How to Choose the Right Butterfly Valve Pressure Rating

What Is a Butterfly Valve Pressure Rating?

1. What Is Butterfly Valve Pressure Rating?

Butterfly valve pressure rating refers to the maximum allowable working pressure a valve can safely handle under specific conditions such as temperature and material grade.

The most common rating systems are:

PN (Pressure Nominal) – used in EN/DIN standards
Class Rating (Class 150 / 300 / 600) – used in ASME/ANSI standards

These two systems are not directly interchangeable, even if their numbers look similar.

What Is PN Rating?

PN rating (Pressure Nominal) is a standard used in EN/DIN piping systems to indicate the maximum allowable working pressure of a valve at 20°C (in bar).

For example:

• PN10 means the valve is designed for a maximum pressure of 10 bar
• PN16 means 16 bar
• PN25 means 25 bar

However, PN rating is defined under standard temperature conditions (20°C), which means the actual allowable pressure may decrease when the system operates at higher temperatures.

PN ratings are commonly used in water supply, HVAC systems, and general industrial piping applications, especially in European-standard projects.

What Is Class Rating?

Class rating (such as Class 150, Class 300, Class 600) is a pressure rating standard defined by ASME/ANSI and widely used in North American and international industrial piping systems.

Unlike PN rating, Class rating is not a fixed pressure value. It is based on a pressure–temperature relationship, meaning the allowable pressure of a valve changes depending on operating temperature and material grade.

For example, Class 150 does not always equal 150 psi under all conditions. As temperature increases, the maximum allowable working pressure will decrease according to ASME pressure–temperature tables.

Common Butterfly Valve Pressure Ratings

For most water treatment, HVAC, and industrial applications, the following are the most commonly used butterfly valve pressure ratings:

Among these ratings, PN16 and Class 150 are the most widely used butterfly valve pressure ratings worldwide.

What Is the Difference Between PN10 and PN16 Butterfly Valves?

The main difference between PN10 and PN16 butterfly valves is their pressure rating.

For building water systems and HVAC applications, PN10 and PN16 are the two most commonly used options.

• PN10 has a nominal pressure rating of 10 bar and is typically used in lower-pressure systems.
• PN16, on the other hand, is rated for 16 bar and provides a greater safety margin.

Based on practical project experience, more and more engineers and contractors are choosing PN16 as the standard specification. The reason is simple: the cost difference between PN10 and PN16 is usually relatively small, while PN16 offers higher pressure capacity and a wider range of applications.

As a result, PN16 has become the preferred choice for many systems, including:

• Chilled water systems
• Cooling tower systems
• Water treatment systems
• Municipal water supply systems

If the project budget allows, PN16 is often considered the safer and more versatile option.

What Is the Pressure Rating of PN16 vs Class 150?

PN16 and Class 150 are often compared because their pressure ratings appear relatively close. However, they belong to two different pressure rating systems and are not the same.

• PN16: Part of the EN, DIN, and ISO pressure rating system, PN16 indicates a nominal pressure rating of approximately 16 bar under normal temperature conditions.
• Class 150: Class 150 is not a fixed pressure value. It belongs to the ANSI and ASME pressure–temperature rating system, where the allowable working pressure varies depending on the valve material and operating temperature.

For typical carbon steel valves at ambient temperature, the allowable working pressure of Class 150 is approximately:

285 psi (19.6 bar)

Therefore, in terms of pressure-handling capability at normal temperature, Class 150 generally provides a slightly higher pressure rating than PN16.

Can PN16 Replace Class 150?

Not necessarily.

Although some dimensions may appear similar, PN16 flanges and Class 150 flanges are designed according to different standards and have several important differences, including:

• Bolt hole dimensions
• Number of bolt holes
• Flange thickness
• Facing dimensions
• Flange outside diameter (OD)

Because of these differences, a PN16 butterfly valve cannot always be directly installed in a Class 150 piping system. In many cases, flange compatibility must be verified, or a transition flange may be required.

What Is the Difference Between Class 150 and Class 300?

The main difference between Class 150 and Class 300 is their pressure-handling capability.

For typical carbon steel valves at ambient temperature:

• Class 150 has an allowable working pressure of approximately 285 psi
• Class 300 has an allowable working pressure of approximately 740 psi

This means a Class 300 butterfly valve can withstand significantly higher system pressures and is generally better suited for high-pressure industrial applications.

However, a higher pressure rating does not always mean a better choice. Compared with Class 150 valves, Class 300 butterfly valves are typically:

• Heavier
• Larger
• More expensive
• More difficult to install

As a result, using a Class 300 butterfly valve in a low- or medium-pressure system can often lead to unnecessary project costs without providing any practical benefit.

How to Choose the Right Butterfly Valve Pressure Rating

When determining the required pressure rating, factors such as system design pressure, operating temperature, pressure fluctuations, and the applicable piping standard (EN/DIN or ANSI/ASME) should all be taken into consideration.

The table below provides general recommendations for common applications:

In many water treatment, chilled water, cooling tower, and municipal water projects, PN16 has become the most commonly specified pressure rating. For ANSI piping systems, Class 150 is typically the standard choice, while Class 300 is generally reserved for higher-pressure industrial applications.

Conclusion

Selecting the right butterfly valve pressure rating is essential for ensuring safe and reliable system operation. For most HVAC, chilled water, cooling tower, water treatment, and municipal water applications, PN16 is capable of meeting the requirements of the vast majority of systems. Class 150 and Class 300 are more commonly used in ANSI piping systems and higher-pressure industrial applications.

As a professional industrial valve manufacturer, Union Valve offers butterfly valves in PN10, PN16, Class 150, and Class 300 pressure ratings for HVAC systems, water treatment plants, cooling systems, municipal water networks, and industrial piping applications. Choosing the appropriate pressure rating based on actual operating conditions can help improve system reliability while keeping overall project costs under control.You can contact us at any time.

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