When the pump stops, if there is a knocking sound, pressure drop, or backflow, both the check valve and the condition of the piping system should be inspected. This article explains the types of check valves and how to use on-site data to identify the cause before replacing the valve or adjusting the system.
What is a Check Valve?
A check valve, or check valve, is a valve that allows fluid to flow in a specified direction and helps limit backflow. The closing mechanism may use a spring, gravity, or fluid force depending on the valve type. Materials and specifications must be suitable for water, air, oil, or actual working fluids.
Principle of Operation of Check Valve
Understanding the principle of operation of the check valve will help you design the piping system effectively. This type of valve relies on the pressure of the fluid in the system as the main control without relying on electrical power Study the operation of the check valve in detail here
Normal Flow Direction (Forward Flow)
When the inlet pressure is sufficient to overcome the closing force, the valve disc begins to open. The pressure difference that starts to open is called cracking pressure and depends on the valve type and spring. When flowing, the valve creates a pressure drop across according to the flow rate.
Backflow Prevention
When the pressure difference decreases, the mechanism of the check valve moves back to the valve seat. Some valve types use springs or gravity to close before significant backflow occurs. The amount of backflow and leakage through the seat depends on the valve type and operating conditions.
Benefits to System Equipment (System Protection)
The quick closure of the check valve helps prevent damage to the water pump or compressor from fluid impact. Installing this type of valve at strategic points can significantly reduce the problem of water hammering or water impact on the pipes. As a result, all equipment in the factory has a longer service life.
How many types of Check Valves are there?
Selecting the correct type of check valve that matches the nature of the work is important in fluid system design. Backflow valves are divided into several forms according to the internal mechanism designed to withstand specific pressures.
Swing Check Valve (Swing Check Valve)
The swing check valve uses a disc flap that opens with the flow and swings back to its seat when the flow decreases. The pressure drop depends on the size, the disc opening, and the flow rate. Check the manufacturer's data before selecting.
Spring Check Valve (Spring Check Valve)
The spring-type valve uses the internal spring pressure to keep the valve disc closed at all times until the water pressure is sufficient to overcome it. Spring check valves can be installed in any direction, whether vertical or horizontal. The spring mechanism allows for rapid prevention of backflow.
Foot Valve (Foot Valve)
The foot valve, also known as a strainer valve, is a backflow preventer installed at the end of the suction pipe. This device stores water in the pipe to prevent it from flowing back out of the pump when the machine is not operating. The valve has a strainer to prevent debris from entering and damaging the internal pump components.
Maintenance of Check Valve
The SCMA engineering team recommends that regular maintenance of check valves is crucial to reducing downtime. Proper maintenance of the check valve will help the system operate at full efficiency for a long time.
Visual Inspection
Start with visual inspection of the check valve every 3 to 6 months to look for signs of abnormalities. Check the joints for leaks, cracks, or rust deposits. Detecting problems early will help prevent damage from spreading to other valves.
Internal Cleaning
Before removing the valve, the responsible personnel should isolate the energy and fluid sources according to the factory procedure. Bleed off and confirm that there is no residual pressure, then clean using the method and materials specified in the manual for that model.
Check of Moving Parts
Inspect the valve disc, valve stem, and spring in detail to find signs of wear or corrosion from chemicals. Components of the check valve that are frequently subjected to impact will deteriorate over time. If any cracks or worn springs are found, a maintenance plan should be prepared immediately for safety.
Parts Replacement
Rubber seals and internal gaskets in the check valve should be replaced immediately upon finding signs of deterioration or hardening. Allowing the seal to leak will cause a massive loss of pressure in the system. Choose genuine parts that are resistant to the temperature of the fluid to extend the maintenance cycle time.
Lubrication
Check the valve manual before lubrication. Some models do not require additional lubrication. If the manufacturer specifies, use the compatible substance and quantity with the seal, material, and fluid.
Application of Check Valves in Industry
The application of check valves in the industrial sector varies according to the type of production process. Backflow valves are installed as a basic safety mechanism that every factory cannot do without.
Preventing Backflow in Pumping Systems
When large water pumps suddenly stop operating, check valves serve to block a massive volume of water from flowing back and damaging the impeller. From the experience of the SCMA engineering team at Chonburi (EEC) branch, who resolved downtime issues for an automotive parts manufacturing plant, we found that installing standardized check valves helps protect the motor from reverse rotation 100%. This mechanism effectively prevents severe damage to the cooling system.
Maintaining Pressure in Compressor Systems
Industries using compressed air or pneumatic systems rely on backflow valves to prevent air from flowing back out of the air receiver tank. Choosing standardized equipment, such as the solution from E.MC PNEUMATIC, helps maintain constant pressure, so the compressor does not have to work hard to pump air from scratch. The system can achieve energy efficiency effectively.
