A information to foam and foam proportioning tools – Part 1

Fire presents many challenges, not least because of the variables that determine which suppression medium is acceptable for a given fireplace state of affairs. Our goal in this two-part article is to offer guidance based on a hazard-specific approach and allow you to make an knowledgeable decision on appropriate fire-suppression measures, especially with regard to the processing and storage of flammable liquids.
Fire hazards are classified as follows:
Class A – carbonaceous or combustible materials

Class B – flammable liquids

Class C – flammable gases

Class D – metals corresponding to magnesium

Class F – fires generally related to cooking corresponding to vegetable oils

Class E – electrical hazards.
As a manufacturer of foam proportioners and firefighting monitors, we specialise primarily in the Class B class: flammable liquids.
Foam is taken into account 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 specifically for deep-seated Class A fires where water solely might not penetrate the fire load successfully.
Fire courses.
How will we make foam?

Finished foam answer includes a simple recipe of froth concentrate, water and air. Foam concentrate is usually blended within the ratio of 1% or 3% to both 99% or 97% water.
Once the solution (premix) is created, it’s pumped to the chosen discharge system – we will cowl proportioning later in this article and discharge methods in Part 2. At this level air is entrained by utilizing gadgets designed to naturally aspirate the answer. The amount of aspiration and the kind of concentrate determines the expansion ratio. This is often cut up between low, medium and high enlargement. Low enlargement is up to 20:1, medium is 200:1 and excessive enlargement is more than 200:1. Only high-expansion foam may need the addition of a water-driven generator fan to broaden the foam adequately, although naturally aspirated generators are also used. The choice to decide on a particular growth ratio is set by the hazard underneath evaluate.
Put simply, water and oil do not mix. Applying solely water to Class B products will not suppress the burning vapours. This is an important level to make as it’s the vapours, not the liquid itself, that burns. We want a medium that enables for the formation of a vapour-suppressing and oxygen-depleting blanket and/or a barrier movie to obtain success. Whatever technique is chosen to provide that blanket or film, the objective is similar.
Steps of foam generation Images supplied by Author / Contributor

A little of the historical past of froth growth

We can date the development of modern foam concentrates from the Nineteen Sixties onwards. Up to that point foam concentrates have been comprised of animal-based protein (typically floor hoof and horn is the bottom component). The main drawback was as a end result of restricted fuel 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 bottom product, synthetic detergents gave foam a larger gas tolerance as properly as forming a vapour-sealing film throughout the floor of the gasoline. Performance is additional enhanced with the formation of a foam blanket when air aspirating devices are fitted.
Nevertheless, AFFF’s development did not utterly substitute using protein-based foam. Fluoroprotein, or FP, meant that protein foam may both fight fuel pick-up (mixing) and supply a good resistance to heat, defined by the business as ‘burn-back resistance’.
Further development in the Eighties took FP to the subsequent stage with film-forming fluoroprotein or FFFP. We now had one of the best of each worlds: a film-forming foam that additionally had good burn-back resistance.
The 1980s further added to our list of acronyms with FFFP-AR – film-forming fluoroprotein, alcohol resistant. Alcohols or polar solvents had all the time offered an additional problem as they were water soluble and foam harmful. The FFFP-AR chemistry included a polymeric barrier, which protected the froth blanket from early destruction. The identical know-how also became available with the model new technology of AFFF-ARs.
In latest years fluorine, one of many cornerstone ingredients to all foams, has become an environmental issue, because of persistence in groundwater. The industry has been introduced with a serious problem to remove the ‘fluoro’ element of all of the totally different foam concentrate types. We have witnessed an era of manufacturers’ claims and counter claims regarding the efficacy of an entire vary of newly formulated fluorine-free foam. The term ‘SFFF’ (synthetic fluorine free foam) or ‘F3’ is used to outline these foams, which have turn into the new regular and first choice for operators changing present stock or reviewing new initiatives. As a foam proportioner producer we must look at the bodily properties of froth fastidiously (especially viscosity) as they influence decisions on the overall proportioning answer. More of this later.
Multi-purpose foams such because the F3 alcohol-resistant varieties are increasingly necessary in the fuel-storage enviornment. The introduction of E10 petroleum, with its 10% ethanol-based biofuel content material, signifies that the alcohol-resistant high quality of SFFF/F3 is critical to fight the small degree of water miscibility of the gasoline.
All foam concentrate producers will naturally promote their product as being extremely effective. The best method of comparing their claims is to familiarise your self with the empirically based mostly standard EN 1568 or UL162. The tests cowl extinction time, foam stability (via drainage time tests) and post-fire security (burn-back test). Hydrocarbons and the more demanding polar solvents are both included in the test protocols. This additionally covers fresh and seawater as nicely as light and forceful utility of the froth. Each foam is given a rating with IA being the most effective, IIID the worst. This means that you could problem foam suppliers to be able to make an informed decision on the best foam for your needs.
Whilst EN 1568 is an excellent benchmark commonplace, awareness of the effects on foam efficiency from factors outdoors the standard tests ought to be famous. For example, notably aggressive solvents can challenge the firefighting effectiveness of certain foams. This can be exacerbated by completely different ambient air temperatures, the application methodology, gas depth and so forth. Our advice can be to understand the details of the exams and attempt to match them to the foam’s appropriateness on your particular person hazards. We would always recommend consulting individual foam producers as they will often present particular in-house fire-performance data against some of the more uncommon fuels.
However, despite the foam manufacturers’ typically conflicting claims on efficiency, the sooner fundamentals of how foam is proportioned nonetheless stay: 1% & 3% concentrates are the norm for producing a completed foam.
Foams in accordance with the growth ratio Images supplied by Author / Contributor

