Bilge separator cleans to 5ppm

18 Mar 2012
Alfa Laval’s PureBilge is tested to perform fully to the DNV Clean Design specification

Alfa Laval’s PureBilge is tested to perform fully to the DNV Clean Design specification

Alfa Laval’s new PureBilge oily water treatment system is claimed to be the first that is certified to meet the DNV ‘Clean Design’ standard, cleaning to 5ppm rather than the IMO minimum 15ppm figure.

PureBilge has been tested by DNV to the5ppm type approval programme No. 771.60, introduced in 2011, and Alfa Laval has obtained Type Approval Certificate No. P-13965 for PureBilge 2005 and 5005 (2.5 m3/h and 5.0 m3/h).

Alfa Laval says that the DNV 5ppm type approval testing follows the same procedure as the standard 15ppm MEPC 107(49) test, with one important difference. DNV requires: “the 5ppm bilge water separator must be designed to operate in each plane that forms an angle of 22.5° with the plane of its normal operating position.”

This simulates a ship listing 22.5°. Thus, Alfa Laval believes that this goes some way towards simulating real life operating conditions at sea, although the company considers that it could have gone even further and simulated sea heave. Alfa Laval claims this additional test gives credence to its assertion that centrifugal separation is the only completely effective technology for bilge water treatment onboard ships.

The company points out that DNV Clean Design class notation is a voluntary newbuilding specification which covers most aspects of ship design and operation. For bilge water, Clean Design stipulates a maximum 5ppm of oil remaining in the water after treatment, prior to pumping overboard. MARPOL regulations stipulate 15ppm. Alfa Laval’s latest-generation PureBilge has also been granted the US Coastguard Certificate of Approval.

According to Alfa Laval, shipowners previously specifying 5ppm have had to take the word of the equipment supplier that the system really does meet the limit, something that has not always been the case, with some systems having difficulty reaching even 15ppm under real life conditions.

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