What Valves Are Used for Drainage Pipes?

The valves used on the water supply pipeline, generally according to the following principles.

 

1. Valve and set the choice of components

The valves used on the water supply pipeline, generally according to the following principles.

● the diameter of the pipe is not greater than 50 mm, it is appropriate to use the globe valve, pipe diameter greater than 50 mm gate valve, butterfly valve. 

● the need to adjust the flow, water pressure, it is appropriate to use the regulating valve, disconnecting valve. 

● requires a small resistance to water flow (such as pump suction pipe), it is appropriate to use the gate valve. 

● the water flow needs two-way The two-way flow of water should be the swivel joint, butterfly valve, can not use the globe valve.

● the installation space of small parts should be used butterfly valve, ball valve. 

● in the often open, close the section of the pipe, it is appropriate to use the globe valve.

● the larger diameter of the water pump discharge pipe should be selected multifunctional valve.

 

2. The advantages and disadvantages of various valves

2.1. Gate valve. 

Gate valve is the closing member (gate) along the axis of the channel vertical direction of movement of the valve, in the pipeline mainly as a cut-off medium, that is, fully open or fully closed use. Generally speaking, gate valves cannot be used as a regulating flow. It can be applied to low temperature pressure and also to high temperature and pressure, and can be different according to the valve material. However, gate valves are generally not used in pipelines that convey slurry and other media. 

 

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Benefits.

 â— Small fluid resistance.

 â— Small opening and closing torque required. 

 â— can be used for media flow in both directions of the ring network pipeline, i.e., the media flow direction is not restricted. 

 â— fully open, sealing surface erosion by the working medium is smaller than the globe valve. 

 â— shape structure is relatively simple, manufacturing process is better.

 â— The structure length is relatively short. 

 

Disadvantages. 

● larger external dimensions and opening height, the space required for installation is also larger. 

● In the opening and closing process, the sealing surface people relative friction, friction loss is large, even at high temperatures easily caused by wear phenomenon.

● general gate valve has two sealing surfaces, adding some difficulty to processing, grinding and maintenance. 

● long opening and closing time.

 

2.2 Butterfly valve. 

Butterfly valve is a valve with a disc-type opening and closing member for about 90 ° reciprocating motion to open, close and adjust the fluid passage. 

 

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Benefits. 

● simple structure, small size, light weight, easy consumables, for large diameter valves. 

● Rapid opening and closing, low flow resistance. 

● It can be used for media containing suspended solid particles, and depending on the strength of the sealing surface, it can also be used for powder and granular media. It can be applied to bi-directional opening and closing of ventilation and dust removal pipelines, and is widely used in metallurgy, light industry, electric power, petrochemical systems, such as gas pipelines, waterways, etc. 

 

Disadvantages.

● The flow adjustment range is not large, and the flow will become more than 95% when opened to 30%.

● Because of the structure of butterfly valve and sealing material restrictions, it is not suitable for high temperature and high pressure pipeline system. The general working temperature is below 300℃ and below PN40. 

● Sealing performance is worse than ball valve and globe valve, so it is used in places where sealing requirements are not very high.

 

2.3. Ball valve. 

Is evolved from the plug valve, its opening and closing member is a ball, the use of the ball around the stem axis rotation 90 ° to achieve the purpose of opening and closing. Ball valve in the pipeline is mainly used to cut off, distribution and change the direction of media flow, designed to V-shaped opening of the ball valve also has a good flow regulation function.

 

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Benefits.

● Have the lowest flow resistance (almost 0). 

● can be reliably applied to corrosive media and low boiling point liquids because they do not clog during operation (in the absence of lubricant). 

● Complete sealing over a wide range of pressures and temperatures is possible. 

● Fast opening and closing is possible, with opening and closing times of only 0.05 to 0.1s for some structures, ensuring that they can be used in test bench automation systems. When opening and closing the valve quickly, the operation is vibration-free. 

● The spherical closure can be automatically positioned at the demarcation position. 

● reliable sealing on both sides of the working medium. 

● The sealing surfaces of the ball and seat are isolated from the medium in full opening and closing, so the medium passing through the valve at high speed will not scour the sealing surfaces. 

