If you’ve ever worked in oil and gas, chemical processing, power generation, or any industrial sector where precise pressure control is non-negotiable, you know that Fisher pilot operated regulators aren’t just pieces of hardware—they’re the unsung guardians of process safety, efficiency, and product quality. As a supplier of these critical regulators, I’ve spent thousands of hours walking alongside plant engineers, maintenance teams, and process operators through every step of their projects, and one question comes up more than any other: “What sealing materials are in Fisher pilot operated regulators, and why does it matter?” Fisher Pilot Operated Regulator
Let me start with a personal story. Early in my career, I was on a site visit with a refinery maintenance manager in the Gulf Coast. We were troubleshooting a series of regulators that were leaking during startup, causing unplanned downtime and costing the plant hundreds of thousands of dollars in lost production. When we pulled the regulators apart, we saw that their old, generic seals had disintegrated from exposure to high-temperature hydrogen sulfide (H₂S) and the volatile hydrocarbons in their feed stream. That’s when it clicked: sealing materials in Fisher pilots aren’t just about stopping leaks—they’re about matching the seal to the application, the media, and the operating conditions.
Today, I want to break down exactly what sealing materials Fisher uses in their pilot operated regulators, why each is chosen, and how that translates to reliable performance for your operations. This isn’t just a list of materials; it’s the knowledge that comes from working alongside Fisher’s engineering team and real-world customers for over a decade.
First, let’s get context on why Fisher seals are engineered the way they are. Pilot operated regulators work on a simple principle: a small pilot valve controls the main regulator valve, adjusting pressure upstream or downstream as needed. The seals here have to do double duty: they must seal the pilot’s small orifices and passages without leakage, while also sealing the main valve’s large seating surface against process media—often in extreme pressure, temperature, or chemically aggressive environments. Cut a corner on the seal material, and you’re looking at downtime, safety risks, or product contamination.
Let’s start with the most common, workhorse sealing material in Fisher pilot operated regulators: Nitrile Butadiene Rubber (NBR), also called Buna-N. I know what you’re thinking—rubber is basic, right? But don’t sleep on NBR for the right applications. Fisher uses NBR in thousands of general-purpose pilot regulators because it balances cost, elasticity, and resistance to common industrial fluids. For low-pressure applications where media isn’t highly aggressive, NBR seals hold up well to mild hydrocarbons, water, and moderate temperatures (typically between -40°F and 225°F, or -40°C and 107°C). I’ve seen NBR hold up for years in natural gas distribution regulators that control pressure to local power plants, where the only media is relatively dry, low-sulfur natural gas. The key here is that NBR is easy to machine into the small, precise shapes needed for pilot seals—no fancy tooling, and easy to replace during routine maintenance. But here’s the catch: NBR won’t hold up to high temperatures, strong acids, or solvents. If you put NBR in a 300°F chemical processing line with caustic soda, it’ll swell, crack, and leak in months. That’s why Fisher has a whole library of specialized seals for more demanding applications.
Next up is Fluorocarbon Rubber, better known as Viton. This is the go-to for medium to high-temperature applications that NBR can’t handle. Fisher uses Viton seals in pilot operated regulators for petrochemical plants, refinery fractionation units, and chemical processing lines where temperatures can range from -20°F to 400°F (-29°C to 204°C), and media includes heavier hydrocarbons, mild acids, and some solvents. Viton’s fluorine content makes it resistant to swelling and degradation from these chemicals, and it maintains its elasticity even at higher temperatures, so it doesn’t harden and crack as it ages. I recently worked with a polyethylene plant that was running a pilot regulator on a high-density polyethylene (HDPE) monomer line, which runs at 350°F. They were using NBR seals that failed every 6 months until we switched them to Viton. The seals have now been in place for over 2 years with no leaks. That’s the kind of difference the right seal material makes. Fisher offers a range of Viton grades too—some for lower-temperature, some for higher-temperature, even some formulated for resistance to H₂S, which is a big deal in oil and gas. For sour gas applications, Fisher will specify a special Viton grade that meets NACE MR0175/ISO 15156 standards, so the seals won’t crack or become brittle when exposed to high H₂S levels.
If Viton isn’t enough, there’s Perfluoroelastomer, or FFKM. This is the top-tier sealing material for the most extreme, aggressive environments. Fisher uses FFKM seals in applications where temperatures go beyond Viton’s limit—up to 500°F (260°C) for many grades—or where media includes strong acids, bases, or highly corrosive chemicals like chlorine, hydrofluoric acid, or aromatic solvents. A customer of mine in semiconductor manufacturing needed pilot regulators for a line that handles corrosive etching chemicals, and Viton seals would swell and fail in weeks. We swapped them for FFKM, and those seals have been running for 3 years with zero leakage. FFKM is expensive, there’s no denying that—costing 5 to 10 times more than NBR—but for critical applications where downtime can cost six or seven figures per hour, it’s a no-brainer. Fisher’s FFKM seals are also formulated to meet strict industry standards, like ISO 10360 for semiconductor processing, so they don’t shed particles that could contaminate products. That’s a key detail for industries like pharmaceuticals or semiconductors, where even a tiny particle can ruin an entire batch.
