Petterson_cut.qxp 27/3/09 02:21 Page 55
Engineering & Construction
Offshore Crane-lifts in Life-cycle Assessment
a report by
Johan Pettersen
Manager, MiSA, and Adjunct Associate Professor, Norwegian University of Science and Technology (NTNU)
Lift operations are an important source of hazards to personnel on during drilling operations are considered in the frequency
offshore oil and gas installations (see Figure 1). North Sea oil and gas calculations. By doing this we achieve a more uniform set of accident
regulators that monitor the development of offshore risk levels records in operational conditions where we know more about the
therefore specifically focus on falling objects and crane-lift accidents.
1
number of lifts performed per hour.
More Lifts and More Hazardous Lifts Implementing these assumptions, we get an end set of 177 cases
Current trends predict greater use of cranes in the future. that involved uncontrolled crane-lifts that resulted in injury to
Regulations concerning the deposition of cuttings are continuously personnel on floating offshore units. These must be distributed by
becoming stricter, and in an increasing number of fields worldwide unit years, taking into account the fraction of time for which units
cuttings drilled with water-based fluids as well as oily cuttings must are in active drilling mode. The results (see Figure 2) may be
be transported to shore. Cuttings waste represents significant interpreted as showing a greater chance of crane-lift accidents on SS
volumes, resulting in a large number of crane-lifts in waste logistics. rigs compared with JU units. However, when taking into account the
More lifts mean an increased risk of lift accidents. This trend is being random nature of accidents, this is expected as a result of variation
exacerbated as offshore activities move into deepwater areas and from year to year. Therefore, the best estimates are found by pooling
territories with harsher conditions, for instance into the Arctic. SS and JU rigs.
Rougher conditions imply a more hazardous risk profile.
Crane-lift Injuries
Although a lot of effort is invested in making practices more safe To get a better picture of the outcome of crane-lift accidents, each
and installing boundaries to limit the probability of personnel accident should be characterised in terms of the resulting injury. We
injuries, lift operations are expected to be an important risk source may do this based on the description of events given in the incident
in the future. It is therefore pertinent to estimate the extent of the reports. The resulting distribution is given in Table 1. About 7% of
health burden that occurs as a result of crane-lift accidents and the all injury incidents end in amputation, while fractures account for
relative importance of crane-lift accidents compared with other one-quarter of all injuries. The most frequent outcome is smaller,
types of health damage from offshore activities. unidentified injuries. Of all the 177 cases in the period 1980–2003,
three ended in fatality.
Important Source of Health Damage
The UK Health and Safety Executive (UK HS&E) maintains regularly Assessing Mortality and Morbidity
updated records of all incidents reported on offshore units. For Life-cycle assessment (LCA) considers several cause–effect chains
simplicity, in this article we will limit ourselves to considering mobile with human health impacts. A means of aggregating multiple impact
(floating) drilling units only.
2
In doing so, we have a total set of chains to one single-score indicator of human health is offered by
about 4,000 reported incidents in the period 1980–2005. Of these, the World Health Organization (WHO) through the disability-
some 400 are reported injuries to personnel. adjusted life-year (DALY) framework.
3
Initially intended as a way to
make the use of resources in international health programmes more
Previous engineering factors for the frequency of crane-lift accidents effective, DALYs allow the aggregation of years of life lost (YLL) due
made no indication of the distribution of personnel injuries from to premature mortality (death from illness or accidents) with years
accidents during lift operations. The probability of a hazardous lost due to disability (YLD).
incident is most often given as the probability of a falling object per
lift. Moreover, these factors did not appreciate that different types YLD are calculated as the product of the weight assigned for the
of lift operation carry different accident probabilities. disability and the duration of the disability. In other words, YLD is an
indication of the quality of life lost due to injury, taking into account
All operations involve some use of cranes to move objects around on
the rig deck. One important step in estimating health impacts per
Johan Pettersen is Manager of MiSA, an independent
crane-lift is to find the frequency of accident per lift. Original
research and consulting company for environmental
statistics report accidents per year per offshore unit, without systems analysis, and an Adjunct Associate
reference to activity. This means that the number of lifts per hour
Professor at the Norwegian University of Science
and Technology (NTNU). He holds a PhD from NTNU
must be found. To achieve this we make two important
in overall environmental evaluation of offshore
assumptions. First, the frequency estimation is limited to considering
drilling technologies.
semi-submersible (SS) and jack-up (JU) units, as the activity of such
E:
johan@misa.no
units is available from commercial actors. Second, only accidents
© TOUCH BRIEFINGS 2009
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