In case of fluid flow systems, check valves play a crucial role in preventing backflow and ensuring efficient operation. In this article we&#;ll delve into the topic of check valves, covering the various types of check valves, different applications across industries, the advantages and disadvantages, the proper installation and maintenance procedures as well as the latest uses in modern engineering. So, let&#;s move on!
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Check valves, called also non-return valves, are very important elements that allow the fluid, either liquid or gas, to flow in one direction only. They are a vital part of stopping the reverse flow which may lead to backflow contamination, system inefficiencies, or water hammer problems. These valves are specially designed to work autonomously, opening with forward flow and closing to prevent reverse flow without any manual operation or external control.
The working principle of the check valve is simple yet ingeniously effective. It works on the principle that the fluid pressure from the upstream side must be greater than the downstream pressure to open the valve. When the forward flow is strong enough to overcome the resistance caused by the valve mechanism (usually a flap, ball or plate), the valve in an open position and the fluid can pass through. The mechanism moves back into position, sealing the valve and stopping any backward flow of fluid when the flow stops or reverses.
Check valves, including ball check valves, swing check valves, lift check valves, etc, come in various designs, each with unique features and advantages. Let&#;s explore five of the most common types of check valves in more details:
Swing Check Valves
Swing check valves are known as the disc that swings around the hinge or trunnion when the liquid flows through. This is the kind of valve that is best suitable for low velocity and pressure systems as it necessitates only a little flow to open. Normally designed from robust materials such as cast iron, stainless steel, or brass, swing check valves are preferred for their simplicity and high efficiency in fluids used in a diverse range of applications.
Lift Check Valves
Lift check valves have a disc or cone that rises vertically away from the seat to permit flow and settles back to the seat to prevent reverse flow. They are ideally suited for applications in high-pressure systems where the flow velocity is sufficient to lift the disc. These valves commonly made of carbon steel or stainless steel are able to withstand the pressure of the aggressive media.
Dual-Plate Check Valves
The dual-plate check valve is designed as a pair of semi-circular plates that are hinged on the central axis and swing together under flow pressure to return to the closed position due to gravity or spring force when the flow stops. These valves being small and lightweight are able to be installed both horizontally and vertically. They are mostly used in applications where leak tightness is a major concern and are made from a variety of materials including cast iron, stainless steel, and alloy materials.
Non-Slam Check Valves
Non-slam check valves are designed to prevent the slamming of the valve disc which can be experienced in fast flow systems. This type of valve usually consists of a spring mechanism which provides for a rapid and controlled closure before the flow reversal and, as a result, dramatically reduces the water hammer and system shocks. The non-slam check valves are frequently involved in the liquid pumping applications which are made of durable metals such as bronze or stainless steel.
Tilting-Disc Check Valves
Tilting-disc check valves have a disc that tilts on a hinge to open, rather than lifting or swinging completely out of the flow path. This design is perfectly suited for quick closure and low-pressure drop, therefore, it works well for applications that require fast response and low flow resistance. They are commonly built from materials that are strong like cast iron or carbon steel to withstand high pressure and temperature.
Here is a concise table summarizing the key features of these check valve types:
Valve TypeMechanismCommon MaterialsIdeal ApplicationsSpecial FeaturesSwing Check ValvesSwinging discCast iron, stainless steelLow pressure, wide range of fluidsSimple, effectiveLift Check ValvesVertical lift discCarbon steel, stainless steelHigh pressure systemsHandles aggressive mediaDual-Plate Check ValvesTwo swinging platesCast iron, stainless steelCompact spaces, both orientationsLightweight, better leak tightnessNon-Slam Check ValvesSpring mechanismBronze, stainless steelHigh flow velocity systemsReduces water hammerTilting-Disc Check ValvesTilting discCast iron, carbon steelFast response required, low resistanceQuick closure, minimal dropCheck valves are used in a wide range of industries because of their fundamental function, which is to ensure that fluids and gases are flowing in the right direction. They can be utilized in different industries for various purposes such as safety, efficiency, and regulatory compliance. Down here are major industries where check valves are widely used.
