Check valves or one-way valves are designed to stop backflow and ultimately protect pumps and compressors.They are available in a variety of styles and sizes, from 1/8″ to the largest size you may need.Check valves are used in many industries in a wide range of applications, from municipal water to mining and natural gas.The three most common types are swing check valves, double-door check valves, and silent spring-assisted axial flow check valves.
This is probably the most common check valve in use today and is a full port design, which means the disc is not in the flow stream when fully open.This type of check valve is ideal for applications with high solids percentage and low number of on/off cycles.Swing check valves close slowly due to the travel distance of the disc.This causes the last reverse flow to push the valve disc closed, causing huge pressure spikes that cause water hammer.Water hammer is a pressure shock when a fluid in motion is forced to stop or suddenly changes direction, creating a pressure wave in a pipe.Such pressure waves can cause major problems ranging from noise and vibration to collapsed pipes.
This valve is similar to a swing check valve and is slightly better at closing because the coil springs help the two cantilevered doors close faster.It turns out that this is not the best choice when facing water hammer, although they perform better than swing check valves.Generally, this valve is considered an off-the-shelf commodity valve with little customization options.
These full-flow valves typically contain a center-guided stem-disc assembly and a compression spring.This means that the disc stays in the flow stream.Media flows around it, without manual or automatic assistance.When the pump is running, the valve opens.When the pump is off, the valve closes slightly before fluid flow reverses due to the compression spring force acting on the disc, which virtually eliminates water hammer.
Most requirements for check valves only consider line size and pressure rating, as medium pressure and flow rates can change dramatically when piping designs are oversized for future problems or undersized due to lack of or incorrect information .This is not always the best approach when deciding which type of valve to use in a system.Other factors to consider are working pressure, flow rate, specific gravity and temperature of the medium.Analysis of the system design is strongly recommended.It is necessary to understand the causes and root causes of valve failure.The most common failure is due to excessive wear on the valve’s internal parts.Premature wear of springs, discs and stems that are not stable during operation.Chattering can occur when the disc is unstable due to insufficient flow to hold it in the fully open position.
Sizing a center pilot valve is not difficult.In addition to the required pipe size, pressure rating and valve type (flange, wafer, etc.), the user also needs the actual working pressure, flow rate, media type, temperature and specific gravity of the media.It might be as simple as building the valve with a lighter spring to fully open the valve.To bring the valve to the fully open position, a lift limiter may be required to reduce the travel of the disc.When the valve is 100% open, it remains stable in flow and reduces premature wear and failure by eliminating the effects of chatter.It is important to remember that these valves are designed for actual flow values, not line size.A properly sized valve will be in the fully open or fully closed position.
Depending on the impact of lost income, wages, and the cost of replacing the valve, the cost of replacing the valve can be quite high.The price of off-the-shelf valves may be attractive, but what is the true cost of ownership?If a valve of one size costs five times as much, but has five times the service life, consider how these affect the financial balance, taking into account maintenance costs and lost production.
While some applications require double-door and swing check valves to function properly and are required, these and other off-the-shelf valves are not the only solution.In any application where a check valve is used, installing a custom valve can improve performance and extend the life of the piping system.This translates into more value and overall, long-term cost savings.
Bruce Ellis is an Inside Sales Consultant for Triangle Fluid Controls Ltd.He can be reached at bruce@trianglefluid.com or 613-968-1100.For more information, visit trianglefluid.com.
Post time: Feb-11-2022
