Check valves

Check valves lifting, working principle:

In the check valve lifting, the shut-off element is a lift valve. Under the influence of water pressure, the spool rises, passing a stream. When pressure drops, the spool lowers onto the seat, obstructing the return flow. Such valves are installed only in horizontal sections of pipelines. A prerequisite is the vertical location of the valve axis.
Valves are divided into four groups according to the mounting method:

• Weld-in mounting: the non-return valve is welded to the pipe. It is applied during the work in hostile environment.
• Flange mount: check valve connects to piping through flanges with seal.
• Clutch mount: the valve is attached to the pipeline through a threaded coupling. It is used in small diameter systems.
• Mounting between flanges: the non-return valve does not have its own mounting unit. Clamped between the flanges of the pipeline. It is used in areas with a limited size.

Lift check valves having a safety net at the inlet and designed to be installed at the beginning of the suction pipe are called check valves.

Lift check valves having a safety net at the inlet and designed to be installed at the beginning of the suction pipe are called check valves.

Advantages of check valves:

• simplicity of design;
• reliable tightness;
• possibility of repair without dismantling the entire valve.

Disadvantages of check valves:

• high hydraulic resistance;
• the possibility of jamming the shutter in the guide part of the cover when using the valve in systems with a contaminated working medium;

Ball Check Valves

In the ball check valve, the ball element serves as a shutter. As a clamping element, a spring is used that presses the ball to the seat. Such valves are usually made for pipelines of small diameters and are used as domestic plumbing equipment. Ball check valve loses to spring disc valve in dimensions.

Swing Check valves, principle of operation:

Swing Check Valves are available in straight body design and y-pattern design. The disk is suspended from the body by means of a hinge pin and seals against the seat which is integral with the body.

These valves are typically used in sizes 2 inches and over. Swing check valves can be installed in both horizontal and vertical position. They are not suitable for pulsating flow.

When the pressure drops below the permissible spool falls and slams the passage channel. In check valves of large diameter, a strong blow of the spool against the seat occurs, which leads to a quick failure of the structure. During further operation, this provokes the occurrence of water hammer when the check valve is activated. Therefore, swing check valves are divided into two groups: Simple - valves with a diameter of up to 400 mm. They are used in systems where shock phenomena cannot seriously affect the operation of the hydraulic system and the valve itself. Shock-free - valves with devices that provide a smooth and soft landing of the valve spool on the seat. The advantage of swing valves is their ability to operate in large systems and low sensitivity to working medium pollution.