NFPA 750 Dropsize Test Protocol
According to NFPA 750, Standard for the Installation of Water Mist Fire Protection Systems, 2000 Edition, drop size distribution alone does not determine the ability of a spray to extinguish a given fire and Scotch Mist® is an advanced system whose nozzles produce a mist which benefits from a variety of droplet sizes.
Drop size distribution, flux density and velocity are all involved in determining the ability of a mist to extinguish a fire in a given scenario [NFPA 750, Cl. A-1-4.21] and Scotch Mist® Blaster nozzles have been tested to establish this criteria. The tests were conducted at Spraying Systems Co. facility in Wheaton, Illinois, USA.
The nozzles were tested in accordance with NFPA 750 Standard on Water Mist Fire protection Systems 2000 Edition and ASTM E799 which require all measurements to be carried out at 1 metre distance. Testing included volume flux measurements and drop size measurements at various pressures, taken at numerous locations within the spray.
The one-component Aerometrics PDPA instrument used in this test has a 100-mWatt Argon-Ion laser to provide the light source. The transmitter and receiver were mounted on a rail assembly with rotary plates. Size range was adjusted to capture the full range of drops produced by the nozzle and, for each test point, 10,000 samples were acquired.
This illustration shows a typical volume flux contour plot, produced using Microcal's Origin 6.0 plotting software. The volume of water collected in each pan was measured and the Origin software set up to generate a 25x25 matrix to provide data for the contour plots.
The data used for establishing Volume Flux Weighting was calculated by using Method 2 as described in NFPA 750 and this illustration shows a typical plot.