PVC pressure pipes are manufactured from PVC resin compounded with stabilisers, lubricants and pigments. They do not contain any plasticisers and hence are known as unplasticised PVC or PVC-U.
PVC-U pipes have been used for pressure applications in Australia since the 1960s, but have a much longer service history elsewhere in the world. Over this time, industry has recognised the many benefits of PVC for pressure pipes: material stability, corrosion resistance, high strength to weight ratio, ease of handling and installation and excellent flow characteristics.
Further developments in PVC pressure pipe technology has led to the introduction of Oriented PVC (PVC-O) and Modified PVC pressure pipes (PVC-M).
PVC is the most commonly used pipe for water reticulation by Australian water agencies. It is used extensively in irrigation and industrial applications.
The size range for PVC pressure pipe in Australia typically extends to 600mm (DN600)
Polyethylene (PE) pipe manufacture commenced in Australia in the 1950′s with small diameter pipes used for rural, irrigation and industrial applications. Since then, PE use and the number of applications for PE pipes has grown enormously particularly in the areas of gas reticulation, coal seam gas, mining and trenchless applications.
The flexibility of PE pipe allows cost savings in installation. Trenchless technology can avoid the need for open trenches and reduce the disturbance to the public and environment by pulling long lengths of PE pipes through holes below ground bored by mechanical moles. PE is often used in renovation of old pipelines as it can be readily inserted as a structural lining into an old pipeline. PE’s resistance to ground instability means that PE gas and water systems were the only systems to survive the major earthquakes in Kobe, Japan in 1995.
PE pipe can be supplied in straight lengths or in coils, reducing the need for joints and fittings. PE pipes can be jointed using butt and electrofusion techniques or using mechanical fittings.
Low density PE – has high flexibility and retention of properties at low temperatures. The main applications of LDPE are in micro irrigation, low pressure drip irrigation, rural irrigation and stock watering applications.
PE 80B has a Minimum Required Strength (MRS) of 8.0 MPa as determined by regression analysis. In the past, this type of PE has been referred to as Medium Density PE or MDPE.
PE 100 is the most recently developed polyethylene grade and has higher strength and toughness than earlier generation materials. PE 100 has an MRS of 10.0MPa.
PE pressure pipes are designated by their outside diameter or DN. For water and other general pressure applications, the maximum allowable operating pressure (MAOP) with a minimum service coefficient is designated by the pressure rating or PN. The SDR of a PE pipe refers to its ‘Standard Dimension Ratio’ which describes the geometry of the pipe and is the ratio of the outside diameter and the minimum wall thickness. Pipes with a higher SDR have a thinner wall than pipes with a low SDR. The SDR can be related to the MAOP using the material MRS and the service coefficient appropriate for the application.
PE pipes are used in a wide range of applications including:
- Water supply
- Compressed Air
- Mine and slurry pipelines
PE is manufactured in Australia in sizes up to 2 metres diameter (DN2000).
PEX (or crosslinked polyethylene) is part of a water supply piping system that has several advantages over metal pipe (copper, iron, lead) or rigid plastic pipe systems. It is flexible, resistant to scale and chlorine, doesn't corrode or develop pinholes, is faster to install than metal or rigid plastic, and has fewer connections and fittings.
PEX tubing is made from crosslinked HDPE (high density polyethylene) polymer. The HDPE is melted and continuously extruded into tube. The crosslinking of the HDPE is accomplished in one of three different methods.
Sizes in PEX are typically available in Australia in sizes up to 50mm.
Polybutylene pipe is widely used for heating and plumbing applications in domestic, commercial and industrial properties. Its principal uses include hot and cold water services, central and underfloor heating installations.
The main aspects which distinguish it are its flexibility and superior resistance to stress over long periods of time at high temperatures. Flexibility is a key factor because it eases installation across a broad range of internal temperature conditions.
The typical size range for these products is less than 50mm.