Automatic Fire Sprinkler Systems in Bangladesh

How does a sprinkler head know when to open?

Each head is held shut by a small glass bulb or a fusible link. The liquid in the bulb expands with heat until the glass breaks, and the water pressure behind it pushes the seal out. Bulbs are color-coded by temperature, with red at 68 °C being the most common rating for ordinary rooms.

Only the heads that reach their rating open. The film image of every head spraying at once is wrong, and it is why sprinklers cause far less water damage than people expect. Most fires in sprinklered buildings are controlled by a small number of heads, often before the fire service arrives.

Why does hazard class matter so much in a factory?

NFPA 13 sets the water density and the operating area from the hazard. An office is light hazard, a sewing floor is typically ordinary hazard, and a warehouse of cartons or rolled fabric stacked high is storage, which needs much more water. Designing a whole building to one class either wastes money or leaves the store rooms underprotected.

High-piled storage is where we see the most mistakes. Standard heads at a high roof may not reach a fire deep in a rack. Depending on the commodity and storage height, the answer may be in-rack sprinklers or ESFR heads, which need their own pump and tank capacity. We size these from the storage plan, so tell us how you stack goods.

Wet, dry, pre-action or deluge?

Almost all sprinkler systems in Bangladesh are wet pipe, with water held in the pipes at all times. Pre-action systems keep the pipes dry until the fire alarm confirms a fire, which suits server rooms and archives where an accidental leak would be costly. Deluge systems use open heads and are reserved for special hazards such as transformer bays.

Dry pipe systems hold air under pressure and are built for places where pipes could freeze, which is rare here outside cold stores. Whatever the type, the sprinkler control valves, flow switches and tamper switches are wired to the fire alarm, so a flowing head or a closed valve shows up on the panel at once.