Tank Fire Extinguishing Stream Dynamics and Plunge Zone Control
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Solution Overview
Problem
In extinguishing full surface liquid tank fires, the 'plunge zone' issues arise both before and after flame collapse, posing challenges in effectively and efficiently extinguishing the fire, particularly with heavy liquids and large tanks, where the foam blanket's effectiveness is hindered by hydrophilic fuels and structural impediments.
Innovation Solution
The method involves using a non-feathered primary stream to achieve flame collapse, followed by diminishing the stream's impact force to allow the foam blanket to heal the plunge zone, and employing a feathered stream for heavy liquids to reduce heat and agitation, along with secondary staging and rooster tailing to overcome structural impediments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a non-feathered primary stream is used to achieve flame collapse, then the fire extinction speed is improved, but the plunge zone instability worsens due to high impact force
Solution Approach 1:
The extinguishing process is divided into two distinct phases: first using a non-feathered primary stream to achieve rapid flame collapse, then transitioning to a feathered stream to stabilize the plunge zone and allow foam blanket healing. This segmentation of the extinguishing action resolves the contradiction by applying different stream types at different stages.
Solution Approach 2:
The nozzle is made dynamically adjustable, allowing operators to switch between non-feathered and feathered stream patterns. This dynamic adaptation enables the system to optimize for flame collapse speed initially, then transition to plunge zone stabilization, resolving the contradiction between extinction speed and stability.
2Stability of the object's composition
If a feathered stream is used for heavy liquids, then the foam blanket stability is improved, but the fire extinction speed decreases
Solution Approach 1:
A feathered stream is applied preliminarily to heavy liquid fires to reduce heat and agitation before the main extinguishing action. This preliminary stabilization of the liquid surface and foam blanket allows subsequent non-feathered streams to achieve rapid flame collapse without being disrupted by liquid agitation, thus resolving the contradiction.
3Area of stationary object
If foam is applied to large tanks with structural impediments, then the foam blanket coverage is improved, but the foam consumption increases due to repeated application needed
Solution Approach 1:
The stream pattern is locally adapted to account for structural impediments. Non-feathered streams are directed at areas needing rapid flame collapse while feathered streams are used where foam blanket stability is needed to overcome structural interference. This local quality adjustment optimizes foam consumption by applying the right stream type in the right location.
4Productivity
If the stream impact force is maintained high, then the flame collapse speed is improved, but the foam blanket healing capability worsens in the plunge zone
Solution Approach 1:
The extinguishing operation uses periodic action by alternating between high-impact non-feathered streams for flame collapse and low-impact feathered streams for foam blanket healing. This periodic switching between high and low impact forces resolves the contradiction by applying each type of force at the appropriate time in the extinguishing sequence.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables cost-effective and timely extinguishment of full surface liquid tank fires by maintaining a stable foam blanket, reducing foam consumption, and effectively addressing plunge flames and structural interference, even in large tanks with complex fire dynamics.
Implementation Method 1
throwing at least one non-feathered primary stream over a tank wall, the stream landing with a force of impact in, and defining, a plunge zone; achieving flame collapse
Implementation Method 2
employing a feathered stream for heavy liquids to reduce heat and agitation
Implementation Method 3
the foam blanket suppresses vaporization; the foam blanket deprives the fire of access to oxygen-combustion usually requires
Data Source
AI summary
A method for extinguishing a full, or substantially full, surface liquid tank fire including addressing large tank, difficult fuel, structural impediment, timing and plunge zone issues, the attack including throwing at least one primary stream over a tank wall, the stream landing with a force of impact in, and defining, a plunge zone; the method including potentially achieving flame collapse leaving a plunge zone flame and subsequently, at least for a period of time, diminishing force of impact per unit area of a primary stream upon said plunge zone flame; alternately the method includes achieving a partial flame collapse including collapse against back tank wall portions and subsequently diminishing stream impact force upon a plunge zone including moving a plunge zone forward in the tank; the method also includes extinguishing a full surface heavy liquid tank fire by teasing the fire prior to employing a non-feathered stream to create a foam blanket; the method may include restaging to create a secondary footprint, and/or coordinating the timing of addressing plunge zone, smiley face and secondary footprint issues; the method may also include teasing and/or rooster tailing structural impediments.