Pressure Rating Guide: PN vs Class vs K Ratings Explained
Every valve and flange carries a pressure rating, but the world uses three different systems to express it: ANSI Pressure Class, the European PN system, and the Japanese JIS K system. Misreading them is a leading cause of failures and costly mismatches. This guide explains each system and how to compare them safely.
1. ANSI / ASME Pressure Class
The ANSI/ASME system (ASME B16.5 for flanges, B16.34 for valves) rates pressure as a Pressure Class: 150, 300, 600, 900, 1500 and 2500 lb. The number is not the actual working pressure. A Class 150 flange allows roughly 285 psi at ambient temperature but far less at higher temperatures. Always consult the pressure–temperature chart for your material.
2. European PN system
DIN EN 1092-1 flanges are rated by PN (Nominal Pressure), expressed in bar: PN6, PN10, PN16, PN25, PN40, PN63, PN100, PN160, PN250, PN400. The number is the nominal pressure at the reference temperature. As with the ANSI system, the actual allowable pressure decreases as temperature rises.
3. Japanese JIS K system
JIS B2220 flanges use the K rating: 5K, 10K, 16K, 20K and 30K. JIS flanges are metric but with their own unique dimensions and bolt patterns. 10K is the most common for general industrial service in Japan and much of Southeast Asia.
4. Rough cross-reference table
| ANSI Class | Approx. PN | Approx. JIS K | Rough max pressure (bar) |
|---|---|---|---|
| Class 150 | PN20 | 10K | ~20 |
| Class 300 | PN50 | 20K | ~50 |
| Class 600 | PN110 | 30K | ~110 |
⚠️ These are only approximate. Bolt circle diameters and bolt hole counts usually differ between systems, so flanges from different standards generally cannot be bolted together.
5. Reading a pressure–temperature chart
The pressure–temperature chart lists the maximum allowable working pressure for a material and class at different temperatures. As temperature increases, allowable pressure decreases. When selecting a valve or flange, always check the rating at your actual operating temperature, not just the class or PN number.
6. Matching ratings across systems
PN16 is roughly close to ANSI 150 lb, and PN40 to ANSI 300 lb — but the bolt patterns and hole counts usually differ, so they are generally not interchangeable without adapters. Always specify the standard first (ANSI, DIN or JIS), then the size, then the exact rating and face type, before ordering.
Frequently Asked Questions
What is the difference between PN and pressure Class?
PN is a metric rating in bar (e.g. PN16); Pressure Class is an imperial rating (e.g. Class 150 lb). They are different systems, and the actual allowable pressure depends on temperature and material in both.
Is PN16 the same as Class 150?
PN16 is approximately close to Class 150 in pressure, but they are different systems with different dimensions, bolt patterns and pressure-temperature curves. They cannot be simply swapped.
What do JIS K ratings mean?
JIS flanges use K ratings (5K, 10K, 16K, 20K, 30K). 10K is the most common for general industrial service. JIS flanges have their own metric dimensions and bolt patterns.
How do I read a pressure-temperature rating chart?
The chart gives the maximum allowable pressure at different temperatures. As temperature rises, allowable pressure falls. Check the rating at your actual operating temperature.
Need to confirm a pressure rating before ordering?
Send us your standard, size, pressure rating and operating temperature — we will confirm the correct valve or flange for your system.
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