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Pollution Prevention— Monitoring—Oily Water Separator—Sewage Treatment
Published in H. D. McGeorge, General Engineering Knowledge, 2012
A major source of oil pollution in the past from the operation of ships was the discharge into the sea of tank washings from tankers. This was reduced by the discharge of tank washings to a slop tank for settling, and discharge overboard of the water while retaining the sludge for pumping ashore to the refinery, with the next cargo. Crude Oil Washing (COW) eliminates the use of water and enables cargo residues to be pumped ashore during cargo discharge because cleaning is carried out simultaneously with the discharge.
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Published in Douglas J. Cusine, John P. Grant, The Impact of Marine Pollution, 2019
The oil and tanker industries, sometimes acting individually and sometimes through various trade associations, have been responsible in large part for the development and improvement of systems dealing with Load-On-Top (LOT) and crude oil washing of tanks—commonly referred to as COW. Both of these techniques are designed to reduce the amount of oily mixtures which are discharged to the sea during routine cleaning of cargo tanks in preparation for clean ballast. LOT involves collecting the oily wastes and oily water from tank washings in a tanker’s slop tank. The process uses the settling of the water and the rising to the top of the oil and the careful decanting of the water minus the oil on the run from discharge port back to the loading port. LOT affords tanker-owners a means of complying with the 1969 Amendments to the 1954 Convention, and its practice is recognised as a requirement in MARPOL. Properly practised, LOT is capable of recovering 99 per cent of the oil from oil-water emulsions resulting from tanker washings and dirty ballast.56 COW involves the use by crude oil carriers of crude oil rather than water to wash tanks which have just carried cargo. The application of this system has minimised the need for water washing and therefore effected a further reduction in operational discharges of oily mixtures. COW has been ‘blessed’ by the 1978 Protocol to MARPOL. As Y. Sasamura noted in the booklet mentioned in the beginning of this chapter, ‘crude oil washing will.. . make a significant contribution to pollution avoidance.’ Although not aimed primarily at preventing pollution, the development of inert gas systems by oil companies and tanker-owners has been a prime contributor to the safety of ships discharging their cargoes. Inert gas pumped into the empty spaces of cargo tanks replaces air, thus eliminating explosive mixtures. The application of this system has been extended in the Tanker Safety and Pollution Protocols of 1978, i.e. from new tankers of 100,000 tons dwt or more as required in the 1974 Safety of life at Sea Convention to all tankers of at least 20,000 tons dwt. Inerting is specifically required when tanks are crude washed.
A study on time constraints and task deviations at sea leading to accidents – a cultural-historical perspective
Published in Maritime Policy & Management, 2019
Asanka Rajapakse, Gholam Reza Emad, Margareta Lützhöft, Michelle Grech
Standardised work tasks in the form of checklists have also introduced higher risks in missing safety critical steps in the work task during time constraints resulting in task deviation (Loukopoulos, Dismukes, and Barshi 2009). Some checklists designed to have high number of steps to be taken in specific order. Since some work tasks could not be sequentially followed due to the non-linear nature of the operation, they were left to be ticked off later but never completed which in some cases lead to dangerous situations. This situation was aggravated when the work task was carried out by a team and only one person was responsible to tick off the checklist. For example, a research participant claimed that as the responsible person to fill the checklist, he conducted crude oil washing (COW) of cargo tanks without checking the Oxygen level in the tank. Although it was included as a safety critical step in the checklist, the team member who was designated to check the Oxygen level failed to check the Oxygen level. Due to the time restrictions on COW during discharging operations, the respondent failed to look back to check whether all tick boxes were ticked. In this specific case due to the nature of the task, it was not practical to follow the checklist and perform the task in the prescribed sequence. Many of our research participants mentioned that seafarers have to rush through large checklists to complete tasks under time pressure. In the process, it is possible that they miss critical work steps even though they ticked the tasks as completed. In these cases, task deviation occurred even when checklists and procedures were used. These systems which put in place by the ship operators to comply with legal instruments and were supposed to assist in aligning WAD and WAI had contributed to their misalignment.