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What is SDR in Pipes?

Published in Pipe Standards 2 mins read

In the context of pipes, SDR stands for Standard Dimension Ratio.

SDR is a method used to rate a pipe's durability against internal pressure. According to Wikipedia, the standard dimension ratio describes the correlation between the pipe dimension and the thickness of the pipe wall. It essentially provides a standardized way to understand the structural characteristics of a pipe relative to its size.

Understanding the Standard Dimension Ratio (SDR)

The SDR value is calculated by dividing the pipe's outer diameter by its wall thickness:

SDR = Outer Diameter / Wall Thickness

This ratio is critical because it directly impacts how much pressure a pipe can safely handle.

How SDR Affects Pressure Rating

  • Higher SDR: A higher SDR value indicates a thinner wall relative to the pipe's diameter. Pipes with higher SDRs are generally used for lower pressure applications.
  • Lower SDR: A lower SDR value indicates a thicker wall relative to the pipe's diameter. Pipes with lower SDRs are more robust and suitable for higher pressure applications.

Think of it this way: for a pipe of a given diameter, a lower SDR number means more material in the wall, making it stronger against pressure.

Common SDR Nominations

The Wikipedia reference mentions several common SDR nominations. These standard values help in selecting the appropriate pipe for specific applications.

  • SDR11
  • SDR17
  • SDR26
  • SDR35

Each of these SDR values corresponds to a specific pressure rating for a given pipe material (like PVC, HDPE, etc.), assuming consistent manufacturing standards.

Example: Comparing SDR Values

Let's consider a hypothetical example comparing two pipes of the same material and outer diameter but different SDRs:

Feature Pipe A (SDR11) Pipe B (SDR26)
SDR Value 11 26
Wall Thickness Thicker Thinner
Pressure Rating Higher Lower
Flexibility Less Flexible More Flexible
Typical Use High-pressure applications Lower-pressure applications

As you can see, the SDR is a simple yet powerful indicator of a pipe's intended use and pressure capacity based on its physical dimensions.

Knowing the SDR is essential for engineers and installers to ensure the correct pipe is selected for a project, guaranteeing safety and performance. For more details, you can refer to the Standard dimension ratio - Wikipedia.