Vessel Decon TESTIMONIAL " We were pleased with the decontamination results and the time savings we were able to achieve during this phase of the TAR. We will certainly look to use this process in future TAR events on the CNOCC assets in the North Sea " TAR Co-ordinator
No.2 CASESTUDY
BUZZARD PLATFORM
OVERVIEW This was the first TAR to be implemented where the decontamination process utilised steam and Zyme-Flow® UN657 to achieve vessel decontamination. The scope of work included Production Separator, 2nd Stage Separator, Degasser, Oil Metering Skid and Flare Drums. CHALLENGES The TAR was planned to be completed within a tight timeframe and expectations were that the Zyme-Flow® process would give significant reduction in time taken to free vessels for entry. As this was the first Zymeflow had been used in a TAR scenario the decontamination operation was subject to close scrutiny with the expected vessel decontamination time for 18 hours per vessel being particularly subject to close monitoring. As the platform did not have its own steam supply it was necessary to utilise Zone II rated hire steam generators.
PAST PROCEDURE In previous plant outages decontamination was achieved by a flushing and N2 purging process. Residual solids had to be brought outside the vessels for washing in order to remove remaining oil before disposal. The time taken for purging and solids washing was considerable and was difficult to quantify at the planning stage thus making overall TAR planning and implementation extremely challenging.
DECON SOLUTION It was agreed that DML would apply a Boil Out process for the large horizontal vessels (separators, drums) and a Vapour Phase of the Oil Metering Skid. Zyme-Flow® UN657 was the chemical used since it had CEFAS certification for use in North Sea. As the TAR scope of work was spread over 3 legs of the platform it was necessary to supply 3 steam boilers in order to complete the TAR within the expected time frame.
RESULTS The decontamination was carried out with all vessels being decontaminated to the required standard with no accidents, incidents or near misses. Decontamination results were acceptable within the 12-hour processing period on all vessels. The residual solids in the vessels were de-oiled and conditioned by the process thus facilitating the speed of removal from the vessels and also their disposal.
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