Flammable liquids are volatile in nature. As they evaporate, they may produce
ignitable vapor/air mixtures. Such hazardous conditions are commonly encountered
in chemical, petrochemical, petroleum and pharmaceutical plants where the
storage, transfer and collection of flammable liquids are part of their daily
operations.
Flame arresters and detonation arresters are passive, mechanical device
installed on a storage tank nozzle or in a flammable vapor piping system. The
arresters' functions are: (1) to allow the passage of vapor under normal
operating conditions and (2) to stop and extinguish any flame front propagating
through the flammable vapor/air mixture under emergency conditions. Stopping the
flame protects the storage tank, or the equipment located in the piping system,
from the catastrophic damage that may result from an uncontrolled ignition. A
variety of arrester designs are available. The choice of a proper arrester
depends on factors such as the location of the arrester with respect to the
ignition source and the flammable properties of the vapor/air mixture.
One common flame arrester configuration is
mounted at the end of a storage tank vent pipe and is identified as an
"END-OF-LINE" flame arrester. This arrester permits normal tank
breathing, while preventing the flashback of an unconfined deflagration (the
ignition of the vapor cloud in the open atmosphere) from flashing back past the
arrester into the piping and the tank's vapor space.
Flame arresters are at times mounted
directly upstream of pressure / vacuum relief vents, or are connected to short
runs of open vent outlet piping. These devices, known as "VENT-LINE /
IN-LINE" flame arresters are designed with flanged or threaded mounting
connections on both the inlet and outlet. It is possible for a flammable vapor /
air mixture to ignite within the confined space of the short outlet pipe or
within the vent body. Such an ignition is referred to as a confined
deflagration. The flame speed is slow and pressures within the vent piping are
relatively low. The Vent-Line / In-Line Flame Arrester is designed to stop this
type of flame front. Note: these arresters have very specific limitations as to
where they can be properly located within the system.
Strict enforcement of environmental
pollution standards has had a dramatic impact on tank storage of flammable
liquids. Rather than expelling vapors into the atmosphere, the trend has been
toward the connecting or manifolding of multiple tanks through common piping to
a central processing unit. These closed piping systems, or vapor recovery /
collection systems, have created unique flammable vapor safety hazards. The
piping runs in these vapor recovery systems tend to be longer and more complex.
Potential sources of ignition may actually be present within the vapor
collection system itself. An ignition within a piping system can result in a
flame front that accelerates very rapidly and generates extremely high
pressures. A low speed, low pressure confined deflagration can readily
transition into a high speed, high pressure confined deflagration and then to a
detonation, which is a flame front moving at the speed of sound in the vapor/air
mixture. "DETONATION" arresters are specifically designed to stop and
extinguish detonations, confined deflagrations and unconfined deflagrations. The
limitations that are placed on the location of end-of-line and vent-line /
in-line flame arresters with respect to the ignition source do not apply to
detonation arresters.
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Last modified: January 22, 2004
One common flame arrester configuration is
mounted at the end of a storage tank vent pipe and is identified as an
"END-OF-LINE" flame arrester. This arrester permits normal tank
breathing, while preventing the flashback of an unconfined deflagration (the
ignition of the vapor cloud in the open atmosphere) from flashing back past the
arrester into the piping and the tank's vapor space.
Flame arresters are at times mounted
directly upstream of pressure / vacuum relief vents, or are connected to short
runs of open vent outlet piping. These devices, known as "VENT-LINE /
IN-LINE" flame arresters are designed with flanged or threaded mounting
connections on both the inlet and outlet. It is possible for a flammable vapor /
air mixture to ignite within the confined space of the short outlet pipe or
within the vent body. Such an ignition is referred to as a confined
deflagration. The flame speed is slow and pressures within the vent piping are
relatively low. The Vent-Line / In-Line Flame Arrester is designed to stop this
type of flame front. Note: these arresters have very specific limitations as to
where they can be properly located within the system.
Strict enforcement of environmental
pollution standards has had a dramatic impact on tank storage of flammable
liquids. Rather than expelling vapors into the atmosphere, the trend has been
toward the connecting or manifolding of multiple tanks through common piping to
a central processing unit. These closed piping systems, or vapor recovery /
collection systems, have created unique flammable vapor safety hazards. The
piping runs in these vapor recovery systems tend to be longer and more complex.
Potential sources of ignition may actually be present within the vapor
collection system itself. An ignition within a piping system can result in a
flame front that accelerates very rapidly and generates extremely high
pressures. A low speed, low pressure confined deflagration can readily
transition into a high speed, high pressure confined deflagration and then to a
detonation, which is a flame front moving at the speed of sound in the vapor/air
mixture. "DETONATION" arresters are specifically designed to stop and
extinguish detonations, confined deflagrations and unconfined deflagrations. The
limitations that are placed on the location of end-of-line and vent-line /
in-line flame arresters with respect to the ignition source do not apply to
detonation arresters.