Cross-linked polyethylene, commonly abbreviated PEX or XLPE, is a form of polyethylene with cross-links. It is formed into tubing, and is used predominantly in hydronic radiant heating systems, domestic water piping and insulation for high tension (high voltage) electrical cables. It is also used for natural gas and offshore oil applications, chemical transportation and transportation of sewage and slurries. Recently, it has become a viable alternative to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) or copper pipe for use as residential water pipes. Copper and CPVC are both trustworthy materials for plumbing systems; but PEX tubes have one or two vital advantages that make it a best choice for water distribution: * PEX requires fewer connections resulting in fewer opportunities for connections to leak and cause water damage. The tubing is available in long coils and is flexible enough to bend   around obstructions without the use of connections. * PEX is easier to install as they have fewer fittings and are lightweight and flexible, resulting in lower labor costs. * PEX reduces maintenance and repair costs. Service is relatively simple, since manifolds are corrosion-resistant and the connections are visible. * PEX improves energy conservation as it decreases the level of heat lost from water in the piping, increases the reply time of hot water, and decreases the quantity of energy the hot    water heater uses to supply hot water. Of all the PEX tubing, cross-linked PEX is most widely used in floor heating systems. In Europe, the demand for cross-linked PEX tubing is estimated at 218 mln meters, representing 53% of all sold PEX tubing systems. Most systems XLPE can withstand temperatures 95oS at a pressure of 1 MPa. In addition, these pipes have good flexibility. The cost of pipe production increases sharply in the manufacture of large diameter pipes, and this is one of the reasons that in most cases, their diameter does not exceed 32 mm. A new method to produce cross-linked PE pipes more quickly has been developed by Borealis (PEX material supplier), Crosslink Finland, Hans Weber & Inoex (machinery suppliers for PEX based peroxide cross linked PEX pipes). This new method is a single stage process that crosslinks PEX pipe immediately after emerging from the extruder head with the help of high power, short wavelength infrared radiation. This new process leads to shorter heating time and special vacuum calibration that produces PEX pipe with narrower tolerances. Inoex’s dosing and control equipment allows this to be done continuously, in-line with the extrusion and crosslinking steps. Weber’s twin-screw extruders run at low temperatures and shorter residence times, which prevents decomposition of the peroxide in the extruder. Borealis developed two new grades for the project: BorPEX HE1878E, a powder, runs at high speed; and BorPEX HE1878E-C2, a fully formulated compound in mini pellet form that only requires the addition of peroxide to produce a PEX pipe. It aims to produce a 5 layer pipe. This project, led by German extrusion consultancy IBA, aims to produce a combined five-layer pipe using both types of PEX. The method will be used to produce under floor heating pipe, using PEX and EVOH. The pipe will be protected by an outer PEX-b layer. A conveyor station is used to add peroxide to the process while a dosing station adjusts measurement, conveyance and mixing. The pipe is cross-linked by passing it through an infrared oven. During the subsequent co-extrusion process, an adhesive agent is added first, followed by the EVOH layer, and another adhesive agent. Then the PEX-b layer is added. Two different coloured stripes are extruded into the PEX-b layer. Digital ultrasonic measurement records the overall geometry of the product. In total, seven extruders produce a five layer product including two colour stripes.