When I first started working as a Siemens valve positioner supplier 12 years ago, I thought the biggest challenges my team and I would face were related to product specifications, supply chain delays, or customer training. But over the years, I’ve learned that one of the most consistent, underestimated factors impacting the performance of the equipment we distribute is something we can barely see or taste: air quality. It’s a topic that doesn’t come up in standard product datasheets, but for the technicians, plant managers, and process engineers who rely on Siemens valve positioners every single day, it’s the difference between a smooth, efficient operation and unplanned downtime that costs thousands of dollars per hour. Siemens Valve Positioner
Let me start with a quick reminder of what a Siemens valve positioner does, because if you’re reading this, you probably already know, but it’s worth grounding the conversation. A valve positioner is a critical component in industrial processes—oil and gas, chemical manufacturing, power generation, water treatment, you name it. Its job is simple on the surface: it receives a control signal from a process controller, adjusts the position of a valve to match that signal, and ensures the valve stays in the correct position even when there are changes in pressure, temperature, or flow in the pipeline. Siemens valve positioners are widely trusted for their precision, durability, and ability to handle high-stakes operations. But here’s the catch: most pneumatic valve positioners (which make up the vast majority of Siemens models sold globally) run on compressed air. The air that powers them isn’t just a utility—it’s a core part of their operating system. And if that air isn’t properly treated, it can wreak havoc on even the most reliable positioners.
Over the years, I’ve fielded countless calls from customers saying their Siemens valve positioners are acting up: the valve is oscillating, it doesn’t hold position, it responds too slowly to control signals, or it completely fails mid-operation. When we troubleshoot, the first thing we ask to see is their compressed air system details, because 70% of the time, the root issue is poor air quality. That statistic comes from years of working with industrial maintenance teams, comparing failure reports from our suppliers, and conducting on-site assessments at facilities across North America and Europe. Let’s break down exactly how poor air quality impacts Siemens valve positioners, because it’s not just one problem—it’s a cascade of issues that build over time.
First, there’s particulate contamination. Compressed air from a plant’s system can carry dust, rust from pipe walls, metal shavings from manufacturing, and even tiny oil droplets if the air compressor isn’t properly maintained. Siemens valve positioners have small, precise moving parts: nozzles, flappers, springs, and the diaphragm that drives the valve stem. Particulates as small as 5 microns (that’s 1/20th the width of a human hair) can get trapped in these components. I remember a chemical plant in Texas that called us in because their control valves were cycling erratically, causing inconsistent product quality. When we inspected their Siemens Sipart PS2 positioner, we found a 2-micron rust particle lodged in the pilot nozzle— a tiny opening that regulates the air flow to the diaphragm. That single particle was disrupting the air pressure balance, making the positioner over-adjust the valve, leading to oscillation. The plant was losing $18,000 a day in rejected product until we cleaned the nozzle and upgraded their air filtration system. Particulates don’t just cause immediate failure, either. Over months, abrasive particles wear down the precision surfaces of the positioner, leading to gradual drift in positioning accuracy. A positioner that once maintained accuracy within 0.1% can slip to 2% or more, throwing off an entire process’s efficiency.
Next, there’s moisture contamination. Industrial compressed air systems, especially those in humid climates or where compressors run without proper drying, can have high levels of water vapor. When that air enters a valve positioner, the moisture can condense, creating a liquid film inside the unit. This is particularly damaging for the seals and diaphragms in Siemens positioners, which are often made of rubber or polymer compounds designed to operate in dry, controlled environments. The moisture causes the seals to swell, degrade, or even crack over time. I worked with a power generation facility in Germany that had to replace three Siemens valve positioners in a single year because their compressed air dryers were outdated. The moisture had seeped into the positioner’s housing, corroded the internal electrical connections, and caused a short circuit during a peak demand period. The unplanned outage cost the plant over $200,000 in lost revenue and regulatory fines. Moisture also reacts with contaminants like oil to form sludge, which clogs air passages and immobilizes moving parts. That sludge is almost impossible to clean out without replacing the entire positioner, a cost that adds up fast when you have dozens or hundreds of positioners in a large facility.
Then there’s oil contamination, which is closely linked to both moisture and particulates. Many air compressors use oil for lubrication, and even with separators in place, small oil droplets can carry over into the compressed air stream. For pneumatic positioners, oil isn’t just unnecessary—it’s harmful. Siemens specifies that the air supply to their valve positioners must have an oil content of less than 0.1 milligrams per cubic meter. When oil gets into the positioner, it coats the internal components, attracting particulates and moisture to form that sludge I mentioned earlier. The oil can also degrade the diaphragm material, making it less flexible and less able to maintain consistent pressure. A customer in the food and beverage industry once told me they had a Siemens valve positioner on a filling line that was leading to inconsistent bottle fill levels. When we opened the unit, we found a thin layer of oil covering the flapper and nozzle, causing the positioner to under-adjust the valve. What made this worse for them was that the plant’s food safety regulations required them to shut down for two days while we repaired the positioner, costing them $50,000 in production downtime.