Reducing Shock from the Water Hammer Phenomenon
Closing the valve after the flow begins to reverse may cause shock from the closure or increase the severity of the Water Hammer. Choosing the appropriate closing characteristics for the system helps reduce the risk, but it must be considered together with the pump, piping layout, and changes in flow velocity.
Advantages of Check Valve
Installing a standard check valve provides a valuable return on investment in industrial piping systems. Backflow prevention valves have several features that help improve overall operational efficiency
Prevent Damage from Backflow
The greatest benefit of a check valve is its ability to completely cut off reverse flow. The system is safe from backflowing chemicals or pressure that could damage pumps, flow meters. This proactive prevention helps save long-term maintenance budget for major machinery
Completely Automatic Operation
The mechanism of the check valve operates in accordance with the pressure of the fluid without relying on electrical systems or external sensors. This purely mechanical operation eliminates problems caused by electronic system failures. The valve is ready to respond 24 hours a day without the need for staff to monitor
Durable Structure for Long-Lasting Use
Check valves are designed to have few moving parts, resulting in a low rate of wear. The materials used to produce this type of valve are resistant to corrosion from industrial fluids. Maintenance is easy, requiring only cleaning and inspection at scheduled intervals
Cost-Effective for Long-Term Investment
The price of a check valve is considered very economical when compared to the value of the equipment that this valve protects. Installing one backflow prevention valve can prevent hundreds of thousands of dollars in hydraulic system damage. Businesses can thus reduce hidden costs from machine downtime in a tangible way
Maintain Fluid System Stability
Backflow prevention valves help retain liquid or gas in the desired pipe side to keep the system always ready for operation. You don't have to waste time priming the system every time you start the machine. This stability helps greatly increase production process speed
How to Choose a Check Valve
When deciding which Check Valve model is suitable, it mainly depends on the environmental factors at the work site. The SCMA team would like to provide a checklist for considering various types of valves and check valves as follows.
Consider the type of fluid in the system to select a durable check valve body material that is resistant to corrosion.
Calculate the flow rate as well as the pressure drop (Pressure Drop) that the valve can withstand.
Check the installation position to determine whether a vertical or horizontal check valve is required.
Select the type of closing mechanism that is suitable for the speed of reverse flow.
Consult with experts to find an industrial valve solution that meets long-term needs.
Warning Signs That the Check Valve Is Having Problems
Record when the symptoms occur, such as during pump shutdown or when the end pressure increases, and compare the data with the valve specifications and pipe type. The following symptoms are the starting point for inspection, but the cause must be confirmed with on-site data.
There is an abnormal noise similar to impact near the valve when the water pump stops operating.
Vibration may occur due to the valve not opening fully, rapid closing, or other causes in the pipe, such as pump operation and pipe fittings. Record the rhythm and location where it occurs.
The pressure drop after the pump stops may be related to leakage through the valve or other leakage points. Check and compare the pressure before and after the valve according to the method approved on-site.
Leakage of the fluid is detected at the flange or connection area of the check valve.
The reverse rotation of the pump set after stopping may be related to backflow. The responsible personnel should check based on system data without approaching moving parts and disconnect the energy before removing the valve.
Summary
In summary, a Check Valve is an important safety device that controls the flow of fluid in one direction. Choosing a standardized check valve or backflow preventer can effectively protect expensive equipment from backpressure. If you are looking for high-quality valves, the engineering team from SCMA is ready to provide advice and design automated system solutions that precisely meet your factory's needs.
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The selection of appropriate equipment directly affects the stability of the production process. Understanding what a Check Valve is is just the beginning of upgrading your factory. If you need high-quality check valves, valves, or backflow preventers, SCMA, as a technically proficient partner, is ready to present solutions Our Services that cover everything from sales to after-sales service SCMA Co., Ltd. is pleased to be part of your success
Frequently Asked Questions
Can the Check Valve be installed in reverse?
No, absolutely not. Installing it in the reverse direction will cause the valve to completely block the flow, and the system will not be able to operate.
What is the average lifespan of a check valve?
The lifespan depends on the type of valve, the fluid, temperature, pressure, number of cycles, and maintenance history. Use leak detection results and component condition together with the manufacturer's criteria to determine repair or replacement timing.
Can swing check valves be installed vertically?
Vertical installation is only possible for models specified by the manufacturer as supporting that orientation and flow direction. Some swing check valve models support upward flow in vertical piping. Check the arrow on the valve body and the manual before installation.
Why does the backflow preventer make noise when closing?
Noise during closing may be caused by the valve disc striking, disc vibration, or pressure surge. Inspect the flow rate, valve size, component condition, and system condition to identify the cause.
How often should check valves be cleaned?
Determine the schedule according to the manual, type of fluid, tendency for sediment buildup, and operating conditions. If leakage or abnormal closing is detected, the responsible personnel should follow the factory's procedures.
