sample picture of a gate valve .
What is a Valve ?.
A valve is a device or natural object that regulates, directs, or controls the flow of a fluid (gas, liquid, flowing solid, or slurry) by opening, closing, or partially blocking various passages .
Although valves are technically fittings, they are usually treated as a separate category.
In an open valve, fluid flows from high pressure to low pressure. The word comes from the Latin valva, meaning the moving part of a door, and in turn comes from volvere, to turn, to turn.
The simplest and very old valve is the free-swivel flapper, which pivots downward to prevent the flow of liquid (gas or liquid) in one direction.
However, when the flow moves in the opposite direction, it is pushed upward by the flow itself. This is called a check valve because it prevents or "controls" flow in one direction. Modern control valves can regulate downstream pressure or flow and operate in highly automated systems.
Valves have many applications, including water control for irrigation, industrial applications for process control, and residential applications such as on/off and pressure control for dishwashers, washing machines, and household faucets.
Valves are also used in the military and transportation sectors. In HVAC ducts and other atmospheric flows, the valve is instead called a damper.
However, compressed air systems use valves, and ball valves are the most common. Valves are used in virtually every industrial process, including water and wastewater treatment, mining, power generation, oil, gas and petroleum processing, food manufacturing, chemical and plastics manufacturing, and many other areas.
People in developed countries use valves in their daily lives, such as plumbing valves such as water faucets, gas control valves on stoves, small valves in washing machines and dishwashers, safety devices in hot water systems, and poppet valves in automobile engines. I'm using. Nature has valves, such as one-way valves in veins, that control blood circulation, and heart valves that control blood flow within the heart chambers and maintain proper pumping action.
Valves can be operated manually using handles, levers, pedals, or wheels. Valves can also be automated and controlled by pressure, temperature, or flow changes. These changes act on the diaphragm or piston and can actuate the valve.
An example of this type of valve is often a safety valve installed in a hot water system or boiler. More complex control systems with valves that require automatic control based on external inputs (i.e., adjusting the flow rate through a pipe to a changing setpoint) require actuators.
Actuators move valves according to inputs and settings, allowing precise positioning of valves to control various requirements. Valves vary greatly depending on their shape and purpose. Size [vague] typically ranges from 0.1 mm to 60 cm. Specialized valves can exceed 5 meters in diameter. [which one?] Valve costs range from simple, inexpensive one-way valves to specialized valves costing thousands of dollars (US) per inch of valve diameter. One-way valves are used in common household products such as mini-pump dispensers and aerosol cans. Common usage of the term "valve" refers to the poppet valves found in the majority of modern internal combustion engines, including most fossil fuel powered vehicles.
Poppet valves control the intake of fuel and air mixtures and exhaust gas ventilation. Valves are very diverse and can be classified into several basic types.
Valves can also be classified according to their type of operation. hydraulic air pressure manual solenoid valve engine Cross section of an open globe valve: body port sheet stem Disc with valve open Handle or handle with valve open engine hood packaging stuffing box nut Fluid flow when the valve is open Disc position when valve is closed Handle or handle position when valve is closed The main parts of the most common type of valve are the body and bonnet.
These two parts form a housing that contains the liquid that passes through the valve. body The valve body is the outer casing of most or all valve parts, including the internal parts or trim.
The hood is the part of the housing that the shaft passes through and provides guidance and sealing for the shaft. The top is usually screwed or bolted onto the valve body.
The valve body is usually made of metal or plastic. Brass, bronze, gun metal, cast iron, steel, alloy steel, and stainless steel are widely used .
In seawater applications such as seawater desalination plants, double valves and super double valves are often used due to their corrosion resistance, especially against warm seawater.
Alloy 20 valves are typically used in sulfuric acid plants and Monel valves are used in hydrofluoric acid (HF acid) plants.
Hastelloy valves are often used in high temperature applications such as nuclear power plants, and Inconel valves are often used in hydrogen applications.
Plastic bodies are used at relatively low pressures and temperatures. PVC, PP, PVDF, and glass-reinforced nylon are common plastics used for valve bodies. [Citation required] engine hood The hood acts as a cover for the valve body. It is usually screwed or bolted semi-permanently into the valve body. When making a valve, you insert the internal parts into the body, then attach the hood to hold everything inside together. Access to the internal parts of the valve typically required removing the hood for maintenance. Many valves do not have hoods. For example, plug valves usually don't have a top. Many ball valves do not have a top. This is because the valve body is assembled differently, such as bolted to the center of the valve body.
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