Chapter 06

© 2008 Delmar, Cengage Learning

Specialized Water-Based Fire Protection Systems

Chapter 6


Learning Objectives

• State three reasons to install other types of water-based fire protection systems instead of standard automatic fire sprinkler systems

• Discuss the characteristics and applications for fixed foam systems

• Discuss the characteristics and applications for water spray fixed systems


Learning Objectives (continued)

• Discuss the characteristics and applications for foam-water sprinkler and foam-water spray systems

• Discuss the characteristics and applications for water mist systems

• Discuss the inspection and test requirements for acceptance of special water-based fire protection systems

• Recognize the possible impairments to special water-based fire protection systems


Introduction

• Water-based systems that protect special hazards:– Low-, medium-, and high-expansion foam systems– Water spray fixed systems– Foam-water sprinkler and spray systems– Water mist systems

• Provide protection where other systems would be inadequate

• Few major differences between these four types


Required Installations

• Models codes establish requirements based on occupancy conditions and use

• Model codes permit alternative suppression systems when approved

• Hazard evaluation determines the best system to provide appropriate protection

• Hazard determines the use of a particular type of system– Certain systems more appropriate for some hazards


Design and Installation Standards

• Water-based protection systems similar in many ways– Different enough to publish separate standards

• Standards do not state where to install these systems

• Design professional determines the type of system that is most appropriate

• Design professional implements the design and installation


NFPA 11, Standard for Low-, Medium-, and High-Expansion

Foam• Class B foam best for flammable and

combustible liquid fires• Standards for foam combine in NFPA 11• Other NFPA standards establish when foam

systems are needed to protect a hazard


NFPA 15, Standard for Water Spray Fixed Systems for Fire

Protection• Water spray fixed systems provide specialized

protection to different hazards– Transformers, motors, flammable liquids

• NFPA covers design, installation, inspection, testing, and maintenance of these systems

• Does not apply to systems in NFPA 13, NFPA 750, monitor nozzles, and explosion suppression


NFPA 16, Standard for the Installation of Foam-Water

Sprinkler and Foam-Water Spray Systems

• Deals with the use of foam• NFPA 16 covers foam-water sprinkler and spray

systems– First published in 1954

• Limited to using low-expansion type foam


NFPA 750, Standard on Water Mist Fire Protection Systems

• Relatively new standard– First appeared in mid-1990s

• Provides minimum requirements for water mist systems

• Does not establish operational measure or specific guidance on how to extinguish a fire

• Standard states that it is not a design handbook• Design requires verification of its viability


Types of Specialized Water-Based Fire Protection Systems

• Fixed automatic foam systems protect flammable and combustible liquid hazards

• Foam is an effective agent to meet all objectives– Foam is less dense than fuel or water– Freely flow over liquid surface

• Foam concentrate mixes with water to form a foam solution

• If proportioning incorrectly or used with incompatible equipment, foam will not work


Figure 6-1 These flammable liquid storage tanks are protected by a foam system that applies the foam onto the surface of the fuel inside the tank.


Foam Products• Low-expansion foam increases at a 2:1 to 20:1

ratio– Protect outdoor storage tanks, interior flammable

liquids, loading racks, diked areas, etc.

• Medium-expansion foam increases 20:1 to 200:1• High-expansion foam increases 200:1 to 1000:1• Medium- and high-expansion protect ordinary

combustibles, flammable liquids etc.


Fixed Foam System Components• Proportioning methods:

– Venturi proportioner method– Pressure proportioners– Balanced pressure proportioner

• Foam concentrate tank• Foam generating/distribution equipment

– Subsurface injection– Oscillating monitor nozzles– Foam maker chambers– Foam generators and pumps


Figure 6-3 Water enters the tank to put pressure on the rubber membrane bladder that in turn pushes the foam concentrate out of the tank.


Water Spray Fixed Systems

• Fixed piping network with specialized spray nozzles

• Designed to:– Protect specific equipment– Protect structural members surrounding equipment– Function as part of an overall fire protection

installation

• System delivers concentrated, directed water spray pattern onto surface of the hazard


Water Spray Fixed Systems (continued)

• Require at least one adequate automatic water supply

• Automatic activation is by a device such as heat, flame, gas detectors, etc.

• Automatic nozzles use the same technology as sprinkler heads

• Ultra-high-speed water spray system applies water to the hazard within 100 milliseconds


Figure 6-5 Water spray nozzles connected to a deluge valve surround this electrical transformer that is protected by fixed water spray system.


Foam-Water Sprinkler and Foam-Water Spray Systems

• Protect Class B flammable and combustible liquids– Acceptable for use with certain Class A hazards

• Primary design goal is extinguishment– Appropriate for prevention, control, exposure

protection

• Foam and water are companion agents• Pre-primed systems have foam and water in the

piping


Figure 6-9 Summary of relationship for systems, discharge devices, and foams.


Water Mist Systems• Discharges fine spray mist of water droplets out of

specialized nozzles– 99% of water mist must be 1000 microns or less– 25,400 microns equal one inch

• Droplets extinguish by cooling, displacing oxygen, blocking radiant heat

• Protect land facilities, marine and offshore facilities• Not appropriate for use with materials that react

with water


Inspection, Testing, and Maintenance Requirements

• Similar approval, inspection, and test processes as standard fire sprinkler systems

• All systems subject to the same acceptance inspections and tests

• All specialized water-based fire protection systems require flushing– Additional requirement to flush or clean the system

piping


Figure 6-9 Summary of required inspections and tests for specialized water-based fire protection systems.


Periodic Inspection, Testing, and Maintenance

• Inspection, testing and maintenance provide a level of confidence in the system

• Maintenance should be in accordance with established intervals in NFPA 25– Depending on conditions, daily to every five years

• Subject to impairments– Lack of proper inspection, maintenance, component

failure, environmental conditions, etc.

• Piping obstructions occur for many reasons


Summary

• Specialized water-based systems provide protection when sprinkler systems inadequate

• Differences from sprinkler systems:– Specialized spray nozzles and discharge devices– Integration of foam agents with water– Use of specialized components for application

• Different types of foam for different hazards• Water mist systems protect land facilities• Periodic system verification necessary

Chapter 06

Business

Transcript of Chapter 06