science

Jet fire

Jet fire is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Jet fire rather than just read about it. In short: 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 gas, liquid or a two-phase mixture.

Key takeaways

Jet fire belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Jet fire to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Jet fire from memory before moving on to harder problems.

Reference excerpt

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

Context The Piper Alpha disaster in 1988 demonstrated how the accidental release of hydrocarbon can lead to the catastrophic failure of an installation with the rupture of major pipeline risers. Jet fires impinged on vessels, pipework and firewalls. Under these conditions the fireproofing 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. 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 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 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'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.

See also High pressure jet Process hazard analysis Process safety

References

Worked examples

Example 1 — a first encounter with Jet fire

Start with the simplest possible case. Write down what Jet fire claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Jet fire before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Jet fire ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Jet fire

In research: Jet fire appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Jet fire in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Jet fire is common in secondary-school and first-year university syllabi. It links to neighbouring topics Combustion, Industrial fires and explosions, Process safety, so understanding it makes those chapters shorter.
In everyday life: Look for Jet fire outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Jet fire in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Jet fire means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Jet fire out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Jet fire in simple terms?

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 gas, liquid or a two-phase mixture.

Why does Jet fire matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Jet fire?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Jet fire.