Critical elements for fulfillment: the time and software rate matrix

Successful extinction of flammable liquid fires depends on two converging and complementary factors: time and the speed at which completed foam is applied. Both are determined by empirically based mostly standards revealed by bodies such because the National Fire Protection Association (NFPA) within the United States and in Europe by the EN standards.
The ‘time’ issue implies that for a given size of fireside space it is needed to apply the foam for lengthy enough to achieve extinction and to forestall re-ignition. This is especially important in manual intervention as firefighter’s shall be in danger throughout post-fire operations. When it comes to fixed safety for hydrocarbon and polar solvent tanks, the appliance time can be as lengthy as 60 minutes for the most important tank diameters.
The software rate refers to the amount of completed foam applied per sq. metre. pressure gauge octa varies based on the fuel and the foam type but is currently no less than four.0 litres per minute per square metre. One of the ongoing developments in foam efficiency is the chance that this shall be reduced, but requirements usually take time to recognise product development. Anything less than the minimum application rate implies that fireplace management is unlikely to be achieved. This implies that firefighting sources, notably in a guide hearth attack, have to be assembled before firefighting commences and this takes time. The benefit in fitting fastened systems is that the resources are already designed and constructed into the system for quick application.
Principle of froth extinguishment Images equipped by Author / Contributor

Foam proportioning strategies: mixing water with foam concentrate

In order to allow readers to make an knowledgeable decision on how best to deal with their explicit fireplace challenges, the next is an summary of the assorted foam proportioning methods.
Foam inductors:
Typically associated with fire service deployment and restricted mounted techniques applications. This uses the venturi precept to create a stress drop in a small aluminium or seawater material appropriate gadget with built-in concentrate pick-up tube. The stress drop created by the venturi draws the froth concentrate from a container where it mixes with water to create foam answer. Both the pick-up tube and physique of the inductor are compact enough to be easily carried on a fireplace equipment or fitted right into a pipework system.
However, while it’s considered to be the simplest technique, it has extreme drawbacks: (i) models are manufacturing facility calibrated so any adjustments to the hydraulics (caused by length of discharge line after the inductor, the elevation of the discharge system or a altering amount of discharge devices) will probably require a system re-design; (ii) system design and sign-off are critical as deviations brought on by pipe diameter modifications will adversely affect proportioning accuracy and probably stop any proportioning; (iii) modifications in focus viscosity will undermine the flexibility of the venturi to draw focus into the downstream traces; (iv) pressure loss is excessive, as a lot as 35%, so obligation pump pressures have to be high enough to allow for it, probably including further cost into the system; (v) foam delivery units need to be sized in order not to limit design flows; (vi) testing can’t be achieved without creating premix and discharging completed foam. This will add to entire lifetime costs as a outcome of foam focus usage, which needs to be changed, and the disposal of premix or foam.
Types of foam agentsImages provided by Author / Contributor

