INTRODUCTION

It is well known that polyethylene pipes offer many advantages over traditional ductile iron and steel pipes. These include high ductility, corrosion resistance, flexibility, coilability, light weightness, and reduced installation costs. These features provide both performance and economic benefits, which in turn have meant that polyethylene has found wide utility in ploughing-in and trenchless technology applications.

Over the past 50 years several improvements in polyethylene product technology have been made. These improvements led to the development of the well known PE80B and PE80C materials which are now widely used within our industry. Both of these polyethylene pipe materials are recognised as offering excellent long term performance as pressure pipes. In particular, the medium density PE80B materials have found great utility in ploughing-in applications due to their flexibility and ease of coiling. Given that PE80 materials already offer such a high level of performance, why do we need PE100 products? In other words, what advantages do PE100 pipe materials offer, particularly for ploughing-in and trenchless technology applications?

There are three main performance benefits offered by PE100 resins. These will be described in more detail later in this paper, but are summarised below for the purpose of this overview;

1. PE100 materials can withstand a minimum circumferential stress (or hoop stress) of 10.0 MPa for 50 years at 20oC. This compares with a performance of 8.0 MPa for 50 years at 20oC for PE80 materials. The higher long term creep resistance of PE100 materials translates in to higher operating pressures at the same wall thickness, or alternatively, thinner walled pipe at the same operating pressure, offering greater hydraulic capacity than PE80 materials.
2. PE100 materials have improved notch resistance compared with PE80 resins. This means they are even less sensitive to surface damage during laying, which has obvious advantages for ploughing in and especially trenchless techniques.
3. Pipes made from PE100 have improved resistance to rapid crack growth. This means that if a fast crack begins to grow in a PE100 pipe, it will be arrested after propagating only a short distance. This is of particular advantage in the distribution of fuel gases at high pressures, where a rapid crack failure could have disastrous consequences. However, there have been no reported incidents of rapid crack propagation (RCP) in PE80B gas pipelines in Australia. The improved rapid crack resistance of PE100 resins does not appear to offer any immediate advantages in the current Australian context.

It is clear that for ploughing-in and trenchless technology applications, the ability to down gauge the pipe and the improved resistance to surface notches offers obvious economic advantages. Furthermore, the higher pressure performance of PE100 has the potential to open up new applications at higher operating pressures. These benefits will be discussed in detail in the following section.

Download the complete story as a Word Document

BACK TO