieving a water-tight seal is sufficient; otherwise, it may become challenging to reopen or cause the rubber lining to peel off. Some valve manufacturers use torque wrenches to control the degree of closure during valve pressure testing, and water utility personnel should follow this closing method when operating the valves.
What are the differences between butterfly valves and gate valves in their usage?
In terms of function and application, gate valves have low flow resistance and excellent sealing performance. However, if the gate valve is not fully closed, causing the medium to impact the gate and induce vibration, it can easily damage the sealing of the gate valve due to the perpendicular angle between the gate disc and the flow direction.
Butterfly valves, also known as flip-disc valves, are simple in structure and commonly used for regulating low-pressure pipeline media. The butterfly valve refers to a type of valve with a circular disc as the closing member (valve disc or butterfly plate), which rotates around the valve shaft to achieve opening and closing. These valves can control the flow of various types of fluids, such as air, water, steam, corrosive media, slurry, oil, liquid metal, and radioactive substances, mainly serving the purpose of cutting off and throttling in pipelines.
The butterfly disc is driven by the valve stem and completes one opening or closing cycle by rotating 90°. By changing the deflection angle of the disc, the flow rate of the medium can be controlled.
Usage Conditions and Medium: Butterfly valves are suitable for various engineering systems, such as blast furnaces, gas, natural gas, liquefied petroleum gas, urban gas, cold and hot air, chemical smelting, power generation environmental protection, and building water supply and drainage systems. They are used for regulating and cutting off the flow of corrosive and non-corrosive fluid media.
Gate valves consist of a gate disc as the closure element, and the movement direction of the gate disc is perpendicular to the fluid direction. Gate valves can only be fully opened or fully closed and are not suitable for throttling applications. The sealing surface angle of the gate valve is usually 5°, but it can vary depending on the valve parameters, typically 2°52' when the medium temperature is not high. To improve its manufacturability and compensate for deviations in sealing surface angles during processing, an elastic gate disc is used.
When a gate valve is closed, the sealing surface can rely solely on the pressure of the medium to seal, known as self-sealing. However, most gate valves use forced sealing, meaning that external force is required to press the gate disc against the valve seat to ensure sealing.
Movement Method: The gate disc of a gate valve moves linearly with the valve stem, also known as a rising stem gate valve. Typically, there is a trapezoidal thread on the rising stem, and the rotational motion is converted into linear motion through the nut on the top of the valve and the guide groove on the valve body. When the gate valve is fully open, the fluid passage is completely unobstructed when the lifting height of the gate disc equals the valve diameter at a 1:1 ratio. However, this position cannot be monitored during operation. In practical use, the vertex of the stem serves as a reference point, indicating the fully open position. To prevent jamming due to temperature changes, the valve is usually opened to the vertex position and then reversed by 1/2 to 1 turn, serving as the fully open position. Therefore, the fully open position of the valve is determined by the position of the gate disc (i.e., the stroke). Some gate valves have the stem nut located on the gate disc, where rotation of the handwheel drives the stem to lift the gate disc, known as a rotary stem gate valve or concealed stem gate valve.
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