Part One of this text described the typical incident situations at tank farm fires and presented foam as essentially the most suitable extinguishing agent along with the firefighting equipment most commonly used. In เกจวัดแรงดัน take a glance at foam focus proportioning applied sciences, cell extinguishing methods and conclude with classes learned.
NFPA eleven describes numerous forms of foam concentrate proportioning gear. In the following, three methods are checked out which are most typical. Tight limits for the proportioning of foam concentrate apply to all of them.
The proportioning fee must not be lower than the permitted values – i.e. 3% for a 3% foam focus or 6% for a 6% foam focus.
The proportioning rate should not exceed 30% above the permitted worth i.e. 3.9% for a 3% foam concentrate or 7.8% for a 6% foam concentrate; respectively, the proportioning fee is allowed to be an absolute most of 1% above the permitted value – i.e. 4% for a 3% foam concentrate or 7% for a 6% foam concentrate (the smaller worth must be used respectively).
To guarantee appropriate proportioning, the proportioner, together with the proportioning rate must be examined at least once a 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 confirmed and cost-effective know-how. The bladder tank is a pressurized vessel with a bladder inside which is crammed with foam concentrate. The tank is pressurized with water from the fire-extinguishing line and discharges the froth focus from the bladder as required. The bladder is related to a proportioner which operates using the venturi precept. When the fireplace pumps are activated, pressure is generated by the pump, causing delivery of foam focus to the proportioner. The extinguishing water flows by way of the venturi proportioner. The ensuing vacuum induces the froth concentrate into the extinguishing water flow.
The benefits of this method are its easy design without moving parts and its easy operation. No external energy is required, and the system is comparatively cheap.
pressure gauge 10 bar is that the system is a pressurized vessel subject to corresponding rules similar to ASME Boiler & Pressure Vessel Codes. In order to refill foam concentrate, the system must be shut down and drained. The rubber bladder is delicate; when damaged, water will contaminate the foam concentrate. At a given proportioning rate, the system is appropriate just for low variations in the extinguishing water circulate strain and volume. Adding or altering particular person foam discharge devices is possible only to a very limited extent. The system can also be unsuitable for proportioning highly viscous foam concentrates.
To conduct any obligatory required annual testing, the system should be activated and premix generated at the venturi proportioner inside the extinguishing water line. The right proportioning fee must be measured within the premix by laboratory evaluation. The generated premix should then be disposed of, and the consumed foam focus within the bladder tank needs to be changed.
Fig. 2: Driven proportioning pump with circulate meter.
Driven proportioning pump with circulate meter

The system consists of an atmospheric tank for the foam focus, an electrical or diesel-powered foam concentrate pump with an electronically controlled valve and a flow meter in the extinguishing water flow line. When the hearth pumps are activated, the froth focus pump drive and digital management system should be activated. The extinguishing water flow rate is measured by the flow meter and the control system adjusts the right foam concentrate quantity through the management valve. The foam concentrate is injected into the extinguishing water move by the foam focus pump. If there’s a change within the flow fee, the amount of injected foam focus is regulated by the management valve.
The system’s advantage lies in the exact proportioning of the froth concentrate, impartial of the extinguishing water pressure or circulate fee. Foam focus may be topped up through the extinguishing operation. The system is able to proportioning highly viscous foam concentrates. For the purpose of annual testing, the system should be activated; however, the delivered foam focus can be measured by way of a return line. The proportioning rate is calculated from the extinguishing water/foam focus move fee. No premix is produced; and as the foam focus is handed back into the tank, no foam concentrate must be refilled.
Disadvantages are the requirement for an exterior interruption-free energy supply for the foam focus pump and the management system, in addition to the necessity for a complicated control system and the comparatively higher purchasing costs. Furthermore, it have to be accepted that a delay occurs between the change of the extinguishing water move rate and the newly adjusted foam focus amount. The foam quality could additionally be compromised when continuously changing operating circumstances as foam discharge units are turned on or off or changed.
Water motor with proportioning pump

The system consists of an atmospheric tank for the foam concentrate, a water motor installed within the extinguishing water move line and a foam concentrate pump which is linked directly to the water motor. Water motor and pump form one compact unit. Upon activation of the fireplace pumps, rotation in the water motor begins. The direct coupling to the foam-concentrate pump gives quick foam-concentrate injection into the extinguishing water. If the circulate fee modifications, the amount of froth focus is tailored instantly.
The benefit of the system is its independence from external power sources in addition to a exact and immediate foam-concentrate proportioning regardless of the extinguishing water pressure or flow rate. If a piston or plunger pump is used, adjustment or calibration after installation just isn’t needed for the explanation that water motor and the pump are volumetric units firmly linked to one another. Foam focus refilling throughout operation is feasible. The system can additionally be capable of proportioning extremely viscous foam concentrates. The system have to be activated for annual testing; nonetheless, the delivered foam concentrate can be measured by way of a return line. The proportioning rate is calculated from the extinguishing water/foam concentrate move rate. No premix is generated; and if the froth focus is passed again into the tank, no foam concentrate needs to be topped up.
The larger design and the comparatively greater purchasing prices are an obstacle of the system.
With any system, consideration should be taken into consideration for the annual testing costs, which could be appreciable when it comes to substitute foam concentrate, disposal of premix and labour prices.
Mobile extinguishing techniques