● Compact structure and light weight, which can be considered as the most reasonable valve structure for low-temperature media system. 

● The valve body is symmetrical, especially the welded body structure, which can well withstand the stress from the pipeline 

● Closing member can withstand the high pressure difference when closed.

● Ball valves with fully welded bodies can be buried directly into the ground, so that the valve internals are not leached, and the longest service life can be up to 30 years, which is the most ideal valve for oil and gas pipelines.

 

Disadvantages. 

● As the most important seat sealing material of ball valve is PTFE, it is inert to almost all chemicals and has comprehensive features such as low friction coefficient, stable performance, not easy to age, wide temperature range and excellent sealing performance. However, the physical properties of PTFE, including high coefficient of expansion, sensitivity to cold flow and poor thermal conductivity, require that the design of the valve seat seal be based on these properties. As a result, seal reliability is compromised when the seal material hardens. In addition, PTFE has a low-temperature rating and can only be used at temperatures below 180°C. Above this temperature, the seal material will be damaged. Above this temperature, the seal material will be damaged. Above this temperature, the seal material will deteriorate. And considering the long-term use, the 

● Regulatory performance is worse than the globe valve, especially pneumatic valves (or electric valves).

 

2.4. Globe valve.

Globe valve is the closing member (valve flap) along the centerline of the valve seat to move the valve. According to this form of movement of the valve valve, the change in seat opening is proportional to the valve stroke. Because of the relatively short opening and closing stroke of the stem of this type of valve and its very reliable globe function, and because the change in seat opening is proportional to the stroke of the valve flap, it is very suitable for the regulation of flow. Therefore, this type of valve is ideal for cut-off or regulation as well as throttling.

 

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Benefits. 

● During the opening and closing process, the valve is wear-resistant because the friction between the sealing surface of the valve flap and the valve body is smaller than that of the gate valve. â‘¡The opening height is generally only 1/4 of the seat channel, so it is much smaller than the gate valve. 

● There is usually only one sealing surface on the valve body and valve flap, so the manufacturing process is better and easy to maintain. 

● Since its packing is usually a mixture of asbestos and graphite, it has a high temperature resistance rating. Generally steam valves are used as globe valves.

 

Disadvantages. 

● The minimum flow resistance of globe valves is also higher than most other types of valves because of the change in the direction of media flow through the valve. 

● Due to the longer stroke, the opening speed is slower than the ball valve.

 

2. 5. Check valve. 

Also known as backflow valve, check valve, back pressure valve, check valve. These valves are automatically opened and closed by the force generated by the flow of the medium itself in the pipeline, and are automatic valves. Check valves are used in piping systems whose main function is to prevent the backflow of media, to prevent pumps and drive motors from reversing, and the release of container media. Check valves can also be used to provide make-up for auxiliary systems, where the pressure may rise above the system pressure. They can be primarily classified as rotary (rotating by the center of gravity) and lift (moving along the axis).

 

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"What are butterfly valves used for?"

"Butterfly valves are generally used for various water fluids, such as domestic water, fire water, process water, circulating water, chilled water, sewage, etc.

Some powder materials can also be used with butterfly valves.

Butterfly valves cannot be used to regulate flow. It can be used to open/close the valve automatically."

 

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"In the official road with large pipe diameter, butterfly valve is usually used to control the flow. For example, DN1000 pipeline, if you use the gate valve or globe valve, how big the valve has to be. But small-diameter pipes are rare." Used to regulate the flow of butterfly valves, one is not well regulated, and the other is poor sealing. Small-diameter butterfly valves are generally used in water pipelines, such as fire water, circulating water, etc., can also be used in places "where sealing requirements are not high, not often switch. Of course, the cost of using butterfly valves on large-diameter pipelines is relatively low."

"The two biggest features of butterfly valves are: large bore and low pressure differential.

Butterfly valve compared with other structure of the valve, the same caliber weight to light, simple structure, small volume, the larger the caliber the more obvious this feature; butterfly valve can adapt to the front and rear pressure difference is small, while the higher the technical requirements and manufacturing cost of butterfly valve sealing."