In industrial valve management, ensuring the right valve for the job is crucial to maintain process control and prevent inefficiencies. While selecting and sizing valves properly at the outset is essential, even the best valve can face challenges once it’s placed in an active process. This is where testing—on the bench and in-line without the process—becomes invaluable.
The Importance of Proper Sizing and Selection
A properly sized valve should perform well in any environment, and if it’s been selected based on the right parameters, process-related issues shouldn’t affect its operation. When tested without process involvement, valves tend to work perfectly because they are adjusted and dialed in. However, the real question arises when the valve is placed in the process—this is where things can get complicated.
When a valve is placed in-line, the process begins to affect the valve, and issues like "hunting" may arise. These are the fluctuations in valve performance that can happen when external factors, like flow rate changes or pressure variations, impact the valve’s performance. The problem may no longer be related to the valve’s construction but rather its initial sizing and selection.
The Evolving Nature of Valve Systems
When valves are first installed, engineers often size them for about 30% more than what the typical operational demand will require. This gives the valve a buffer to accommodate fluctuations, operating around 70-75% of its total capacity. This margin helps to ensure the valve can handle slight changes in pressure or flow. But as systems age and companies push for more efficiency, they often demand higher flows or more pumps. This can push the valve closer to its limits, increasing the risk of process-related issues such as actuator hunting.
As the valve system ages and operational demands grow, the 30% buffer that was initially factored in begins to close, which can cause the actuator to struggle with the pressure or flow rate, leading to overshooting, erratic movements, and poor regulation. This is where the sizing and selection issue re-emerges. Despite the valve performing well initially, the process has evolved to a point where the valve may no longer be the optimal choice for the application.
How Testing Reveals Hidden Issues
The key takeaway from this scenario is that process-related issues often aren’t visible until the valve is actively in use. Testing a valve on the bench before installation helps to ensure the valve works within its intended parameters, but it’s only by testing it in-line with the actual process that engineers can see if those parameters hold up under real-world conditions. The discrepancies between testing and actual process conditions may highlight the need for adjustments like different actuators, springs, or trim to accommodate the changes in flow or pressure.
As companies grow older and their systems evolve, the need to adjust valve components—whether by replacing actuators, modifying springs, or updating trim—becomes more apparent. These mechanical adjustments are crucial to maintaining optimal valve performance and addressing the growing challenges caused by the process.
The Bottom Line
Proper valve selection and sizing at the beginning are key to ensuring long-term performance, but over time, as systems evolve and processes change, testing becomes more important than ever. Regular testing, along with the readiness to adapt and make necessary adjustments, can help ensure valves continue to meet the demands of an ever-changing industrial environment. Ultimately, the goal is to keep processes running smoothly without unexpected valve failures, and testing is an essential step in that direction.
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