As the stationary foam discharge gear can be damaged in extensive fires within the tank or within the dyke area and thus lose effectiveness, mobile fireplace screens and foam pipes could also be used.
Foam pipes

Foam pipes are usually held by firefighters, making them very versatile. Yet they have only limited extinguishing agent circulate rates and reaches.
Firefighting displays

Firefighting screens are discharge devices mounted on automobiles or trailers and available in plenty of sizes. The extinguishing agent move price can be up to 60,000 litres/min and the reach may be up to 180m if the pressure of the fire pumps is enough. They are suitable to discharge foam, e.g., to extinguish a surface hearth in a tank, or water, to chill down a neighboring tank or the tank wall of a burning tank in order to forestall it reaching the crucial temperature for a boilover, or to maintain the flames from spreading. The accumulation of water contained in the dyke area ought to always be noticed to avoid an overflow of the dyke.
Mobile hearth screens could be supplied both by the extinguishing water of the stationary fireplace pumps or by mobile pumps. The injection of the foam concentrate often takes place through cellular proportioners. This clearly points in path of the benefit of vitality independence for water-motor-driven proportioning pumps.
The strategic decision for the sizes of cell items available as back-ups is proven by the following instance for the placement of screens for fire extinguishing at tanks that are 45m in diameter and 15m excessive.
According to NFPA, 32,000 litres of premix per minute are required. This leads to several alternatives for the monitors. Generally, foam-concentrate proportioners for no less than 32,000 litres/min are required, which should be capable of handle various flow charges to ensure flexibility during extinguishing operations. Depending on the native circumstances, the displays will need to hold a minimal distance to the burning tank or may not have the power to be positioned near to the tanks due to particles. In addition, it won’t at all times be possible to place several screens across the tank. It should be ensured the monitor has adequate throwing peak in relation to the tank height, to ship foam into the inside of the tank.
The dimensioning of the whole firefighting system is made following authorized laws in addition to suggestions by associations like NFPA and isn’t looked at more intently in the present article.
Fig. four: Trailer with monitor M4, water motor with proportioning pump FD8000 and foam focus tank.
Lessons realized

As mentioned in the introduction to Part One of this text, it seems that many authorities and companies have not realized the required classes from disastrous fireplace incidents of previous years. Tank farm fires in the oil and petrochemical trade don’t happen incessantly. When they do, they often have devastating consequences. Let us keep in mind the tank farm fireplace at Deer Park, Texas in March 2019 mentioned in the introduction.
The fire developed after over 30,000 litres butane-enriched naphtha had been leaking from a defective valve for half-hour and caught fireplace for but unknown reasons. The plant had no gasoline warning system and no remote-controlled valves to close off the leaking fluid. In addition, some areas didn’t have mounted extinguishing methods installed. All 15 tanks have been surrounded by one single dyke. The owner had relied on the local fire service, which was on the spot in a quick time but couldn’t take management over the hearth with the tools obtainable, partially because flammable substance was continuously leaking from the tank. Thirty-six hours after the fireplace had broken out, a contract was made with an external firefighting company to do the extinguishing work. Mobilization of kit and foam focus as well as the preparation of a plan of action took roughly thirteen hours. The hearth was lastly extinguished after 14 hours of firefighting, 63 hours after it initially broke out. Extinguishing attempts have been remodeled three days, with foam focus and water shortages occurring within the meantime. In complete, over 500,000 litres of froth concentrate have been used. Instead of a fire within the dyke area, 11 of the 15 tanks burnt down.
It is very probable that the fire would have been extinguished quickly if the warning methods and valves had labored and a onerous and fast fireplace extinguishing system had existed. It is also probable that the fire would have been extinguished shortly if the extinguishing operation, which succeeded eventually, had been started earlier. Both instances would have resulted in notably less injury.
Summing up, the following points ought to be discovered as a minimum. As far as they haven’t yet been carried out, or just partly, they want to function a foundation for discussions about one’s personal fire-protection idea:
Have an appropriate fire-protection concept together with various situations which adapt to the given situation frequently.
Always have เกจวัดแรงดัน of mobile extinguishing systems as a backup to fastened extinguishing methods.
Stock an acceptable foam concentrate.
Ensure sufficient foam concentrate supply.
Ensure sufficient water supply.
Keep well-maintained, rapidly and well-accessible, strategically placed and functioning extinguishing gear obtainable in a enough number.
Have educated personnel available in a enough quantity.
Ensure a quick implementation of an appropriate plan of motion.
For more information, go to www.firedos.com

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