A guide to foam and foam proportioning gear – Part 1

Fire presents many challenges, not least because of the variables that determine which suppression medium is appropriate for a given fire situation. Our goal on this two-part article is to offer steerage based mostly on a hazard-specific strategy and help you make an knowledgeable choice on applicable fire-suppression measures, particularly with regard to the processing and storage of flammable liquids.
Fire hazards are classified as follows:
Class A – carbonaceous or combustible supplies
Class B – flammable liquids
Class C – flammable gases
Class D – metals such as magnesium
Class F – fires typically related to cooking corresponding to vegetable oils
Class E – electrical hazards.
As weksler pressure gauge ราคา of froth proportioners and firefighting screens, we specialise mainly within the Class B class: flammable liquids.
Foam is considered to be the best fire-extinguishing medium for both hydrocarbons and polar solvents. In addition, certain types of foam (known as wetting agents) are particularly for deep-seated Class A fires the place water only may not penetrate the fireplace load successfully.
Fire lessons.
How will we make foam?
Finished foam resolution comprises a simple recipe of foam concentrate, water and air. Foam focus is usually mixed in the ratio of 1% or 3% to both 99% or 97% water.
Once the answer (premix) is created, it is pumped to the chosen discharge gadget – we are going to cover proportioning later on this article and discharge strategies in Part 2. At this level air is entrained through the use of gadgets designed to naturally aspirate the answer. The quantity of aspiration and the kind of concentrate determines the growth ratio. This is typically break up between low, medium and high expansion. Low expansion is as much as 20:1, medium is 200:1 and excessive growth is greater than 200:1. Only high-expansion foam may have the addition of a water-driven generator fan to increase the foam adequately, though naturally aspirated mills are also used. The decision to choose on a particular growth ratio is set by the hazard under review.
Put merely, water and oil don’t mix. Applying solely water to Class B merchandise won’t suppress the burning vapours. This is a crucial point to make as it is the vapours, not the liquid itself, that burns. We want a medium that permits for the formation of a vapour-suppressing and oxygen-depleting blanket and/or a barrier film to obtain success. Whatever methodology is chosen to produce that blanket or film, the objective is similar.
Steps of foam era Images provided by Author / Contributor
A little of the historical past of froth development
We can date the event of modern foam concentrates from the Sixties onwards. Up to that point foam concentrates were comprised of animal-based protein (typically floor hoof and horn is the base component). The main drawback was due to limited gasoline tolerance, which meant it was vulnerable to gas pick-up (mixing). A breakthrough got here with aqueous film-forming foams or AFFF’s. Instead of utilizing protein as the bottom product, artificial detergents gave foam a larger gasoline tolerance in addition to forming a vapour-sealing film throughout the floor of the fuel. Performance is further enhanced with the formation of a foam blanket when air aspirating devices are fitted.
Nevertheless, AFFF’s growth didn’t utterly exchange the use of protein-based foam. Fluoroprotein, or FP, meant that protein foam may both fight gas pick-up (mixing) and supply an excellent resistance to warmth, defined by the industry as ‘burn-back resistance’.
Further development in the 1980s 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 list of acronyms with FFFP-AR – film-forming fluoroprotein, alcohol resistant. Alcohols or polar solvents had always offered a further problem as they were water soluble and foam destructive. The FFFP-AR chemistry included a polymeric barrier, which protected the froth blanket from early destruction. The same technology additionally turned available with the new technology of AFFF-ARs.
In latest years fluorine, one of the cornerstone ingredients to all foams, has turn into an environmental concern, because of persistence in groundwater. The industry has been offered with a serious problem to get rid of the ‘fluoro’ element of all of the different foam concentrate varieties. We have witnessed an period of manufacturers’ claims and counter claims concerning 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 model new normal and first alternative for operators changing present inventory or reviewing new projects. As a foam proportioner producer we must study the physical properties of froth rigorously (especially viscosity) as they affect decisions on the general proportioning answer. More of this later.
