The Fire Sprinkler System

The sprinkler system is an automatic heat-based fire suppression system provided by a mechanical building services engineer to control fire at its incipient stage. The system is based on a hydraulically designed piping network to different sprinkler head units that open when heated at a certain temperature, control valves, water flow alarm, and drains.

Designing an efficient sprinkler system is of great concern in the building industry because of their direct relations to home occupant life and property. The layout drawing must indicate the positions of fire sprinklers, zone control valves, pipes, and their sizes.

Sprinkler system design and installation should also be based according to standards for an applicable system type. The sprinkler system Standards represent a consensus of what is necessary to provide an acceptable degree of protection while the three sprinkler system types are:

Wet pipe sprinkler system

Dry pipe sprinkler system

Preaction sprinkler system

The wet type sprinkler system contains water in its entire pipe network and thus discharge water immediately a sprinkler opens. This system is predominantly in use in the industry.

The Dry pipe sprinkler system network is filled with build air. The system uses a dry pipe valve to prevent connected water source to enter the piping network but opens the moment pressure builds up due to an opened sprinkler head. This system is a bit slow but is often used in a temperate climate where the piping network is susceptible to freezing.

The Preaction sprinkler system is an advanced version of the dry pipe sprinkler system with an independent means of fire detection other than the sprinkler head. This system typically uses a preaction valve to withheld water back from the piping network but opens only after the detection system verifies the fire. This thus adds extra security to prevent accidental discharge and is implored in an area sensitive to water such as libraries, museums, and data centers.                         

Types of Sprinkler Head

fire sprinkler

Fire sprinkler heads are the sensing devices of a fire suppression system. They are bulbs that melt or valves that open when the heat of a fire reaches a set temperature. They can be categorized in three ways:

1- According to the operation concept

2- According to the head response

3- According to the head coverage

4- According to the flow direction

Sprinkler head according to the operation concept can be Glass bulb type when its temperature sensing and flow preventer unit is made up of a frangible glass bulb containing liquid or a Fusible link type metal. This unit prevents water to be pushed out of the orifice by pressure in the piping network.

The sprinkler head divides the sprinkler head into the Standard response head, the Quick response head, and the Window sprinkler head. The Quick response head has its bulb size relatively thinner than the standard type and thus a higher time index can be achieved while the window sprinkler heads are designed to spray an even coat of water mostly for a flat, vertical glass surface.

fire sprinkler

The sprinkler head coverage sizes divided sprinkler into two: those with Standard spray sizes as specified by the NFPA and those with an Extended spray coverage diameter.

Mechanical building services designers are more concerned about sprinkler classification according to the flow direction which is empirically based on the installation method. Based on this, the fire sprinkler head is of 3 types:

fire sprinkler

The Pendant sprinklers hangs down from the ceiling and spray water in a circular pattern, the Upright sprinklers project upward into space, while the Sidewall sprinklers spray away from the wall in a linear or crescent pattern.

Sprinkler Hazard Classification

The effect of fire in our buildings varies for different projects to construction types. Identifying the fire effect level for a project is the first step in designing an efficient fire sprinkler system. The fire regulation bodies classified building projects into three hazard categories:

Light hazard occupancies

Ordinary hazard occupancies               

Extra hazard occupancies

The light hazard occupancies are building projects with low combustibility contents and low heat rate. This hazard classification includes residential projects, institutional, business apartments, and educational projects except for large stack rooms.

The Ordinary hazard occupancies can be divided into group 1 and group 2 hazard types.

The Ordinary groups 1 hazard are projects or project portions where combustibility is low but with moderate fire and heat rates. This hazard classification includes industrial apartment projects, commercial projects and occupancies having uses and conditions includes automobile showrooms, bakeries, manufacturing and processing houses, etc.                         

The Ordinary group 2 hazard are projects with moderate combustibility and fires rate but high heat is expected to be released. Example of such occupancies includes storage apartment project, utility apartment project, industrial apartment project, and occupancies having used such as large stack room areas, machine shops, post offices, printing and publishing, repair garages.

The Extra hazard occupancies on the other hand are also divided into group 1 and group 2 hazard types.

The Extra group 1 hazard is occupancy with very high combustibility contents, fire rate, and heat but with little or no flammable liquids. An example of such occupancies includes industrial apartment projects.

Extra group 2 hazards are occupancies with very high combustibility content, fire rate, heat, and substantial amounts of flammable liquids. This hazard classification includes a high hazard apartment project, and some industrial projects such as plastics processing, paint, and oil quenching industry.

Each Hazard classification has its design criteria to which the Sprinkler system design is based. 

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