Abstract Background Studies on work–leave rotation pattern and work place injuries among offshore oil and gas workers have been few and limited to a 2- or 3-week rotation schedule. Aims To examine incidence of workplace injury in relation to the duration of time into work rotation for extended work schedules up to 24 weeks. Methods Six-year injury data on four offshore installations were extracted. Data were analysed for incidence of injury over time and relative risk using linear trend lines and regression. Results In total, 311 injuries for 1302 workers were analysed, 39% with rotation schedule of 4 weeks work and 4 weeks rest, 27% 8 weeks work and 4 weeks rest, 23% 16 weeks work and 4 weeks rest and 10% 24 weeks work and 4 weeks rest. Incidence of injury decreased as duration of time into the work rotation increased, corrected for exposure, and this was statistically significant for all rotations in first 4 weeks (P < 0.01). Negative correlation between time offshore and injury was observed in all schedules and consistent for age groups, categories of work, shifts and severity of injury. There was no difference in relative risk of injuries between the four schedules, when corrected for exposure and occupational risk of injury. Conclusions These results are at variance with previous studies, although no prior study has looked beyond 3-week rotation schedule. Longer offshore schedules are safely possible and this could help decrease manpower and logistics costs for oil and gas companies coping with unprecedented low oil prices. Offshore oil and gas, work–leave rotation, workplace injury Introduction Offshore facilities are remotely located and function around the clock, every day. Daily commute by boat or helicopter is impractical making extended work schedules necessary. Workers stay and work offshore continuously for a few weeks (work rotation) then have leave for a few weeks (leave rotation or rest rotation). These work–leave schedules continue in a regular pattern. The work–leave schedule is 2–2 or 3–3 weeks in UK North Sea and 2–3 or 2–4, with longer rest, on the Norwegian side. Australia has 1–1, Caspian Sea has 1–1 or 2–2 and South East, 2–1 or 1–1 rotations. Brazil has 2–2 rotation for local staff and 4–4 for expatriates. Expatriate workers in the Middle East and Africa have 4–4, 8–4 and even longer rotations. Safety on an offshore platform is the major determinant of work–rest rotation pattern. Studies suggest that long work rotation increases fatigue  and hence accidents and injury . Paucity of studies on the incidence of injuries and the length of offshore rotation , and absence of regulatory recommendations , makes optimal work–leave rotation a subject of controversy and legal debate . This study examined whether incidence of workplace injury increased with increasing duration into work rotation, and whether workers with longer work rotations had higher injury rates. Extended work–leave patterns, 4–4 to 24–4 weeks, provide a unique opportunity to examine this relationship. Methods Six-year workplace injury-related data on two offshore oil and gas platforms and two drilling rigs, in the Persian (Arabian) Gulf, were extracted from the operator’s records. Data comprised work rotation schedule, days into work rotation when injury occurred and related measures including age, type of work, day or night shift and severity of injury. Incidence of injury over time into work rotation was analysed using scatterplots, linear trend lines and regression to obtain goodness of fit (R2), means’ variation (F), relationship strength (t) and significance (P). Age, occupational category, shift pattern, and severity of injury were analysed as possible confounders. Relative risk of injury among different rotation schedules was calculated after correction for exposure and occupational category. The University of Manchester provided ethics approval. The operator had no influence on study results. Results The study covered 1302 offshore workers and 311 injuries during the 6-year period. Rotation schedule studied included 4 weeks work–4 weeks rest (39% workers; 43% injuries), 8 weeks work–4 weeks rest (27% workers; 22% injuries), 16 weeks work–4 weeks rest (23% workers; 27% injuries) and 24 weeks work–4 weeks rest (10% workers; 8% injuries). Injuries in other rotations and in visitors (1%) were excluded. First aid cases accounted for 82% injuries. There was no cluster of injury, mass injury or fatality. Offshore work, categorized on physical effort and exposure to hazards, showed relative risk of injury to be similar for administrative-catering (0.95) and maintenance- production (0.87) but significantly high for drilling (1.82) (P < 0.05). Drillers had more severe injuries than others (P < 0.001). Longer schedules had younger workers (P < 0.01) but no correlation was seen between age and frequency or severity of injury. There were 200 injuries in the first 4 weeks for all schedules. A significant negative relation between the frequency of injury and the days into the work rotation was seen (Figure 1). Figure 1. View largeDownload slide Frequency of injury—week 1–4—all workers. Figure 1. View largeDownload slide Frequency of injury—week 1–4—all workers. Eliminating two outlier values (day 7 and 26) improved R2 to 0.213 and t to −3.104 with P <0.001. The 4–4 schedule, with maximum workers (40%) and maximum injures (43%) showed a significant (P < 0.01) inverse relation between the frequency of injury and days into work rotation (Figure 2). Figure 