What is the PN Rating in a Valve? A Guide to Class & PN Conversion

Understanding the PN rating in a valve is essential if you work across European and American standards. 

Here’s a clean and clear guide that walks you through what PN means, how it compares to ANSI class, why a direct swap isn’t always accurate, and how to ensure you’re using the right valve for the job.

What Does Pressure Nominale (PN) Mean?

PN, or Pressure Nominale, is a European standard for valve pressure ratings, commonly used across DIN, EN, ISO, and other global valve standards. 

Marked in bars (e.g. PN 16 equals 16 bar ≈ 232 psi), the number represents the pressure a routing component can handle at a reference temperature—commonly around 120 °C.

Understanding the ANSI/ASME Class Rating System

The ANSI/ASME Class system, used mainly in North America, assigns pressure ratings like Class 150, 300, or 600. 

Rather than directly representing pressure, these classes refer to allowable pressure at specified temperatures per standards like ASME B16.34 (for valves) and B16.5 (for flanges).

ANSI Class	Approx. Pressure at Room Temp
Class 150	~19 bar / 285 psi
Class 300	~51 bar / 740 psi
Class 600	~102 bar / 1480 psi

Why Direct Conversion Isn’t Always Possible (Temperature & Material Factors)

Direct conversion between PN and Class is an approximation at best. This is because:

• Temperature baselines differ: PN typically uses 120 °C, while Class 150 uses 260 °C and others use 454 °C.
• Material & flange design influence performance: Actual pressure capacity changes with construction material (carbon steel vs. stainless) and flange or valve body design per ASME pressure-temperature charts.

A Practical Conversion Chart (PN to Class)

Use this as a quick reference. Remember: verify with material & temperature specifications before finalizing.

Approx. PN (bar)	Approx. ANSI Class
PN 20	Class 150
PN 50	Class 300
PN 100	Class 600
PN 160	Class 900
PN 250	Class 1500
PN 420	Class 2500

How CLDG Ensures the Correct Rating for Your Application

At CLDG, we understand how critical matching pressure rating to application is. That’s why:

• Each valve is clearly marked with its PN and/or Class rating.
• We support both DIN/ISO (PN) and ASME (Class) systems and help you select the right pressure-temperature spec.
• Every forged valve undergoes material certification, and pressure testing aligned to industry standards.

When in doubt, our team can guide you toward the correct flange rating and material combo to ensure safe, compliant operation.

Need to convert a PN rating to an ANSI class—or the other way around? Get in touch, and we’ll guide you through the process.For CLDG’s full line of tested, certified valves built to both PN and Class standards, explore our catalog: CLDG Valve Products.