September 12, 2024

The SDR pipe is the "Standard Dimensional Ratio" and refers to the geometry of the pipe. SDR is defined as the ratio of the nominal outside diameter to the nominal wall thickness. The SDR value of Polyethylene Pipe is the main factor in determining the resistance of the pipe against the forces during installation and work pressure.

SDR = D/S

SDR (Standard Dimension Ratio) is an important parameter of polyethylene pipes, which is used to indicate the ratio of the wall thickness to the outer diameter of the pipe. In HDPE pipes, the larger the SDR value, the smaller the wall thickness of the pipe; conversely, the smaller the SDR value, the larger the wall thickness of the pipe. This parameter is crucial to ensure the structural strength, durability and applicability of the pipeline. For example, SDR11 means that the outer diameter divided by the wall thickness is equal to 11, while SDR17.6 means that the outer diameter divided by the wall thickness is equal to 17.6, which directly reflects the structural design characteristics of the pipeline.

On **HDPE Natural Gas Pipes**, SDR is usually marked together with the nominal outer diameter (DN), such as DN110*SDR11, which means that the nominal outer diameter is 110mm and the SDR value is 11. This marking method makes it easy for users to select the appropriate pipe specifications according to their needs. The selection of SDR value depends on the specific application scenario, such as pressure requirements, working environment, etc., to ensure the safety and reliability of the pipeline.

SDR is also related to the price of the pipe. Under the same outer diameter DN, the larger the SDR value, the smaller the wall thickness of the pipe, and the lower the price; while the smaller the SDR value, the thicker the wall thickness of the pipe, and the higher the price. This is because the increase in wall thickness will directly affect the amount of material used and the manufacturing cost. Therefore, SDR is not only a technical parameter, but also affects the cost and market positioning of HDPE pipes to a certain extent.

Definition of SDR with an example

For example, SDR11 means that the outer diameter of the PE pipe is 11 times of the wall thickness. As a result, the higher the SDR, the

SDR

lower the pipe pressure will be. The details are discussed below.

For PE pipes, a dimensionless number is also defined, which is the ratio of the pipe diameter to the thickness of the pipe, which is referred to as the SDR. For example, for a 110 mm PE pipe with a pressure of 4 times made of PE80 materials, weighing 1.17 kg, it is SDR33, and for an PE pipe with a diameter of 110 mm made of PE80, weighting 1.77 kg, it is SDR21. Therefore, for a 110 mm diameter pipe, SDR decreases as the thickness increases due to the constant diameter (leading to increased pressure). SDRs range from 5 to 51, and the smaller the SDR is, the greater the pipe thickness and the lower pipe diameter will be.

What SDR means

Standard Dimension Ratio or SDR describes a pipe's geometry, it is simply the ratio of outer diameter of the pipe to its wall thickness. As an example, a pipe with SDR11 has an outer diameter that is 11 times its wall thickness. Therefore, if the outer diameter or OD of the pressure pipe is known, then the wall thickness can be calculated for any given SDR number.

The Higher the SDR number the thinner the pipe wall is in relation to its Outer Diameter.

The Lower the SDR number the thicker the pipe wall will be in relation to its Outer Diameter.