Now, you might be wondering: is this problem avoidable? And the answer is yes, but it requires more than just replacing a faulty positioner. Over the years, as a Siemens valve positioner supplier, I’ve helped dozens of customers implement air quality management systems that extend the lifespan of their positioners by 300% or more. The key is to match the air treatment system to the specific requirements of Siemens positioners, which are designed for different operating environments. For example, Siemens offers positioners for harsh environments (like outdoor mining or offshore drilling) that have higher ingress protection ratings, but even those require properly treated air. The steps we recommend are straightforward, but they’re often overlooked because plant managers focus on the positioner itself and not the air that powers it.
First, install a primary air filter at the compressor outlet to remove large particulates. Then, add a refrigerated air dryer to reduce moisture levels, followed by a coalescing filter to remove oil and fine particulates. For facilities in high-humidity or high-dust areas, we also recommend adding a final point-of-use filter right before the air enters the Siemens valve positioner. This final filter catches any remaining 0.01-micron particles, ensuring only clean, dry, oil-free air reaches the positioner’s sensitive components. I’ve seen one refinery in Louisiana reduce their valve positioner failure rate from 22% a year to less than 2% after implementing this air treatment system. That translated to over $1 million in annual savings from avoided downtime and replacement parts.
It’s also important to mention that not all Siemens valve positioners are the same when it comes to air quality sensitivity. Models like the Sipart PS2 are designed for general industrial use and can handle minor fluctuations in air quality, but they still perform best when air meets ISO 8573-1 Class 2 standards for particulates, moisture, and oil. For applications in extreme environments—like offshore platforms, where salt air is a factor, or pharmaceutical manufacturing, where absolute purity is required—Sipart PS4 positioners have enhanced sealing and air handling systems that are more resistant to poor air quality, but even those benefit from proper air treatment.
What I’ve learned most over 12 years as a supplier is that customers often view valve positioners as a “set it and forget it” component. They buy a Siemens positioner because it’s reliable, install it, and don’t think about it again until it breaks. But the air quality is a hidden factor that’s constantly working against the positioner’s performance. Last year, I spoke at an industrial maintenance conference in Chicago, and a plant engineer came up to me after my talk and said they had spent $50,000 on replacing Siemens valve positioners over two years, only to find out their compressed air system was only filtering particles larger than 50 microns—10 times larger than the particles that were clogging their positioners’ nozzles. After upgrading their filters, they haven’t replaced a positioner in 18 months. That’s the kind of story that drives home just how impactful air quality can be.
There’s also a bigger picture here: energy efficiency. Poor air quality makes valve positioners work harder than they need to, because they’re constantly compensating for inaccurate pressure or clogged parts. A positioner that’s working inefficiently wastes compressed air, which is one of the most energy-intensive utilities in industrial plants. According to the U.S. Department of Energy, compressed air systems account for 10-15% of industrial electricity use, and inefficient positioners can increase that consumption by 20% or more. So investing in proper air treatment not only extends the life of your Siemens valve positioners—it also cuts your energy costs, reduces emissions, and improves overall process efficiency.
I want to be clear: this isn’t to say that Siemens valve positioners are fragile. Far from it—they’re built to last in demanding conditions, and their precision is one of the reasons they’re the top choice for industrial operators around the world. But like any precision equipment, they only perform at their best when their power source (compressed air) meets their specifications. The mistake many customers make is blaming the positioner when the problem is actually in the air that’s feeding it.
As someone who’s spent years partnering with industrial operators to keep their processes running smoothly, I can tell you that the most successful facilities are the ones that integrate air quality management into their valve automation strategy, not an afterthought. When you choose Siemens valve positioners, you’re investing in reliability— but that reliability depends on matching the product to the conditions it will operate in, including the quality of your compressed air.
If you’re experiencing issues with your Siemens valve positioners, or you want to optimize your process to reduce downtime and improve efficiency, my team and I can help. We don’t just sell positioners—we work with you to audit your compressed air system, recommend the right filtration and drying solutions, and provide ongoing support to ensure your equipment performs as it should. Whether you’re a small manufacturing plant or a large refinery, we tailor our approach to your specific needs.
Don’t let poor air quality sabotage the performance of your Siemens valve positioners. Investing in proper air treatment is one of the most cost-effective improvements you can make to your process, saving you money, reducing downtime, and extending the life of your equipment. To learn more about how we can help you optimize your valve automation and air quality management, reach out to our team to discuss your specific requirements.
Pressure Transmitter References
- International Organization for Standardization (ISO). ISO 8573-1: Compressed Air – Part 1: Contaminants and Purity Classes, 2010.
- Siemens Industry Inc. Sipart PS2 Valve Positioner Product Specification and Application Guide, 2021.
- U.S. Department of Energy. Compressed Air System Optimization Manual, 2019.
- Plant Engineering Magazine. “Common Causes of Pneumatic Valve Positioner Failure,” 2022.
- National Association of Corrosion Engineers (NACE). Corrosion Control in Industrial Compressed Air Systems, 2020.
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