- High
Velocity Water Spray System
High
Velocity Water spray systems are installed to extinguish
fires involving liquids with flash points of 650 C (1500
F) or higher.
Some
of the worst fires which have occurred in the history of
fire fighting have been those involving oils and similar
inflammable liquids. Unless promptly tackled at the source,
such fires can rapidly grow to catastrophic proportions,
often with irreparable damage to valuable plant.
Fires
involving the heavier oils, with flash points above 650
C can be extinguished by properly applied fixed water spray
systems.
At
one time to recommend the application of water to an oil
fire was considered to be heresy. Some forty years ago it
was discovered that by applying the water to oil in particular
manner, a non inflammable, oil and water emulsion can be
formed. In this emulsion each droplet of oil is encapsulated
in a bubble of water which prevents the escape of vapours,
without which the fire can not be sustained. Extinguishment
of oil fires is dramatic in effect and even large fires
can be completely extinguished in a matter of 2 to 3 seconds.
The emulsion persists for 2 to 3 hours and there is no danger
of re-ignition. While cooling and smothering play a part
in extinguishment the main mechanism is the emulsification
process. Similarly at one time anybody advocating the application
of water to high voltage electrical fires was thought to
be out of his mind.
It was
found however that water applied in the form of the finely
broken needles to create an emulsion possessed a high resistance
to electric current. This equipment is now more or less standard
for live oil filled electrical gear and is quite commonly
installed for the protection of electrical equipment carrying
voltage of 400 KV or more.
Scope
of application
The
system is effective against fires of all flammable liquids
which are not miscible with water. The following are the
most important in every-day-use.
Liquids
which emulsify readily and form fairly stable emulsion
:
Mineral
Oils
Lubricating
oil, transformer oil, switch oil, diesel engine oil, gas
oil, boiler fuel oil.
Vegetable
Oils
Turpentine,
cotton seed oil, soya been oil, linseed oil, castor oil,
olive oil, coconut oil.
Animal
Oils
Whale
oil, cod-liver oil, halibut oil.
Principle
Unlike
the automatic sprinkler system, this application requires
a forceful directional water discharged achieved by specially
designed nozzles operating at a minimum pressure of 40 P.S.I.
or more according to the risk and environment. The discharged
is broken into droplets of water travelling at high velocity
which provide the necessary mechanical agitation and cooling
at the surface of the burning liquid.
Usually
this type of system is arranged with the nozzles or projectors
in groups having its own automatic control or detection
system. Careful hydraulic calculations are necessary in
the design of the system to ensure that each group of nozzles
which may be simultaneously operated is served with the
correct quantity of water and with required minimum pressure
at each nozzle. In the absence of which, emulsification
will not be achieved and the system will fall.
-
Medium
Velocity Water Spray System
Advance
in technology have brought about much wider usage in industry
of highly inflammable liquids, gases and solids. The fire
problems so produced have required new thinking and development
of new technologies. With fire risks involving the lighter
oils, liquefied petroleum gases and other flammable liquids
with flash points below 650 C it may not be possible or
even desirable to extinguish the fire completely. Under
such circumstances the aim is to achieve controlled burning.
Adequate control of such fires and also protection of vessels
and plant exposed to surrounding fire can be achieved by
properly designed medium velocity water spray system. Cooling
smothering and dilution play apart in varying degrees with
such a system and a well known example of such a system
is the PROTECTOSPRA SYSTEM. This type of system utilizes
sprayers which produce a medium velocity water discharged
with directional properties operating at a minimum water
pressure of approximate 20 P.S.I. sprayers can be arranged
for individual automatic operation or for automatic and
manual operation in groups to command the plant or fire
area concerned. Here again, the essence of the design is
proper discharged pattern, careful hydraulic calculation
and balance of flow and pressures. All systems are fitted
with alarm equipment and monitoring devices as required.
General
Information
Medium
velocity water spray system has been developed and extensively
installed for the following applications.
For fire risks involving the lighter oils, liquefied petroleum
gases, and other inflammable liquids, where it may not
be possible or desirable to extinguish the fire completely.
For
the protection of vessels, plant, and structures exposed
to heat from adjacent and surrounding fires.
