Check valves are considered shut-off valves and are used to pass liquid or air in one direction. Such devices are used in many industries, utilities, and in the fuel system of automobile engines.
The main task of absolutely any reverse action valve is to protect a certain system from affecting the mechanism of the flow of a substance in the opposite direction of its movement. The device and principle of operation of the check valve must be known to any mechanic servicing technical systems or repairing equipment.
Return valve for water
To understand the principle of operation and why a check valve for water is needed, it is necessary to imagine how the mechanism will behave if the liquid pressure pump stops. It is the discharge of water into a well or well in the event of a pump failure that can lead to the reverse movement of the impeller, and, as a result, to the breakdown of the entire unit.
Valve mechanismreverse motion prevents the reverse movement of water, which protects the equipment or water supply system from water hammer. The shutter of the device allows you to keep the pipes filled with water, increasing the efficiency of the suction and submersible pumps. This is the basis of the principle of operation of the check valve for water.
The design of shut-off valves is carried out on the basis of special regulatory requirements. In the passport of the finished product, the manufacturer must indicate the main technical characteristics of the locking device.
The device and the principle of operation of the water valve
Structurally, the non-return valve is quite simple, even an inexperienced plumber can deal with it during repairs.
The design of the valve includes the following elements:
- metal case consists of two threaded parts;
- shutter made of metal or plastic;
- gasket;
- spring that supports the shutter.
The principle of operation of the check valve for water is quite simple. If water does not enter the system, then under the influence of the spring, the locking device is in the closed position. When pressure appears, the valve opens, thereby allowing the flow to enter the pipeline. When the pump is subsequently turned off, the water pressure in the system drops, and the action of the spring helps to block the flow of fluid. This principle of operation of the check valve, the purpose of which is to function in variouswater systems is the same for all locking devices.
Types of check valves
Water shut-off valves may vary in design depending on installation location and specific water supply applications.
Check valves are classified according to the following parameters:
- character of locking device;
- valve mounting method;
- check valve size;
- production material.
Types of locking elements
Depending on the design of the main element that closes the flow of water in the reverse movement, the valves are divided into the following types:
- Lifting locking elements. Move up and down. Under the action of water pressure, the valve opens, and when the pressure decreases, under the action of a spring, it closes.
- Rotary shutters. They are a flap that opens with fluid flow and closes with a return spring when pressure is released.
- Ball valves. They have the shape of a ball, which is supported by a spring. When water is supplied, the ball moves and allows flow into the system.
- Flanged butterfly valves rotate on a central axis under spring tension and water flow.
- Bivalve valves have two connected leaflets that fold when fluid passes and lock when no fluid passes.
In domestic conditions, lift valves are most often used. In case of failure, the spring is simply replaced.
Classification of valves by size
From sectionpipeline, as well as its functional purpose, depends on the size of the used check valves.
By size, valves are divided into the following types:
- standard products - used in many types of plumbing;
- small locking devices - mounted at the outlets of water meters;
- miniature non-return valves - fixed inside squeegees if there is not enough space for a standard product;
- large size valves - made of cast iron and installed in industrial pipelines or domestic water supply systems.
Material for the manufacture of valves
The principle of operation of the check valve is also determined by the material of its manufacture. The main materials that are used in the construction of locking devices are:
- Brass. It is considered the most reliable metal for domestic use. Corrosion resistance and low maintenance are the main characteristics of such products.
- Cast iron. Mainly used for large valves. Such valves are mainly used on pipes of large cross section. In everyday life, cast iron products are not used, as they are subject to corrosion and fouling.
- Stainless steel. Corrosion resistant and durable. Has no drawbacks, but is expensive, which limits its use.
Return valve installation locations
With minimal plumbing knowledge, installation of a valve on water can be doneon one's own. The main thing at the same time is to know the device and the principle of operation of the check valve.
The locking device is installed in the following places:
- At the end of the pipe, which is lowered into the water so that the surface pump works. In this case, water is retained in the nozzle.
- If the submersible pump is lowered into the well, then the valve is placed at its outlet so that when the engine is turned off, the water does not flow back.
