FIRE DEPARTMENT HYDRAULICS

Unit 4 SeminarDischarge

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

What is the importance of sprinklers in a building??

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

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

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

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

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

SprinklersSprinklers

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

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.

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

Nozzle PressureNozzle 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

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

Nozzle DischargeNozzle 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

Mahoney, Hannig, Fire Department Hydraulics, 2nd Ed. ©2009 by Pearson Education, Inc., Upper Saddle River, NJ

Nozzle DischargeNozzle 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