One-way valves are generally installed on pipelines to prevent backflow. A one-way valve is actually a type of valve in which only free movement in one direction is possible, but if the flow reverses, the one-way valve closes from the reverse flow to protect pipes, other valves, pumps and other equipment. If the flow reverses and a one-way valve is not installed in it, there is a possibility of ram impact phenomenon. Ram impact often occurs with very strong pressure and damages the pipes and their components.
Application of one-way valves
One-way valves have many different applications. For example, it is generally installed on the outlet side of a pump to protect it against reverse flow. Centrifugal pumps are among the most common types of water pumps that are not automatic, so it is necessary to have a one-way valve to keep water inside the pipes. Check valves are also used in hvac ventilation systems (heating, ventilation, air conditioning systems). Hvac ventilation systems are used, for example, in large buildings where coolants are pumped to many floors.
Virtually any applicable piping or liquid transfer application, be it industrial, commercial or domestic, requires a one-way valve. One-way valves, although invisible, are actually an important part of our daily life. Municipal sewage, water treatment, medicine, chemical processing, power generation, pharmaceutical industry, chromatography industry, agriculture, hydro power plant, petrochemical, food and beverage processing industries all use one-way valves in their daily operations to prevent reverse flow. Because they prevent defects in product performance and there is no need to monitor them during work, the presence of control valves is not only desirable, but often according to the law, to ensure the safety of gas pressure and water pressure, industries are required to install one-way valves. .
To explain the use of a one-way valve at home, one-way valves help to open and close the flow of water. They are used in water heaters, internal plumbing, faucets and dishwashers, as well as advanced equipment such as metering pumps, blenders, mixers and flow meters. Industrial one-way valves systems inside nuclear power plants, chemical factories, aircraft hydraulic systems (vibration temperature and corrosive substances), spacecraft and launch systems (reaction control, propulsion control, altitude control) and gas flow control systems ( prevent gas combination) are monitored.
History of the one-way valve
Frank P. Cather invented the first one-way valve in 1907. Installing, testing and repairing his valve was very easy. In 1916, Nikola Tesla invented another one-way valve, which became known as the Tesla valve. He registered his invention, which was a simple one-way liquid valve, in 1920 exclusively in his name.
When plastic technology and manufacturing advanced enough, manufacturers started making plastic diaphragm one-way valves, which are very common in the medical industry.
Over the years, manufacturers have been required to comply with various regulations. For example, in January 2014, Congress passed the Drinking Water Act, according to which any part related to drinking water can contain a maximum of 0.25% lead. This has caused manufacturers to spend a lot of time replacing old, lead-based water storage plumbing fixtures with systems that feature prominent components such as one-way valves made of plastic or stainless steel.
Outline
Although the overall design and operation of the one-way valve is quite simple, manufacturers consider many important things when designing their product diagram. To ensure that the material passes through the valve and backflow is adequately prevented.
First, they choose the material used to make the one-way valve, which affects the correct operation of the part. If manufacturers use inappropriate materials, the milk will cause abrasion or erosion or contamination of the process flow. Manufacturers choose the material used to make a one-way valve from a multitude of plastic, metal, and synthetic materials. These materials include PVC, brass, ductile iron (for iron bodies), copper, polyethylene, polypropylene, aluminum, carbon steel, stainless steel (for stainless steel body and spring) and rubber. The selection of ingredients is very important and sometimes milk is named after its ingredients. (Example of cast iron one-way valve)
Then, manufacturers determine the size of the check valve. The sizes of one-way valves are very different. The most important point about the size is the diameter of the seat and the duct, which should usually be less than an inch or several feet. One-way valves whose sizes are accurately determined using pipe or tube dimensions are easily installed on existing flow lines.
The size of the valve also affects the pressure of the valve or its breaking pressure. This is the minimum pressure at which the valve operates or opens. If the valve is too big and bulky, the pressure created in the continuous flow will not be able to open it even when the opposite pressure increases. The small device moves a continuous current and never shuts off. Such defects in product performance are the result of faulty equipment, substandard materials and potentially dangerous cross-contamination.
Other factors such as the temperature of the material in the flow, the differential pressure and the flow coefficient of the valve should also be considered. All factors and even the type of one-way valve depend on the use of the valve. In order to produce valves for special applications, manufacturers often make customized one-way valves.
Specifications of one-way valves
One-way valves are very popular due to their simple design and easy use. They have a relatively simple mechanism. As mentioned earlier, the operation of the one-way valve is completely determined by the process diagram, that is, there is no need for additional drive mechanisms. In general, the valve is installed as a cylindrical piece to the pump head located at the outlet and inlet of the pipes. With both sides of the valve open, the working part cuts the chamber in half and divides the flow into upstream and downstream. The seat extends from the walls of the cylinder and there is a valve suitable for the passage of process flow.
The ball, conical cylinder, disc and other large parts are located in front of the seat on the downstream side of the check valve. A slight stimulation causes the connected part to not fall down. As the flow moves in the specified direction at the required pressure, the joint is separated from the seat, allowing fluid or gas to enter through the gap created. As the pressure increases, the cap snaps back into the seat, preventing backflow.
Gravity or the compression mechanism of the stainless steel spring is usually responsible for the return movement, although in some cases the increased pressure on the downstream side of the valve is sufficient to move the part back. Closing the valve, even at high pressure, prevents mixing of downstream materials with upstream materials. The cap used for the valve is different depending on the type of one-way valve installed.
As the name suggests, one-way ball valves use balls. One-way push valves use a disk or a conical cylinder, which is connected to a rod like a guide, ensuring that the part returns to its specified place on the seat. Hinged check valves use one or more discs to close the gap in the valve seat.
