A information to foam and foam proportioning tools – Part 1

Fire presents many challenges, not least due to the variables that determine which suppression medium is suitable for a given fireplace scenario. Our goal on this two-part article is to offer steerage based on a hazard-specific strategy and allow you to make an informed choice on acceptable fire-suppression measures, especially with regard to the processing and storage of flammable liquids.
เกจปรับแรงดันแก๊ส 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 usually related to cooking similar to vegetable oils
Class E – electrical hazards.
As a manufacturer of foam proportioners and firefighting displays, we specialise primarily in the Class B class: flammable liquids.
Foam is considered to be the best fire-extinguishing medium for each hydrocarbons and polar solvents. In addition, sure types of foam (known as wetting agents) are specifically for deep-seated Class A fires the place water only may not penetrate the fire load successfully.
Fire lessons.
How do we make foam?
Finished foam answer includes a easy recipe of foam focus, water and air. Foam focus is often combined in the ratio of 1% or 3% to either 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 methods in Part 2. At this point air is entrained through the use of gadgets designed to naturally aspirate the solution. The quantity of aspiration and the type of focus determines the enlargement ratio. This is often break up between low, medium and high growth. Low expansion is up to 20:1, medium is 200:1 and excessive enlargement is more than 200:1. Only high-expansion foam may have the addition of a water-driven generator fan to expand the foam adequately, although naturally aspirated generators are additionally used. The determination to decide on a particular growth ratio is decided by the hazard underneath evaluation.
Put simply, water and oil do not combine. Applying only water to Class B merchandise won’t suppress the burning vapours. This is a crucial level to make as it is 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 film to be successful. Whatever technique is chosen to produce that blanket or film, the objective is the same.
Steps of foam technology Images supplied by Author / Contributor
A little of the history of froth development
We can date the development of modern foam concentrates from the 1960s onwards. Up to that point foam concentrates were comprised of animal-based protein (typically floor hoof and horn is the bottom component). The primary drawback was due to limited gas 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 higher gas tolerance in addition to forming a vapour-sealing movie across 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 didn’t fully replace the use of protein-based foam. Fluoroprotein, or FP, meant that protein foam might each fight gas pick-up (mixing) and offer a great resistance to warmth, defined by the industry as ‘burn-back resistance’.
Further growth in the 1980s took FP to the following stage with film-forming fluoroprotein or FFFP. We now had the most effective of each worlds: a film-forming foam that additionally had good burn-back resistance.
The Eighties further added to our list of acronyms with FFFP-AR – film-forming fluoroprotein, alcohol resistant. Alcohols or polar solvents had at all times presented an additional problem as they have been water soluble and foam damaging. The FFFP-AR chemistry included a polymeric barrier, which protected the froth blanket from early destruction. The same know-how also grew to become out there with the brand new generation of AFFF-ARs.
In recent years fluorine, one of many cornerstone elements to all foams, has turn into an environmental issue, because of persistence in groundwater. The industry has been presented with a major problem to eliminate the ‘fluoro’ factor of all of the totally different foam concentrate sorts. We have witnessed an period of manufacturers’ claims and counter claims relating to the efficacy of a complete range of newly formulated fluorine-free foam. The term ‘SFFF’ (synthetic fluorine free foam) or ‘F3’ is used to define these foams, which have become the new regular and first selection for operators altering current stock or reviewing new initiatives. As a foam proportioner manufacturer we must examine the physical properties of froth carefully (especially viscosity) as they influence selections on the general proportioning answer. More of this later.
Multi-purpose foams such because the F3 alcohol-resistant sorts are more and more essential in the fuel-storage area. The introduction of E10 petroleum, with its 10% ethanol-based biofuel content, implies that the alcohol-resistant high quality of SFFF/F3 is important to combat the small degree of water miscibility of the gas.
All foam concentrate producers will naturally promote their product as being highly effective. The best way of evaluating their claims is to familiarise yourself with the empirically based normal EN 1568 or UL162. The tests cover 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 check protocols. This also covers recent and seawater as properly as gentle and forceful utility of the foam. Each foam is given a rating with IA being one of the best, IIID the worst. This means that you can challenge foam suppliers to be able to make an informed decision on the best foam on your needs.
Whilst EN 1568 is a wonderful benchmark standard, consciousness of the effects on foam efficiency from elements outdoors the standard tests should be famous. For instance, notably aggressive solvents can challenge the firefighting effectiveness of sure foams. This could be exacerbated by completely different ambient air temperatures, the applying technique, fuel depth and so on. Our advice could be to know the details of the exams and attempt to match them to the foam’s appropriateness in your individual hazards. We would always advocate consulting individual foam producers as they can often present specific in-house fire-performance information towards a number of the more uncommon fuels.
However, despite the froth manufacturers’ generally conflicting claims on performance, the sooner fundamentals of how foam is proportioned nonetheless remain: 1% & 3% concentrates are the norm for producing a finished foam.
Foams in accordance with the expansion ratio Images provided by Author / Contributor
Critical factors for success: the time and software rate matrix
Successful extinction of flammable liquid fires is determined by two converging and complementary elements: time and the speed at which completed foam is utilized. Both are decided by empirically primarily based standards published by bodies such as the National Fire Protection Association (NFPA) in the United States and in Europe by the EN requirements.
The ‘time’ issue implies that for a given measurement of fireside space it is necessary to use the froth for lengthy enough to attain extinction and to prevent re-ignition. This is very important in handbook intervention as firefighter’s will be at risk during post-fire operations. When it involves fastened safety for hydrocarbon and polar solvent tanks, the applying time could be as lengthy as 60 minutes for the biggest tank diameters.
