Can installing a check valve prevent water hammer

Can installing a check valve prevent water hammer?

"Check valve" refers to a valve whose opening and closing parts are circular valve discs and rely on their own weight and medium pressure to act to block the reverse flow of the medium. It belongs to the automatic valve category, also known as check valve, one-way valve, return valve or isolation valve. Check valves are often used as foot valves in water pumping devices to prevent the backflow of water. Check valves and stop valves are used in combination to provide safe isolation.

Commonly used movement modes of check valves:

The movement mode of the check valve is mainly classified according to the movement form of the valve disc, which can be divided into the following categories: 

Lift check valve

Working principle of lift check valve:

The working principle of the check valve is to rely on the weight of the opening and closing parts (valve disc) and the pressure of the medium to realize automatic opening and closing, thereby preventing the reverse flow of the medium. When the medium flows in from the inlet end and flows out from the outlet end, the valve disc opens under the action of the medium pressure. When the inlet pressure is less than the sum of the weight of the valve disc and its flow resistance, the valve closes to prevent the medium from flowing back.

DN80 Stainless steel Lift check valve of Features:

The valve disc moves up and down along the axis perpendicular to the center line of the valve body.

Lift check valve of Classification:

Vertical lift check valve: the valve disc moves up and down along the center line of the valve body.

Horizontal lift check valve: the valve disc moves up and down along the axis parallel to the center line of the valve body.

Lift check valve of Working principle:

When the medium flows in from the inlet end, the valve disc is pushed open under the action of the medium pressure, allowing the medium to flow; when the medium flows backward, the valve disc closes under the dual effects of its own weight and the backflow medium pressure to prevent the medium from flowing back. .

Lift check valve of advantage:

①Simple structure: Composed of valve body, valve disc, valve seat and spring, etc., easy to manufacture and maintain.

②Wide range of application: Can be used in a variety of fluid media and temperatures.

③Rapid opening and closing: Good sealing performance and low resistance when fluid passes through.

④Easy to install: Both horizontal and vertical pipes can be used.

Lift check valve of shortcoming:

①Louder noise: The valve disc needs to overcome the resistance of the spring during the opening and closing process, which may produce loud noise.

②The spring is easily damaged: The spring is easily corroded and worn by the medium, which affects its service life.

Stainless steel Swing check valve

Features of swing check valve:

The valve disc rotates around the pin outside the valve seat.

Classification of swing check valves: 

Single-disc swing check valve: Has only one valve disc and is suitable for smaller diameter pipelines.

Double-disc swing check valve: It has two valve discs and is suitable for larger diameter pipelines.

Multi-disc swing check valve: It has multiple valve discs and is suitable for larger diameter pipelines.

Working principle of swing check valve:

When the medium flows in from the inlet end, the valve disc rotates around the pin axis and opens under the action of the medium pressure, allowing the medium to flow; when the medium flows backward, the valve disc rotates around the pin axis and closes under the action of the backflow medium pressure and its own weight, preventing Medium flow back.

Advantages of swing check valve:

①Small fluid resistance: Strong flow capacity, suitable for fluids with high viscosity and solid particles.

②Low noise: The noise during the opening and closing process is relatively small.

③Smooth opening and closing: The valve disc rotates around the axis of the valve seat to open and close, and the process is smooth.

Disadvantages of swing check valve:

①Complex structure: Compared with the lift check valve, the structure is more complex and the manufacturing cost is higher. 

②High installation requirements: It is necessary to ensure that the valve disc can rotate smoothly, and the requirements for the installation position are high.

Butterfly type check valve

The characteristics of butterfly check valve: The valve disc is disc-shaped and rotates around the central axis of the valve seat.

The working principle of the butterfly check valve: When the medium flows in from the inlet end, the valve disc rotates and opens around the central axis under the action of the medium pressure, and the medium can flow; when the medium flows backward, the valve disc rotates under the pressure of the reverse medium and its own weight. It rotates around the central axis and closes to prevent the medium from flowing back.

Advantages of butterfly type check valve:

①Compact structure: small fluid resistance, suitable for large diameter pipelines.

②Easy installation and maintenance: simple structure, relatively easy to install and maintain.

③Rapid opening and closing: good sealing performance and rapid opening and closing. 

