Water Spray Protection of Machinery Spaces

This report provides an evaluation of the firefighting capabilities of fixed pressure water spray systems for machinery spaces as described in Regulation 10 of Safety of Life at Sea (SOLAS). The objective of this evaluation was to determine if a system meeting the minimum SOLAS requirement can provide adequate protection of shipboard machinery spaces. To meet this objective, the capabilities and limitations of twelve water spray systems were determined using the International Maritime Organization (IMO) test protocol for water mist systems (MSC 668 and 728) as the basis for this analysis. The tests were conducted in a simulated 500-m3 machinery space onboard the U.S. Coast Guard's test vessel STATE OF MAINE. Generally speaking, the trends in performance of water spray systems were similar to those observed for water mist systems. All systems were capable of extinguishing larger fires (4 kW/m3 and greater) with variations in system capabilities becoming apparent as the fire size was reduced (2 kW/m3 and below). Only about half of the systems were capable of extinguishing the 1.0 MW obstructed spray fire located on the side of the engine mock-up (similar to IMO-6). Water mist systems typically exhibit slightly better capabilities primarily against the smaller fires. It was concluded that the capabilities of these systems cannot be associated with a single parameter such as application rate and must be determined empirically. As a result, the approval of these systems needs to be performance based as with all other fire suppression systems required by SOLAS. It was recommended that SOLAS Regulation 10 be re-written to cover all water based machinery space systems with the caveat that they pass a modified IMO test protocol based on the one currently used for approving water mist systems [MSC 668 and 728].