Industrial valves used in process plants must operate safely under varying pressure and temperature conditions. The ability of a valve to withstand internal pressure depends on its material strength and the operating temperature of the system.
Pressureβtemperature ratings define the maximum allowable pressure that a valve body can safely handle at a specific temperature. These ratings are standardized by international engineering codes to ensure safe and reliable operation of piping systems.
The most widely used pressureβtemperature rating standards for industrial valves are defined in American Society of Mechanical Engineers ASME B16.34.
These standards are commonly used in industries such as:
Valve pressure classes represent standardized pressure ratings that valves can withstand under specified temperature conditions.
The most common pressure classes used in industrial valves include:
Each class corresponds to a specific pressure rating depending on temperature and valve material.
| Pressure Class | Approx Maximum Pressure |
|---|---|
| Class 150 | ~19 bar |
| Class 300 | ~51 bar |
| Class 600 | ~102 bar |
| Class 900 | ~153 bar |
| Class 1500 | ~255 bar |
These values vary depending on the valve body material and operating temperature.
As temperature increases, the allowable pressure rating of a valve decreases. This happens because metals lose mechanical strength at elevated temperatures.
For example:
A valve rated for 19 bar at 38Β°C may only be able to withstand 10β12 bar at 400Β°C.
Therefore, engineers must always verify both pressure and temperature simultaneously when selecting industrial valves.
| Temperature | Allowable Pressure (Class 150) |
|---|---|
| 38Β°C | 19 bar |
| 100Β°C | 17 bar |
| 200Β°C | 15 bar |
| 300Β°C | 13 bar |
| 400Β°C | 11 bar |
These limits are defined according to ASME B16.34 pressure-temperature tables.
| Temperature | Allowable Pressure (Class 150) |
|---|---|
| 38Β°C | 20 bar |
| 100Β°C | 19 bar |
| 200Β°C | 17 bar |
| 300Β°C | 15 bar |
| 400Β°C | 14 bar |
Stainless steel maintains better strength at higher temperatures compared to cast iron.
Mechanical engineers must evaluate several parameters before selecting valve pressure class.
A safety margin is always applied above normal operating pressure to ensure reliable operation.
Typical pressure class: Class 150
Used for:
Typical pressure classes:
Used for:
Typical pressure classes:
Used for:
Typical pressure classes:
Used for:
Valve size and pressure class are independent parameters.
For example:
DN50 valve may be Class 150
DN50 valve may also be Class 600
The pressure class is determined by system pressure requirements, not by valve size.
Proper pressureβtemperature selection ensures:
Incorrect pressure class selection can result in:
Therefore engineers must always verify pressureβtemperature ratings during the design stage.
Marck & Care Engineers Limited manufactures industrial valves designed according to international pressureβtemperature standards.
Our valves are engineered to comply with:
This ensures reliable performance in demanding industrial environments including water treatment plants, chemical plants, steel mills, and cement manufacturing facilities.