A guide to foam and foam proportioning tools – Part 1

Fire presents many challenges, not least due to the variables that decide which suppression medium is acceptable for a given fireplace situation. Our objective on this two-part article is to offer steerage based mostly on a hazard-specific strategy and help you make an knowledgeable choice on acceptable fire-suppression measures, particularly with regard to the processing and storage of flammable liquids.
Fire hazards are categorized as follows:
Class A – carbonaceous or flamable materials
Class B – flammable liquids
Class C – flammable gases
Class D – metals similar to magnesium
Class F – fires generally associated with cooking corresponding to vegetable oils
Class E – electrical hazards.
As a producer of froth proportioners and firefighting monitors, we specialise mainly in the Class B category: flammable liquids.
Foam is considered to be the most effective fire-extinguishing medium for both hydrocarbons and polar solvents. In addition, sure types of foam (known as wetting agents) are particularly for deep-seated Class A fires where water only could not penetrate the fireplace load effectively.
Fire classes.
How will we make foam?
Finished foam answer comprises a easy recipe of froth concentrate, water and air. Foam focus is usually mixed within the ratio of 1% or 3% to either 99% or 97% water.
Once the solution (premix) is created, it’s pumped to the chosen discharge gadget – we’ll cover proportioning later on this article and discharge strategies in Part 2. At this point air is entrained by using devices designed to naturally aspirate the solution. The amount of aspiration and the sort of focus determines the growth ratio. This is often split between low, medium and high expansion. Low growth is as a lot as 20:1, medium is 200:1 and high expansion is more than 200:1. Only high-expansion foam might have the addition of a water-driven generator fan to broaden the foam adequately, although naturally aspirated turbines are additionally used. The determination to choose on a particular growth ratio is determined by the hazard beneath review.
Put merely, water and oil do not mix. Applying solely water to Class B products won’t suppress the burning vapours. This is a vital point to make as it is the vapours, not the liquid itself, that burns. We need a medium that allows for the formation of a vapour-suppressing and oxygen-depleting blanket and/or a barrier movie to obtain success. Whatever methodology is chosen to produce that blanket or movie, the target is the same.
Steps of foam technology Images provided by Author / Contributor
A little of the historical past of foam growth
We can date the event of modern foam concentrates from the Sixties onwards. Up to that point foam concentrates had been comprised of animal-based protein (typically ground hoof and horn is the base component). The main downside was because of restricted gasoline tolerance, which meant it was susceptible to fuel pick-up (mixing). A breakthrough got here with aqueous film-forming foams or AFFF’s. Instead of utilizing protein as the base product, synthetic detergents gave foam a greater gas tolerance in addition to forming a vapour-sealing film across the surface of the fuel. Performance is additional enhanced with the formation of a foam blanket when air aspirating gadgets are fitted.
Nevertheless, AFFF’s development did not fully substitute the use of protein-based foam. Fluoroprotein, or FP, meant that protein foam might both fight gasoline pick-up (mixing) and supply a great resistance to warmth, outlined by the trade as ‘burn-back resistance’.
Further growth in the Nineteen Eighties took FP to the subsequent level with film-forming fluoroprotein or FFFP. We now had the most effective of both worlds: a film-forming foam that also had good burn-back resistance.
The Nineteen Eighties further added to our listing of acronyms with FFFP-AR – film-forming fluoroprotein, alcohol resistant. Alcohols or polar solvents had all the time introduced an additional problem as they had been water soluble and foam destructive. The FFFP-AR chemistry included a polymeric barrier, which protected the froth blanket from early destruction. The similar expertise additionally turned out there with the new technology of AFFF-ARs.
In current years fluorine, one of many cornerstone elements to all foams, has turn into an environmental concern, because of persistence in groundwater. The industry has been presented with a major challenge to remove the ‘fluoro’ component of all of the totally different foam focus varieties. We have witnessed an period of manufacturers’ claims and counter claims concerning the efficacy of a whole vary of newly formulated fluorine-free foam. The time period ‘SFFF’ (synthetic fluorine free foam) or ‘F3’ is used to outline these foams, which have become the brand new normal and first selection for operators altering current inventory or reviewing new initiatives. As a foam proportioner manufacturer we must examine the bodily properties of froth fastidiously (especially viscosity) as they influence choices on the general proportioning solution. More of this later.
