Design & Testing # 1998 Gothenburg
Over the last two decades substantial development in Polyethylene (PE) pipe resins took place, but it was in the last five years that this range of PE-resins has been broadened with materials having a new design of molecular structure. A number of these resins are now in the market and are known as bimodal PE, with some of them having a PElOO classification.
The field of application for which these PE-resins were intended was to replace alternative pipe materials such as steel and ductile iron, and PVC, because of the higher pressure rating that was reached and as such improving the economical aspects of PE.
For several reasons this initial intention is not followed up, and is the PElOO replacing quote often PE80. without any good technical reason.
It is widely recognized that the primary properties of a PE-resin in pipe form are the following :
- the long term hydrostatic strength (LTHS and MRS)
- the resistance to slow crack growth (SCG)
- the resistance to rapid crack propagation (RCP)
Some secondary range properties have llowever not to be underestimated because of their practical value in manufacturing and use :
- ease of processing and handling
- material availability and consistency
- welding capability and compatibility
- injectability in fitting manufacturing
- economical aspects of the compound and end-product.
The above properties and performances refer to the base products. PE-resins and pipelfitting products. It should however not be forgotten to think about aspects of the fina! network.