2. View largeDownload slide Frequency of injury and days into work rotation 4–4 schedule. Figure 2. View largeDownload slide Frequency of injury and days into work rotation 4–4 schedule. Similar negative trends were observed in the 8–4 week rotation (t = –0.667; P < 0.05), 16–4 week rotation (t = −3.722; P < 0.01) and 24–4 rotation schedule (t = −107.5; significance not computable). Injury in the first 4 weeks of rotation was analysed for possible confounders. No significant difference was seen between the various age groups, categories of workers, shift or injury severity. The relative risk of injury for different rotation schedules was corrected for exposure (longer rotations occupy longer time offshore) and for work category (drillers have more injuries). Relative risk of injury corrected for exposure was 1.14 for 4–4 schedule; 0.81 for 8–4; 0.92 for 16–4 and 0.62 for 24–4 schedule. Corrected for work category it was 1.08 for 4–4 schedule; 0.69 for 8–4; 1.27 for 16–4 and 0.87 for 24–4 schedule. In both cases, the difference in relative risk among rotations was non-significant. Discussion This study found that the incidence of injury gradually decreased with time into work rotation for all four schedules, 4–4 to 24–4, with statistical significant change in 2. No significant difference was observed in the injury frequency between the various schedules, short and long, when corrected for exposure and type of work. Very few studies have examined the relationship between workplace injuries offshore and duration of time into work rotation. No prior study has looked beyond 3-week rotation schedule or examined difference in injury between different schedules. Parkes and Swash  and Mikkelsen and others  on either side of the North Sea, demonstrated an increase in workplace injury with duration of time into work rotation. This study, a decade later, contradicts these results. In this study, no cause for these observations was evaluated. Previous research has primarily focused on physical factors (long hours, shift work, night duty, sleep problems, fatigue psychological stress) as main contributors to offshore injuries . These worsen with longer work time. During the last decade, improvement in physical aspects of safety, including living conditions, environment, safety and personal protective equipment, has led to a downward trend in injury incidence . Behavioural aspects of injury, including organization safety culture  and individual safety behaviour , currently under focus, improve with time offshore and could possibly explain the study findings. Larger studies are required to test this further. This study suggests that longer offshore schedules are safely possible and this could help decrease manpower and logistics costs for oil and gas companies, coping with unprecedented low oil prices. Key points Various offshore schedules of up to 24 weeks rotation were analysed for incidence of injury in relation to the duration of time into work rotation. Incidence of injury decreased as duration of time into work rotation increased. When corrected for exposure there was no difference in the relative risk of injury between different schedules. Longer offshore schedules are safely possible and this could help decrease manpower and logistics cost of oil and gas companies. Competing interests None declared. References 1. Akerstedt T , Wright KP Jr . Sleep loss and fatigue in shift work and shift work disorder . Sleep Med Clin 2009 ; 4 : 257 – 271 . Google Scholar CrossRef Search ADS PubMed 2. Parkes K , Swash S. Injuries on Offshore Oil and Gas Installation—An Analysis of Temporal and Occupational Factors . OTO 1999-097. London : Health and Safety Executive , 2000 . 3. Parkes K. Offshore Working Time in Relation to Performance, Health and Safety: A Review of Current Practice and Evidence . RR772. London : Health and Safety Executive , 2010 . 4. HSE . Health and Safety Executive Policy on Working Hours Offshore . 2009 . http://www.hse.gov.uk/offshore/infosheets/is8-2008.htm ( 10 April 2017 , date last accessed). 5. UK Supreme Court . Russell and Others v Transocean International Resources Limited and Others . British and Irish Legal Information Institute , 2011 . http://www.bailii.org. ( 15 January 2017 , date last accessed). 6. Mikkelsen A , Ringstad A , Steineke J . Working time arrangements and safety for offshore workers in the North Sea . Safety Sci 2004 ; 42 : 167 – 184 . Google Scholar CrossRef Search ADS 7. Parkes K . Shift schedules on North Sea oil/gas installations: a systematic review of their impact on performance, safety and health . Safety Sci 2012 ; 50 : 1636 – 1651 . Google Scholar CrossRef Search ADS 8. Health and Safety Executive . Offshore Oil & Gas Sector Strategy 2014 to 2017, Aims & Objectives . 2014 . http://www.hse.gov.uk/offshore/offshore-oil-and-gas.pdf ( 15 April 2017 , date last accessed). 9. Kilparthi J . Assessment of safety culture in global offshore environments . J Envior Prot 2014 ; 5 ; 1003 – 1021 . Google Scholar CrossRef Search ADS 10. Havold J . National cultures and safety orientation: a study of seafarers working for Norwegian shipping companies . Work Stress 2007 ; 21 : 173 – 195 . Google Scholar CrossRef Search ADS © The Author(s) 2018. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: firstname.lastname@example.org This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)
Occupational Medicine – Oxford University Press
Published: Feb 28, 2018
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