13.07.2026 11:46
PN10, PN16, PN25 and PN40 are nominal pressure classes for valves, flanges and pipeline equipment: PN10 means 10 bar, PN16 16 bar, PN25 25 bar and PN40 40 bar.
Definition of the PN Pressure Rating
PN refers to the nominal pressure rating used for valves, flanges, pipes, fittings and other pipeline components.
The letters PN originate from the term Pression Nominale, meaning Nominal Pressure. The PN value is a reference classification used to define the mechanical and dimensional characteristics of pressurised pipeline equipment.
For example:
PN10: Nominal pressure class of 10 bar
PN16: Nominal pressure class of 16 bar
PN25: Nominal pressure class of 25 bar
PN40: Nominal pressure class of 40 bar
However, these values do not necessarily mean that the valve can continuously operate at the stated pressure under all temperature conditions.
The actual allowable working pressure depends on:
Body material
Fluid temperature
Valve type
Sealing material
Connection standard
Pressure-temperature rating
Operating conditions
Therefore, the PN value should not be used alone as the final design pressure.
PN Pressure Class Comparison
Pressure class Nominal pressure Approximate MPa Approximate PSI General application level
PN10 10 bar 1.0 MPa 145 PSI Low and medium pressure
PN16 16 bar 1.6 MPa 232 PSI Medium pressure
PN25 25 bar 2.5 MPa 363 PSI Medium and high pressure
PN40 40 bar 4.0 MPa 580 PSI High pressure
These figures are approximate values used to explain the pressure classes. Final product selection must always be made according to the relevant product standard and the manufacturer’s pressure-temperature tables.
What Is PN10?
PN10 indicates that the pipeline component belongs to the nominal 10 bar pressure class.
PN10 valves and flanges are generally used in low- and medium-pressure systems.
Common applications
Drinking and utility water systems
Irrigation systems
Wastewater installations
Low-pressure HVAC systems
Water tanks
Pumping stations
Low-pressure industrial fluid lines
General characteristics of PN10
Nominal pressure level: 10 bar
Approximate pressure value: 1.0 MPa
Approximate pressure value: 145 PSI
Suitable for low- and medium-pressure systems
May have a lighter body and flange construction than higher PN classes
Pressure surges and water hammer must be considered
Even when the normal operating pressure is below 10 bar, a PN10 valve may not be suitable for every application. Temperature, fluid characteristics, pump pressure and temporary pressure surges must also be evaluated.
What Is PN16?
PN16 indicates that the equipment belongs to the nominal 16 bar pressure class.
PN16 is one of the most widely used pressure classes in water installations and general industrial systems. It provides higher mechanical strength than PN10.
Common applications
Drinking and utility water systems
Fire protection systems
Pump and booster lines
Heating and cooling systems
HVAC installations
Industrial water lines
Irrigation and infrastructure projects
Compressed-air systems
Suitable industrial fluid applications
General characteristics of PN16
Nominal pressure level: 16 bar
Approximate pressure value: 1.6 MPa
Approximate pressure value: 232 PSI
Suitable for medium-pressure systems
Offers greater mechanical strength than PN10
Widely used in fire systems, pump outlets and municipal water networks
Flange dimensions must be checked according to the applicable standard
In certain nominal diameters, PN10 and PN16 flange dimensions may be similar. However, this does not apply to every diameter, product or standard. Connection compatibility must not be determined by visual inspection alone.
What Is PN25?
PN25 indicates that the valve or pipeline component belongs to the nominal 25 bar pressure class.
PN25 products are used in systems where PN16 is not sufficient. Their bodies, covers, fasteners, flanges and sealing systems are designed for higher mechanical loads.
Common applications
High-pressure pumping lines
Pressure-boosting stations
Industrial process plants
High-rise building installations
Pressurised water systems
Energy and manufacturing plants
Boiler feedwater systems
Hot-water and thermal systems with suitable materials
General characteristics of PN25
Nominal pressure level: 25 bar
Approximate pressure value: 2.5 MPa
Approximate pressure value: 363 PSI
Suitable for medium- and high-pressure systems
May require a thicker and stronger body than PN16
Flange thickness, bolt dimensions and connection details are designed for higher pressure
Gaskets, stem seals and sealing components must also be suitable for PN25 conditions
Using a PN25 valve alone does not make the entire installation suitable for 25 bar. Pipes, flanges, gaskets, expansion joints, fittings and all other components must comply with the system design pressure.
What Is PN40?
PN40 indicates that the pipeline component belongs to the nominal 40 bar pressure class.
PN40 valves are generally used in high-pressure industrial applications. Body strength, material quality, flange design, fasteners and sealing performance are particularly important in this class.
