Part One of this article described the everyday incident eventualities at tank farm fires and introduced foam as the most suitable extinguishing agent together with the firefighting equipment mostly used. In Part Two we have a glance at foam concentrate proportioning applied sciences, mobile extinguishing techniques and conclude with lessons learned.
NFPA 11 describes varied types of foam concentrate proportioning tools. In the next, three systems are checked out that are most typical. Tight limits for the proportioning of froth concentrate apply to all of them.
The proportioning fee should not be less than the permitted values – i.e. 3% for a 3% foam concentrate or 6% for a 6% foam focus.
The proportioning rate should not exceed 30% above the permitted value i.e. 3.9% for a 3% foam focus or 7.8% for a 6% foam concentrate; respectively, the proportioning rate is allowed to be an absolute maximum of 1% above the permitted worth – i.e. 4% for a 3% foam concentrate or 7% for a 6% foam focus (the smaller value have to be used respectively).
To assure correct proportioning, the proportioner, including the proportioning price should be examined no less than every year and its appropriate functioning should be checked.
Fig. 1 Bladder tank with proportioner.
Bladder tank with proportioner

The bladder tank with a proportioner is a proven and cost-effective technology. The bladder tank is a pressurized vessel with a bladder inside which is full of foam concentrate. The tank is pressurized with water from the fire-extinguishing line and discharges the froth concentrate from the bladder as required. The bladder is linked to a proportioner which operates using the venturi precept. When the fire pumps are activated, strain is generated by the pump, causing delivery of foam concentrate to the proportioner. The extinguishing water flows via the venturi proportioner. The ensuing vacuum induces the foam focus into the extinguishing water move.
The advantages of this method are its easy design with out moving components and its simple operation. No exterior power is required, and the system is relatively inexpensive.
A drawback is that the system is a pressurized vessel topic to corresponding rules similar to ASME Boiler & Pressure Vessel Codes. In order to refill foam concentrate, the system should be shut down and drained. The rubber bladder is sensitive; when broken, water will contaminate the foam concentrate. At a given proportioning price, the system is suitable only for low variations within the extinguishing water move stress and quantity. Adding or changing particular person foam discharge units is feasible only to a very limited extent. The system can also be unsuitable for proportioning extremely viscous foam concentrates.
To conduct any mandatory required annual testing, the system must be activated and premix generated at the venturi proportioner within the extinguishing water line. The correct proportioning rate have to be measured within the premix by laboratory analysis. The generated premix should then be disposed of, and the consumed foam concentrate in the bladder tank needs to be changed.
Fig. 2: Driven proportioning pump with flow meter.
Driven proportioning pump with flow meter

The system consists of an atmospheric tank for the foam focus, an electrical or diesel-powered foam concentrate pump with an electronically managed valve and a circulate meter within the extinguishing water flow line. When the hearth pumps are activated, the froth focus pump drive and digital management system have to be activated. The extinguishing water circulate price is measured by the circulate meter and the control system adjusts the correct foam focus amount by way of the management valve. The foam focus is injected into the extinguishing water flow by the froth concentrate pump. If there’s a change in the flow rate, the amount of injected foam focus is regulated by the control valve.
The system’s benefit lies within the exact proportioning of the froth concentrate, unbiased of the extinguishing water pressure or flow rate. Foam focus may be topped up through the extinguishing operation. The system is capable of proportioning extremely viscous foam concentrates. For the purpose of annual testing, the system should be activated; however, the delivered foam focus could be measured by way of a return line. The proportioning rate is calculated from the extinguishing water/foam concentrate flow price. No premix is produced; and as a result of the foam focus is passed back into the tank, no foam focus must be refilled.
Disadvantages are the requirement for an exterior interruption-free power supply for the froth concentrate pump and the management system, in addition to the need for a sophisticated management system and the comparatively larger purchasing costs. Furthermore, it have to be accepted that a delay occurs between the change of the extinguishing water circulate fee and the newly adjusted foam focus amount. The foam high quality could also be compromised when constantly changing working situations as foam discharge devices are turned on or off or changed.
Water motor with proportioning pump

The system consists of an atmospheric tank for the froth focus, a water motor installed within the extinguishing water flow line and a foam concentrate pump which is related on to the water motor. Water motor and pump kind one compact unit. Upon activation of the hearth pumps, rotation within the water motor begins. The direct coupling to the foam-concentrate pump offers quick foam-concentrate injection into the extinguishing water. If the circulate fee adjustments, the amount of foam focus is adapted immediately.
The benefit of the system is its independence from exterior power sources as properly as a precise and instant foam-concentrate proportioning regardless of the extinguishing water stress or move rate. If a piston or plunger pump is used, adjustment or calibration after installation just isn’t needed because the water motor and the pump are volumetric units firmly connected to one another. Foam concentrate refilling throughout operation is possible. เพรสเชอร์เกจ can also be able to proportioning extremely viscous foam concentrates. The system have to be activated for annual testing; nonetheless, the delivered foam concentrate could be measured by way of a return line. The proportioning price is calculated from the extinguishing water/foam focus move fee. No premix is generated; and if the froth concentrate is handed back into the tank, no foam focus needs to be topped up.
The larger design and the comparatively larger purchasing prices are a drawback of the system.
With any system, consideration should be taken into account for the annual testing costs, which may be appreciable when it comes to substitute foam concentrate, disposal of premix and labour prices.
Mobile extinguishing techniques

