What Is the Difference Between PN16 and PN40 Pressure Classes?

25.08.2026

One of the most critical parameters in industrial piping systems and valve selection is pressure classification. The 'PN' (Pressure Nominal) designation, widely used under European standards and DIN norms, expresses in bar the maximum working pressure the equipment can withstand at a defined reference temperature. Two classes commonly compared in facilities are PN16 and PN40.

The Basic Meaning of PN16 and PN40

The PN designation generally indicates working pressure at a 20°C reference room temperature:

• PN16: Indicates the equipment can withstand a maximum working pressure of 16 bar at the reference temperature.
• PN40: Indicates the equipment is manufactured to withstand a maximum working pressure of 40 bar at the reference temperature.

However, as fluid temperature rises, the mechanical strength of metals decreases, so the allowable maximum working pressure gradually drops as well. This is why valve selection should consider not just pressure but also pressure-temperature (P-T) rating curves.

Mechanical Design, Wall Thickness, and Flange Dimensions

The core difference between PN16 and PN40 valves shows up in body construction, bolt circle, and material thickness:

• Body Wall Thickness: To withstand higher pressure, PN40 valves have thicker body walls and a reinforced seat structure compared to PN16 models.
• Flange Dimensions and Bolt Count: At the same nominal diameter (e.g., DN50 or DN100), PN16 and PN40 flanges can differ in bolt hole diameter, bolt circle diameter, or number of holes. As a result, a PN16 flange cannot be bolted directly to a PN40 flange.
• Weight and Strength: PN40 products contain more raw material and reinforced bolting, giving them higher resistance to mechanical stress.

Applications and Sector Preferences

Both pressure classes serve different parts of a facility depending on process requirements:

• PN16 Applications: General cooling water lines, low-pressure steam and condensate systems, food processing, paper mills, and standard auxiliary utility lines.
• PN40 Applications: High-pressure superheated steam lines, oil refineries, power plants, fuel terminals, LPG facilities, and high-pressure chemical feed lines.

The Importance of Choosing the Correct Pressure Class

Choosing too low a pressure class (using PN16 where PN40 is required) creates serious safety risks such as bursting and leaks. Conversely, specifying PN40 valves and flanges on a low-pressure line creates unnecessary upfront investment cost. Facility engineers should evaluate the line's maximum design pressure, test pressure, and temperature range in line with DIN standards.