Check valves are not limited to traditional applications, they are also part of cutting-edge systems with the progress in technology. Check valves are finding their way in a variety of modern engineering fields. These applications frequently require valves with specific features like the ability to handle high flow rates with lowest possible pressure loss, withstand extreme force, or provide easy access for maintenance purposes. Below are some of the latest applications for check valves.
Microfluidics: In microfluidics, check valves can be miniaturized to control the flow of fluids in micro-channels, which allows for the precise control and manipulation of small volumes of liquids. Such is relevant in drug discovery, point-of-care diagnostics, and lab-on-a-chip devices.
Aerospace: Check valves are very important in aerospace applications, such as fuel systems, hydraulic systems, and environmental control systems. In these applications, check valves must operate under extreme force and within gas lines at high altitudes with minimal pressure loss. High-end check valves, for instance, those which are built with lightweight materials and redundant safety mechanisms, are designed to perform reliably and reduce safety risks. Aerospace check valves usually contain a closing mechanism that can prevent backflow even in an event of an abnormally high flow rate, and thus protect the valuable equipment from being damaged.
Biomedical Devices: Check valves are used in a wide range of biomedical devices like prosthetic heart valves, ventricular assist devices as well as dialysis machines. These valves must be made of materials that are biocompatible, durable and accurate in terms of flow control to guarantee patient safety and effective treatment. Biomedical check valves are typically overdesigned with a too high safety margin to reduce the risk of valve failure and are subject to extensive research and testing to guarantee their reliable performance. Some biomedical check valves can be equipped with advanced options like sensors that can provide important notifications about valve function and patient health.
Renewable Energy: In renewable energy systems, as in the case of solar thermal and geothermal power plants, check valves play a vital role of preventing reverse flow and ensuring the smooth flow of heat transfer fluids. These valves must be able to function well under high temperatures and pressures with acceptable pressure loss. The latest valve designs, including those with non-slam features and corrosion-resistant materials, certainly improve the reliability and the performance of the system. In certain instances, renewable energy systems may be equipped with particular types of check valves, such as excess flow check valves, which can automatically cut the flow in the event of an abnormally high flow rate, and this thereby prevents equipment malfunctions and reduces the potential financial consequence.
When considering the implementation of check valves in a fluid system, it&#;s essential to weigh the advantages and potential drawbacks. This section will provide a detailed overview of the pros and cons associated with using check valves.
Advantages of Check Valves
Prevents Backflow: The main benefit of check valves is that they stop reverse flow of fluids in systems. These valves are designed to allow flow in only one direction and will automatically close when flow stops or reverses, thus protecting the equipment, processes and system integrity from the damaging effects of backflow.
Low Maintenance Requirement: Check valves are designed with few moving parts which results in less wear and tear. The straightforwardness of this type of valve leads to a lower maintenance requirement than the more complex valve systems. For the industries where downtime means a significant financial loss, such as in oil and gas production or manufacturing, the low maintenance feature of check valves ensures continuous operation and minimize the chances of an unplanned shutdown.
Versatility: Check valves are of a very high level of versatility and may be used in a wide range of applications from simple domestic water systems to complex chemical processing plants. They can be made from different sizes, materials, and designs of which each is suitable for a particular medium, pressure and flow. This characteristic makes them suitable for almost any system that needs flow control.
Disadvantages of Check Valves
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Potential for Water Hammer: While check valves are a good solution to backflow, they can sometimes lead to risk of water hammer&#;especially in systems with high flow speed, or when the valve closes quickly. A water hammer is a pressure surge that happens when a moving fluid is stopped or changed direction abruptly and can result in system damage or failure.
Susceptibility to Clogging: Clogging can be observed in check valves that are designed to handle fluids with high particulate content or viscosity. When the debris accumulates, it can hinder the valve from being closed completely, which reduces the effectiveness of the valve in preventing backflow and might lead to system contamination or damage. Additionally, excessive fluid release can occur if the valve is unable to close properly, leading to potential hazards and damage.
