For pipeline systems across Europe and many parts of Asia, the selection of industrial flanges is governed by the German Institute for Standardization (Deutsches Institut für Normung), known as the DIN flange standard. Unlike the American system (ASME), the DIN standard utilizes the Pressure Nominal (PN) rating system to define the maximum operational pressure of a fitting.
Understanding the difference between ratings like PN10, PN16, and the higher PN40 is fundamental to correctly designing a robust and compliant pipeline. This guide explores the structure of DIN standards and provides clarity on the selection process based on PN ratings.
What is the DIN Flange Standard?
The DIN standard provides comprehensive specifications for materials, dimensions, testing, and marking of various flange types. It dictates precise measurements for bolt circles, bore sizes, and flange diameters, ensuring interchangeability and safety within systems designed to European specifications.
The DIN system is often used to specify carbon steel flange PN10 and carbon steel flange PN16, as these ratings are common in general-purpose and utility systems.
Decoding the Pressure Nominal (PN) Rating
The PN rating system is the cornerstone of the DIN standard. PN is an abbreviation for Pressure Nominal or Nominal Pressure, and the number that follows (e.g., PN10) indicates the pressure rating in bar (at room temperature, typically $20^\circ\text{C}$).
It is critical to note that the PN rating is not the absolute maximum burst pressure but rather the standardized maximum allowable working pressure. The most common PN ratings used across industrial applications range from PN6 up to PN40, with specialized applications going higher.
| PN Rating | Nominal Working Pressure (Bar) | Typical Application Environments |
| PN10 | 10 Bar | Low-pressure applications, large diameter utility lines, water treatment. |
| PN16 | 16 Bar | General industrial piping, non-critical process lines, common for carbon steel flange PN16. |
| PN25 | 25 Bar | Medium-pressure applications, general process lines, steam. |
| PN40 | 40 Bar | High-pressure industrial systems, elevated temperatures, chemical processes. |
Selecting the Right PN Flange: PN10 vs. PN16
For most industrial projects, the choice often narrows down to PN10 or PN16.
Carbon Steel Flange PN10
A carbon steel flange PN10 is frequently chosen for large-volume, low-pressure water and gas transport. The lower pressure rating allows for a thinner flange structure compared to higher PN ratings, often leading to material and cost savings. If your maximum system pressure is below 10 bar and the temperature is mild, PN10 is the economical and appropriate choice.
Carbon Steel Flange PN16
The carbon steel flange PN16 is arguably the most common DIN flange rating in European industry. It provides an essential safety margin for general systems where pressures might occasionally spike above 10 bar. Given its versatility, PN16 flanges are often considered the default for many non-critical pipelines, offering a robust balance of cost and operational reliability.
The Role of Temperature in PN Selection
While PN ratings are standardized at room temperature ($20^\circ\text{C}$), the maximum safe working pressure decreases as the operating temperature rises. Engineers must refer to standardized pressure-temperature $(P/T)$ tables specific to the flange material (e.g., Carbon Steel, Stainless Steel) and the DIN standard. A PN40 flange used at $300^\circ\text{C}$ will have a significantly lower maximum allowable working pressure than 40 bar.
Deepen Your Flange Knowledge
Understanding DIN standards is just one part of correct flange selection. To fully master the subject, explore our related technical guides:
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Global Standards Comparison: Compare the DIN system with American and Japanese standards:
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Material Selection: See how DIN flange material choice impacts its pressure-temperature performance:
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Core Flange Resource: Return to our complete overview of all flange types and pipe fittings:
Need assistance in converting an existing system from an ASME flange to a DIN flange? Contact us for a Technical Inquiry.
