This is a two-part white paper with Part 1 focusing on what nozzles do and nozzle types available in today’s market. Part 2 concentrates on some considerations for selecting a nozzle.
PART 1:
What Nozzles Do
Nozzles are designed to help put out fires by getting the right amount of water, in the right form, in the right place. Nozzles deliver the following:
- Control Water or Foam Flow. The size of the orifice in the outlet of the nozzle controls the flow.
- Provide Reach. The nozzle creates a restriction at the end of the waterway, which changes water pressure to velocity. Velocity provides the reach, which is necessary to get the water to where it is needed.
- Create Shape. Different situations require different methods of applying water or foam. Some situations require the reach and penetration of a smooth bore or straight stream, while others require the heat adsorption capability or radiant heat protection of a wide-angle fog spray.
Nozzle Options
There are five basic nozzle types:
- Smooth or solid bore
- Fixed orifice or single gallonage (sometimes called variable pressure/variable flow)
- Selectable or adjustable gallonage
- Automatic or constant pressure
- Multi-purpose nozzle (combination smooth bore and fog)
Of the five, the latter four make up a group of nozzles commonly called combination nozzles because they produce both a straight and a fog stream. Below is an overview of each type of nozzle.
Smooth or Solid Bore Nozzle
The smooth or bore nozzle is the most basic of the five nozzle types, both in design and function. Its purpose is to produce a solid stream of water with large droplets, which provides maximum reach and penetration. The smooth bore is typically available as a tip or in a break-apart configuration.
Fixed Orifice (Single, or Variable Pressure/ Variable Flow Gallonage) Nozzle
The fixed orifice nozzle, the simplest form of the combination or fog nozzle, provides flow at a predetermined rate of pressure that cannot be altered significantly while in use. However, when the nozzle pressure is varied, the flow varies either increasing or decreasing based on changes in the pump discharge pressure. Most of today’s fixed orifice nozzles can provide quality patterns even at reduced nozzle pressures as low as 50 psi. The fixed orifice is typically available as a nozzle, tip or in a break-apart configuration.
Selectable (Adjustable) Gallonage Nozzle
Today’s selectable gallonage nozzles allow the nozzle operator to manually select a desired gallonage (flow) without shutting down. Like the fixed orifice nozzle, selectable gallonage nozzles can provide quality patterns even at reduced nozzle pressures. The selectable gallonage is typically available as a nozzle, tip or in a break-apart configuration.
Automatic (Constant Pressure) Nozzle
An automatic nozzle is designed to maintain a relatively constant pressure over a wide range of flows. This is accomplished by a mechanical mechanism (typically a spring) in the nozzle that automatically adjusts to increase or decrease flow to maintain an outlet pressure, and thus provide optimum stream performance. It should be noted, that automatic nozzles when operated in low pressure conditions reduce flow in an effort to maintain optimum reach. The automatic is typically available as a nozzle, tip or in a break-apart configuration.
Multi-Purpose Nozzle
A combination smooth bore and fog nozzle, provides the maximum reach and penetration of a smooth bore, while still enabling the benefits of a fog stream at the same time or independently. This versatile type nozzle has the ability for large flows at reduced pressures, and is well suited for multiple applications: interior, exterior, and high rise attacks, CAFS systems, foam applications, direct and indirect attacks, cooling, protection, and ventilation. The multi-purpose is typically available as a nozzle.
