Petterson_cut.qxp 27/3/09 02:22 Page 56
Offshore Crane-lifts in Life-cycle Assessment
Figure 1: Cause of Incidents on Offshore Units in UK Waters, 1980–2005
the duration of the injury. Table 1 presents two general types of
injury: those that can be remedied (e.g. fractures and minor injuries)
100
and those that remain throughout the expected lifetime of the victim
90
(e.g. amputations).
80
70
The expected remaining life depends on the average age of
60
employees exposed to crane-lift accidents. A few years ago,
50
Norwegian operators reported that the average age of offshore
40
Other
workers was 45–50 years; this is probably higher today. However,
Reported incidents (%) 30
Fire
several studies have reported that young employees are more
20
Falling object
vulnerable to accidents, due to either less experience or the fact that
10
Crane
they perform more exposed tasks. A study from 1997 found the
Contact
0
average age for drilling crew injured in the North Sea to be about 30
Floating units Fixed units
years.
4
This gives an average remaining lifetime of 47 years,
Spills and releases excluded. Source: UK Health, Safety and Environment Executive. according to UK male life expectancy in 2002.
Table 1: Outcomes Observed from Crane-lift Accidents
The weighting for the injuries listed in Table 1 ranges from 0.1
Outcome Cases Percentage (minor injuries) to 0.3 (foot amputation). Fatality carries a weight of
Fatality 3 2
1. The duration of smaller injuries is usually up to six weeks.
Amputation – thumb 2 1
Amputation – finger 7 4
Amputation – toe 1 1 Fatality Matters Most
Amputation – foot 1 1
The frequency of an accident with personnel injury is a distributed
Fractures 45 25
probability. The UK HS&E data support an average of 0.2 injuries per
Other injuries 118 67
Total 177 100
unit year of active drilling in the period 1990–2003. This estimate
may be described statistically with a given distribution. A
Figure 2: Observed Crane-lift Accidents with Personnel Injury per
complementary distribution for the number of lifts per time in
Unit Year in Drilling Mode, 1990–2003
drilling mode is found from an estimated eight to 10 lifts per hour
on rigs in drilling mode. Similarly, a distribution is assigned to the
0.8
health outcome in case of an injury.
0.6
Considering all factors, we find an average of four accidents with
injury to personnel per million lifts. The probability boundary for this
0.4
estimate is 0.5–15 accidents per million lifts.
In terms of health burden, each crane-lift contributes about 4.5
0.2
DALYs per million lifts, with a boundary of 0.6–17 DALYs per million
Injury incidents per active drilling year lifts. Fatality carries the largest portion of the burden of accidents,
0.0
equivalent to two-thirds of the total health burden. The remainder is
SS JU MODU
represented by amputation cases. Other minor injuries and fractures
do not contribute significantly to the total health damage from
Represented averages are indicated by darker dots. Numbers separate semi-submersible (SS) units, jack-up
(JU) units and mobile offshore drilling units (MODUs). crane-lift accidents.
Figure 3: Comparison of Overall Health Impacts from Cranes and the
Pneumatic System
Life-cycle Assessment
Accidents are one health implication of offshore crane-lifts.
50
However, an overall assessment must also consider the health
impacts caused by producing, using and maintaining the crane.
40
Recently, a pneumatic pump intended to replace the use of cranes
was installed on a drilling rig equipped to operate in the Norwegian
Barents Sea.
5
This alternative technology removes the risk of crane-
30
lift accidents at the cost of higher fuel use and the need for an
additional system to be installed on the rig. Fuel production and use
20
leads to emissions, which in turn will have health impacts owing to
emissions on the rig and in offshore processes. A fair comparison of
D
A
L
Ys per million tonnes loaded
10
the health benefit of either solution must encompass health impacts
from both potential for accidents and emissions to the environment.
0
Crane-lifts Indicated uncertainty Pneumatic
in accident risk pump
LCA provides a structural framework to model the health impacts
Crane-lift accidents System operation System construction
from these processes. Health impact models according to the DALY
56
EXPLORATION & PRODUCTION – VOLUME 7 ISSUE 1
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