In industrial fluid control systems, valves play a critical role in regulating, isolating, and directing flow. However, choosing the right valve isn’t just about type and size—pressure-temperature ratings are equally essential. These ratings define the safe working limits of a valve under varying temperatures and pressures, ensuring reliability, safety, and compliance with standards.

This guide covers pressure-temperature ratings for ball valves, gate valves, and globe valves—three of the most commonly used types in industrial applications.

🔧 What Are Pressure-Temperature Ratings?

A pressure-temperature rating defines the maximum allowable pressure a valve can handle at a given temperature. As temperature increases, the strength of the valve material typically decreases, which in turn reduces the pressure the valve can withstand.

These ratings are governed by international standards such as:

• ASME B16.34 – Valves: Flanged, Threaded, and Welding End

• API 6D – Pipeline Valves

• ISO 5208 – Industrial Valves Pressure Testing

• EN 12516 – Valves for Pressure Applications

Each valve type and material combination will have its own pressure-temperature chart, usually provided in the manufacturer’s technical datasheets.

⚙️ 1. Ball Valve Pressure-Temperature Ratings

🟠 Overview

Ball valves are commonly used for quick shut-off and low to high pressure applications. Their design includes a rotating ball with a hole that aligns with the flow when open and blocks it when closed.

🔍 Key Factors Affecting Ratings

• Body material (e.g., carbon steel, stainless steel, brass)

• Seat material (e.g., PTFE, PEEK, TFM, Metal)

• Design type (floating ball vs trunnion-mounted)

📊 Typical Ratings

• Carbon Steel Ball Valve Class 300:

  • 740 psi @ 100°F

  • 675 psi @ 200°F

  • 500 psi @ 400°F

• Stainless Steel Ball Valve with PTFE Seat:

  • 275 psi @ 100°F

  • 150 psi @ 300°F

  • 75 psi @ 450°F

💡 Note: The seat material usually limits the rating more than the valve body. For example, PTFE seats degrade above 450°F, whereas metal-seated valves can go beyond 1000°F.

🛠️ 2. Gate Valve Pressure-Temperature Ratings

🟤 Overview

Gate valves are designed for on/off service in full open or full closed positions. They are not recommended for throttling applications due to erosion risks.

🔍 Key Influences

• Wedge design (solid, flexible, or split)

• Bonnet construction (bolted, pressure-sealed)

• End connections (flanged, welded, threaded)

📊 Typical Ratings

• Carbon Steel Gate Valve Class 600:

  • 1480 psi @ 100°F

  • 1265 psi @ 300°F

  • 1025 psi @ 600°F

• Stainless Steel Gate Valve Class 1500:

  • 3705 psi @ 100°F

  • 3000 psi @ 500°F

  • 2325 psi @ 800°F

Gate valves are ideal for high-pressure systems but must be selected with accurate knowledge of thermal stress limits.

🌐 3. Globe Valve Pressure-Temperature Ratings

🔵 Overview

Globe valves are used for precise flow regulation. Their throttling ability makes them suitable for applications requiring fine control, but they experience more pressure drop due to flow path changes.

🔍 Key Factors

• Disc and seat design (plug, composition, needle)

• Flow direction (always follow arrow marking to reduce pressure shock)

• Material compatibility with media and temperature

📊 Typical Ratings

• Cast Iron Globe Valve Class 125:

  • 200 psi @ 100°F

  • 150 psi @ 250°F

• Carbon Steel Globe Valve Class 600:

  • 1480 psi @ 100°F

  • 1200 psi @ 500°F

  • 925 psi @ 800°F

Because of their versatility in flow modulation, globe valves are popular in power plants, refineries, and HVAC systems.

📈 How Temperature Affects Pressure Ratings

Temperature significantly impacts pressure ratings. Most materials lose tensile strength as temperature rises. For instance:

• Carbon steel loses ~25% strength from 100°F to 800°F

• PTFE seats degrade above 450°F

• Stainless steel retains better strength at high temperatures

Always consult the pressure-temperature curve provided by the valve manufacturer. These charts are crucial when sizing valves for steam systems, thermal oil applications, or cryogenic services.

⚖️ Comparative Table: Ball vs Gate vs Globe Valves

🧠 Best Practices for Selecting Pressure-Temperature Ratings

1. Understand your system conditions: Know your maximum operating pressure and temperature.

2. Review material compatibility: Choose valves built from materials that withstand both pressure and temperature extremes.

3. Check seat and seal limits: For ball valves, seat materials like PTFE or elastomers have lower temp limits than metal seats.

4. Use safety margins: Always choose a valve with a pressure rating above your operating pressure, especially in dynamic systems.

5. Refer to standards: Rely on ASME, API, and ISO charts for pressure-temperature thresholds by material class.

🧯 Consequences of Incorrect Pressure-Temperature Ratings

• Seal failure

• Leakage or blowouts

• Valve distortion

• Non-compliance with regulations

• Shutdowns and costly downtime

Never assume a valve rated for high pressure can handle high temperature—or vice versa. The combination of both defines the real safe operating limit.

Conclusion

Pressure-temperature ratings are essential specifications that ensure valves perform safely and efficiently under various industrial conditions. Whether you're using ball valves for shut-off, gate valves for isolation, or globe valves for flow control, understanding these ratings helps you:

• Avoid system failures

• Improve safety

• Extend valve life

• Maintain regulatory compliance

Always consult with your valve supplier or an engineer to verify the correct valve class for your application. Smart valve selection starts with knowing your system—and respecting the limits of your equipment.