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.
Check valves are fixtures that let fluid flow in only one direction. Backflow prevention is the most prominent feature of a check valve. Spring and Swing check valves are crucial check valve types. They prevent backflows in systems using different mechanisms as per their structure. Here is the difference between the swing and spring check valves.
The swing check valve allows or stops the flow of fluids by swinging a flapper. This mechanical device relies on the swinging motion of a flap or a hinged disc. The flapper turns away from the seat to allow the liquid, giving fluids enough space to escape. For the valve to close, the flapper turns back towards the seat and blocks backflow.
The situation creates automatic valve closure on decreasing pressure in the system. The valve&#;s swinging operation enables it to bear large flow capacity easily. At the same time, due to swing motion, these valves cannot perform well in horizontal or upward vertical conditions.
Bronze swing check valve drawing and spare partsSwing Check Valves: Pros and Cons.
Swing Check valves have the following set of advantages and disadvantages.
Pros of Swing Check Valves:
&#;Moderate Flow Capacity:
Swing check valves are suitable for applications having moderate flow rates. This property also makes them adhere to variable flow in many systems.
&#;Minimum Clogging:
Swing check valves have the least risk of clogging among all check valves. This is because the swinging motion dislodges the debris and prevents blockage.
&#;Less Pressure Drop:
These check valves are best for applications where minimizing pressure loss is essential. They can perform far better than other check valves in such requirements.
&#;Low Cost:
Another aspiring advantage of swing check valves is their low cost. They give reliable performance within a very economical budget.
&#;Large Flow Capacity:
Spring check valves are excellent products to manage large flow capacities.
Cons of Spring Check Valves:
&#;Slow Closure:
Spring check valves do not offer quick closure like some check valves. It can lead to water hammering in conditions where immediate valve closure is necessary.
&#;Limited Reverse Flow Tolerance:
In case of high reverse flow pressure, swing check valves may not provide an effective seal. The disc gets limited at high pressure and can lead to leaks.
&#;Slamming:
As swing check valves are limited to high flow, they can be prone to slamming at high flow. Yet, this effect can be reduced by using a damping device.
A few applications of swing check valves are as follows.
Municipal System:
Swing check valves prevent flood in the sewage system. They also block the backflow of gases and liquids through various channels in municipal systems. They also manage and avoid contaminations from entering into clean water.
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Fire Protection System:
Swing check valves are applicable in water sprinklers in fire protection systems. They ensure no backflow occurs as a fire-fighting equipment blockage can cause potential damages.
Marine Environment:
Swing check valves mark the effective working of ships by managing backflows. They prevent seawater and fuel from backflowing.
Industrial Processes:
Swing check valves are widespread in almost every industrial process. They block reverse chemical and other fluids flow in refineries and chemical plants.
Petrochemicals:
These valves are efficient in controlling various fluids in the petrochemical industry. Their primary function is to prevent mixing different chemicals and make processes go smoothly.
Brass swing check valveSpring check valves operate via a spring mechanism. They contain large stoppers in hollow bodies actuated by spring pressure. When fluid flows forward at high pressure, it causes the spring to open. The situation arises when the force of fluid overcomes spring pressure. Thus, the path is open, and liquid can move across.
Spring Check Valve: Pros and Cons.
Here is a list of advantages and disadvantages of the Spring check valve.
Pros of Spring Check Valve:
&#;High Flow Rates:
Spring check valves can undertake high flow rates as they can handle large volumes.
&#;Quick Closure:
The spring in the valve offers efficient and quick closure in case of backflow. This property saves from hydraulic issues like water hammering.
&#;Flow Orientation:
Spring check valves are not limited to only vertical or horizontal flow. Instead, unlike swing check valves, they can manage fluid in any direction. They can also handle upward and downward flow because gravity does not influence the spring&#;s working.
&#;Versatile:
Spring check valves are one of the most versatile among all check valves. Their design can be adaptable for multiple industries and suits many applications.
&#;Positive Sealing:
Spring provides the most reliable positive sealing in case of reverse flow. They also keep a check when the direction of backflow changes.
Cons of Spring Check Valve:
&#;Spring Fatigue:
Spring in check valve can be prone to fatigue over time. It can result in lesser sealing capacity and poor efficiency of the valve.
&#;Limited to Low-Flow:
Spring check valves have a design that suits high flow rates. Thus, they are limited to low-flow applications and may need to improve in these conditions.
&#;Higher Maintenance:
The spring in the check valve takes more maintenance to keep working. They usually need more care and inspections than swing check valves.
Applications of Spring Check Valve:
Spring check valves can be applicable in the following industries.
Irrigation System:
In the agriculture field, spring check valves ensure a unidirectional water flow. It saves irrigation lines from contaminating due to backflow.
Aerospace:
Spring check valves are applicable in the aerospace industry to ensure the system&#;s safety. They prevent the backflow of hydraulic fluids and fuel.
Automotive Industry:
In automobiles, spring check valves make brake operation workable. They block the backflow of brake fluid.
Residential Plumbing:
Residential plumbing systems use spring check valves on a large scale. They let fluid flow in one direction only in water supply lines and pumps, etc.
Hydraulic Systems:
In different hydraulic systems, spring check valves manage hydraulic fluids for the safe working of the system.
inline spring loaded check valveHere are some general differences between the swing and spring check valves.
PropertySwing Check ValveSpring Check ValveDesignCompact DesignBulkier design due to springClosure MechanismSwing Disc or a FlapDisc pushed by SpringClosure SpeedSlow closure speedQuick closure speedPressure DropLower pressure dropModerate pressure dropRange of Flow RateSuitable for low to moderate rateSuitable for high-flow rateResistance to CloggingLess prone to CloggingLess prone to CloggingApplicationsBest for low or moderate-flow rate applications.Versatile and can apply in multiple applications.Differences in specifications of check valvesSwing and spring check valves offer many features, making them a top choice for non-return valves. While selecting between spring check valves vs. swing check valves, consider application demands a top priority. Plumberstar offers many reliable check valves curated to meet industry standards. Mark your requirements and get the most suitable check valve for your system.
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