Multi-purpose foams such as the F3 alcohol-resistant types are more and more necessary within the fuel-storage arena. The introduction of E10 petroleum, with its 10% ethanol-based biofuel content material, signifies that the alcohol-resistant high quality of SFFF/F3 is important to combat the small degree of water miscibility of the gasoline.
All foam concentrate manufacturers will naturally promote their product as being extremely effective. The best way of evaluating 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 each included within the test protocols. This also covers fresh and seawater as well as mild and forceful application of the foam. Each foam is given a rating with IA being the best, IIID the worst. This means that you can challenge foam suppliers to be able to make an informed choice on the best foam on your needs.
Whilst EN 1568 is an excellent benchmark commonplace, consciousness of the results on foam efficiency from factors outside the standard checks ought to be noted. For example, notably aggressive solvents can problem the firefighting effectiveness of sure foams. This can be exacerbated by totally different ambient air temperatures, the applying technique, fuel depth and so on. Our recommendation would be to grasp the small print of the checks and try to match them to the foam’s appropriateness for your individual hazards. We would at all times advocate consulting particular person foam manufacturers as they can usually provide specific in-house fire-performance information towards a variety of the extra unusual fuels.
However, regardless of the foam manufacturers’ generally conflicting claims on performance, the earlier fundamentals of how foam is proportioned nonetheless remain: 1% & 3% concentrates are the norm for producing a completed foam.
Foams in accordance with the growth ratio Images supplied by Author / Contributor
Critical factors for fulfillment: the time and utility price matrix
Successful extinction of flammable liquid fires is determined by two converging and complementary elements: time and the rate at which finished foam is utilized. Both are decided by empirically based standards published by our bodies such because the National Fire Protection Association (NFPA) in the United States and in Europe by the EN standards.
The ‘time’ issue means that for a given measurement of fire space it is necessary to apply the froth for lengthy sufficient to attain extinction and to forestall re-ignition. This is especially crucial in handbook intervention as firefighter’s shall be in danger during post-fire operations. When it comes to fastened safety for hydrocarbon and polar solvent tanks, the applying time can be so lengthy as 60 minutes for the most important tank diameters.
The application rate refers again to the amount of finished foam utilized per sq. metre. This varies according to the gas and the froth kind but is currently at least 4.0 litres per minute per square metre. One of the continuing developments in foam performance is the probability that this might be lowered, but standards often take time to recognise product improvement. Anything less than the minimum software rate implies that fireplace control is unlikely to be achieved. This implies that firefighting sources, particularly in a handbook fire assault, have to be assembled earlier than firefighting commences and this takes time. The benefit in fitting mounted systems is that the assets are already designed and constructed into the system for quick application.
Principle of foam extinguishment Images equipped by Author / Contributor
Foam proportioning strategies: mixing water with foam focus
In order to permit readers to make an informed decision on how best to tackle their specific fireplace challenges, the next is an summary of the varied foam proportioning strategies.
Foam inductors:
Typically related to hearth service deployment and limited fixed methods functions. This uses the venturi precept to create a strain drop in a small aluminium or seawater materials suitable device with built-in concentrate pick-up tube. The strain drop created by the venturi draws the foam concentrate from a container where it mixes with water to create foam resolution. Both the pick-up tube and body of the inductor are compact sufficient to be easily carried on a hearth equipment or fitted into a pipework system.
However, whilst it’s considered to be the best methodology, it has extreme drawbacks: (i) models are factory calibrated so any changes to the hydraulics (caused by size of discharge line after the inductor, the elevation of the discharge system or a changing quantity of discharge devices) will likely require a system re-design; (ii) system design and sign-off are critical as deviations brought on by pipe diameter changes will adversely have an effect on proportioning accuracy and doubtlessly stop any proportioning; (iii) adjustments in concentrate viscosity will undermine the flexibility of the venturi to attract focus into the downstream strains; (iv) strain loss is high, as a lot as 35%, so responsibility pump pressures have to be high enough to allow for it, probably including additional cost into the system; (v) foam supply units need to be sized so as not to prohibit design flows; (vi) testing cannot be achieved with out creating premix and discharging finished foam. This will add to complete lifetime costs on account of foam focus utilization, which must be changed, and the disposal of premix or foam.
