Pipe Express? (PEX) is a semi-trenchless process where larger diameter pipelines (36-60-inch) with lengths of up to 6,500ft (2,000m) can be installed. During the installation process, the soil is excavated by a tunnelling machine and transported to the surface by chain trencher and conveyor belt. The tunnelling machine is accompanied on the surface by a buggy and the operator’s control vehicle. The pipe thruster installed in the launch pit pushes the machine and the pipeline through the ground. The simultaneous excavation of the soil and insertion of the product pipe creates an optimum pipe bedding situation. The PEX system is used on projects where the open-cut installation of pipelines would cause high investment due to special requirements. The system has many advantages in unstable soil or where the open-cut installation of pipelines would require measures such as groundwater lowering. A narrower construction easement is needed for the pipeline corridor when using PEX technology; this reduces land disturbance and rehabilitation which is very important, especially in environmentally sensitive areas. With daily advance rates of up to 3,250ft (1,000m), PEX is very competitive compared to conventional open-cut methods. In November 2012 the first gas pipeline was installed in the Netherlands using PEX technology. The 48-inch gas pipeline had a total length of about 1,600ft (500m) and was laid in two pipe sections. Further installations of a 42- inch gas pipeline are being executed in Thailand using PEX technology in by 2014.
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