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 USA round robin test programmes to evaluate the new Small Scale Steady State (S4) laboratory test methid.
These critical pressures are compared with the results on the same pipes using the full-scale test method so as to try and establish a correlation factor between them. Once established, it is intended that the relatively inexpensive S4 method will replace full-scale testing.
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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...
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...
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
Raised levels of jointing...
A novel die-drawing process has been developed at Leeds
University. By incorporating a mandrel, pipes may be expanded
hoopwise whilst being drawn axially. Such biaxially-oriented
pipes have properties better suited to the transmission of gases
and liquids than either isotropic or longitudinally-drawn pipes.
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.
gas pipe currently
its good stress
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,...