Check valves are considered to be valves and serve to pass liquid or air in one direction. Such devices are used in many sectors of industrial production, utility systems, as well as in the fuel system of automobile engines.
The main task of absolutely any reverse-acting valve is to protect a certain system from acting on the mechanism of the flow of matter in the opposite direction of its movement. The device and principle of operation of the non-return valve must be known to any mechanic servicing technical systems or repairing equipment.
Check 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 the 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.
The operating mechanism of the reverse valve 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 save the filling of pipes with water, increasing the efficiency of functioning of suction and submersible pumps. It is on this that the principle of the check valve for water is based.
The design of shut-off valves is based on 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 principle of operation of the water valve
Structurally, the check valve is arranged quite simply, even an inexperienced plumber can deal with it during the repair.
The valve includes the following elements:
- the metal case consists of two parts provided with a thread;
- a shutter made of metal or plastic;
- gasket;
- spring that supports the bolt.
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 shutter is unlocked, thereby allowing the flow to flow into the pipeline. Upon subsequent shutdown of the pump, 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 a non-return valve, the purpose of which is to operate in various water systems, is the same for all locking devices.
Types of Check Valves
Water shut-off valves can vary in design depending on the installation location and the solution of certain water supply problems.
Classification of check valves is carried out according to the following parameters:
- the nature of the locking device;
- valve mounting method;
- check valve size;
- manufacturing material.
Types of Locking Elements
Depending on the design of the main element, which 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 influence of water pressure, the valve opens, and when the pressure decreases, under the action of a spring, it closes.
- Rotary locks. They are a flap that opens with a fluid flow and locks with a return spring when pressure decreases.
- Ball valves. They have the shape of a ball, which is supported by a spring. When water is supplied, the ball shifts and passes the flow into the system.
- Flanged butterfly valves rotate on the central axis under the stress of the spring and the flow of water.
- Bicuspid valves have two connected flaps that fold when fluid passes, and in the absence, they lock.
In domestic conditions, lifting valves are most often used. In case of failure, the spring is simply replaced in it.
Size classification of valves
The size of the used check valves depends on the cross section of the pipeline, as well as its functional purpose.
By size, the valves are divided into the following types:
- standard products - are used on many types of water supply systems;
- small locking devices - mounted on the outputs of water flow meters;
- miniature check valves - are strengthened inside the drives if there is not enough space for a standard product;
- large valves - made of cast iron and installed on industrial pipelines or inlet systems for domestic water supply.
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 when 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. Used mainly for large valves. Such valves are used mainly on pipes of large cross-section. In everyday life, cast-iron products are not used, as they are susceptible to corrosion and fouling by deposits.
- Stainless steel. Corrosion resistant and durable. It has no shortcomings, but is expensive, which limits its use.
Check Valve Locations
Possessing minimal plumbing knowledge, the valve can be installed on water independently. The main thing 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 nozzle, which is lowered into the water, so that the surface pump works. In this case, the water is retained in the pipe.
- If the submersible pump is lowered into the well, the valve is placed at its outlet so that when the engine is turned off, water does not flow back.
- When installed in a boiler, the valve is located at the inlet of a cold water supply,
- In the heating system, the installation of a check valve is a necessary technological operation.
- On water pipelines, with the simultaneous use of cold and hot water, a reverse-acting tap should be installed in each line to prevent reverse fluid flow.
- On water metering devices to prevent reverse flow of water.
Methods of fastening products
In water supply systems, three main methods of fastening the locking elements are used:
- Most valves are clutch-mounted. For this, adapters are used with threads on both sides, the diameter of which depends on the cross-section of the pipes.
- The flange method provides reliable fixation of valves to pipelines using special flanges. In this way, the cast-iron elements used on large-diameter pipes are mainly fixed.
- The wafer mount is between the flanges and tightly clamped by bolts.
Purpose and principle of operation of the check valve for sewage
The movement of water always occurs along the path of least resistance. Therefore, if at least a small blockage appears in the sewer system, then the waste fluid 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, since water from the system flows through the nearest free point, and these are toilet bowls on the ground floor. But do not rejoice and those living upstairs, because a blockage may appear in the beds between the floors.
The device and principle of operation of the sewage check valve are largely similar to water locking devices, but differ in their dimensions. It consists of:
- housing;
- valves of membrane type, which blocks the reverse movement of wastewater;
- forward fluid lever;
- removable type covers necessary to clean the device in case of clogging or forced closure of the membrane.
Types of Sewer Check Valves
The principle of operation of the reverse sewer 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.
By the type of such obstacles and the nature of the work, the equipment also differs:
- In petal (rotary) valves, a spring-loaded round membrane is mounted. When the wastewater moves in the right direction, it rises, in another case, it simply presses against the valve rim, blocking the course of the drains.
- Lift check valve got its name from the principle of action. The principle of operation of the non-return valve is simple: under the pressure of the drains, the membrane simply rises, opening the passage. In the absence of drains, the passage closes, and if the fluid flows in the opposite direction, it is impossible to open the passage due to the special non-linear shape of the housing. The reliability of such a valve is very high, but it is often clogged, so regular cleaning is required.
- The principle of operation of a ball- type check valve is based on the movement of a special ball inside the housing. In such a device, the main role is played by the structure of the body. Under the pressure of drains, the ball opens the passage.
- The wafer type check valve is widely used due to its small size. By design, it 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 carry out cleaning - you have to disassemble the entire housing.
Check valve for ventilation
In apartment buildings, a situation often occurs when the ventilation system does not cope with its direct purpose, and air from neighboring apartments enters another room. All rooms with a ventilation duct can be affected by this effect. To avoid this trouble, ventilation systems use non-return valves that do not allow air to flow in the opposite direction.
The principle of operation of the ventilation check valve is in many ways similar to the operation of the water valve. In this case, the structurally locking device is thought out so that it is possible to regulate the flow of air entering the room.
Manufacturers offer various check valves for ventilation, which vary:
- in the form of the device;
- according to the material of manufacture;
- at the place of installation;
- if possible let a certain amount of air pass;
- by the way of work.
Fuel check valve
Such a 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 well-calibrated seat made of soft metal. Fuel enters the carburetor in only one direction, so to prevent it from moving back, a locking device is put.
A non-return valve is installed in injection vehicles in a housing on the fuel rail between the nozzles and the gas tank. In diesel engines, a valve is located between the high-pressure pump and the low-pressure hand pump.
The high performance of the fuel pump ensures a continuous supply of fuel, so the use of a valve is a prerequisite for trouble-free operation of the mechanism.
The principle of operation of any type of non-return valve is very simple, therefore, it can be carried out by a person without extensive experience as a plumber. At the same time, this simple device significantly improves people's lives, especially in multi-apartment buildings.