THE FIRST paper in this issue (on pages 189-199) combines the experience of an operating company and an engineering research centre who have looked in depth at the issue of quantitative pipeline risk assessment and maintenance optimization. As part of their study, the authors used a quantitative risk assessment tool to calculate the failure rates, failure consequences, and risk levels along the pipeline under investigation. The ‘safety risk’ was characterized by the ‘individual risk ratio’, defined as the maximum individual risk associated with a given segment divided by the tolerable individual risk. Tolerable individual risk values were further defined as a function of population density, following the approach developed by the Major Industrial Accidents Council of Canada (MIACC) and the UK’s Health and Safety Executive (HSE). Financial risk was expressed in dollars per km-year and included a dollar equivalent for public perception.
The recommended maintenance plan was then based on minimizing cost while achieving a tolerable safety risk. The first step in developing the plan was to identify all segments that did not meet tolerable risk criteria (the segments with an individual risk ratio greater than unity), for each of which a number of potential maintenance scenarios that address the dominant failure threats were selected. A cost-optimization analysis was then carried out in which the total expected cost associated with each maintenance option was calculated as the sum of implementing the option plus the corresponding financial risk component, amortized over the inspection interval. This analysis was used to identify the minimum cost alternative that met the individual risk constraint, and the outcome of the analysis then provided the best maintenance option (for example, in-line inspection, hydrostatic test) and the optimal time interval for re-evaluation. This is a subject of considerable practical significance to pipeline operators, and the authors’ paper will doubtless be read with interest.
ON PAGES 200-210, there is a second paper of considerable practical significance, particularly for areas where ambient temperatures are low, pipeline product temperatures are high, or heating is seen as a viable alternative to diluent addition in order to reduce a fluid’s viscosity. In their paper on high-temperature pipeline design, the authors primarily focus on two fundamental design issues for a hot bitumen pipeline: modeling the restart problem, and establishing the maximum practical operating temperature.
The concept of flow capacity is introduced to model the transient behavior during restart of a high-temperature pipeline filled with a high-viscosity fluid that has cooled during a shutdown. The heat lost from a buried high-temperature pipeline causes environmental disturbance by elevating the ground temperature near the pipeline, and this can alter growing conditions above even an insulated, deeply-buried, pipeline. Results are presented for a hypothetical case modeled using a thermal simulator developed by one of the authors.
Axial thermal loads increasingly constrain the design and operation of a buried pipeline as higher operating temperatures are considered. Strain-based design affords the opportunity to design for higher operating temperatures than allowable stress-based design techniques. With either design method, there is a temperature at which expansion loops are required partially to relieve the thermal stress although, as the design temperature increases, there is a temperature at which an above-grade pipeline becomes an attractive option.
Pipelines and politics
OUR EARS always prick up when, while listening to the TV or radio news, the word ‘pipeline’ is used in its correct sense. All of a sudden a sadly-mundane broadcast becomes something to listen to with alerted attention, the children are told to be quiet, the volume turned up. Sometimes it is a false alarm: poor English usage and the necessity for obfuscating brevity brings forth statements like "there is a new hospital in the pipeline" or "the government’s plans for …such and such a development.. are still in the pipeline ….". We’ve all heard these, and muttered ineffectively about standards, editorial integrity, and general misuse of the language.
But occasionally the word is used in its correct sense, and then one finds one’s friends and acquaintances expressing surprise that such structures exist…and that they transport gas, oil, fuel, etc., …and that our countries and economies rely on them…and that they are in fact of great interest. Probably luckily for the industry, however, the fuss soon dies down, and society as a whole relaxes back to its happy ignorance.
It is likely, however, that this state of ignorance will gradually be eliminated, as the issue of how the world should share out its energy reserves becomes both more and more political, and more and more a factor of our lives, certainly in Western Europe. This was typified this month (December) with the debate between Russia and Ukraine about transit fees and the price of gas to Ukraine when – for what was probably the first time – many people outside the pipeline industry suddenly began to realize the significance of pipelines as critically-important conduits of energy. During the much-publicized discussions about how much Ukraine should pay for Russian gas, several Western European countries actually found their own gas supplies from Russia being reduced, and the UK began publicly to appreciate that its reliance on clean gas for electricity generation would mean that in a few years that gas would have to be imported from the other side of the Urals.
Just as the Russian and Ukrainian discussions were reaching their peak, the construction of the West European Gas Pipeline was started, in a ceremony on December 9 at the Russian town of Babayevo, where there was a symbolic welding together of two pieces of pipe. "Today we have launched a great European project... This is a new export route that will increase Europe’s energy security," Alexey Miller, chairman of Russian gas major Gazprom, said at the gathering. [The 994-mile long, 48-in diameter, gas pipeline will initially transmit around 27.5bn cum/yr of Russian gas to Germany, from where a sizeable proportion will be supplied to the UK.] A cynic might say that this event was probably stage-managed by the Russians deliberately to annoy the Ukrainian and Polish governments, who had already taken a stance of objecting to this ‘by-pass’ of their countries and the concomitant loss in future revenue from transit fees.
But at the same time the Ukrainians, certainly, could be seen to be adopting a head-in-the-sand attitude to this new development, claiming publicly that such a pipeline could never be built, was not technically feasible, and that all Russian gas exports would have to continue to transit their country, etc. Indeed, our sister publication Global Pipeline Monthly (GPM – www.globalpipelines.com) was invited to take part in a broadcast on the subject by the BBC World Service, in which the previous speaker – a representative of the Ukrainian parliament – displayed amazing ignorance of what could or could not be achieved by perfectly-normal current pipeline engineering and pipelaying technology.
Leaving European energy supplies to one side for the moment, and looking around the world, a glance at the articles and news pages in GPM shows that such issues are also very close to the surface in Central Asia, China, Japan, and South America. In Central Asia, the ‘Great Game’, so styled by the Victorians, is being played again across the borders between Iran, Afghanistan, Pakistan, and India. Unlike in Rudyard Kipling and John Buchan’s days, the prize is energy – a ‘power’ of a different type. In China, a political-energy axis is developing with Kazakhstan in the South and Russia further North, to the exclusion of Japan who thought it was playing a defining role. In South America, the Venezuelan president is seeking to dominate energy by creating pipeline links with Colombia and Brazil, in a Great Game of a different sort, the target of which seems to be to remove the perceived neo-colonial dominance of the United States in the region. In all these places, pipelines are the common factor, and international cross-border pipelines are developing a political science all of their own. Even Australia is for the first time embarking on importing gas by pipeline, from Papua New Guinea, by comparison a remote, inhospitable, and under-developed country which lags several decades behind its continental neighbor in many of its attributes.
Another critically-important ‘crunch-point’ where the future is by no means clear is how the pipeline industry is going to be able to obtain the pipes it needs for the developments it is planning. In fact, there is a forecast shortage not only of the linepipe required in the next five years, but also of the raw material to make it. These subjects are to be discussed at an industry-wide event being organized by GPM on behalf of EPRG and IPLOCA in Amsterdam on March 6-8: readers can see details at www.pipespec2006.com, and are encouraged to consider attending.