Availability
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Availability
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Last updated: 02.02.10
In Operational Availability, not all the contributory factors are under the control of the plant operator. Such external factors include:
Other factors are, of course, possible, depending upon particular situations.
Illegal acts are used here in the sense of acts such as theft that are intended to profit the perpetrator but are not intended to damage the plant, though they often do. One very common example is the tapping of pipelines to steal fuel, a practice that has become notorious in Nigeria, but is more widespread, though less well reported, in the Ex-Communist countries of Europe. These events are reported regularly in the Incident Histories. However, the incidents occur on such a wide variety of pipelines, and data on downtime is so sparse that it has proved impossible to establish availability figures.
Strikes, in this context, includes any action by labour, whether organised or not, that interrupts plant activities.. Apart from labour disputes between workers and plant management, which are becoming increasingly rare in the Western countries, persons with grievances against governments have become increasingly aware of the vulnerability of energy sources and distribution infrastructure. This was particularly noticeable in the protests against fuel prices that swept through Europe in September of 2000. This trend is likely to continue.
Equally important to recognise are the disruptions caused by environmental protesters. These have frequently caused disruptions and sometimes damage.
Few plants can function without external supplies of materials. These may be interrupted through a variety of factors but, since they are outside the plant operator's control, they need to be taken account of -- typically through historical statistics.
War -- declared or undeclared -- should be self-evident. Fortunately, wars are rare and generally localised. However, a war in one country can interrupt the transport of plant feedstocks between two other countries. An example of this is the blocking of the Danube river as a result of the various wars in Yugoslavia, which has interrupted oil traffic by barge.
Pipelines
in particular are vulnerable to damage by terrorism or war. A notorious example
is the Cano Limon-Covenas crude oil pipeline in Colombia. Attacks on this pipeline
are well reported and consequently we have been able to establish availability
data, shown in the figure, left.
With regard to attacks on pipelines, it should be noted that, not only does the downtime include the time to repair the damage but also to secure the area. Most terrorist attacks on pipelines occur in remote areas, taking advantage of the fact that it is almost impossible to guard the whole length of the line.
It should also be noted that there is a distortion in the monthly availabilities in above figure. The database in which incidents are recorded associates the down-time with the date of the incident. However, in many cases, the down-time occurs in part in two separate months. For example, the figure shows that the pipeline had zero availability in February and 0.84 in March. In fact, the February figure is higher, that for March, lower, because some of the recorded down-time for February actually occurred in March. The cumulative figures are unaffected with regard to value but may deviate with respect to time.
All plants are vulnerable to loss of utilities, particularly electricity and, to a lesser extent, water.
Offshore oil and gas extraction is subject to disruption by the weather. However, this is fairly rare since such facilities are usually designed to withstand the weather in the area. Coastal refineries and other installations may also be shut down when severe weather -- hurricanes, typhoons -- approaches.
One
type of installation frequently affected by the weather is an oil port or terminal,
which may be closed if sea conditions prevent ships from loading or unloading
safely.
The figure, left, shows availability for the Russian Black Sea port of Novorossiisk, a facility that is frequently closed by storms.