Ignition arises when sufficient
temperature is produced to cause ignition. Factors influencing resultant
combustion from a given ignition source are temperature, exposure time, and
energy. Ignition sources that may be present in offshore production operations
a. Chemical Reactions. Chemical reactions may produce heat.
This heat can ignite the substances reacting, products of the chemical
reaction, or nearby materials. A chemical reaction that might occur on an
offshore platform is spontaneous combustion.
Offshore facilities producing
hydrogen sulfide may develop iron sulfide as a product of corrosion. Iron
sulfide may be a source of heat and ignition due to spontaneous combustion when
exposed to air.
b. Electric Sparks and Arcs. An electric spark is the discharge of electric current
across a gap between two dissimilarly charged objects. Although static
electricity and lightning are forms of electric spark, they are listed as
separate ignition sources to empha- size their importance. Electric sparks from
most electric supply installations will usually ignite a flammable mixture
because the spark intensity and duration create enough heat for combustion. An
electric arc occurs when an electric circuit carrying current is interrupted,
either intentionally as by a switch or accidentally as when a contact or
terminal becomes loosened or a current-carrying conductor is broken. The arc
can be considered electric momentum. Electric current that is flowing through a
contact will try to keep flowing when the contact is broken. The same charge
will travel across a wider gap as an arc than as a spark. For this rea- son,
the opening of switches is a potentially greater ignition source than the
closing of switches. Sources of electric sparks and arcs could include but are
not limited to the following:
motors and generators.
Switches, relays, and other arcing components of electric circuits under normal
operating conditions. Electric wiring and equipment malfunctions.
Electric arc welding.
Fired vessel ignition devices.
Internal combustion engine ignition systems.
Electric powered hand tools.
c. Lightning. Lightning is the discharge of an electric charge on a
cloud to an opposite charge on another cloud or on the earth. Lightning can
develop very high temperatures in any material of high resistance in its path.
Lightning tends to discharge to high points such as antennae and flare stacks.
See API RP 521 and NFPA 78 for additional information that may be useful to the
d. Static Electrical Sparks.
If two objects are in physical contact and then separated, the objects
sometimes collect an electric charge through friction or induction. Similar
electric charges can be generated by rapid flow ofgases or liquids. fthe
objects are not bonded or grounded, they may accumulate sufficient electric
charges that a spark discharge may occur. The terms bonding and grounding are
sometimes used interchangeably; however, the terms have different meanings.
Bonding is done to eliminate a difference in potential between objects.
Grounding is done to eliminate a difference in potential between an object and
grOlmd. API RP 2003 Protection Against Ignitions Arising Out o fStatic,
Lightning, and Stray Currents can be referenced for additional information.
Static electrical sparks are
normally ofvery short duration and do not produce sufficient heat to ignite
ordinary combustible mate- rials, such as paper. Some, however, are capable of
igniting flammable vapors and gases. This situation is more common in a dry
atmosphere. Static electrical sparks may be a problem in situations such as the
containers, tanks, and pressure vessels.
exit fluid velocities. Drawing samples.
belt operation. Abrasive blasting.
e. Flame. When common
fuels are burned, energy is released in the form of heat. The burning is
generally accompanied by a luminosity called flame. Examples of situations
where flames may be present on a platform are the following:
I. Hydrocarbon flaring.
2. Fired production equipment burner
3. Gas welding and cutting.
4. Engine operation (backfires and hot
5. Heating, cooking, and other appliances
f. Hot Surfaces. Hot
surfaces can be a source of ignition. These sources may include the following:
I. Welding slag.
2. Fired vessel stacks.
3. Hot process piping and equipment.
4. Engine exhaust systems.
5. High-temperature electrical devices such
as incandescent lighting fixtures.
6. Frictional heat such as a slipping belt
against a pulley, unlubricated bearings, etc.
7. Heating and cooking appliances.
8. Hot metal particles from grinding.
9. Clothes dryers and exhaust systems.
g. Heat of Compression. If
a flammable mixture is compressed rapidly, it will be ignited when the heat
generated by the com- pressing action is sufficient to raise the temperature of
the vapor to its ignition point. Combustion as a result of heat of compression
may occur when hydrocarbon vapors or gases are mixed with air under situations
such as the following:
Improper purging of pressure
vessels and other equipment when introducing hydrocarbons. Packing or seal failure
that allows supply air to mix with supply or process hydrocarbons. Lubricating
system failure in air compressors.
Admission of air into the suction of hydrocarbon gas compressors.