In SOLAS chapter II-2 as amended in 2000, the following vessels having machinery spaces of category A above 500 m3 in volume are required to be installed with a fixed water-based or equivalent local application fire-fighting system (hereinafter, referred to as "the system") to protect the fire hazard portions in the machinery spaces.
(1) Passenger ships of 500 gross tonnage and above, and cargo ships of 2000 gross tonnage and above, constructed on or after 1 July 2002; and
(2) Passenger ships of 2,000 gross tonnage and above, constructed before 1 July 2002. (the system should be installed not later than 1 October 2005)
The system is required to be of approved in accordance with the guidelines developed by IMO (MSC/Circ.913), however, the unified interpretations for the guidelines are still being discussed in IMO/FP and IACS WP/FP&S.
As the interpretations for the guidelines partially informed in previous ClassNK Technical Information No. TEC-0453, in addition, please be notified of ClassNK provisional interpretations for the system on the basis of the interpretations agreed in IMO, IACS and/or the sectional meeting of The Shipbuilding Research Association of Japan (Sectional meeting Code : RR-S4) so far, as follows;

1. Definitions

(1) Protected space is a machinery space, which the system is installed in accordance with the requirements of Reg.II-2/10.5.6 of SOLAS amendments.
(2) Protected area is an area which is required to be protected by the system in accordance with the requirements of Reg.II-2/10.5.6 of SOLAS amendments.
(3) Assigned protected area is an area which is assigned according to the result of tests based on MSC/Circ.913. (Refer to Fig.1)
(4) Water mist affected area is, in general, as follows:
(I) horizontally, within radius of S (maximum allowable spacing between nozzles determined as one of the design criteria of the fire fighting systems) of each nozzle. (Refer to Fig.1)
(ii) vertically, from the level of nozzles down to the nearest deck or similar construction.
(5) Overhead crane operation area is an area which maneuvering of the crane and move of goods is affected by the installation of the system.

(To be continued)