FIRE PROTECTION DESIGN

When designing the fire protection systems for warehouses type occupancy, in addition to commodity classification and storage configuration, there are many other variables, to consider, such as storage height versus building height, aisle width, and specific design feature of automatic sprinkler systems – that include temperature rating, orifice design, response time, and in rack sprinklers.

Other than the fire properties of the commodities themselves, the one condition that has the greatest influence on the progress of fire in a storage facility and on the difficulty of fire control than storage height.  Rack storage to heights of 40 feet or higher in buildings with a ceiling or roof height of 45 feet or above is common.  It is very possible to have automated storage and retrieval systems which use computer controlled robots for material handling operations to be as tall as 100 feet with very narrow aisles.

Aisle width is determined by the horizontal distance between the faces of the storage racks.  Aisles are usually four to eight feet wide, and the aisles allow for water from the ceiling sprinklers to reach a fire, help keep a fire from jumping from rack to rack and provide egress for firefighters and their equipment.

Many different models and styles of automatic sprinklers are available.  It is critical that the type of sprinkler head selected is approved by a nationally recognized testing agency and installed for the specific application.  Sprinklers are divided into two categories based upon the mechanism by which they are designed to attack fire.  Control mode sprinklers rely on cooling and pre-wetting. Allowing the fire to continue to burn in the area of ignition while controlling roof and ceiling temperatures and preventing fire spread until firefighters arrive or the fuel is consumed and the fire goes out.   These types of sprinklers are characterized by a relatively large area of operation, ie – 15-50 sprinklers.  Suppresion Mode or Early Suppression Fast Response (ESFR) sprinklers rely on penetration to stop fire growth quickly and drastically reduce heat release.  Usually 6 or fewer of this type of sprinkler is required.

NFPA 13 outlines the characteristics of a sprinkler head that define its ability to control or extinguish a fire.  Those characteristics include:

Thermal Sensitivity which measures the speed with which the thermal element operates as installed in a specific sprinkler or system.

Temperature Rating usually ranges from 165 degrees F to 286 degrees F

Orifice Size is the opening through which water flows depending on the amount of water needed to protect the occupancy.

Installation Orientation can be sidewall, pendent, or upright

Water Distribution Characteristics is the application rate and discharge pattern.

Special Service Conditions include dry sprinklers, corrosion resistant, rack storage sprinklers

With any sprinkler system, it is imperative that an adequate and reliable water supply is in place to ensure that the design requirement are met for ceiling sprinklers, in rack sprinklers, hydrants, standpipes, and hose systems.  A booster fire pump may be needed to assure the water requirement are met.