Specifications

• PN: This stands for “Pressure Nominal” and refers to the nominal pressure rating of the pipe, which is the maximum pressure that the pipe can withstand under normal operating conditions. PN is typically expressed in units of bars or megapascals (MPa).
• SDR: This stands for “Standard Dimension Ratio” and refers to the ratio of the outside diameter of the pipe to its wall thickness. SDR is an important specification for polyethylene pipes because it affects the pipe’s pressure rating and its ability to withstand bending and other stresses. A higher SDR value indicates a thinner wall and a lower pressure rating.
• PE: This stands for “Polyethylene” and refers to the material used to make the pipe. Polyethylene is a strong, flexible, and durable material that is resistant to corrosion, chemicals, and UV radiation. It is commonly used for pipe applications because of its properties and ease of installation.

Explanation of Material / SDR Relationship

The pressure rating of pipe (PN) is determined by the diameter, wall thickness, and material types and
is expressed as: PN – Pressure pipe rating at 20°C (MPa x 10)

The basic polyethylene (PE) material types used for pipe production are PE63, PE80 and PE100, the number indicating long term strength.

The term SDR, Standard Dimension Ration, is introduced to describe the pipe, in combination with the material type.

SDR = Min. OD/Min. Wall Thickness

The higher the SDR, the thinner the pipe, and the lower the pressure rating. AS/NZS 4130 uses a standard SDR series, in combination with the three material types, to provide standard pipe pressure ratings as shown in the table. The field conditions under which poly pipe is welded have a considerable effect on the strength of the joint. Any contamination of the weld, whether it be oxidised polyethylene, water, dust, oils etc can ruin joints.

Material Properties

Strong and Durable, the pipes are manufactured from PE-100 polyethylene resin, pre-compounded with black or coloured pigment. Anti-oxidants used in the compounding process inhibit oxidisation while the use of carbon black at a concentration of 2.25 ± 0.25% by mass ensures ultra violet radiation is absorbed.

Thermal Properties

It is important to be aware of the thermal properties of polyethylene pipe, especially when used in conjunction with steel. This is because polyethylene, by nature of its material properties, expands and contracts with temperature change much more than steel.
At ambient levels, polyethylene will expand or contract in the range of 1.2 to 2.4 x 10-4 per degree C, which is approximately 20 times the rate of steel. If restrained by a steel support structure, expansion will be restricted and stress will occur over time. This will reduce the pipe’s useable life.
A safe level of stress can be maintained when the ambient temperature fluctuation is less than 40°C, due to polyethylene’s relatively low tensile deformation modulus. Over time, the rigidity of the polyethylene will relax, enabling it to accommodate higher thermal strains.
Conductivity of polyethylene also varies with temperature, almost linearly and typically 0.47W/m L at 0°C to 0.37W/m K at 70°C. The heat of polyethylene will vary with temperature from 1800 Joules/kg.K at 0°C to 2200J/kg.K at 60°C.
At temperatures above 25°C, it is essential to reiterate polyethylene pressure pipe systems.
See below table for guidance on the maximum operating pressure of PE100 pipes at temperature. Note, at constant temperatures greater than 40°C, the pipe’s 50 year design life may be reduced.

NOTE: Testing has shown that the potential minimal usable life of polyethylene
pipe meets standards for maximum pipe life set by ISO9080.