Passive fire protection is defined as any fire protection
system that by its nature plays an inactive role in the protection of person-
nel and property from damage by fire. Appendix F contains additional
information on passive fire protection maintenance, rat- ings, and
penetrations. Passive fire protection is quite often generically referred to as
Structural Fire Protection (SFP), particularly in governmental regulations.
Examples of passive fire protection systems would be spray-on insulating
materials or insulating blankets of fireproof materials. Conversely, examples
of active fire protection systems would be tire water, APPP, CO, or dry
chemical systems. API Publ 2218 Fireproofing Practices in Petroleum and
Petrochemical Processing Plants can provide useful information regarding
fireproofing practices, materials, etc.
passive fire protection is not used as the only means of fire protection, but
rather it is used in concert with active fire protection systems. This is
because passive fire protection does not, in and of itself, provide inherent
protection and is normally effective only for a finite time period. Once
passive fire protection is exhausted, the protected component is vul- nerable
to damage by fire. Examples of where passive fire protection is used are:
critical structural steel, living quarters, firewalls, etc.
Them are many types
of fireproofing materials available and in use throughout the industry. These
materials are lightweight con- cretes, preformed inorganic panels, masonry
blocks and bricks, man-made mineral fibers, and subliming, intumescent, and
mastics. However, the fireproofing materials that have been most commonly used
in the offshore petroleum industry, and which will be addressed here, can be
broken down into two generic groups; active and inactive insulants. The active
insulants undergo chemical and physical changes when exposed to fire and the
inactive insulants do not.
fnsulants. The active insulants are generally available as
ceramic fiber (or similar fireproof materials) structures in an epoxy-based
matrix which contains additional chemicals designed to cause some chemical or
physical reaction upon exposure to heat. The active insulants typically are
available in multiple-part mixtures which when mixed together form a slurry
suitable for spray application. However, they can be purchased in pre-cast
panels which can be bolted in place. Active insulants are also known as
intumescent materials because when they are exposed to heat, they undergo a
physical and chemical change which causes them to expand to several times their
applied volumes, thereby providing enhanced insulation.
Inslliants. The inactive insultants can be grouped into two
general groups: cementitious materials and man-made fibers, such as ceramic
fiber or mineral wool. The cementitious materials, as the name implies, are
essentially cement-based mate- rials of a fire brick refractory blend, which
are normally mixed as a slurry and spray-applied; however, these materials are
also available in precast slabs which can be bolted in place. Man-made fiber
insulants come in many different forms: blankets, bulk, panels, etc. These
systems are installed by mechanically supporting them in or on a wall or
forming additives increase the effectiveness ofwater in controlling pooled
liquid-hydrocarbon fires. A tire fighting foam is a stable aggregation of small
bubbles of lower density than water or oil having a tenacious quality for
covering and clinging to horizontal or inclined surfaces. It has the capability
of flowing freely over a burning liquid surface, cooling the liquid, and form-
ing a tough, air-excluding, continuous blanket to seal combustible vapors from
access to air. Foam systems are not effective on gas pressure tires or grated
areas. NFPA 11 Foam Extinguishing Systems should be consulted when
planning, designing, or installing foam systems.
may be employed using (I) hose stations, (2) fixed systems, or (3) portable
extinguishers and should capable of being actuated manually. The foaming agent
may be applied by directly introducing foam concentrate into the fire water
system or may be applied as a premixed solution of concentrate and water.
may be stored in a tank or in the vendor’s shipping container. The storage
location(s) of foam concentrate and premixed solutions should be selected
considering the difficulty to replenish the system during an emergency, and the
minimum ambient temperature because foam concentrates and premixed solutions
are subject to freezing. The foam concentrate must be kept in ade- quate supply
and not contaminated or diluted and the operator should follow the
manufacturer’s recommendation for testing. When dry chemical and foam
extinguishing agents can be used at the same location, compatibility of the two
products should be confirmed with the manufacturer(s).
Concentrate Proportioning. Foam concentrates are available for mixing
with water in fixed proportions; commonly, one through 6% mixtures with water.
The correct amount of concentrate may be introduced directly into the fire
water system by use o f either eductor stations or diaphragm tanks.
Eductor Stations. A simple means to supply foam to a hose station is
through the use of an eductor to pick up the foam and proportion it into the
water stream. The main disadvantage of an eductor is the pressure loss across
it (on the order of one- third). This loss must be taken into account in the
design of a system. Conventional fire hose nozzles are available that will
provide sufficient aeration to form a foam. Because eductors are sensitive to
back pressure, fixed rate nozzle gallonage rating and eductor ratings must
match. Manufacturers’ data should be consulted for maximum lengths of hose that
can be used. Actual length of hose used should not exceed the manufacturers’
recommendation less equivalent lengths of fittings, etc., downstream ofthe
eductor. Eductor concentrate hose stations can be provided in a package
containing all the components pre- assembled, including a concentrate storage
Premix Systems. Premix systems may be used when a self-contained fire
fighting system is desired. A means of storing the solution is required along
with a means to expel the solution. Commercial equipment is available for this
purpose and must be tai- lored to fit a particular application. Premixed
foam-water solutions should be periodically tested and replaced to ensure their
proper concentration and chemical integrity.
DRY CHEMICAL SYSTEMS
chemicals extinguish by interrupting the chemical reaction of the fire. Dry
chemical is very effective at reducing flame, but does not cool or provide
reflash protection. Dry chemical is most commonly used in portable or
semi-portable extinguishers, but may be used in hose reel or fixed system
applications. Fixed systems are typically employed over cooking surfaces or
deep fat fryers. Dry chemical is deployed as a powder driven by a compressed
gas propellant. The powder poses risk of injury if inhaled, and can be
dissipated by wind, reducing its effectiveness in exterior applications. The
powder can be corrosive to electrical com- ponents. The nature of potential
fires should be carefully considered in selecting and sizing the type of dry
chemical and equip- ment. NFPA 17 Dry Chemical Systems should be
consulted when planning, designing, or installing dry chemical systems.
Types o/Dry Chemical Agents. Dry chemical agents are available for all
classes of fires. The terms “regular dry chemical” and “ordinary
dry chemical” refer to powders that are listed for use on Class B and
Class C fires. “Multipurpose dry chemical” refer
Watermist, or tine
water spray systems extinguish fires by rapid cooling effect, combined with
localized displacement of oxygen at the flame source as the mist is flashed
into steam. Watermist systems may be used in applications suitable for a fixed
gaseous or sprinkler system. Watermist utilizes stored fresh or distilled water
and leaves no residues. Electrical equipment should be de-ener- gized before
deployment ofwatermist, although it can be safely discharged while electrical
equipment is energized.
Types o f
Watermist Systems. Watermist
systems may be designed to protect a single location or multiple locations. The
systems come in two basic configurations:
systems provide fresh water propelled by Nitrogen or other compressed gas at
pressures of 150 psi – 4,000 psi. Water is distributed by a single
high-pressure piping system to nozzles, where the water is atomized into a fine
mist as it passes through an orifice.
2. Low-pressure systems operate at under 150 psi. Water and compressed air are
separately piped to each nozzle, where they mix to create a mist.
b. Fixed System
Considerations. Watermist systems typically use far less water than
sprinkling systems. The space and volume requirements for watermist systems are
comparable to that for a fixed gaseous system.