1. Fire Department Hydraulics
Unit 4 Seminar
Discharge

2. What is the importance of sprinklers in a building??

3. Sprinklers
Sprinkler systems have been around since the mid-1800s, with the first sprinkler head invented in 1874.
The standards for sprinkler systems are contained in NFPA 13.
The NFPA has estimated that sprinklers typically reduce the chances of dying in a home fire by one-half to two-thirds

4. Sprinklers There are four basic types of systems: Wet-pipe system
Dry-pipe system
Pre-action system
Deluge system

5. Sprinklers Wet-Pipe System
Wet-pipe systems are the most common and reliable of the four types of systems.
The wet-pipe system is filled with water under pressure at all times.
This type of system is used in areas that are not subject to freezing.

6. Sprinklers
Water is held in place within the head by a fusible link or a similar device that is designed to melt or break at a predetermined temperature, thereby releasing water onto the fire.
The typical discharge of water from the sprinkler head is approximately 15 gpm.
Each sprinkler head will protect approximately 100 square feet of floor space.

7. Sprinklers Dry-Pipe System
A dry-pipe sprinkler system is one that is designed for use where freezing conditions are present or likely to occur.
In lieu of water, the system is filled with air under pressure.
When a fire occurs and ruptures a sprinkler head, the air escapes, which trips the dry-pipe valve.

8. Sprinklers Pre-Action System
A pre-action system is similar to a dry-pipe system.
The difference between the two systems is in the manner that water is allowed to enter the system.
With a pre-action system, water is held back from entering the sprinkler system by an electrically operated valve known as a pre-action valve.

9. Sprinklers
The pre-action valve identifies a developing fire which opens the pre-action valve.
A sprinkler head operates to permit water to flow onto the fire.
When the fire is extinguished, a separate thermal device cools, which shuts off the water flow.

10. Sprinklers Deluge System
The deluge system is equipped with open sprinkler heads.
The tripping of the fire detection system trips a deluge valve, which immediately releases water to all the open heads.
Deluge systems are primarily found in specialized industrial situations where a fast-moving fire may make it necessary to quickly extinguish the fire.

11. Sprinkler Heads Sprinkler heads are the heart of a sprinkler system.
The typical head has a 1/2-inch opening.
The operating temperatures of sprinkler heads vary from 135 degrees to 575 degrees.
The temperature rating of a sprinkler head can be identified by the color-coding on the sprinkler frame or the frangible glass bulb.

12. Sprinkler Heads
A simple formula for use with 1/2-inch heads, which has been in the fire service for a long time, follows:
Discharge = P/2 + 15
Let’s use this formula to solve the previous problem.
Discharge = 25/2 + 15
Solution: 27.5 gpm
When the sprinkler head has a 1/2-inch diameter, the solution obtained by either formula will provide a good approximation of the discharge.

13. Sprinklers
Some departments have a policy that the first or second engine company arriving at a sprinklered occupancy should lay a line into the fire department connection to support the sprinkler system.
The pump operator should start water flowing and maintain a pressure at the pump of 150 psi until the number of heads going off is known.
A sprinkler system should not be shut down until the officer-in- charge is certain that the fire has been extinguished or is under absolute control.

14. Nozzle Pressure
Many fire departments have standardized pressures for certain lines and nozzles:
50 psi for smooth-bore handline
80 psi for smooth-bore master stream
100 psi for fog nozzles, both handlines and master streams

15. Nozzle Discharge Comparing Discharge
The simple formula for comparing discharge when nozzle pressures are identical but the nozzle sizes are different is:
(D/d)²
D = larger tip size
d = smaller tip size

16. Nozzle Discharge
So how much more water can we flow through a 2-inch tip compared with a 1-inch tip when the pressures are the same?
Plug the numbers into the formula (D/d)2.
Solution: four times as much water