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DN means “Diameter Nominal” for flanges. It’s a standard to show a flange’s size with a matching bolt circle diameter. DN isn’t about measuring the flange’s actual size. It’s an industry trick to keep things the same across makers. The DN system is often used for flanges made under BS EN 1092, a European rule for circular steel flanges. These work for low and high temps and pressures.
PN stands for “Pressure Nominale.” It’s a prefix for a flange’s pressure rating. For instance, a PN16 flange can handle up to 16 bar at 20°C. Common ratings are PN6, PN10, PN16, PN25, PN40, PN64, and PN100.
Standards like ISO 7005-1 or DIN EN 2501, with PN10, PN16, PN25, and PN40 series, set pressure classes and metric flange sizes using the metric system. But PN flanges made for ANSI standards, like AWWA, ASA, or old British inch-based specs, might not match up.
American Class series flanges and European PN series flanges are the top two systems in engineering. They differ in pressure ratings, uses, and design. These differences affect picking equipment and keeping it running smoothly.
The PN series comes from the European standard EN 1092-1. It matches China’s HG/T20592 chemical rule. This system is super popular in Europe, Asia, and global projects. It’s big in chemicals, petroleum, and machine-making.
On the flip side, Class series flanges follow the American ASME B16.5 standard, linked to China’s HG/T20615. This system shines in petrochemicals and aerospace, especially in the USA and Canada. It’s built for reliability in super hot and high-pressure settings.
A flange’s pressure strength depends a lot on material and temp. For instance, a PN25 flange made of 304 stainless steel holds only 23 bar at 20°C, not the full 25 bar.
Likewise, a Class150 flange manages about 19.0 bar at 38°C, not a straight psi swap.
This shows picking a flange isn’t just about the listed pressure. Material, working temp, and environment matter a ton. Class series flanges usually stay steadier in hot conditions. PN series might save cash in room-temp setups.
When picking flanges, DN and PN gotta team up.
The DN shows if it fits the pipe. The PN says if it can take the system’s pressure. Mixing them wrong—like slapping a PN6 flange on a 20-bar system—can spell big trouble. Even if sizes match, it might fail.
Flanges often have both DN and PN marked on them (like “DN100 PN16”). They also show the material grade and standard (like EN 1092-1). This means the flange nails both size and pressure needs.
For heavy-duty systems like industrial, water, or chemical processing, size alone won’t cut it. Here’s the game plan:
· Check the DN matches the pipe bore.
· Pick a PN rating higher than the system’s max pressure.
· Make sure the PN beats the system’s top operating pressure.
· Ensure the flange follows standards like EN, ISO, or ASME.
FLUIDO offers custom flanges built with tight quality checks.With 10 years of casting and forging know-how, FLUIDO makes pipe fittings, flanges, and valves to exact ideas. Almost any doable product can be crafted.
For quality:
· All factories meet ISO9001 standards.
· Products get tough tests before shipping.
· FLUIDO has CE certification for valves and flanges.
Whether slip-on or blind flanges are needed, meeting DIN, ANSI, or custom designs, FLUIDO delivers trusty service with years of know-how.
Contact FLUIDO at info@fluidovalve.com or +86 532 88550858 for expert help with custom pipe fitting needs.
