Stem seal leakage in control valves is a problem that often flies under the radar, but it shouldn’t. When specifying a control valve, we usually follow a familiar decision-making process: evaluate materials, capacity requirements, and process conditions. But the reality is, not all process streams are created equal.
Some process fluids don’t stay neatly within the piping system. When molecules can permeate diaphragms, thin foils, or seals, it’s time to take a closer look. Even common liquids can present sealing challenges, especially when elevated temperatures are involved. Take heat transfer oil, for example. It’s notorious for leaking through seals, packing, and threaded connections. Aside from the mess, leaks can introduce serious safety concerns if the fluid is flammable or hazardous.
In these situations, traditional globe valves often fall short in containing the process. This issue is especially common in chemical plants and petroleum refineries. While bellows-sealed globe valves offer a tighter seal, they can be cost-prohibitive.
More and more facility owners are turning to rotary-operated valves instead of rising-stem designs. Why? Because rotary valve stems seal against the same surface every time, which minimizes the impact of external conditions and significantly reduces leakage. Plus, rotary valves are no longer limited to high-flow, moderate pressure-drop applications. Newer designs now handle low flow coefficients, too. This was once exclusive to globe valves.
While globe valves remain important in some severe-service and high-precision applications, many industries now rely more heavily on rotary valve technologies. Rotary options now provide viable, and often superior, solutions for many critical processes.
If you're specifying a valve for a process where leakage could be an issue, don’t go it alone. Reach out to one of our experts, and we’ll help you navigate your options. And for a deeper dive into this topic, check out Valin expert Peter Jessee’s article published last year in Chemical Engineering Magazine.
Partner with Valin for all of your control valve needs. Contact us today at (855) 737-4714 or fill out our online form to learn more.