Valve Chatter: In certain situations, this valve may produce chatter or vibration because of the quick opening and closing of the valve disc. This can happen at the flow regime that is very close to the valve&#;s cracking pressure or when the system experiences pressure changes. Valve chatter causes noise, wears the valve parts, and damages the adjacent piping. In order to overcome this problem, it&#;s necessary to choose a valve with the correct cracking pressure and maybe use non-slam or spring loaded design in cases where the chatter is common.
Through the comprehension of the benefits and possible disadvantages of check valves, system designers and engineers can make educated choices when choosing and using these devices in fluid systems. The right valve selection, installation and maintenance will be able to make check valves work better and have less negative effects.
Selecting the appropriate check valve is of high importance for the piping system&#;s performance and safety. The choice process should take into account the parameters like fluid type, pressure, temperature, flow dynamics and environment. Besides, it&#;s necessary to take into account the particular attributes of different types of check valves, like cracking pressure, resistance to clogging, and ease of maintenance.
For example, a rapid closing check valve should be installed in systems that are prone to water hammer to prevent pressure surges. Another important aspect is the selection of the valve body with the right material for the fluid. For instance, the fuel system valve body may require different materials than the one used for the water systems. The inlet and outlet ports of the valve have to match the size and type of pipeline, ensuring easy access for maintenance and inspection. Additionally, pressure loss should be kept at the minimum to maintain the system efficiency&#;the selection of a valve that ensures the lowest possible pressure loss is often fundamental, especially in the cases of centrifugal pumps, which are commonly used as the most common type of water pumps in large buildings.
Discussing with valve manufacturers and referring to detailed product specifications will be a good idea and it can help in making the correct choice.
The installation and maintenance that are well-performed are important for the check valve&#;s life and functioning. Make sure that the flow turns into the inlet port without any obstructions and with the marked direction on the valve body, when you install a check valve. This alignment is important for systems with high flow conditions, where the fluid is able to create a lot of force and could wear out the components if they are not aligned correctly.
The routine maintenance with different types of tools should involve the visual inspection of wear and tear of the movable disc and other internal parts. It is vital to carry out such checks with different tools, mainly after any dramatic changes in the system operation or a certain problem with performance. Additionally, it is essential to guarantee that there is no hose failure or leakage around the valve which can avoid higher pressure loss and provide higher safety margins within the system.
In the world of engineering, the application of check valves is like a team coordinator in a way that it gathers all the necessary elements together and arranges them in a coherent manner, just like a Chuck Norris video. These valves which are essential for the healthy aging of piping systems, control flow direction and fight back against internal enemies such as backflow and pressure surges. They act as individual contributors at the same time and the entire method is a success because of their coordination with different types of tools&#;from content tools to collaboration tools&#;to make sure that the project due dates are not compromised.
In the water treatment, oil and gas, chemical manufacturing and HVAC systems industries, check valves are among the most important components that guarantee the flow of fluids in one direction and keep reverse flow prevented. Choosing the correct valve for an application not only improves system efficiency but also minimises safety risks and prevents financial losses. Engineers, system designers and their entire team can improve the reliability and performance of their systems significantly, by knowing the specific attributes and operational aspects of the various check valves. It is our wish that this blog post has provided a full understanding and glance insight on check valve applications for you.
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The slanted seat check valve also offers enhanced resistance to water hammer. The valve has a double eccentric shaft position as well as an increased seating angle. This yields a shorter valve stroke, thus reducing the time taken for the door to close.
Hydraulic dampers are recommended, especially when the valves are installed on a pumping station where high frequency opening and closing of the valve is required. The valve disc closes quickly over the first 85% of its angular travel before meeting the hydraulic damper. The damper then dissipates the kinetic energy of the disc and forces it to open slightly. The disc closes until it contacts the damper again and this cushions the disc until it returns to its fully closed position, sealing the valve. This function greatly reduces the onset of water hammer due to the damped and controlled method of valve closure.Hydraulic dampers are recommended, especially when the valves are installed on a pumping station where high frequency opening and closing of the valve is required. The valve disc closes quickly over the first 85% of its angular travel before meeting the hydraulic damper. The damper then dissipates the kinetic energy of the disc and forces it to open slightly. The disc closes until it contacts the damper again and this cushions the disc until it returns to its fully closed position, sealing the valve. This function greatly reduces the onset of water hammer due to the damped and controlled method of valve closure.
