If you’ve ever worked with industrial piping—whether you’re a plumber, pipeline engineer, or someone who just orders parts for a manufacturing plant—you’ve probably run across flanges. And when you did, you definitely saw those two abbreviations: PN and ANSI. I know, I used to mix ’em up too, back when I first started selling PN flanges. I’d get calls from people asking for “ANSI PN flanges” like they were the same thing, and man, I had to correct that so many times. So today, let’s break this down like we’re chatting over a coffee (and no boring textbook stuff, promise). PN Flanges
First off, let’s start with what a flange even does, just to set the scene. A flange is basically a metal ring that connects pipes, valves, pumps, or other equipment together. It’s got holes around the edge for bolts, so you can clamp two flanges tight, make a leak-proof seal. The number on a flange—like PN16 or ANSI 150—is its pressure rating. That’s super important, right? If you use the wrong one, say a low-pressure flange on a pipeline carrying hot, high-pressure gas, you’re gonna have a bad time. Leaks, downtime, maybe even safety issues. That’s why knowing the difference between PN and ANSI isn’t just technical—it’s practical.
Let’s tackle PN first, since that’s what I sell every day. PN stands for “Pressure Nominal” (though sometimes folks say “Nominal Pressure” and it means the same thing). PN is a metric system rating, used mostly in Europe, Asia, Africa, and a lot of places outside North America. The number next to it? That’s the maximum working pressure the flange can handle at a specific temperature—usually 20°C (68°F), which is like room temperature. Wait, important caveat here: PN isn’t in psi (pounds per square inch), it’s in bar. So PN16 is 16 bar, which converts to roughly 232 psi. Got that? Metric pressure, metric unit, tied to 20°C. Another thing about PN: it’s standardized by the International Organization for Standardization (ISO), so PN10, PN16, PN25, PN40 are all common sizes. And here’s a key point for my customers: PN flanges also tie to metric pipe sizes. So a PN16 flange for a 100mm pipe is gonna have different bolt hole spacing than an ANSI flange for a 4-inch pipe. No mixing those up—you can’t just swap a PN flange for an ANSI one on the same pipe, even if they look similar. That’s a mistake I’ve seen way too many new guys make.
Now ANSI flanges. That’s North America’s go-to standard, right? ANSI stands for American National Standards Institute. Their rating system uses psi, and the numbers are like ANSI 150, ANSI 300, ANSI 600. ANSI 150 is about 150 psi at 20°C, which is way lower than PN16 (232 psi) — that’s a big difference! Another thing: ANSI’s pressure rating is actually for a higher temperature, wait—let me double-check that. Yeah, ANSI flanges are rated for their maximum pressure at a higher temp, like 100°F or sometimes 200°F, depending on the material. So as temperature goes up, the pressure rating of both PN and ANSI goes down, but ANSI’s curve is a bit different. Also, ANSI uses imperial pipe sizes—4 inches, 6 inches, etc.—so flange dimensions are in inches, not millimeters. Bolt hole sizes, the distance between bolt centers, the outer diameter of the flange—all imperial for ANSI, metric for PN. That’s why when you order, you have to know which standard your system uses first. I’ve had a customer call once, he thought he needed PN25 (25 bar, ~362 psi) but his pipeline was set up for ANSI 300 (300 psi, ~20.7 bar). Total mix-up, almost cost him a wrong order and a headache.
Wait, let’s talk about materials too, because that ties into the rating. PN flanges are usually made from carbon steel, stainless steel, or alloy steel, same as ANSI, but the way they’re tested? ISO for PN, ANSI/ASME for ANSI. ASME is the American Society of Mechanical Engineers, they work hand-in-hand with ANSI on flange standards. So when a flange is ANSI-rated, it’s tested to ASME B16.5, which is the standard for pipe flanges and flanged fittings. PN flanges follow ISO 7005, that’s the main one for metallic flanges. So those are two different testing bodies, which is why their pressure ratings don’t line up one-to-one. Like, PN16 ≠ ANSI 150, even though their numbers are close. PN16 is higher pressure, so you can’t use an ANSI 150 flange if your system calls for PN16—same vice versa, don’t use a PN16 on a system rated for ANSI 300. That’s a common misconception because the numbers look similar, but they’re totally different units and standards.
Another big difference: flange faces. The face is the part of the flange that touches the gasket between the two flanges. PN flanges often use a flat face (FF) or raised face (RF), same as ANSI, but sometimes the finish is different? Wait, no—actually, the key here is that the gasket size depends on the flange’s nominal size, which is metric for PN, imperial for ANSI. So a PN16 flange for 100mm pipe needs a metric gasket, while an ANSI 150 flange for 4-inch pipe needs an imperial gasket. If you get the wrong gasket, you’ll get a leak, no question. I always tell my customers: don’t just buy a flange, bring your pipe spec—whether it’s metric (mm, bar) or imperial (inches, psi)—that’s the first thing to confirm.
