Water Mist Protection Requirements for Very Large Machinery Spaces

摘要

This report provides an evaluation of the fire fighting capabilities of water mist fire suppression systems in large (caret)3000 m(exp 3) machinery spaces. The primary objective of this investigation was to evaluate the applicability of the International Maritime Organization test protocol to larger, Class 3 machinery spaces (>3000 m(exp 3). Four generic water mist systems produced using off-the-shelf industrial spray nozzles were included in this evaluation. The capabilities of both total protection and zoned total protection systems were identified during this investigation. The zoned systems demonstrated the same extinguishment capabilities as the total protection systems. The systems were evaluated against a series of heptanes spray and pan fires ranging in size from 2.5 - 10.0 MW. The fires were located under a 1.0 m horizontal obstruction plate adjacent to a bullhead similar to the fires conducted in MSC Circular 668. The capabilities observed for the water mist systems (both zoned and total flooding) in the 3000 m(exp 3) machinery space followed the same trends found throughout literature on water mist. The steady- state extinguishment model developed during previous phases with this investigation showed reasonably good agreement with the results of these tests. The strengths and weal messes of the IMO test protocol were also identified. The conservative nature of the protocol (due to the high ventilation rates and smaller fire sizes (i.e., 1.0 MW)) will limit the use of water mist in larger machinery spaces. Based on this analysis, it was concluded that it is highly unlikely that any system discharging only water will ever successfully complete the protocol for volumes greater than 2000 m(exp 3).