- When installed in a boiler, the valve is placed at the cold water inlet,
- In the heating system, the installation of a check valve is a necessary technological operation.
- On plumbing systems where cold and hot water are used simultaneously, a reverse-acting valve must be installed in each line to prevent backflow of fluid.
- On water meters to prevent water flow in the opposite direction.
Methods of fastening products
In water systems, there are three main ways to attach locking elements:
- Most valves are coupled. For this, adapters with threads on both sides are used, the diameter of which depends on the pipe section.
- The flange method provides for reliable fixation of valves to pipelines using special flanges. In this way, cast-iron elements used on large diameter pipes are mainly attached.
- Wafer fastening is carried out between the flanges and tightlyclamped with bolts.
Purpose and principle of operation of the check valve for sewerage
The movement of water always takes the path of least resistance. Therefore, if even a slight blockage appears in the sewer system, then the sewage liquid can change its direction. It is for this reason that flooding of neighbors occurs in apartment buildings. To eliminate such unpleasant situations, a sewer check valve is used.
Most often, residents of the lower floors of apartment buildings suffer from blockages, as water flows out of the system through the nearest free point, and these are toilets on the first floor. But do not rejoice and living upstairs, because the blockage may appear in the sun loungers between floors.
The device and principle of operation of the sewer check valve are in many ways similar to water locking devices, only differ in their dimensions. It consists of:
- body;
- membrane-type valves that block the reverse flow of wastewater;
- forward flow lever;
- removable type cover needed to clean the device in case of clogging or forced closing of the membrane.
Types of sewer shut-off valves
The principle of operation of the sewer check valve is based on blocking the flow of fluid going in the opposite direction. A movable barrier is mounted inside the device, which performs the main function of the valve.
The equipment differs according to the type of such an obstacle and the nature of the work:
- The reed (rotary) valves have a spring-loaded round diaphragm. When the drains move in the right direction, it rises, otherwise it simply presses against the valve rim, blocking the flow of drains.
- The lift check valve gets its name from the way it works. The principle of operation of the check valve is simple: under the pressure of the effluents, the membrane simply rises up, opening the passage. In the absence of drains, the passage is closed, and if the liquid flows in the opposite direction, then it is impossible to open the passage due to the special non-linear shape of the body. The reliability of such a valve is very high, but it often becomes clogged, so regular cleaning is required.
- The principle of operation of the ball type check valve is based on the movement of a special ball inside the body. In such a device, the main role is played by the structure of the case. Under the pressure of the drains, the ball opens the passage.
- The wafer type check valve is widely used because of its small size. By design, this is a small cylinder, inside of which a rotary damper is mounted. True, it is rarely used in sewer systems, since it is very difficult to clean - you have to disassemble the entire body.
Check valve for ventilation
In apartment buildings, a situation often occurs when the ventilation system does not cope with its intended purpose, and air from neighboring apartments enters another room. All rooms where there is a ventilation duct can be exposed to this effect. To avoid this trouble, check valves are used in ventilation systems that do not allow air to pass in the opposite direction.
The principle of operation of the ventilation check valve is in many ways similar to the operation of a water valve. In this case, the locking device is designed in such a way that it is possible to regulate the flow of air entering the room.
Manufacturers offer various check valves for ventilation, which vary:
- according to the shape of the device;
- according to the material of manufacture;
- at the place of installation;
- let a certain amount of air through if possible;
- by way of work.
Fuel check valve
This valve is used in injection engines, in diesel engines, as well as in gasoline carburetors of all cars. The principle of operation of the fuel check valve is quite simple. It resembles a ball valve with a perfectly calibrated soft metal seat. Fuel enters the carburetor in only one direction, so a locking device is installed to prevent its movement back.
A check valve is installed in injection cars in the housing on the fuel rail between the injectors and the gas tank. Diesel engines have a valve between the high pressure pump and the low pressure hand pump.
Highthe performance of the fuel pump ensures a continuous supply of fuel, so the use of a valve is a prerequisite for the trouble-free operation of the mechanism.
The principle of operation of any kind of non-return valve is very simple, so its maintenance and repair can be carried out by a person without rich plumbing experience. At the same time, this simple device greatly improves people's lives, especially in apartment buildings.
