In valve selection, pressure rating is one of the most critical parameters. PN10, PN16, and Class 150 are the three most commonly used pressure ratings in engineering, yet in practice, their meanings and differences are not always fully understood.
A clear understanding of these pressure ratings and how they differ is essential to ensure proper valve selection, system compatibility, and long-term reliable operation.
What Is a Valve Pressure Rating?
A valve pressure rating refers to the maximum allowable working pressure a valve can withstand at a specified temperature. It is determined by factors such as material properties, design standards, and operating temperature.
It is important to note that a pressure rating is not a fixed value, but an engineering parameter that varies with temperature.
PN Ratings Explained (PN10 / PN16)
PN stands for Nominal Pressure and is commonly used in European (DIN/EN) and Chinese (GB) standards, with the unit expressed in bar.
- PN10 → 10 bar (1.0 MPa)
- PN16 → 16 bar (1.6 MPa)
PN ratings are defined at ambient temperature (around 20°C), making them straightforward and easy to understand. They are widely used in water supply systems, HVAC applications, and general industrial piping.
It is important to note that as temperature increases, the allowable working pressure of the valve decreases.
ANSI Class Explained (Class 150)
Class refers to the pressure class used in American standards, based on the ASME / ANSI system, with pressure typically expressed in psi.
Unlike PN, Class is not a fixed pressure value. It is determined based on a pressure–temperature relationship.
For example, for Class 150:
At approximately 38°C (100°F), the maximum allowable working pressure is about 285–290 psi (around 19–20 bar)
It is important to emphasize that Class 150 does not mean 150 psi, nor can it be directly converted to a specific PN value.
PN vs Class: Key Differences
Comparison Criteria | PN (DIN / EN / GB) | Class (ASME / ANSI) |
Pressure System | Metric (bar) | Imperial (psi) |
Pressure Definition | Fixed reference value | Varies with temperature |
Standard System | EN / DIN / GB | ASME / ANSI |
Flange Standard | EN 1092-1 / GB/T 9119 | ASME B16.5 |
Units | Millimeters (mm) | Inches (inch) |
Typical Applications | Water treatment, HVAC, municipal systems | Oil & gas, power generation, energy industries |
PN10 / PN16 vs Class 150: Can They Be Interchanged?
At ambient temperature, Class 150 typically has a higher pressure capacity than PN16 (approximately 19–20 bar vs. 16 bar).
However, it is important to understand that PN and Class belong to different standard systems and cannot be considered equivalent or used interchangeably.
The differences go beyond pressure values and also include:
- Flange dimensions and bolt hole patterns
- Bolt specifications
- Design and manufacturing standards
How Material Affects Valve Pressure Rating
Pressure rating is not only determined by standards, but is also closely related to the valve material.
- Cast iron: commonly used for PN10 / PN16, suitable for low-pressure systems
- Ductile iron: suitable for PN16 and above, offering a good balance of strength and toughness
- Carbon steel (WCB): commonly used for Class 150 and higher ratings
- Stainless steel: suitable for high-pressure or corrosive applications
It is important to understand that even under the same pressure rating, different materials have different pressure–temperature limits. In standards such as ASME B16.34 and EN 12516, each material grade has its own rating table.
When selecting a valve, the allowable pressure must be verified based on the actual operating temperature and media conditions, using the specific material rating table, rather than relying solely on the nominal pressure rating.
How to Choose the Right Pressure Rating
1. Based on System Pressure
- PN10: Suitable for low-pressure systems, such as water supply, drainage, and irrigation
- PN16: Suitable for general water treatment, HVAC systems, and standard industrial pipelines
- Class 150: Commonly used in petrochemical, natural gas, and ASME-standard projects
2. Based on Flange Standards (Most Critical)
In practical engineering, the flange standard usually determines the valve selection:
- DIN / GB pipeline standards → choose PN series
- ASME / ANSI pipeline standards → choose Class series
Mixing PN and ANSI flanges is not recommended, as it may lead to installation issues and sealing failure.
3. Based on Temperature Conditions
As temperature increases, the allowable working pressure of a valve decreases.
At higher temperatures (such as 180–200°C):
- Both PN16 and Class 150 will have reduced pressure capacity
- Class 150 typically retains a slightly higher allowable pressure
However, it is important to note:
The actual allowable pressure must be verified based on the specific material (such as WCB or stainless steel) and the applicable standard (EN / ASME) by referring to pressure–temperature rating tables.
PN and ANSI Class are two different pressure rating systems and cannot be directly equated or used interchangeably. Proper selection must consider pipeline standards, working pressure, temperature conditions, and material characteristics together.
TFW Valve specializes in industrial valve manufacturing, offering butterfly valves, gate valves, and check valves in compliance with EN, DIN, and ASME standards. We provide professional selection support based on specific operating conditions, helping projects achieve the best balance between safety and cost.
If you have project details available, feel free to contact us for a quick quotation and technical support.
FAQ
No. PN16 is a fixed reference pressure (16 bar), while Class 150 varies with temperature and is typically higher at ambient conditions.
No. Their bolt patterns and dimensions are different, so they are not directly compatible.
Because the project standard and flange system determine the valve type, not just the pressure level.
Yes. As temperature increases, the allowable working pressure of the valve decreases.