Common applications
High-pressure industrial process lines
Power generation plants
Steam and hot-water systems
Petrochemical plants
Compressed-air and gas lines
Boiler and auxiliary systems
High-pressure pumping stations
Chemical and process industries
General characteristics of PN40
Nominal pressure level: 40 bar
Approximate pressure value: 4.0 MPa
Approximate pressure value: 580 PSI
Designed for high-pressure applications
Requires stronger body and flange construction
Bolts and connection components are designed for heavy-duty conditions
Allowable working pressure may decrease as temperature increases
Material certificates and pressure-test records are especially important
For steam, thermal oil or high-temperature fluids, PN40 must not be interpreted as “40 bar under all conditions.” The manufacturer’s pressure-temperature rating must always be checked.
Is the PN Value the Maximum Working Pressure?
The PN value helps identify the nominal pressure class. However, it must not always be considered the exact maximum working pressure.
The actual allowable working pressure depends on the following factors:
1. Body material
Cast iron, ductile iron, carbon steel, stainless steel and bronze have different pressure and temperature limits.
2. Operating temperature
As temperature increases, the allowable working pressure of many materials decreases.
3. Fluid type
Water, steam, natural gas, compressed air, oil and chemicals require different materials and sealing systems.
4. Gasket and elastomer material
EPDM, NBR, PTFE, FKM and metallic sealing materials have different temperature and chemical-resistance properties.
5. Valve standard
Valve design, manufacturing, testing and connection requirements must comply with the relevant EN, ISO, API or ASME standard.
6. Dynamic pressure
Pump start-up, rapid valve closure and water hammer can temporarily increase the system pressure above the normal operating level.
Difference Between Working Pressure, Design Pressure and Test Pressure
Working pressure
The actual pressure to which the system is exposed during normal operation.
For example, a water line may normally operate at 8 bar.
Design pressure
The pressure used for the safe engineering design of the system. It may be higher than the normal operating pressure and may include temperature effects, pressure surges and a safety margin.
Test pressure
The pressure applied during production or commissioning to verify body strength and sealing performance.
A product’s ability to withstand a certain test pressure does not mean that it may continuously operate at that pressure.
Difference Between DN and PN
DN and PN must not be confused.
DN: Indicates the nominal diameter.
PN: Indicates the nominal pressure class.
For example:
DN100 PN16 gate valve
means:
DN100: The nominal connection diameter is 100 mm.
PN16: The valve belongs to the nominal 16 bar pressure class.
Even when components have the same DN and PN values, the flange standard, number of bolt holes, bolt-hole diameter, sealing face and connection type must also be checked.
Can PN16 Be Used Instead of PN10?
A PN16 valve may generally be used instead of PN10 when the operating conditions and connection dimensions are suitable.
The following points must be checked:
Flange outside diameter
Number of bolt holes
Bolt-hole diameter
Flange thickness
Sealing face
Gasket dimensions
Pipeline standard
Valve face-to-face dimension
Fluid compatibility
Temperature suitability
A higher PN class is not automatically the best choice. An unnecessarily high pressure rating may increase product weight, installation requirements and overall project cost.
How Should the Valve Pressure Class Be Selected?
The correct PN class must not be selected solely according to the normal operating pressure.
The following information should be evaluated together:
Maximum working pressure
Design pressure
Maximum and minimum temperature
Fluid type
Chemical characteristics of the fluid
Temporary pressure surges
Water-hammer risk
Pump discharge pressure
Pipeline pressure class
Flange and connection standard
Body material
Gasket and elastomer material
Applicable valve standard
Project safety factor
Example selection approach
If a system normally operates at 9 bar, selecting PN10 based only on this value may be unsafe. If pump shut-off pressure, water hammer or temperature effects can increase the pressure above 10 bar, PN16 or a higher class may be required.
Similarly, if a system operates at 15 bar, PN16 may represent a borderline selection. Depending on the design conditions and required safety margin, PN25 should be evaluated.
Are PN and ASME Class the Same?
PN and ASME Class are different classification systems.
European and ISO-based systems commonly use:
PN10
PN16
PN25
PN40
ASME-based systems commonly use:
Class 150
Class 300
Class 600
Class 900
The ASME Class number does not directly indicate pressure in PSI. Allowable working pressure depends on the material group and operating temperature.
Therefore, PN16 and Class 150 must not be considered unconditional equivalents.
General Evaluation
PN10, PN16, PN25 and PN40 are basic technical classifications used to define the pressure ratings of valves, flanges, pipes and fittings.
PN10: Low- and medium-pressure systems
PN16: General installations and medium-pressure industrial systems
PN25: Medium- and high-pressure applications
PN40: High-pressure and heavy-duty applications
Correct pressure-class selection is essential for system safety, sealing performance, service life and operational continuity.
In addition to the PN value, operating temperature, body material, fluid type, connection standard and manufacturer’s pressure-temperature tables must always be considered.
VANEX VALVE Technical Approach
VANEX VALVE products are evaluated according to the project requirements, with different pressure classes, connection dimensions and material options.
For correct valve selection, nominal diameter, pressure class, fluid type, operating temperature and application conditions must be assessed together.
VANEX VALVE – The Strong Brand of Reliable Flow
