What Are the Different Types of PN Flanges?

When choosing metric flanges for your piping system, it’s important to know: what are the different types of PN flanges? 

PN (Pressure Nominal) flanges are defined by pressure class (e.g., PN6, PN10, PN16) and standardized dimensions under EN/DIN/ISO norms. They’re widely used in water, HVAC, and industrial applications across Asia, Europe, and beyond.

What the “PN” Rating Means

“PN” stands for nominal pressure, expressed in bars. For example, a PN16 flange is rated for a maximum of 16 bar (~232 psi). These flanges are sized under EN 1092-1 (formerly DIN 2501) and ISO 7005, ensuring bolt patterns, diameters, and thickness meet international requirements.

Common PN Types and Where They’re Used

PN flanges are categorized by pressure class, with each level suited to different system demands. Here’s how the most common types break down and where they’re typically applied:

• PN6 is used in low-pressure pipelines such as irrigation, basic drainage, and gravity-fed systems. It’s a fit for non-critical, low-flow installations.
• PN10 supports moderate pressure and is often found in municipal water distribution, HVAC loops, and compressed air systems.
• PN16 is the most widely used across industries. It handles pressures up to 16 bar and is ideal for water, gas, and basic chemical transport.
• PN25 and PN40 flanges are suited for systems operating at higher pressures, such as steam service, industrial cleaning lines, or heavy-duty plant piping.
• PN64 and above are specialized flanges designed for power generation, heavy chemical processing, or hydraulic systems operating at extreme pressures.

Plate flanges

Plate flange is the most common flange, the pressure is PN2.5, PN6, PN10, PN16, PN25.

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PN Flange Types: Face and Connection Styles

Beyond pressure rating, PN flanges also vary in face style and connection type—both of which affect how they’re installed and sealed in a pipeline.

• Weld neck PN flanges have a sloped hub that connects directly to the pipe, helping to spread stress evenly and reinforce the joint. This makes them ideal for high-stress environments where shock, vibration, or temperature changes are common.
• Slip-on and socket weld types are often used in lower-cost setups and are commonly applied in compact or lower-capacity pipelines. They’re easier to align during installation and work well up to PN40 pressure classes.
• Blind flanges are solid plates used to close off a pipeline or pressure vessel. They’re common at inspection points or system ends.
• Lap-Joint flanges are used with a stub end and are ideal for systems where disassembly or realignment is frequent.
• Threaded, reducing, and expanding PN flanges are also available for specialized systems, especially when transitions between sizes or fittings are needed.

PN Flanges vs ASME Flanges

PN flanges follow EN 1092-1 standard and use metric pressure units (bar), while ASME flanges follow B16.5 standard and use pressure classes (psi).

Key takeaway: PN and ASME flanges are NOT directly interchangeable without engineering verification.

What to Know When Buying PN Flanges

Choosing the right PN flange goes beyond just matching the pressure class. Keep the following factors in mind when selecting a PN flange:

• Material selection is key. You can source PN flanges in various materials, including stainless steel, carbon steel, and specialty metals depending on the application. For example, stainless steel PN flanges are preferred in corrosive or hygienic environments like food, pharma, and water treatment.
• Make sure it meets the correct standard. PN flanges should conform to EN 1092-1. If you’re integrating with an ANSI system, check if ASME flanges are more appropriate to avoid fitment issues.
• Always factor in pressure margin. Don’t choose a flange that matches your exact operating pressure—build in some safety headroom to extend flange life and avoid performance drops.

How to Choose the Right PN Flange

Instead of selecting by pressure alone, engineers should consider:

1. Operating Pressure + Safety Margin

Always select a PN rating higher than actual working pressure.

2. Medium Type

• Water → PN10 / PN16
• Steam → PN25 / PN40
• Chemicals → Stainless steel PN flanges

3. Temperature Conditions

Higher temperature reduces allowable pressure rating.

4. Standard Compatibility

Ensure compliance with EN 1092-1 or matching system standard.

Result: correct sealing performance + longer service life.

What Are the Different Types of PN Flanges: Conclusion

The different types of PN flanges are defined by pressure rating (PN6 to PN100+), face type (weld-neck, slip-on, blind, etc.), and compliance with EN 1092-1 standards. Matching flange type, pressure class, and material to your system ensures a reliable seal and lasting performance.

Need help selecting the right PN flange? Longan Flange stocks certified stainless and alloy options, ready to meet your industrial, chemical, or water system needs. Contact us right now for more info!

Frequently Asked Questions About PN Flanges

What are the 6 types of flanges?

PN flanges include Weld Neck, Slip-On, Blind, Lap Joint, Socket Weld, and Threaded types.

Are PN10 and PN16 the same?

No. PN10 is rated for 10 bar pressure, while PN16 is rated for 16 bar. They differ in thickness and application.

What are PN10, PN16, and PN25 standards?

They are pressure classes under EN 1092-1 standard, indicating maximum working pressure in bar at 20°C.

Are PN16 and PN40 flanges the same?

No. PN40 is designed for much higher pressure systems and has thicker flange construction.