Now, not all seals in Fisher pilot operated regulators are rubber. For high-pressure, high-temperature applications—like power generation, where regulators handle steam at 1500 psi and temperatures up to 600°F—Fisher uses metal seals. I know metal seals sound heavy, but they’re precision-machined from materials like stainless steel, Inconel, or Hastelloy, and shaped to seat perfectly on the regulator’s valve body. Unlike rubber seals, metal seals can handle pressure up to 10,000 psi and temperatures over 1000°F. I was on a combined cycle power plant last year where their main steam regulator was leaking after a valve replacement, and the problem was that their rubber seals couldn’t withstand the 950°F steam. We installed a metal seal from Fisher, and the leak was gone immediately. Metal seals don’t degrade from chemicals the way rubber does, but they’re more susceptible to scratching and require precise installation—you can’t just swap them in without making sure the seat is clean and undamaged. That’s why we always include training with every regulator we supply, so maintenance teams know how to handle metal seals correctly.
Wait, there’s one more seal material I need to mention because it’s becoming more important as industries focus on sustainability: PTFE, or Teflon. Fisher uses PTFE seals and O-rings in pilot operated regulators for low-temperature applications—like cryogenic lines handling liquefied natural gas (LNG) or liquid nitrogen. PTFE has a working temperature range from -450°F to 500°F (-268°C to 260°C), which makes it the only rubber or polymer material that can handle extreme cold without becoming brittle. I worked with an LNG terminal last winter where their pilot regulators on the storage tank lines were failing because rubber seals cracked when exposed to -20°F LNG vapor. Swapping to PTFE seals fixed the problem, and they haven’t had a cold-related leak since. PTFE is also chemically inert, so it won’t react with LNG or other cryogenic fluids, which is a huge safety plus. The downside is that PTFE has lower elasticity than rubber, so it doesn’t seal as well on irregular surfaces. That’s why Fisher uses it only in applications where temperature or chemical resistance is the top priority, and the mating surfaces are precision-machined to tight tolerances.
Now, a lot of customers ask me: does Fisher ever use generic off-the-shelf seals in their regulators? The answer is a hard no. Every seal is tested by Fisher’s engineering team to match the exact application parameters—pressure, temperature, media, and operating cycle. For example, a seal for a regulator that cycles 10 times a minute is different from one that only cycles once a day, because it’s exposed to more fatigue. Fisher also tests every seal for compatibility with process media, so you don’t have the kind of swelling or degradation that happened to that Gulf Coast refinery early in my career.
But here’s the thing: even the best seal in the world won’t work if it’s not specified correctly. That’s why as a supplier, I don’t just sell regulators and seals— I work with customers to match the right seal to their needs. If you’re operating in a general natural gas distribution system, NBR is probably all you need. If you’re in a petrochemical plant with high temperatures and sour gas, Viton or H₂S-resistant Viton is the way to go. For critical pharmaceutical lines, FFKM is non-negotiable. For cryogenic LNG lines, PTFE is a must. For power generation steam regulators, metal seals are the only option.
I’ve seen too many plant teams cut costs by buying cheaper seals, and every time it leads to unplanned downtime. Last year, a mid-sized chemical plant tried to save $200 on a set of seals for their pilot regulators, using generic seals from a local supplier. Those seals failed within a month, costing them $120,000 in lost production. That’s the kind of hit that makes the extra cost of Fisher’s original seals worth every penny.
At the end of the day, the sealing materials in Fisher pilot operated regulators are a testament to the brand’s focus on solving real industrial problems. They’re not just materials—they’re engineered solutions tailored to the most demanding applications across every sector. If you’re looking to replace seals, upgrade your regulators, or just have questions about what materials are right for your specific process, my team and I are here to help. We work with plants of all sizes, from small local facilities to global industrial giants, and we’ll walk you through every step of choosing the right sealing materials for your Fisher pilot operated regulators. Don’t let avoidable leaks, downtime, or safety risks hold your operations back. Reach out to our team to discuss your needs and get customized guidance for your application.
AUMA Electric Actuator References
Fisher Controls International. (2022). Fisher Pilot Operated Regulator Sealing Materials: Engineering for Industrial Application. Emerson Industrial Automation.
NACE MR0175/ISO 15156. (2021). Petroleum and Natural Gas Industries – Materials for Use in H2S-Containing Environments. NACE International.
ASTM D2000. (2020). Standard Classification System for Rubber Products in Automotive Applications. ASTM International.
ISO 10360. (2019). Geometrical Product Specifications (GPS) – Acceptance and Verification Tests for Coordinate Measuring Machines. International Organization for Standardization.
Century Weiye (Dalian) Control Equipment Co., Ltd.
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