Disadvantages of butterfly check valve:

①The noise may be loud: Because the valve disc needs to rotate a large angle during the opening and closing process, a certain amount of noise may be generated.

②High installation requirements: It is necessary to ensure that the valve disc can rotate smoothly, and the requirements for the installation position are high.

Butterfly wafer double-disc check valve:

The wafer double-disc check valve is composed of a valve body, a valve disc, a valve stem, a spring and other parts, and is connected by a wafer. Since the valve disc has a short closing stroke and is spring-loaded, it can prevent the medium from flowing back and significantly reduce water hammer. This valve is mainly suitable for water supply and drainage pipe networks in cities, industries and high-rise buildings. Since its structural length is shorter than ordinary check valves, it is most suitable for places with limited installation space.

Features of butterfly wafer double-disc check valve:

①Small size, light weight, compact structure and easy maintenance;

②The valve plate adopts a dual type, which can quickly close automatically under the elastic force of the spring;

③Due to the quick-closing effect, the medium can be prevented from flowing back;

④The valve body structure has small length and good rigidity; 

⑤It is easy to install and can be installed in both horizontal and vertical directions.

Can installing a check valve prevent water hammer?

There are many factors that cause water hammer. The biggest cause of water hammer in the condensate recovery line is the backflow of condensate from the riser. Installing check valves in these locations can be of great help in preventing water hammer caused by backflow. 

One of the causes of water hammer is the backflow caused by the riser in the recovery pipeline.

If the condensate discharge is controlled by an intermittent operating pump (such as the TLV PowerTrap® series or a switch-controlled power pump), and there is a section of horizontal pipeline in front of the riser, then the condensate flowing back from the riser may be The newly discharged condensed water collides with each other, causing water hammer. Similarly, when PowerTrap® discharges high-temperature condensate, the generated flash steam and backflow colliding with the condensate are another possibility of water hammer.

Under such working conditions, installing a check valve at a suitable location in the system (such as the starting position of the riser) can be of great help in preventing water hammer.

The following matters need to be paid attention to during the installation and use of the check valve to ensure its normal operation and extend its service life:

Check valve installation precautions

①Directivity: When installing the check valve, attention must be paid to the direction of the medium flow being consistent with the direction of the arrow marked on the valve body to ensure that the check valve can properly prevent the reverse flow of the medium.

②Pipeline support: In the pipeline system, do not let the check valve bear the weight. Large check valves should be independently supported so that they are not affected by the pressure generated by the pipeline system.

③Vertical and horizontal installation: Lift-type vertical flap check valves should be installed on vertical pipes, while lift-type horizontal flap check valves should be installed on horizontal pipes.

④Avoid direct connection: A telescopic tube should be used between the wafer check valve and the butterfly valve to avoid direct connection with other valves to reduce potential damage to the check valve.

⑤ Space reservation: When installing a wafer check valve at the outlet of the water pump, a space of at least six times the diameter of the valve should flow out to ensure that the butterfly plate is eventually affected by the fluid.

Precautions for use and maintenance of check valves

① Prohibition of reverse flow: The check valve should be installed on the pipeline of the flowing medium to ensure that the fluid can only flow in one direction and no reverse flow is allowed. If reverse flow is likely to occur, other measures should be taken, such as installing a two-way check valve, etc.

②Inversion is prohibited: The check valve should be installed correctly in the direction indicated by the arrow on the installation mark or instruction manual, and inversion is prohibited. Inversion will prevent the check valve from functioning properly.

③Avoid over-tightening: During installation, check valves or pipe connections should not be over-tightened to avoid damage to the valve body and sealing surface.

④Select the appropriate sealing material: When selecting the sealing material, the appropriate material should be selected based on the fluid properties and working conditions. Do not use sealing materials that are incompatible with the fluid to avoid leakage or corrosion.

⑤ Avoid high temperature and high pressure operations: Under high temperature and high pressure conditions, the pressure in the pipeline should be gradually released first, and then the check valve should be opened after the pressure drops to a safe range to avoid danger.

⑥ Avoid cutting or welding: During installation and maintenance, cutting or welding on the installed check valve should be avoided to avoid damaging the valve body and sealing surface and affecting normal use.

⑦ Pay attention to the flow limit: According to the rated flow of the check valve, the appropriate valve size and pipe size should be selected. It is prohibited to exceed the rated flow rate of the check valve to avoid affecting the valve performance and life.