For more details, please see our slanted seat check valve product information.
Nozzle check valves are designed with the valve disc connected to the stem which is guided on the central horizontal axis. A spring is positioned between the disc and the diffuser sleeve. When flow enters the valve, the hydraulic force exerted onto the front face reacts against the spring, causing the spring to compress and allow the valve to open. When the flow stops, the spring forces the disc to return to the closed position.
Due to the spring-assisted closure and the short linear valve stroke, the nozzle check valve is one of the quickest acting check valves available and is commonly used in pumped systems where water hammer is a potential concern. Because the disc is constantly in the direct line of flow, the head loss characteristics of this valve are higher compared to that of conventional swing check valves.
For more details, please see our nozzle check valve product information.
In order to choose the right check valve for your application, several selection criteria should be considered. First, however, there is not one type of check valves being the best choice for all applications, and the selection criteria may not be equally important for all cases. Some of the things you may need to consider are fluid compatibility, flow characteristics, head loss, non-slam characteristics and total cost of ownership.
All check valves referred to in this article are designed for water and treated wastewater applications, but using the valves for raw wastewater/sewage applications may cause some issues. When selecting a valve for these fluids, you should consider how the presence of solids may potentially affect operation of the valve.
If a check valve closes very fast, it may prevent slamming against upstream equipment such as pumps. However, the rapid closure will not protect against the surges caused by pumps being started and shut down. If the valve opens (and closes) quickly, the flow will change rapidly and thus increase likeliness of surge occurrence.
Head loss is, among other things, a function of fluid velocity. The head loss through a valve is determined by the internal design of the valve and the opening degree. When a valve is designed with a restricted (narrowed) opening compared to the pipeline, the velocity will increase through the valve, increasing the head loss as a result. Vice versa, if a valve is designed with less restriction and bore is equal size to the pipeline, the head loss will be smaller, and the valve will in practice not affect the overall head loss of the system. There are a number of values for head loss, amongst others zeta values, Kv and Kvs values.
The costs for your check valve consist of more than just the purchase price. For some installations, the most important costs may be purchasing and installation, but in other cases, maintenance or energy costs may be equally or even more important. Also protecting more valuable equipment such as e.g. pumps has to be considered, and looking at the valve performance will be crucial. When considering costs as a selection criterion for your check valve, the total costs over the life of the valve should be considered. In general, the simpler the valve construction is, the lower are the maintenance requirements. The higher the Kv value, the lower the energy consumption. The higher the performance, the better the protection ability.
Check valve slam can affect pressure surges in a negative way. First step of the process is when the pump stops, starting the pressure surge. Second step is, when the flow is reversed, slamming against the fully closed check valve. If the check valve closes too fast, the kinetic energy is turned into high pressure, stressing the pipes, and causing high noise.
A slam sounds like if the disc or the ball from the check valve is hitting the seat and can make quite some noise. However, the sound is not caused by the physical closing but by a sound wave arising from a pressure spike stretching the pipe wall.
To prevent the occurrence of check valve slam, the valve should close in a controlled way and slower when near closed position. For a check valve to close slowly, it requires additional ancillary equipment, such as hydraulic dampers, which act as a cushion to the valve door, as it comes into its seated position. This slower closure allows the fluid to pass through the check valve until it closes, causing less kinetic energy turning into high pressure, and thus less energy to feed and maintain the surge. Consideration must be given to the upstream pump to ensure that it is suitable for reverse spin and flow.
As swing check valves have the disc in the flow stream, helping with rapid closure, they have better non-slam characteristics. However, today many pumps are frequency converted, enabling them to adjust the start-up and closure time to avoid water hammer.
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