Multi-purpose foams such as the F3 alcohol-resistant sorts are more and more important in the fuel-storage enviornment. The introduction of E10 petroleum, with its 10% ethanol-based biofuel content, implies that the alcohol-resistant quality of SFFF/F3 is critical to combat the small degree of water miscibility of the gasoline.
All foam focus producers will naturally promote their product as being extremely effective. The finest means of comparing their claims is to familiarise your self with the empirically primarily based normal EN 1568 or UL162. The checks cowl extinction time, foam stability (via drainage time tests) and post-fire security (burn-back test). Hydrocarbons and the extra demanding polar solvents are both included within the test protocols. This also covers contemporary and seawater as nicely as mild and forceful software of the froth. Each foam is given a ranking with IA being the most effective, IIID the worst. This means that you can problem foam suppliers in order to make an knowledgeable decision on one of the best foam for your needs.
Whilst EN 1568 is a wonderful benchmark commonplace, consciousness of the consequences on foam efficiency from components exterior the usual tests must be famous. For instance, significantly aggressive solvents can problem the firefighting effectiveness of certain foams. This could be exacerbated by different ambient air temperatures, the appliance methodology, fuel depth etc. Our advice could be to know the primary points of the exams and attempt to match them to the foam’s appropriateness in your individual hazards. We would all the time recommend consulting individual foam producers as they will often present particular in-house fire-performance data towards a few of the more unusual fuels.
However, despite เพชเชอร์เกจ conflicting claims on efficiency, the sooner fundamentals of how foam is proportioned still stay: 1% & 3% concentrates are the norm for producing a completed foam.
Foams based on the growth ratio Images provided by Author / Contributor
Critical elements for success: the time and utility fee matrix
Successful extinction of flammable liquid fires depends on two converging and complementary components: time and the speed at which completed foam is applied. Both are decided by empirically based requirements revealed by bodies such because the National Fire Protection Association (NFPA) within the United States and in Europe by the EN standards.
The ‘time’ factor implies that for a given dimension of fireplace space it is essential to apply the froth for lengthy enough to achieve extinction and to prevent re-ignition. This is very important in handbook intervention as firefighter’s might be in danger throughout post-fire operations. When it involves fixed protection for hydrocarbon and polar solvent tanks, the application time could be so long as 60 minutes for the most important tank diameters.
The application rate refers back to the quantity of completed foam applied per square metre. This varies in accordance with the fuel and the foam kind however is at present at least 4.zero litres per minute per square metre. One of the continued developments in foam efficiency is the chance that this shall be lowered, but standards typically take time to recognise product development. Anything less than the minimum utility rate means that fire control is unlikely to be achieved. This means that firefighting resources, notably in a manual fire assault, must be assembled before firefighting commences and this takes time. The advantage in becoming fastened techniques is that the resources are already designed and built into the system for quick software.
Principle of foam extinguishment Images equipped by Author / Contributor
Foam proportioning strategies: mixing water with foam concentrate
In order to permit readers to make an knowledgeable decision on how best to sort out their particular hearth challenges, the following is an overview of the assorted foam proportioning methods.
Foam inductors:
Typically related to fireplace service deployment and limited fixed methods purposes. This makes use of the venturi principle to create a pressure drop in a small aluminium or seawater materials compatible gadget with built-in concentrate pick-up tube. The pressure drop created by the venturi attracts the foam concentrate from a container the place it mixes with water to create foam answer. Both the pick-up tube and body of the inductor are compact enough to be easily carried on a fire appliance or fitted into a pipework system.
However, while it’s thought-about to be the only method, it has severe drawbacks: (i) items are manufacturing unit calibrated so any modifications to the hydraulics (caused by length of discharge line after the inductor, the elevation of the discharge device or a altering quantity of discharge devices) will doubtless require a system re-design; (ii) system design and sign-off are critical as deviations attributable to pipe diameter modifications will adversely have an effect on proportioning accuracy and doubtlessly stop any proportioning; (iii) changes in concentrate viscosity will undermine the flexibility of the venturi to draw focus into the downstream traces; (iv) stress loss is excessive, as a lot as 35%, so obligation pump pressures need to be excessive sufficient to permit for it, probably adding extra price into the system; (v) foam supply units have to be sized in order to not restrict design flows; (vi) testing can’t be achieved with out creating premix and discharging finished foam. This will add to whole lifetime costs on account of foam focus utilization, which needs to be replaced, and the disposal of premix or foam.
