How to Diagnose a Bad Valve Plate
Valve plates are essential components of an entire valve assembly. There different types of plates available that perform different functions. Plates can be used as valves themselves or to provide cushion, dampening or a spring effect. They are flat, relatively thin, rest on the valve seat and are secured with a center bolt to create a tight seal when the valve is closed. This seal is important for fully blocking the flow of fluid through the valve and building proper pressure inside the equipment.
Valve plates can be made from metallic and non-metallic materials such as thermoplastics. The type of material chosen for the application depends on the characteristics of the internal fluid, temperature range inside the equipment and aggressiveness of the environment. All valve plate materials must be able to withstand:
- High temperature
- High pressure
- Contact with corrosive chemicals
- Harsh conditions
- High stress and strain
Valves plates must be designed and manufactured with precision to provide effective valve operation and keep the equipment functioning correctly. A bad valve plate can disrupt the efficiency of equipment or prevent the equipment from operating at all. Here are some valve plate issues operators may encounter and how to correctly diagnose a bad valve plate.
Common Problems Associated With Valve Plates
Equipment problems can be divided into electrical problems and mechanical problems. In the case of mechanical problems, the underlying issue typically involves a worn or damaged parts. Some parts wear over time from normal use and natural degradation of the material. However, parts can also break, warp, corrode and experience other types of damage due to problems within the equipment such as:
- Particulate matter in the fluid
- Excessive heat or pressure
- Imperfect seals
- Improperly installed components
- Loose hardware
- Vibration or high impact environments
Abnormal wear, warping and corrosion are commonly due to fluid characteristics. For example, some types of material are not appropriate for exposure to hydrocarbons or chemicals, and particulate matter within the fluid can cause damage in the form of cracks or breaks.
Other than wear, valve plates can be the cause of issues such as excessive noise, discharge temperature or slow pressure buildup.
Diagnosing a Bad Valve Plate
There is a basic method for troubleshooting a bad valve plate. The key is to clearly identify the problem, potential areas where the problem is originating and specific components that are likely culprits. Once these items are identified, the equipment can be disassembled and inspected to determine the actual issue.
Bad valve plates typically cause the following types of problems:
- Excessive noise – Excessive noise with a definitive beat and rhythm that corresponds to the valve opening and closing timing is typically due to the piston hitting the valve plate. This is usually caused by particulate matter between the piston and the valve plate, which can be removed, cleaned and reassembled. Unless the plate shows signs of damage, replacement is usually not required. Upstream filtration equipment may need to be inspected and cleaned if particulate matter presents a frequent problem.
- Excessive discharge temperatures – Excessive discharge temperatures are usually caused by worn valve assemblies. In this case, the valve no longer functions properly and needs to be replaced. Check the valve plates for the type of damage such as warping to corrosion to determine whether there are issues with the internal fluid and whether preventive measures should be established.
- Slow internal pressure buildup – Broken or worn valve plates also cause pressure to build too slowly inside the equipment. If all upstream filters are clean, gaskets are intact, belts are functioning and the equipment speed is accurate and adjusted correctly, worn valve assemblies are likely the cause.Replace and reassemble all valve plates and test the operation to ensure adequate pressure builds within an acceptable time.
- Fluid leakage – When fluid leaks through the valve during normal operation, it is likely that the valve is not sealing correctly due to warped or damaged plates. Disassemble and inspect the valve assembly, carefully looking at the condition of each individual plate. The plates should stack evenly and should sit flush upon the valve seat when closed. Even if one plate of the entire assembly is damaged, replace the entire set to help guarantee a tight seal. After reassembly, check intake and discharge flow rates to make sure the desired flow is achieved and that replacing the valve assembly fixed the problem. Also, check the discharge flow when the equipment is shut down and the valve is in the closed position to see whether fluid flows through the equipment at rest.
The Importance of Correctly Diagnosing the Problem
A bad valve plate can affect internal equipment operation and cause both upstream and downstream issues. When choosing valve plates, carefully evaluate the operating temperature range, characteristics of the fluid being pumped and other environmental factors to ensure that the correct plate material is selected.
Keen troubleshooting skills are needed when diagnosing mechanical equipment problems, but valves are viable suspects when temperature, pressure, noise and flow suddenly become irregular.Be sure to keep sensors and gauges properly calibrated so that readings are accurate and problems can be identified quickly. Make sure that all operations and maintenance personnel thoroughly understand how the equipment works, can identify all the major components and understand how the components work together and rely on one another. Full knowledge of the equipment itself is extremely helpful for efficient and correct diagnoses.
Also, establish a preventive maintenance schedule to anticipate issues before they occur. For example, a manufacturer might guarantee the life of the valve based on the materials of construction. As the end of life approaches, maintenance staff can proactively replace the valve plates to prevent unnecessary failure.If changes to the fluid or environment occur, evaluate how such changes can affect the components based on their composition. For instance, if materials are not designed to withstand certain chemicals or temperature ranges, a full valve replacement may be necessary to prevent disruption in service.
Overall, choose the right valve and the right material for the job. Know the signs and symptoms of valve wear, damage and malfunction to effectively diagnose problems. Include valve inspections in a regularly scheduled preventive maintenance schedule to proactively respond to changes in the equipment.
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