How can we choose the right valves in water treatment projects? (Part 1)

Types of valves:

Classification by function and purpose

(1) Cut-off valve: The cut-off valve is also known as a closed-circuit valve or a cut-off valve, whose function is to connect or cut off the medium in the pipeline. The types of shut-off valves include gate valves, globe valves, plug valves, ball valves, butterfly valves, and diaphragm valves.

(2) Check valve: Check valve is also called one-way valve or check valve, its function is to prevent the medium in the pipeline from flowing back. Its main function is to prevent the medium from flowing backwards, to prevent the pump and drive motor from reversing, and to discharge the container medium. The bottom valve of the pump to close the water also belongs to the non-return valve category.

(3) Safety valve: The function of safety valve is to prevent the pressure of the medium in the pipeline or device from exceeding the specified value, so as to achieve the purpose of safety protection.

(4) Regulating valves: Regulating valves include regulating valves, throttle valves and pressure reducing valves, whose function is to regulate the pressure, flow and other parameters of the medium.

(5) Diversion valve: Diversion valves include various distribution valves and traps, etc., whose function is to distribute, separate or mix the medium in the pipeline.

(6) Exhaust valve: Exhaust valve is an indispensable auxiliary component in the pipeline system, which is widely used in boilers, air conditioners, oil and gas, and water supply and drainage pipelines. It is often installed at high points or elbows to remove excess gas in the pipeline, improve the efficiency of pipelines and roads, and reduce energy consumption.

Application and characteristics of common water treatment valves:

1. Gate valve

The advantages of the gate valve: small fluid resistance, small erosion and erosion of the sealing surface by the medium; labor-saving opening and closing; unrestricted flow direction of the medium, no turbulence, no pressure reduction; simple shape, short structure length, good manufacturing technology, and application wide range.

Disadvantages of gate valve: Erosion and scratches between the sealing surfaces are easy to cause, and maintenance is difficult; the external size is large, opening requires a certain space, and the opening and closing time is long; the structure is more complicated; solid matter is easy to deposit in the valve seat groove to close Lax. Therefore, it is not suitable for pipelines with fibrous or solid substances in the fluid. It is often used in the conveying pipeline of air, steam, and oil media, and also used as a vent valve and a valve in a low vacuum system.

The gate valve is one of the commonly used cut-off valves, which is mainly used to connect or cut off the medium in the pipeline, and is not suitable for adjusting the flow of the medium. The gate valve is suitable for a wide range of pressure, temperature and diameter, especially suitable for medium and large diameter pipelines.

The installation and maintenance of the gate valve should pay attention to the following items:

(1) Handwheels, handles and transmission mechanisms are not allowed to be used for lifting, and collisions are strictly prohibited;

(2) The double gate valve should be installed vertically (that is, the valve stem is in the vertical position, and the handwheel is on the top);

(3) The gate valve with a bypass valve should be opened before opening (to balance the pressure difference between the inlet and outlet and reduce the opening force);

(4) The gate valve with transmission mechanism should be installed in accordance with the product manual;

(5)If the valve is frequently opened and closed, lubricate at least once a month;

2. Ball valve

Advantage:

(1). The fluid resistance is small, and the full-bore ball valve basically has no flow resistance.

(2). Simple structure, small size and light weight.

(3). Close and reliable. It has two sealing surfaces, and the current sealing surface materials of ball valves are widely used in various plastics, which have good sealing performance and can achieve complete sealing. It has also been widely used in vacuum systems.

(4). It is easy to operate and open and close quickly. It only needs to rotate 90° from fully open to fully closed, which is convenient for remote control.

(5). The maintenance is convenient, the structure of the ball valve is simple, the sealing ring is generally movable, and it is convenient to disassemble and replace.

(6). When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the medium will not cause erosion of the valve sealing surface when the medium passes.

(7). It has a wide range of applications, with a diameter ranging from a few millimeters to a few meters, and can be applied from high vacuum to high pressure.

(8). Since the ball valve has wiping properties during opening and closing, it can be used in media with suspended solid particles.

Shortcoming:

The processing accuracy is high, the cost is expensive, and it is not easy to use in high temperature. If there are impurities in the pipeline, it is easy to be blocked by the impurities, resulting in the valve cannot be opened.

Applications of Ball Valve:

Ball valves are also suitable for piping systems with light structure, low pressure cut-off (small pressure difference), and corrosive media. Ball valves can also be used in low temperature (cryogenic) devices and pipeline systems. In the oxygen pipeline system of the metallurgical industry, ball valves that have undergone strict degreasing treatment are required. When the main lines in the oil and gas pipelines need to be buried underground, full-diameter welded ball valves are required. When adjusting performance is required, a ball valve with a special structure with a V-shaped opening should be selected. In petroleum, petrochemical, chemical, electric power, and urban construction, metal-to-metal sealed ball valves can be used for piping systems with operating temperatures above 200 degrees.

See the models:KPQ11 Ball valve

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