POSITION YOUR GAS NOZZLE
Distribution and locating gas nozzles to ensure full room coverage of your gas system is one of the most important factors.
Nozzles
Nozzles are available in 180° and 360° discharge patterns from most suppliers. The 180° (sidewall) nozzle is designed for installation along the walls of the hazard, with the discharge directed away from the wall on which it is installed. The 360° nozzle is designed to be installed in the centre of the area being protected.
CO2 nozzles are also supplied in a variety of styles for local application use.
Design
The hydraulic design programme calculates the size of the nozzle and its orifice size. These are drilled by the supplier and numbered as to the specific place in the pipe network that they must be installed.
Positioning
Nozzles shall be positioned to ensure the design concentration of the gas is achieved in all parts of the enclosure. The velocity of discharge should not adversely affect the enclosure or contents. The rate of discharge can blow loosed items around the room. The rate of discharge should not pose a threat to persons within the protected area.
Ceiling Clearance
Using test protocols nozzles should be placed a maximum of 300mm from the ceiling.
Nozzles must be installed so that the orifices are located close to the ceiling. Ref: SANS 14520 C3.2 a)
Maximum Ceiling Height
A maximum ceiling height when using discharge nozzles is specified by the manufacturer and should be kept to. This is generally around 5m. For hazard volumes higher than 5 meters, an additional row of nozzles is required at ceiling height.
Nozzle Area Coverage
Both the 180° and 360° nozzles will have a maximum coverage distance, these distances will vary for 180° and 360° nozzles. These parameters will show a straight-line distance from the nozzle to the farthest corner of the protected space.
These distances may vary from supplier to supplier and must be checked before installation.
Typical nozzle placement and coverage
180° Nozzles
180° nozzles for either engineered or pre-engineered systems should follow the following rules.
Nozzles must be located from 300mm to 50mm from a wall, with the orifices directed away from the wall. The nozzle shall be located as close to the centre of the wall as possible, but at least 1/3 of the way along the wall.
180° nozzles can be used in a back-to-back configuration.
360° Nozzles
360° Nozzles must be located as close to the centre of the enclosure as possible.
Walls and Obstructions
Chemical agents and CO2 discharged from the nozzle require a certain length from the nozzle to atomize into a gas. If the chemical agent comes into contact with a surface before the agent is fully atomized, frosting can occur. As a result, the concentration throughout the enclosure will be less than the required to appropriately protect the space. Therefore, nozzles must be located at least 1.2 to 1.8 m clearance from walls and/or significant obstructions (e.g. high rise racking and columns).
If this requirement cannot be met, additional agent may be discharged to compensate for this agent “loss”.
Reduced Area Coverage
Consideration should be given to reducing nozzle spacing when obstructions that would impede the uniform distribution of the chemical agent throughout the area are present.
Painting of nozzles
Nozzles must not be painted under any circumstances.
Always check with your supplier the discharge patterns etc of the nozzles supplied before installation.