A jet fire is a high temperature flame of burning fuel released under pressure in a particular orientation. The material burned is a continuous stream of

flammable A combustible material is a material that can burn (i.e., sustain a flame) in air under certain conditions. A material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort ...

gas, liquid or a two-phase mixture. A jet fire is a significant hazard in process and storage plants which handle or keep flammable fluids under pressure. The

heat flux In physics and engineering, heat flux or thermal flux, sometimes also referred to as heat flux density, heat-flow density or heat-flow rate intensity, is a flow of energy per unit area per unit time (physics), time. Its SI units are watts per sq ...

of the jet flame can cause rapid mechanical failure thereby compromising structural integrity and leading to incident escalation.

Context

The

Piper Alpha disaster Piper Alpha was an oil platform located in the North Sea about north-east of Aberdeen, Scotland. It was operated by Occidental Petroleum (Caledonia) Limited (OPCAL) and began production in December 1976, initially as an oil-only platform, but ...

in 1988 demonstrated how the accidental release of hydrocarbon can lead to the catastrophic failure of an installation with the rupture of major

pipeline A pipeline is a system of Pipe (fluid conveyance), pipes for long-distance transportation of a liquid or gas, typically to a market area for consumption. The latest data from 2014 gives a total of slightly less than of pipeline in 120 countries ...

risers. Jet fires impinged on vessels, pipework and firewalls. Under these conditions the

fireproofing Fireproofing is rendering something (Building, structures, materials, etc.) resistant to fire, or incombustible; or material for use in making anything fire-proof. It is a passive fire protection measure. "Fireproof" or "fireproofing" can be u ...

material was compromised within a few minutes rather than one to two hours, which had been specified. Even without direct impingement, the high thermal radiation emitted by jet flames also affected plant and would have been fatal to personnel.

Characteristics

A jet fire, also known as a spray fire if the fuel is a liquid or liquefied gas, is a turbulent diffusion flame of flammable material. The characteristics of a jet fire depend on a number of factors. These include: fuel composition; release conditions; release rate; release geometry; direction; and ambient wind conditions. For full details of the mechanism and structure of jet fires see

High Pressure Jet A high pressure jet is a stream of pressurized fluid that is released from an environment at a significantly higher pressure than ambient pressure from a nozzle or orifice, due to operational or accidental release. In the field of safety engineer ...

. Some characteristics of specific jet fires are: * Sonic releases of natural gas are characterized by high velocity, low buoyancy flames that are relatively non-luminous with low radiative energy, * A jet flame of higher

hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may b ...

is lazy, buoyant, luminous, with the presence of black smoke at the tail of the flame, they are highly radiative, * The surface emissive power (SEP) of jet flames is in the order of 200 kW/m² to 400 kW/m². Such flames have a temperature of 1350 °C. These high heat fluxes can readily compromise the integrity of structures and vessels and can lead to mechanical failure of plant and equipment. * A jet fire is a particular hazard to personnel. People are able to survive and escape from exposure to heat fluxes less than 5 kW/m², while higher fluxes can be fatal.

Designing for jet fires

Process plant is generally protected by a pressure relief system. However, local heating of a pressure vessel by a jet fire may compromise the integrity of the vessel before the pressure relief device operates. The measures taken for protection against jet fires are as follows: * Prevention of leaks using effective maintenance *

Flange A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of a steel beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer o ...

orientation and elimination * Blowdown systems, to reduce the inventory and pressure in the plant * Isolation of leaks * Robust external insulation * Emergency response Water deluge can reduce the heat loading of plant so that its temperature is maintained below that at which failure occurs, or that the temperature rise is sufficiently reduced such that shutdown and depressurization can take place. Older plants may have been sized on an earlier version of the

American Petroleum Institute The American Petroleum Institute (API) is the largest U.S. trade association for the oil and natural gas industry. It claims to represent nearly 600 corporations involved in extraction of petroleum, production, oil refinery, refinement, pipeline ...

's ''Pressure-Relieving and Depressuring Systems'' standard, which did not include consideration of jet fires. The international standard publication ISO 22899 (''Determination of the Resistance to Jet Fires of Passive Fire Protection Materials'') sets requirements for the specification of passive fire protection against jet fires.

References

{{reflist Industrial fires and explosions Process safety Types of fire Combustion

Context

Characteristics

Designing for jet fires

See also

References