Types of froth agentsImages supplied by Author / Contributor
Balanced strain proportioners:
These use an electrical or a mix of electric and diesel pumps to provide foam concentrate into a proportioner at a better strain than the incoming water-line stress. The proportioner is put in into the water line and regulates the mixing.
They are actually associated with older methods, where disadvantages embrace: (i) additional costs in hardware and design time; (ii) the foam pump is generally restricted to a a lot tighter working vary, although the proportioner itself can accommodate extensive ranges in flows; (iii) the foam pump wants a further power supply, other than water, so just isn’t as reliably safe as a system with a potential single level of failure, similar to a wholly water-driven system; (iv) usually, these techniques are very advanced and trigger high efforts on the buyer with set-up, commissioning and testing; (v) the recirculation of unused foam concentrate creates unnecessary agitation that has the potential to damage the froth concentrate and entrain air, which in flip can undermine correct foam proportioning and foam extinguishing effectiveness.
Bladder tanks:
Comprised of a steel pressure vessel containing a versatile bladder (typically a butyl material) linked to a foam focus proportioner much like the ones fitted to balanced pressure proportioners. The incoming pressurised water compresses the foam stuffed bladder so that foam focus could be proportioned with water using the same provide. The venturi principle is again brought into play because it creates a pressure drop on the level of injection for the froth concentrate. Testing cannot be achieved without creating premix and discharging finished foam. This will add to complete lifetime costs as a result of foam focus utilization, which must be changed, and the disposal of premix or foam.
However, the bladder itself is seen as a weak point because great care is needed to avoid a broken bladder when commissioning a brand new set up. It is never straightforward to work within the steel strain vessel ought to issues happen, particularly if and when a substitute bladder may be required: all of it provides to the problem and cost.
Compressed air foam (CAFS):
This isn’t a proportioning method in the standard sense as the foam is already proportioned using one of the earlier methods. However, pressurised air is then added forcefully rather than naturally entrained or aspirated. As the name suggests, CAFS injects compressed air into the foam solution at the point of discharge. The consensus view is that CAFS enhances the finished foam’s capacity to cling to vertical surfaces permitting better penetration and cooling. This is also a benefit in wildfire situations by coating weak constructions to mitigate fire growth. The limited water supplies related to remote wildfire areas implies that the resource may be fully optimised. However, as with balanced strain proportioner foam pumps, a further level of failure is possible as a result of additional CAFS apparatus.
Water driven or turbine foam proportioners:
FireDos have turn out to be synonymous with their distinctive water-driven foam proportioner. Now in its third era, the product is solely mechanical and extremely reliable. A water-driven rotor provides the motive force to drive a instantly coupled positive-displacement plunger or piston pump. This is equipped with foam concentrate via an atmospheric foam tank adjacent to the FireDos unit. The proportioning pump is factory set to the required proportioning price and can proportion the froth focus accurately throughout a large operating vary. The purely mechanical system provides cost-efficient and eco-friendly proportioning price testing, utterly without utilizing any foam concentrate or creating premix or firefighting foam.
FireDos GEN III foam proportioned. Images supplied by Author / Contributor
The advantages of FireDos Gen III FM accredited foam proportioners embody:
Reduced costs: proportioning rate is tested with out using foam or creating premix or foam – value effective and eco-friendly.
Improved efficiency: fixed proportioning price throughout a large working range.
Optimised delivery of high-viscosity foam concentrates with improved suction capacity.
25% reduction in strain loss, compared to older generations, through hydraulic optimisation.
Improved cylinder cut-off for easy and quick adjustment to a special proportioning price.
FM accredited FireDos Gen III proportioners are to date the only FM approved water motor coupled variable proportioners using FM approved circulate meters. Using the test return line this offers the possibility to verify the proportioning price during commissioning in addition to for annual tests, with out creating any premix, which is a really massive profit for the consumer and relieves the setting.
In the second a half of this feature we are going to explore the results of viscosity on foam proportioning and typical foam software areas and beneficial discharge devices.
For extra information, go to www.firedos.com
Written by
David Owen
Andreas Hulinsky

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