The software fee refers back to the quantity of finished foam applied per sq. metre. This varies in accordance with the gasoline and the froth sort but is at present no less than four.0 litres per minute per square metre. One of the continuing developments in foam efficiency is the probability that this shall be reduced, but requirements typically take time to recognise product development. Anything lower than the minimum utility price signifies that fire control is unlikely to be achieved. เกจวัดน้ำยาแอร์refco signifies that firefighting sources, significantly in a handbook fire assault, have to be assembled earlier than firefighting commences and this takes time. The benefit in fitting fastened techniques is that the assets are already designed and constructed into the system for quick application.
Principle of foam extinguishment Images supplied by Author / Contributor
Foam proportioning methods: mixing water with foam focus
In order to allow readers to make an informed choice on how finest to deal with their particular fire challenges, the following is an overview of the assorted foam proportioning strategies.
Foam inductors:
Typically associated with fire service deployment and restricted fastened systems applications. This uses the venturi principle to create a pressure drop in a small aluminium or seawater materials appropriate gadget with built-in focus pick-up tube. The strain drop created by the venturi draws the foam focus from a container where it mixes with water to create foam solution. Both the pick-up tube and body of the inductor are compact sufficient to be simply carried on a fireplace equipment or fitted into a pipework system.
However, whilst it’s thought-about to be the only method, it has extreme drawbacks: (i) units are manufacturing unit calibrated so any modifications 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 crucial as deviations caused by pipe diameter changes will adversely have an result on proportioning accuracy and potentially stop any proportioning; (iii) adjustments in focus viscosity will undermine the flexibility of the venturi to attract concentrate into the downstream strains; (iv) pressure loss is high, as much as 35%, so obligation pump pressures must be high sufficient to permit for it, probably including extra value into the system; (v) foam delivery devices need to be sized in order to not prohibit design flows; (vi) testing cannot be achieved with out creating premix and discharging finished foam. This will add to entire lifetime costs on account of foam focus utilization, which needs to be replaced, and the disposal of premix or foam.
Types of foam agentsImages equipped by Author / Contributor
Balanced pressure proportioners:
These use an electric or a mixture of electrical and diesel pumps to produce foam concentrate right into a proportioner at a higher pressure than the incoming water-line strain. The proportioner is put in into the water line and regulates the blending.
They at the moment are related to older methods, where disadvantages embrace: (i) extra prices in hardware and design time; (ii) the froth pump is generally restricted to a much tighter working range, although the proportioner itself can accommodate wide ranges in flows; (iii) the foam pump wants an additional power source, apart from water, so isn’t as reliably secure as a system with a possible single level of failure, corresponding to a completely water-driven system; (iv) usually, these systems are very complicated and trigger excessive efforts on the buyer 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 pressure vessel containing a flexible bladder (typically a butyl material) linked to a foam concentrate proportioner much like the ones fitted to balanced strain proportioners. The incoming pressurised water compresses the froth crammed bladder so that foam concentrate may be proportioned with water utilizing the identical provide. The venturi precept is again brought into play as it creates a stress drop on the level of injection for the foam focus. Testing can’t be achieved without creating premix and discharging finished foam. This will add to complete lifetime prices because of foam focus usage, which has to be changed, and the disposal of premix or foam.
However, the bladder itself is seen as a weak spot as a outcome of nice care is needed to avoid a damaged bladder when commissioning a brand new installation. It is rarely straightforward to work within the steel strain vessel should issues occur, particularly if and when a replacement bladder could also be required: all of it provides to the issue and cost.
Compressed air foam (CAFS):
This just isn’t a proportioning technique within the standard sense as the foam is already proportioned using one of the earlier methods. However, pressurised air is then added forcefully somewhat than naturally entrained or aspirated. As the title suggests, CAFS injects compressed air into the foam answer on the point of discharge. The consensus view is that CAFS enhances the finished foam’s capacity to cling to vertical surfaces permitting higher penetration and cooling. This can be a profit in wildfire conditions by coating vulnerable buildings to mitigate fireplace growth. The restricted water supplies associated with distant wildfire areas implies that the resource can be totally optimised. However, as with balanced stress proportioner foam pumps, a further level of failure is feasible due to the further CAFS equipment.
Water driven or turbine foam proportioners:
FireDos have turn into synonymous with their distinctive water-driven foam proportioner. Now in its third era, the product is purely mechanical and extremely reliable. A water-driven rotor supplies the motive force to drive a immediately coupled positive-displacement plunger or piston pump. This is supplied with foam concentrate through an atmospheric foam tank adjacent to the FireDos unit. The proportioning pump is manufacturing facility set to the required proportioning fee and can proportion the foam focus precisely throughout a large working vary. The purely mechanical system supplies cost-efficient and eco-friendly proportioning price testing, completely with out utilizing any foam focus or creating premix or firefighting foam.
FireDos GEN III foam proportioned. Images provided by Author / Contributor
The advantages of FireDos Gen III FM accredited foam proportioners include:
Reduced prices: proportioning price is examined with out utilizing foam or creating premix or foam – price effective and eco-friendly.
Improved efficiency: fixed proportioning rate throughout a large working range.
Optimised supply of high-viscosity foam concentrates with improved suction capacity.
25% reduction in pressure loss, in comparison with older generations, via hydraulic optimisation.
Improved cylinder cut-off for simple and quick adjustment to a unique proportioning price.
FM permitted FireDos Gen III proportioners are to date the only FM approved water motor coupled variable proportioners using FM permitted move meters. Using the test return line this offers the chance to examine the proportioning price during commissioning in addition to for annual exams, without creating any premix, which is a very big profit for the person and relieves the surroundings.
In the second a part of this function we will discover the effects of viscosity on foam proportioning and typical foam application areas and really helpful discharge gadgets.
For extra data, go to www.firedos.com
Written by
David Owen
Andreas Hulinsky

Scroll to Top