What is valve authority?
A new Equilibar video and web page answer this question and demonstrate specific advantages of dome-loaded direct sealing diaphragm technology for addressing valve authority concerns.
In short, Valve Authority is a concept used to determine the optimal size of a control valve. It describes the correlation between control valve resistance and resistance across the frictional components of an entire system.
Valve Authority is expressed as the ratio of differential pressure (dP) across the control valve (dPv) compared to the total dP across all frictional components in a system (dPsys).
Mathematically, Valve Authority = dPv / dPsys.
Valve Authority is important when designing a system because control problems are likely to occur if a valve is either oversized or undersized. A common rule of thumb is that traditional control valves must consume at least 25% (if not 50%) of all system dP to have good control and avoid control valve hunting, which refers to rapid opening and closing of a control valve as it struggles to settle on the proper position.
Using Valve Authority for control valve sizing is commonly required in hydronics, which refers to the control of thermal water circulating loops. It is also an issue for valve designers in the process industries, especially in applications such as dosing or blending.
Over the years, Equilibar engineers have discovered that the 1000:1 turndown ratio offered by our dome-loaded direct sealing diaphragm control valves is able to sidestep the valve authority limitation and provide stable control with ratios down to 1 or 2%. This capability offers radical advantages for engineers facing complex system challenges.
More details and schematics are available on our new Valve Authority page. We also invite you to watch a video demonstrating the concept and the advantages of Equilibar technology:
And, as always, we invite you to contact one of our experienced application specialists to discuss your fluid control challenges.