Balanced strain proportioners:
These use an electric or a combination of electrical and diesel pumps to produce foam focus right into a proportioner at a higher stress than the incoming water-line pressure. The proportioner is installed into the water line and regulates the mixing.
They at the moment are associated with older methods, the place disadvantages embrace: (i) additional costs in hardware and design time; (ii) the foam pump is generally restricted to a a lot tighter operating vary, though the proportioner itself can accommodate wide ranges in flows; (iii) the foam pump wants an additional energy supply, other than water, so is not as reliably secure as a system with a possible single level of failure, such as an entirely water-driven system; (iv) usually, these systems are very complicated and trigger excessive efforts at the customer with set-up, commissioning and testing; (v) the recirculation of unused foam focus creates unnecessary agitation that has the potential to damage the froth concentrate and entrain air, which in flip can undermine accurate foam proportioning and foam extinguishing effectiveness.
Bladder tanks:
Comprised of a steel strain vessel containing a versatile bladder (typically a butyl material) linked to a foam concentrate proportioner much like those fitted to balanced stress proportioners. The incoming pressurised water compresses the foam filled bladder so that foam concentrate could be proportioned with water utilizing the same provide. The venturi precept is once more introduced into play because it creates a strain drop on the level of injection for the foam focus. Testing can’t be achieved with out creating premix and discharging finished foam. This will add to complete lifetime costs because of foam focus utilization, which must be replaced, and the disposal of premix or foam.
However, the bladder itself is seen as a weakness as a result of great care is needed to avoid a broken bladder when commissioning a new installation. It isn’t straightforward to work within the steel stress vessel ought to issues occur, especially if and when a alternative bladder could additionally be required: all of it adds to the issue and cost.
Compressed air foam (CAFS):
This is not a proportioning methodology in the conventional sense as the foam is already proportioned using one of many previous methods. However, pressurised air is then added forcefully somewhat than naturally entrained or aspirated. As the identify suggests, CAFS injects compressed air into the foam answer at the level of discharge. The consensus view is that CAFS enhances the finished foam’s capacity to cling to vertical surfaces allowing better penetration and cooling. This can be a profit in wildfire conditions by coating weak buildings to mitigate hearth progress. เกจวัดแรงดัน limited water provides associated with distant wildfire areas means that the resource may be fully optimised. However, as with balanced stress proportioner foam pumps, a further level of failure is possible because of the extra CAFS equipment.
Water pushed or turbine foam proportioners:
FireDos have become synonymous with their unique water-driven foam proportioner. Now in its third era, the product is only mechanical and highly dependable. A water-driven rotor provides the motive force to drive a immediately coupled positive-displacement plunger or piston pump. This is provided with foam focus via an atmospheric foam tank adjoining to the FireDos unit. The proportioning pump is factory set to the required proportioning rate and will proportion the foam concentrate precisely throughout a large working range. The purely mechanical system offers cost-efficient and eco-friendly proportioning rate testing, utterly with out utilizing any foam focus or creating premix or firefighting foam.
FireDos GEN III foam proportioned. Images supplied by Author / Contributor

The benefits of FireDos Gen III FM accredited foam proportioners embody:
Reduced costs: proportioning rate is tested with out utilizing foam or creating premix or foam – price effective and eco-friendly.
Improved efficiency: fixed proportioning fee throughout a large working vary.
Optimised supply of high-viscosity foam concentrates with improved suction capacity.
25% reduction in stress loss, compared to older generations, by way of hydraulic optimisation.
Improved cylinder cut-off for straightforward and fast adjustment to a different proportioning price.
FM accredited FireDos Gen III proportioners are to date the only FM approved water motor coupled variable proportioners utilizing FM approved move meters. Using the test return line this presents the likelihood to examine the proportioning rate throughout commissioning as nicely as for annual exams, without creating any premix, which is a very massive profit for the person and relieves the environment.
In the second part of this function we’ll discover the results of viscosity on foam proportioning and typical foam application areas and really helpful discharge units.
For extra information, go to www.firedos.com

Written by

David Owen

Andreas Hulinsky


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