High Strength Oriented HDPE Pipes [PE]

Author(s) : Ian Aldridge, Declan Robinson, Dave Smart, Chris Reed, Martyn, Greig, Trevor Stafford, David Christie-Lowe, Alec Erskine

For the UK polyethylene (PE) gas pipe network, the first installations now exceed 40 years in the ground, with an original design life of 50 years. It was thus timely to review the current condition and performance history of these first generation PE materials. A major 4 year project was started in 2010 to examine...

Author(s) : Ewing, Greig, Stafford

Funded by a UK government “Smart” Award, the authors have researched, and partially developed, a novel concept for temporarily reducing the external diameter of a PE pipe and then allowing recovery to full diameter as a close fit within a host main. The novelty lies in the four-lobed collapsed pipe geometry, which...

Author(s) : Soliman, Voets, Raven, Kleppinger, Ward

The Leeds die-drawing process has been used to produce biaxially oriented polypropylene pipes with significant enhancement of hoop mechanical properties in terms of tensile modulus and tensile strength due to a unique orientation of the a-crystallites throughout their cross section. Pendulum impact tests and...

Author(s) : Taraiya, Ward

Over the last decade Leeds University has developed a continuous die-drawing process to produce thick uniaxially and biaxially oriented polymeric products. Die-drawing offers a simple and effective route to stronger and stiffer polymer products. Biaxially oriented pipes with their improved hoop strength offer...

Author(s) : Taraiya, Ward

The die-drawing process was developed in this laboratory to produce thick uniaxially or biaxially oriented products.'" Earlier efforts to produce oriented polymer tubes at Leeds University were based on hydrostatic extrusion. Hope et a17 showed that, by using a stationary mandrel and converging die arrangement, round...

Author(s) : Greig

One of the main design criteria for limiting the operational pressures of polyethylene (PE) gas pipes is its resistance to rapid crack propagation (RCP). Below a critical pressure the crack arrests but above the whole pipeline may be fractured. The paper discusses the critical pressures measured during European and...

Author(s) : Ewing, Greig

Operation of high density polyethylene (HDPE) pipes at 7 bar has been very successful in British Gas over the last few years. Using HDPE pipes at higher pressures requires a high level and correct balance of pipe properties of strength, stress crack and rapid crack propagation resistance. Raised levels of jointing...

Author(s) : Marhsall, Harry, Ward, Pearson

Existing test methods used for the characterisation of long term strength properties of plastic materials for use in pressure pipe duties have been reviewed. A notched "C" ring type test has been developed to define the long term crack resistance and strength properties of a CPE modified PVC. Since materials of this...

Author(s) : Greig

The catastrophic phenomenon of rapid crack propagation in 250 mm diameter polyethylene pipes has been investigated at a full scale test facility. Tests at +3°C were conducted with pipes, either completely fully of water or containing a small percentage of air. The safe, maximum pressures were measured. Rapid crack...

Author(s) : Greig, Lawrence

Hydrostatic s~ress rupture testing at 80°C of polyethylene gas pipe currently takes sver 1000 ho7.1rs to determine its good stress cracking performance. This is excessively long for quailty control purposes so a rapid rest is being developed using fatigue pressurlsac. :on, 2gajn on notched...

Author(s) : Greig

As polyethylene pipes increase in size above 250 mm, the avoidance of high-speed brittle fracture propagation becomes of overriding importance. More stringent operating and test pressures have had to be introduced. A full scale test programme on a variety of pipe sizes is being conducted by British Gas. In this paper,...

Author(s) : Greig, Ewing

Fracture propagation is a phenomenon in which a long brittle crack runs along the pipeline at high speeds of...