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.
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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.
For individuals looking for strong, durable check valves that will work seamlessly under extreme conditions, swing check valves are the perfect option. Their extensive range of applications, from simple industrial uses to the most complex of systems, makes them especially ideal for those searching for reliable valves to protect their machinery.
The question is - how do you choose the perfect swing check valve for your specific needs? With so many different types of swing check valves available in the market, selecting the right one can be a daunting task. That's why we've curated a list of four tips that will help you choose the best swing check valve for your requirements.
Tip 1: Know What You Need.
Before you choose the perfect swing check valve, one of the first things you must know is the job you need it for. Different valves have distinct features and capabilities. For instance, if you require a valve that will prevent backflow in your plumbing system, then a horizontal swing valve would be ideal. On the other hand, if you require a valve that can withstand high flow rates, then vertical type swing valves would work well.
In addition, it would be best if you also thought through factors such as pressure and temperature requirements, media compatibility, the size of the pipes, and many others. Ensuring you know what you need beforehand will help you make a wise choice when it comes to selecting the right swing check valve.
Tip 2: Think About Operational Cost.
Swing check valves come in different material build, models, and designs, each with its unique benefits. However, one factor that often gets overlooked is operational costs. Before you choose a new swing check valve, it's essential to understand its operational cost.
Certain swing check valves may be cheaper initially, but tend to have high maintenance costs and require more frequent repair. On the other hand, some valves may be costlier upfront but tend to last longer and have lower maintenance costs, resulting in significant cost savings in the long run.
Consider the long-term cost implications before making your purchase. Look for the best quality swing check valves that meet your budget and maintenance requirements.
Tip 3: Look for Quality and Durability.
Durability is vital in selecting the right swing check valve. The valve's quality, material build, and design determine its lifespan. When choosing a valve, look for something that meets your requirements over extended use. Ensure you purchase a high-quality valve that can last for many years without needing frequent replacement or upkeep.
Some of the critical factors to consider when assessing the quality and durability of your swing check valve include the material construction of the valve, the valve's internal components, and the valve's design. It is important to consider all of the features the valve offers so you can make an informed decision that will save you money in the long run.
Tip 4: Availability of Spare Parts.
You might find that at some future point, a spare part may become necessary for your swing check valve. It's always a good idea to ensure spares are available before purchasing the valve. Just like any other mechanical tool, swing check valves may require maintenance or repair from time to time, therefore, having easy access to spare parts ensures that the repair process runs more smoothly and any downtime is minimized.
Ensure that the vendor you purchase from can provide you with all the necessary parts in case of an emergency, and that the parts can be quickly delivered to save time and reduce system downtime.
Conclusion.
In conclusion, when selecting the perfect swing check valve for your needs, it's essential to think through what you need, operational costs, quality and durability, and the availability of spare parts. All of these factors will help you make an informed decision and ensure that you choose a reliable, efficient, and long-lasting swing check valve that meets your specific needs. With careful consideration, you can easily find the right swing valve that will work best for your system while saving you time and money in the long run.
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