Check Valve

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How does a check valve work?

Cracking pressure

A check valve requires a minimum upstream pressure (pressure differential between inlet and outlet) to open the valve and pass the media through it. This minimum upstream pressure at which the valve opens is called the check valve's ‘cracking pressure.’ The specific cracking pressure changes based on the valve design and size, so ensure that the system’s pressure can generate the cracking pressure of the chosen check valve(s).

Closing

If the upstream pressure falls below the cracking pressure or there is back pressure (flow attempting to move from the outlet to the inlet), the check valve will close. Typically, check valves have a gate, ball, diaphragm, or disc that is pressed against a seal to close the check valve. Gravity or spring can assist the closing process. As the inlet pressure decreases below the cracking pressure or there is backpressure, the valve closes by gravity, spring, and/or by using the backpressure.

Installation orientation

As a one-way valve only allows flow in one direction, it is crucial to know the correct installation orientation. Typically, an arrow on the valve’s housing indicates the flow direction. If there isn’t an arrow, examine the valve to ensure it is installed in the intended flow direction. If the valve is installed backward, media will not be able to move through the system, and the resulting pressure build-up can cause damage.

Normally open and normally closed check valves

A normally open check valve allows the medium to flow freely but shuts off the flow in case of backflow. A normally closed check valve prevents the flow of media through it until the cracking pressure builds up, at which point the valve opens.

Check valve types

Check valves operate differently depending on their design. The most common check valve is a spring-loaded in-line check valve; however, we will discuss multiple types below.

Spring-loaded in-line check valve

In-line spring-loaded check valves are common, easy to understand and have a simple design. Figure 2 shows a spring-loaded in-line check valve in the open and closed positions. The arrows indicate flow direction. When flow enters the input port of the valve, it should have enough pressure (force) to overcome the cracking pressure and the spring force. The pressure pushes the disc, opening the orifice and allowing flow to move through the valve. When the input pressure is no longer high enough or there is enough back pressure, the back pressure and spring push the disc against the orifice and seal the valve shut. The spring, along with the short travel distance for the disc, allows for a quick reaction time for closing. This valve design also prevents pressure surges in the line, preventing water hammer.

Common types of spring-loaded in-line check valves are also called:

nozzle check valves

poppet check valves

axial check valves

excess flow check valves

silent or quiet check valves

antiwater hammer check valves

They can be installed in a vertical or horizontal orientation. However, as they are in line with the system, they must be fully removed from the line to be inspected and/or maintained. A dual plate check valve has two spring-loaded plates mounted on a central pin. This design prevents slamming and water hammer effectively.

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Check Valve Details：

We Offer Different check valves  

Swing check valve, also known as check valve or check valve, its role is to prevent the medium in the

pipeline flow back. Opening and closing parts on the medium flow and force to open or close, to prevent the medium back flow valve called check valve. Check valve belongs to the automatic valve class, mainly used for medium one-way flow on the pipeline, only allow medium to flow in one direction, to prevent accidents. This type of valve should be installed horizontally in the pipeline.

Standard

Design: EN558-1

Face to face: API609 / EN593 / EN558 / DIN3202 F6

Flange drilling: DIN2501 / ANSIB16.10 / EN1092 / DIN2531 / DIN2532 / DIN2533 / EN1092

Working temperature:0-100℃

Working pressure: PN10/PN16

Main Parts and Material:

Unit: mm

For other sizes not mentioned above, please contact us.We have right to change the data without further notice.

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Our Capability

HAOZHIFENG manufactures and designs complete series of Valves according to DIN/BS/EN/API/ANSI/AWWA

/ASME/ Russian and other major standards.

-Gate Valves,

-Butterfly Valves,

-Check Valves,

-Y-Strainers

-Air Release Valves

-Globe Valves

-Fire Hydrant

The Valves supplied by SYI Pipelines are mainly used for adjusting water, steam, oil, gas, and natural gas in chemical industries, acid, alkali, and salt working pipelines. Sizes from 50-2000mm can meet full requirements from customers.

A group of highly experienced technical engineers are right here waiting for any of your request. Professional software used for design and test.

We are able to use most of the world-wide engineering software, including AUTO Cad, Pro Engineer, Solid Works and etc.

SYI is keeping on designing the series of valves for pursuing the better performance and easier operation.

New design and patterns could be developed based on customers’ requirement.

FAQs

What is a check valve?

A check valve is a unidirectional valve that passes fluid in one direction but prevents any flow in the opposite direction.

What is the purpose of a check valve?

The main purpose of a check valve in a system is to prevent backflow, which could damage equipment or contaminate media upstream.

What are common check valve problems?

Common check valve problems are noise, water hammer, vibration, reverse flow, sticking, leakage, and component wear/damage.

Will a check valve stop water hammer?

A check valve can prevent water hammer if it is fast-acting like a spring-actuated check valve. This prevents pressure surges, which create shock waves throughout the media.