As the stationary foam discharge equipment can be damaged in extensive fires in the tank or in the dyke area and thus lose effectiveness, mobile fireplace monitors and foam pipes could additionally be used.
Foam pipes

Foam pipes are usually held by firefighters, making them very flexible. Yet they’ve solely restricted extinguishing agent move charges and reaches.
Firefighting monitors

Firefighting displays are discharge gadgets mounted on vehicles or trailers and out there in many sizes. The extinguishing agent circulate fee may be as much as 60,000 litres/min and the reach could be as much as 180m if the stress of the hearth pumps is adequate. They are suitable to discharge foam, e.g., to extinguish a surface fire in a tank, or water, to chill down a neighboring tank or the tank wall of a burning tank to be able to stop it reaching the critical temperature for a boilover, or to maintain the flames from spreading. The accumulation of water inside the dyke space ought to at all times be noticed to avoid an overflow of the dyke.
Mobile fireplace monitors can be equipped either by the extinguishing water of the stationary hearth pumps or by cellular pumps. The injection of the foam focus normally takes place via cellular proportioners. This clearly factors in path of the benefit of power independence for water-motor-driven proportioning pumps.
The strategic decision for the sizes of cell models available as back-ups is proven by the following instance for the position of displays for fire extinguishing at tanks which are 45m in diameter and 15m excessive.
According to NFPA, 32,000 litres of premix per minute are required. This results in several alternate options for the displays. Generally, foam-concentrate proportioners for at least 32,000 litres/min are required, which ought to be in a position to handle varying flow charges to guarantee flexibility throughout extinguishing operations. Depending on the native conditions, the displays will want to maintain a minimum distance to the burning tank or may not have the flexibility to be positioned close to to the tanks because of particles. In addition, it won’t at all times be attainable to position a quantity of displays across the tank. It must be ensured the monitor has adequate throwing top in relation to the tank top, to deliver foam into the inside of the tank.
The dimensioning of the whole firefighting system is made following authorized rules as nicely as recommendations by associations like NFPA and is not looked at more closely within the current article.
Fig. 4: Trailer with monitor M4, water motor with proportioning pump FD8000 and foam focus tank.
Lessons learned

As mentioned in the introduction to Part One of this article, it seems that evidently many authorities and companies have not realized the mandatory lessons from disastrous fireplace incidents of past years. Tank farm fires within the oil and petrochemical industry don’t occur incessantly. When they do, they normally have devastating penalties. Let us bear in mind the tank farm hearth at Deer Park, Texas in March 2019 mentioned within the introduction.
The fireplace developed after over 30,000 litres butane-enriched naphtha had been leaking from a faulty valve for 30 minutes and caught fire for but unknown reasons. The plant had no fuel warning system and no remote-controlled valves to shut off the leaking fluid. In addition, some areas didn’t have fixed extinguishing methods installed. All 15 tanks have been surrounded by one single dyke. The owner had relied on the native fire service, which was on the spot in a brief time however couldn’t take control over the fire with the tools available, partially because flammable substance was continuously leaking from the tank. Thirty-six hours after the hearth had damaged out, a contract was made with an external firefighting firm to do the extinguishing work. Mobilization of kit and foam concentrate as nicely as the preparation of a plan of action took approximately 13 hours. The fire was lastly extinguished after 14 hours of firefighting, 63 hours after it initially broke out. Extinguishing attempts were remodeled three days, with foam focus and water shortages occurring in the meantime. In total, over 500,000 litres of froth focus were used. Instead of a hearth in the dyke area, 11 of the 15 tanks burnt down.
It may be very possible that the fire would have been extinguished rapidly if the warning techniques and valves had worked and a fixed fire extinguishing system had existed. It can be possible that the fire would have been extinguished rapidly if the extinguishing operation, which succeeded ultimately, had been began earlier. Both circumstances would have resulted in notably less damage.
Summing up, the next points ought to be learned at least. As far as they haven’t but been applied, or simply partly, they should function a basis for discussions about one’s own fire-protection idea:
Have an acceptable fire-protection idea together with alternative eventualities which adapt to the given state of affairs frequently.
Always have a enough variety of mobile extinguishing methods as a backup to fixed extinguishing methods.
Stock an appropriate foam concentrate.
Ensure sufficient foam concentrate supply.
Ensure sufficient water provide.
Keep well-maintained, quickly and well-accessible, strategically positioned and functioning extinguishing tools available in a sufficient quantity.
Have skilled personnel obtainable in a enough quantity.
Ensure a fast implementation of a suitable plan of action.
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