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, ratings,
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 abla-
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).
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.
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
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.
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:
I. High-pressure 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