Let’s throw in a real-world example to make this concrete. Suppose you’re building a new water pipeline in Germany (they use PN standards mostly). You need a flange for a 50mm pipe, operating at 16 bar. You’d order a PN16 50mm flange. Now, if that same pipeline was in Houston, Texas, you’d need an ANSI flange: 2-inch pipe, ANSI 150. If you tried to use the PN16 flange there, it’s not just that the pressure is different (16 bar = ~232 psi vs 150 psi), but the bolt holes would be the wrong size (metric vs imperial), the outer diameter would be off, and the gasket wouldn’t fit. It’d be like trying to put a European car tire on an American rim—doesn’t work, even if they’re both rated for similar weight.
Wait, what about when someone says “PN vs ANSI for high pressure”? Let’s see: the highest common PN is like PN100, right? That’s 100 bar (~1450 psi). The highest common ANSI is ANSI 2500, which is 2500 psi (~172 bar). So at the super high end, ANSI goes higher in psi, PN goes higher in bar. But again, that’s different units, so you can’t just convert them directly. You have to look at the actual spec sheet, not just do a quick math conversion.
Now, why does this matter for you, especially if you’re ordering flanges? Let’s say you’re a maintenance manager at a chemical plant. Your equipment was installed in 2010, and the old flanges are PN25. If you replace one, you can’t just buy a PN16 thinking “close enough”—PN25 is higher pressure, so it’s thicker, the bolts are stronger, and the bolt holes are spaced for higher stress. If you use a PN16 replacement, it might bend or crack under the chemical’s pressure, leading to a shutdown. Or if you’re expanding a pipeline in a country that uses both standards (some places mix metric and imperial), you have to make sure every connection is on the same standard. I’ve had customers who work on international projects—they’ll ask me, “Can you ship PN flanges that fit an ANSI 6-inch pipe?” The short answer is no, because the nominal sizes don’t match. So always, always confirm: is your system metric or imperial? What’s its pressure rating in bar or psi? That’s non-negotiable.
I sell PN flanges, so let me add a bit of context from my side. A lot of people come to me because they’re working on projects that follow ISO standards—whether it’s in Europe, Southeast Asia, or parts of South America. They don’t have to deal with the conversion mess between metric and imperial, so they stick with PN. But sometimes, those same customers have to connect to ANSI equipment when they import a pump from the US or a valve from Canada. For those cases, I can help them find transition flanges—flanges that are one side PN, one side ANSI, so you can bridge the two standards. But I always warn them: transition flanges are temporary fixes, not long-term solutions. It’s better to design your system entirely on one standard if you can, to avoid leaks and delays.
Wait, let’s clear up another myth: some people think PN is only for carbon steel, and ANSI is for stainless steel. No, that’s not true. I sell PN stainless steel flanges just as much as carbon steel, and ANSI flanges come in both materials too. The material is separate from the standard—it’s about the pressure and size, not the metal. So that’s a mistake a lot of new buyers make, assuming material ties to PN/ANSI, but it doesn’t.
Let’s recap the key differences to make sure it’s all stuck:
- Units: PN uses bar (metric), ANSI uses psi (imperial)
- Origin: PN is ISO/metric (global mostly outside US/Canada), ANSI is ASME/imperial (US/Canada)
- Size labels: PN numbers (PN10, PN16) don’t convert directly to ANSI numbers (ANSI 150, 300)
- Dimensions: Metric bolt holes, pipe sizes for PN; imperial for ANSI
- Temperature rating: Both go down as temp rises, but their base ratings are at different temps (usually 20°C for PN, higher for ANSI)
Now, if you’re reading this and thinking, “Okay, so I need flanges—how do I get the right ones?” Don’t stress. All you need is a few quick specs from your system:
- Pipe nominal size: Millimeters (metric) or inches (imperial)
- Pressure rating: Bar or psi
- Material: Carbon steel, stainless steel, etc.
- Flange type: Raised face, flat face, etc.
When you have that, hit me up to discuss your exact needs. I work with all kinds of industries—pipeline, chemical, food and beverage, manufacturing—and I can help you pick the right PN flange that fits your system. No guesswork, no wrong orders, just parts that work. Whether you need a single flange or a whole batch, I’ve got you covered. Don’t let a mix-up between PN and ANSI slow down your project—get the right flange the first time.
PN Flanges References
- ISO 7005-1:2011, Metallic flanges – Part 1: Steel flanges
- ASME B16.5-2021, Pipe Flanges and Flanged Fittings: NPS 1/2 Through NPS 24 Metric/Inch Standard
- "Pressure Ratings for Pipe Flanges" by the American Institute of Steel Construction
Zhejiang Chengjiu Pipeline Co., Ltd.
Zhejiang Chengjiu Pipeline Co., Ltd. is one of the most professional pn flanges manufacturers and suppliers in China, specialized in providing high quality customized service. We warmly welcome you to buy high-grade pn flanges from our factory. For price consultation, contact us.
Address: NO.9-1 Hengsheng Road, Jinchuan Street, Changshan Prefecture, Quzhou, Zhejiang Province, China
E-mail: sale@cncjflange.com
WebSite: https://www.cncjflange.com/
