Introduction
In industrial piping systems, selecting the correct pressure rating for valves, flanges and piping components is essential for safe and reliable operation.
Two commonly encountered designations are PN16 and Class 150. Although both are used to classify pressure-rated components, they belong to different standards systems and cannot be treated as equivalent based on their names alone.
Understanding their differences helps engineering, procurement and project teams select components that meet the requirements of the application.
The Challenge
During equipment procurement, maintenance or replacement, teams may assume that PN16 and Class 150 components can be substituted for one another because their pressure capabilities may appear similar under certain conditions.
However, pressure ratings depend on factors such as material, operating temperature and the applicable standard. Components may also differ in flange dimensions, bolt patterns, facing and other design details.
Selecting an unsuitable component can lead to installation difficulties, non-compliance with design requirements and potential operational risks.
Understanding PN16 and Class 150
PN16 — Pressure Nominal 16
- Used within standards systems such as EN 1092-1 for steel flanges and related European-standard component specifications.
- PN16 is a nominal pressure designation; it does not guarantee a universal maximum allowable working pressure of 16 bar under every operating condition.
- Pressure capability depends on the component standard, material and temperature.
- Commonly encountered in water systems, utilities, HVAC and various industrial applications.
Class 150
- Used within ASME standards, including ASME B16.5 for pipe flanges and flanged fittings.
- Class 150 does not mean a pressure rating of 150 psi.
- The allowable pressure varies with material group and operating temperature.
- Commonly encountered in oil and gas, petrochemical, refinery and process-industry applications.
For example, a carbon-steel flange made to ASTM A105 under ASME B16.5 may have an allowable pressure of approximately 19.6 bar at 38°C (100°F), subject to the applicable edition and material-group pressure–temperature table. This value should not be assumed for every Class 150 component.
Comparison at a Glance
| Parameter | PN16 | Class 150 |
|---|---|---|
| Rating system | PN designation | ASME Class designation |
| Common standards | EN/DIN standards, depending on component | ASME standards, depending on component |
| Meaning | Nominal pressure designation | Pressure class, not a psi value |
| Allowable pressure | Depends on component standard, material and temperature | Depends on material group and temperature |
| Dimensions | Governed by the applicable component standard | Governed by the applicable ASME standard |
| Interchangeability | Must be verified | Must be verified |
Practical Application in CNG and CBG Projects
Consider a gas infrastructure project where a valve or flange needs to be replaced during installation or maintenance.
The existing piping design specifies a particular component standard and pressure class. A proposed replacement has a similar-looking rating but follows a different standard.
Before approving the replacement, the engineering team should:
- Confirm the original design specification and applicable standard.
- Verify operating and design pressure, temperature and service conditions.
- Check the material grade and its suitability for the gas and environment.
- Compare flange dimensions, facing, bolt-hole arrangement and other interface requirements.
- Confirm the component’s pressure–temperature rating and compatibility with the complete piping system.
- Obtain the required engineering approval before installation.
This process helps avoid relying on rating labels alone when selecting pressure-containing components.
Key Lessons
- Never compare ratings by number alone. PN16 and Class 150 follow different rating systems.
- Check pressure and temperature together. Allowable pressure can change with operating conditions.
- Verify dimensions and materials. A similar pressure designation does not guarantee physical compatibility.
- Follow the approved design. Any substitution should be checked against project specifications and applicable codes.
- Prioritise safety and compliance. Correct component selection supports system integrity and reliable operation.
Relevance to Urjika Consulting & Engineering Solutions Pvt. Ltd.
In CNG, CBG and natural gas infrastructure, valves, flanges, tubing, fittings and other pressure-containing components must be selected according to the system’s design requirements.
For technical sales, procurement, engineering and project-execution teams, understanding pressure-rating systems helps improve specification reviews, supplier coordination and component selection.
The correct choice must always be confirmed against the applicable standard, component documentation, operating conditions and approved project design.
Conclusion
PN16 and Class 150 are different pressure-rating designations, and neither should be treated as a direct substitute for the other. A safe selection requires verification of the applicable standard, material, pressure–temperature rating, dimensions and service conditions.
Understand the rating. Verify the standard. Select the right component.
