Industrial Valve Pressure Ratings Explained: A Complete Guide

Industrial valves are designed to safely contain and control fluids under a wide range of pressures and temperatures.
Understanding valve pressure ratings is essential for selecting the right product, ensuring plant safety, and meeting regulatory standards.
This guide covers key pressure rating systems, selection tips, and common questions.

What Are Valve Pressure Ratings?

A pressure rating defines the maximum allowable working pressure (MAWP) a valve can safely withstand at a specified temperature.
Exceeding this limit risks leakage, damage, or catastrophic failure.

Pressure ratings are expressed in different systems depending on region and standard:

• Class (ANSI/ASME) – e.g., Class 150, 300, 600, 900, 1500, 2500

• PN (Pressure Nominal, DIN/EN) – e.g., PN10, PN16, PN40

• JIS – Japanese standard, e.g., 10K, 20K

• API Pressure Classes – used for specific applications such as oil & gas pipeline valves.

Common Pressure Rating Systems

1. ASME/ANSI Class

• Widely used in North America and internationally.

• Ratings range from Class 150 to Class 2500.

• Pressure capability depends on material and temperature.

  • For example, a Class 150 carbon steel valve is rated around 285 psi (20 bar) at 100 °F, but this decreases at higher temperatures.

2. PN (EN 1092/DIN)

• Common in Europe and many global markets.

• Expressed in bar (e.g., PN16 ≈ 16 bar at 20 °C).

• PN40 valves handle roughly 40 bar at 20 °C.

3. API 6D / 6A

• API 6D covers pipeline valves with ANSI Classes 150–2500.

• API 6A (wellhead equipment) includes PSL (Product Specification Levels) and higher pressure ratings up to 20,000 psi.

4. JIS (Japanese Industrial Standard)

• Uses “K” to denote kgf/cm².

• Example: 10K ≈ 16 bar, similar to PN16.

Factors Affecting Pressure Ratings

1. Material of Construction

   • Carbon steel, stainless steel, alloy steels each have different temperature/pressure limits.

2. Operating Temperature

   • Higher temperatures reduce pressure capacity.

3. Valve Type

   • Ball, gate, globe, and butterfly valves may have different seat and body pressure limits.

4. End Connections

   • Flanged, threaded, or welded ends can influence allowable pressure.

Selection Guidelines

• Match System Standard: Choose ANSI, PN, or JIS based on project specification.

• Check Design Temperature: Verify the pressure rating at the operating temperature, not just ambient.

• Consider Pressure Surges: Allow a safety margin for water hammer or transient spikes.

• Account for Corrosion Allowance: Especially for aggressive fluids or sour gas service.

Conversion Quick Reference

*Approximate only—verify with ASME B16.5 tables.

Maintenance and Testing

• Hydrostatic Testing: Confirms body and seat integrity at 1.5× rated pressure.

• Periodic Inspection: Monitor gaskets, bolting, and body for erosion or pitting.

• Pressure Relief Systems: Always include safety valves and pressure relief devices.

FAQ

Q1: Can I use a Class 150 valve at 400 °F?
Check ASME B16.34 tables—its allowable pressure drops to around 185 psi (12.8 bar).

Q2: Are PN ratings interchangeable with ANSI Classes?
Not directly. Use conversion tables and always verify temperature conditions.

Q3: Why do stainless steel valves often have higher ratings at high temperature?
Stainless retains strength better than carbon steel at elevated temperatures.