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Almost every industry that uses pipelines to transport fluids relies on the use of check valves. Check valves-also called check valves, check valves, or check valves-allow flow in only one direction while preventing flow in the opposite or opposite direction. These valves only open and close based on the hydraulic pressure generated by the water flow acting on the valve mechanism.
Check valves are commonly used in steam lines, condensate lines, water lines, HVAC systems, and chemical feed pumps, just to name a few common applications. These valves are critical components in many cases, because reverse flow can cause great damage to some equipment. Therefore, the symptoms of check valve failure must be detected as early as possible to prevent facility downtime and expensive repairs.
Wear of elastomers and seat seals and high operating temperatures may also cause check valve failure.
The key to preventing check valve failure and ensuring valve service life is proper and regular preventive maintenance.
The first and most effective step to avoid valve failure is to keep the pipes and valves clean and free of debris. This can be achieved by installing filters and covers where needed. The piping system can also be flushed regularly to remove deposited debris and minimize the accumulation of contaminants.
Valve lubrication is another effective way to prevent premature valve failure. A check valve is composed of several moving parts; therefore, minimizing friction between these parts through lubrication can extend the service life of valve parts, improve overall performance, and ensure efficient operation.
Finally, the valve must be installed correctly and used as directed. Improper installation of the valve or using the wrong type of check valve will shorten the service life of the valve. A regular maintenance plan should also be implemented to ensure that faulty valves are replaced at the first signs of failure.
When choosing a valve size, remember to evaluate the check valve for a given application, not the size of the pipe.
Taking into account future capacity requirements, increasing the size of the pipeline is a common practice. However, a larger pipe diameter will produce a lower flow rate, which means that there may not be enough fluid velocity to fully open the check valve. This causes the rotary valve, which is sized according to the pipe diameter, to swing back and forth between partially open and closed positions. This phenomenon is called chattering. The frequency of motion caused by vibration will eventually increase the valve wear rate and cause component failure, which will further damage other downstream equipment.
Therefore, the check valve must be selected according to the expected flow rate. This involves selecting a valve with an appropriate valve coefficient (CV) value. The CV value describes the ability of the flowing medium to fully open the valve; the higher the CV, the greater the flow required to open the valve.
You must also consider the type of medium that will pass through the valve. For example, corrosive or abrasive media may require the use of certain valve materials, such as carbon steel, stainless steel, or brass. In addition, it is necessary to consider the characteristics of the fluid passing through the pipeline to ensure uninterrupted flow. Solids, liquids, and gases are all different in viscosity, density, and quality. The internal valve mechanism must allow these unique media to be accommodated.
Valve orientation is also important to determine the correct type of check valve for a given application. When installed under vertical flow conditions, some valves may not work as expected. In addition, if the valve is deemed suitable for vertical flow, the direction (up or down) must be determined because these conditions have unique requirements.
Although all check valves perform the same function, their internal mechanisms allow for one-way flow in different ways. Each of these mechanisms is suitable for different situations; therefore, it is necessary to understand the basic operating modes of these valves to determine which application they are most suitable for.
Different types of check valves—although they are conceptually similar—are very different in terms of internal valve mechanism, cracking pressure (related to CV), and materials of construction. The internal devices of these valves are also sensitive to debris, flow rates and pressure peaks. Therefore, proper valve selection and proper routine inspections are the key to preventing premature failure of check valves in any type of application.
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Post time: Aug-16-2021