Types of froth agentsImages equipped by Author / Contributor
Balanced pressure proportioners:
These use an electric or a mixture of electrical and diesel pumps to supply foam concentrate into a proportioner at a higher strain than the incoming water-line stress. The proportioner is put in into the water line and regulates the mixing.
They at the moment are related to older techniques, where disadvantages include: (i) extra costs in hardware and design time; (ii) the foam pump is often restricted to a much tighter operating range, although the proportioner itself can accommodate wide ranges in flows; (iii) the froth pump needs a further power supply, aside from 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) typically, these methods are very advanced and trigger high efforts at the buyer with set-up, commissioning and testing; (v) the recirculation of unused foam focus creates pointless agitation that has the potential to break the froth focus and entrain air, which in flip can undermine correct foam proportioning and foam extinguishing effectiveness.
Bladder tanks:
Comprised of a steel strain vessel containing a flexible bladder (typically a butyl material) linked to a foam focus proportioner similar to those fitted to balanced pressure proportioners. The incoming pressurised water compresses the froth crammed bladder in order that foam focus may be proportioned with water utilizing the identical supply. The venturi principle is again brought into play because it creates a stress drop on the level of injection for the froth concentrate. Testing can’t be achieved with out creating premix and discharging completed foam. This will add to complete lifetime prices on account of foam concentrate utilization, which has to be replaced, and the disposal of premix or foam.
However, the bladder itself is seen as a weakness as a end result of nice care is needed to avoid a broken bladder when commissioning a new set up. It is rarely straightforward to work within the metal pressure vessel ought to problems happen, especially if and when a alternative bladder may be required: all of it provides to the problem and value.
Compressed air foam (CAFS):
This just isn’t a proportioning methodology in the standard sense as the foam is already proportioned using one of many previous strategies. However, pressurised air is then added forcefully rather than naturally entrained or aspirated. As the title suggests, CAFS injects compressed air into the froth resolution on the level of discharge. The consensus view is that CAFS enhances the completed foam’s ability to cling to vertical surfaces permitting better penetration and cooling. This can be a profit in wildfire situations by coating vulnerable constructions to mitigate fireplace development. The restricted water supplies associated with distant wildfire areas implies that the useful resource could be absolutely optimised. However, as with balanced pressure proportioner foam pumps, a further level of failure is feasible due to the additional CAFS equipment.
Water pushed or turbine foam proportioners:
FireDos have turn out to be synonymous with their unique water-driven foam proportioner. Now in its third technology, the product is solely mechanical and highly reliable. A water-driven rotor supplies the driving force to drive a immediately coupled positive-displacement plunger or piston pump. This is equipped with foam concentrate through an atmospheric foam tank adjoining to the FireDos unit. The proportioning pump is manufacturing unit set to the required proportioning rate and can proportion the foam concentrate accurately throughout a wide operating vary. The purely mechanical system provides cost-efficient and eco-friendly proportioning fee testing, completely without utilizing any foam concentrate or creating premix or firefighting foam.
FireDos GEN III foam proportioned. Images supplied by Author / Contributor
The benefits of FireDos Gen III FM approved foam proportioners include:
Reduced prices: proportioning price is tested with out using foam or creating premix or foam – value effective and eco-friendly.
Improved performance: constant proportioning fee across a wide operating range.
Optimised delivery of high-viscosity foam concentrates with improved suction capability.
25% reduction in strain loss, in comparability with older generations, through hydraulic optimisation.
Improved cylinder cut-off for simple and quick adjustment to a different proportioning rate.
FM accredited FireDos Gen III proportioners are to date the only FM approved water motor coupled variable proportioners using FM permitted flow meters. Using the check return line this presents the possibility to examine the proportioning price during commissioning in addition to for annual checks, without creating any premix, which is a very massive profit for the consumer and relieves the setting.
In the second part of this characteristic we will discover the effects of viscosity on foam proportioning and typical foam utility areas and beneficial discharge devices.
For more information, go to www.firedos.com
Written by
David Owen
Andreas Hulinsky

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