Types of one-way valves
Large one-way valve
These types of valves have no return path and are used in domestic, commercial, and industrial uses and are responsible for the safe and continuous passage of various materials such as water, oxygen, fuel, acids, raw materials, sludge, slurry, and even hazardous waste. are.
Small check valve
The small one-way valve or the micro one-way valve has the same mechanism as the large one-way valve, only in terms of size, they are very small. These valves are used precisely to regulate the one-way flow of gas or fluid in small spaces.
safety valve
Safety valves, also known as safety valves, are durable systems that resist chemical corrosion and continuous wear. They are generally made of PVC, stainless steel, brass or aluminum. The purpose of these valves is to prevent dangerous pressure from high-closed ducts and piping systems. These valves are usually closed before reaching the set pressure.
ball valve (Korean)
The one-way ball valve uses a suspended ball as a plug. Its material may be cast iron, plastic or stainless steel. For use in regulating fluids, there are different types of ball valves such as spring loaded ball valves, reverse flow ball valves and three way ball valves. The spring-loaded one-way valve ball cap uses a stainless steel spring to keep the passage closed. Reverse flow ball valves work without springs. The valve uses reverse flow to return the ball to its seat, which acts as a sealing mechanism. Three-way ball check valves use a ball cap or gate valve cap, or a ball valve cap in the center of the check valve.
Disc check valve
It is a valve that uses a disc-like piece as a cap. There are types of one-way disc valves: pressure one-way valves, hinged one-way valves (oscillating, valve), butterfly valves and wafer valves. Since the types of one-way disc valves are completely different from each other, below we will discuss the independent definitions of each type of valve.
One-way pressure valve (rising)
A type of check valve is a disc that has a disc known as a "top" that can move upwards from its seat. The lift element operates when the pressure (PSI) of the inlet or upstream fluid increases, causing the fluid to move downstream. When the pressure drops, high pressure from downstream or gravity causes the disc to return to its original position. Pressure one-way valves, also known as piston one-way valves, are usually used as safety valves or control valves.
Hinged one-way valve (valve, oscillating)
Hinged check valves have a flat disc that swings or rotates on a hinge pin. These types of valves do not need a stainless steel spring to work. When they swing on the seat, they prevent reverse flow, and when they rotate away from the seat, they cause the flow to move forward. Also classified as check valves.
Butterfly check valve
One-way butterfly valves are designed to regulate flow pressure in large pipes. They have a tube-shaped disc that always stays on track. Adjusts the current while the disc rotates. These valves are made of cast iron or stainless steel. Butterfly valves are used in a wide variety of industries, including: food and beverage industries, pharmaceutical chemistry.
Wafer one-way valve
Wafer check valves are one-way valves that prevent reverse flow by allowing fluid to pass in one direction only. The pressure of the forward flow of the fluid opens the disc check valve and the pressure created by the reverse flow closes it. This one-way hinged valve is made of stainless steel or cast iron.
One-way spring valve (valve)
Spring loaded check valves use a stainless steel spring to increase the pressure required to open the valve and to help maintain shutoff. When the differential pressure passing through the valve is high, the spring one-way valve is used due to the increase in the flow in the lower arm, to prevent the noise and overflow of the valve. It is also used to protect against the ram blow caused by the strong countercurrent of the upper arm.
Double check valve
These valves use several interconnected valves. They usually have a cast iron, stainless steel or plastic body. They are used to reduce wear and protect against reverse flow caused by counterflow pressure, cross contamination and flooding.
One-way valve with pilot
It is a small but non-modular valve that works with high pressure flow. A flanged style design, or connection through a metallic tube, prevents reverse flow while allowing flow to flow freely from the check valve into the actuator. One-way pilot valve is known for its unique high sealing capability. It is best used to close and hold. However, it cannot be used for overflow control or for cylinders.
solenoid valve
They are compact and energy-efficient valves that are controlled by an electric current passing through a solenoid. They use ports and fluid paths. In addition to the variety of designs, most solenoid valves have two ports (2-way valves). When the valve is open, both ports are connected and fluid flows freely. When the valve is closed, fluid flow cannot pass from one port to another. In three-way valves, the flow is moving between the inlet port and the other two ports. These other two ports are usually an exhaust port and a supply port. Solenoid valves are commonly used in fluids, and provide safe and effective flow switching between two ports. The usual tasks of these valves include: combining, closing, releasing, supplying or distributing fluids.
One-way anti-ram valve
As the name of the valve suggests, a ram-proof one-way valve is designed for noiseless operation. In this regard, it opens and closes quickly and reduces the noise of the ram. To prevent shock and increase lubrication in the system process, the valve is closed before the fluid flow returns.
Advantages of one-way valve
One-way valves have many advantages. First, they can control the amount of flow pressure in different industrial sectors. In fact, these valves can be used at the very high pressure required to extinguish fires as well as at the controlled pressure required to operate in diving tanks. Another advantage of one-way valves is that they can prevent cross-contamination of fluids and fresh water.
Accessories
One-way valves have different types of accessories depending on their application. Including: controls, stainless steel casing bolts, gear operators, stainless steel springs, high definition displays and valve status monitors.
Standards related to one-way valves
The standards that a one-way valve should have are different according to their application in the industry and region. For example, if you live in the United States and deal with oil, you must follow API (American Petroleum Institute) standards. API specifies different types of standards depending on their application (pipeline valves, flanged steel pressure relief valves, seat range of pressure relief valves, etc.). Another important American standards development organization is ASME (American Society of Mechanical Engineers) and ASTM International (American Society for Testing and Materials). There are also numerous international standards specific to each country, such as ISO, BSI (British Standards), DIN (German Standards) and JIS (Japanese Standards).