Nozzles & monitors
Published: 01 September, 2006
There is a great debate raging worldwide over nozzles and application of water in the fire rooms. What seems to be the best balance for interior structural fire attack is a solid bore nozzle or a combination nozzle always operated on straight stream. A 15/16th-inch solid bore nozzle will discharge 180 gpm onto the fire at 50 psi nozzle pressure assuming the water supply is adequate.
When the nozzle is operated in a clockwise manner into the fire area, the water is bounced off the ceiling, breaking it into large drops that rain down in the room onto the fuel to stop combustion, thereby putting the fire out, says Jerry Knapp.
Fog Nozzles
Industrial settings provide a classic application arena for fog nozzles. Industrial facilities usually have large quantities of combustible or flammable gases and liquids. Obviously fog streams will fight fires involving these fuels. Combustible liquids with relatively high flash points can be extinguished with fog lines by lowering the temperatures in and around the fire, the smothering effect of the subsequent steam, the cooling of hot metal and burning ordinary combustibles in the fire area.
Fog streams can also be used effectively to hold flammable gas fires at bay long enough to shut off a valve or pinch off a leaking and burning supply pipe. Fog streams can be employed to reduce the effect of radiant heat on storage tanks to prevent ignition or major container failures due to internal over- pressurisation and subsequent rupture due to heat.
Automatic Nozzles
A major weakness of both fixed gallonage fog and solid bore nozzles is that they need relatively specific water volumes and pressures to operate to produce an effective stream. The automatic nozzle has resolved this problem. Using a spring mechanism built into the nozzle, it senses the amount of water being sent to the nozzle and adjusts the tip size to maintain appropriate pressure for that nozzle.
This creates the proper nozzle pressure, resulting in a stream with the proper reach and shape. Many automatics operate over a wide flow range, some as much as 50-300 gpm. It is important to remember that because the nozzle is always producing a stream at the proper pressure, the water volume must be supplied to ensure the stream not only looks good but is also discharging enough water to put the fire out.
Using monitors tactically
Only through the use of ‘high-flow’ nozzles and firefighting monitors can the ‘tactical solutions’ associated with hard-hitting masterstreams of water be fully realised, writes Paul Grimwood.
A firefighting monitor excels not only in its striking power but also in its ability to gain maximum ‘reach’ advantage during its application of water and foam.
Accordingly, the tactical use of high-flow nozzles & monitors covers a broad range. Obviously the greatest need for high performance monitor systems exists in the industrial and petrochemical sectors and equipment is specifically designed to match the risk.
Methods for optimising the configuration and aim of monitor fire streams, with respect to burning fuel tanks have been developed and the Williams Fire and Hazard Control organisation is an innovators in what it terms ‘Footprint Technology’ (US Patent) - which is a method for extinguishing flammable and combustible liquid tank fires.
Focusing upon the more traditional ‘surround & drown’ techniques, the footprint technology concentrates on specific features of a tank fire, noting that the fire will actually be ‘breathing’ in an area known as the ‘sweet spot’ - this is where the fire takes in air (oxygen).
Adjacent to this ‘sweet spot’ the fire will pulsate. A combination of sweet spot, breathing and thermal drafts would normally drive foam back and away from the middle of the tank surface. Experience has demonstrated that this ‘sweet spot’ normally lies just off the centre of the tank and ‘footprint technology’ methods aim to place the foam predominantly toward this area.
Mid-Range Monitors
Popular with the process and petrochemical sectors, fixed mid-range monitors include the Elkhart Spitfire which flows up to 7,500 lpm (2,000 gpm) and the Akron StreamMaster with similar flows. The Groupe Leader (France) has a range which can offer the higher flow 9,000 lpm (2,400 gpm) Projet version or the Task Force Tips waterway of the Petro-Jet (Protector) monitor flowing up to 4,700 lpm (1,200 gpm). All monitors work within a range of 50 - 75 metres horizontal throw capability.
Moving on up the scale, we are able to appreciate the awesome flows achieved by monitors such as the Angus Mega-Colossus 40,000 lpm (10,500 gpm) high-capacity foam system - an exceptional aspirating foam cannon delivering stable amounts of foam 90-100 metres from the monitor. The smaller Colossus version throws its 15,000 lpm (4,000 gpm) of foam 85 metres ground-to-ground.
The Chubb Fire Slimjet range of foam/water monitors offers ‘mortar’ looking designs capable of flowing straight streams in excess of 43,000 lpm (11,400 gpm) of aspirated foam or 7,275 lpm (2000 gpm) of water over 100 metres horizontally and 60 metres vertically. In the same league, the massive 17,000 lpm (4,500 gpm) Hyper-Projet from Task Force Tips can discharge its water-fog or jet stream up to 100 metres on the horizontal.
However, the highest flows are reserved for the Williams Fire & Hazard Control Trailer mounted monitor - Bigfoot - which at 53,000 lpm (14,000 gpm) will discharge its monumental ‘tower’ of water in excess of 135 metres horizontally and 35 metres vertically.
Oscillating monitors may be either fixed, portable or trailer mounted. A wide range of oscillating type monitors is available which provide a powerful, sweeping waterstream for high-performance attack and protection.
