จำหน่ายเกจวัดแรงดัน Pressure Gauge ทุกยี่ห้อ

ศูนย์รวมเครื่องมือวัดความดัน

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 mostly used. In Part Two we take a glance at foam focus proportioning technologies, cellular extinguishing systems and conclude with classes realized.
NFPA eleven describes varied kinds of foam focus proportioning equipment. In the next, three techniques are checked out that are most typical. Tight limits for the proportioning of froth concentrate apply to all of them.
The proportioning rate should not be lower than the permitted values – i.e. 3% for a 3% foam concentrate or 6% for a 6% foam focus.
The proportioning rate must not exceed 30% above the permitted worth i.e. 3.9% for a 3% foam focus or 7.8% for a 6% foam concentrate; respectively, the proportioning price is allowed to be an absolute maximum of 1% above the permitted value – i.e. 4% for a 3% foam concentrate or 7% for a 6% foam focus (the smaller worth must be used respectively).
To guarantee appropriate proportioning, the proportioner, together with the proportioning fee must be tested no less than every year and its right functioning have to be checked.
Fig. 1 Bladder tank with proportioner.
Bladder tank with proportioner
The bladder tank with a proportioner is a confirmed and cost-effective technology. The bladder tank is a pressurized vessel with a bladder inside which is full of foam focus. 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 utilizing the venturi precept. When the fire pumps are activated, pressure 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 froth focus into the extinguishing water move.
The advantages of this system are its simple design without transferring components and its simple operation. No external energy is required, and the system is relatively inexpensive.
A drawback is that the system is a pressurized vessel topic to corresponding regulations corresponding to ASME Boiler & Pressure Vessel Codes. In order to refill foam focus, the system should be shut down and drained. The rubber bladder is delicate; when damaged, water will contaminate the foam concentrate. At a given proportioning fee, the system is suitable just for low variations in the extinguishing water circulate strain and quantity. Adding or changing particular person foam discharge gadgets is possible only to a really restricted extent. The system can additionally be unsuitable for proportioning highly viscous foam concentrates.
To conduct any mandatory required annual testing, the system should be activated and premix generated on the venturi proportioner inside the extinguishing water line. The correct proportioning fee must be measured within the premix by laboratory evaluation. The generated premix must then be disposed of, and the consumed foam focus in the bladder tank needs to be changed.
Fig. 2: Driven proportioning pump with circulate meter.
Driven proportioning pump with flow meter
The system consists of an atmospheric tank for the froth focus, an electrical or diesel-powered foam concentrate pump with an electronically managed valve and a move meter within the extinguishing water circulate line. When the fire pumps are activated, the foam focus pump drive and digital control system must be activated. The extinguishing water move fee is measured by the move meter and the control system adjusts the correct foam focus amount via the control valve. The foam concentrate is injected into the extinguishing water circulate by the foam focus pump. If there’s a change within the circulate fee, the quantity of injected foam concentrate is regulated by the control valve.
The system’s benefit lies within the exact proportioning of the foam concentrate, independent of the extinguishing water strain or circulate fee. Foam focus may be topped up during the extinguishing operation. The system is able to proportioning extremely viscous foam concentrates. For the aim of annual testing, the system have to be activated; nevertheless, the delivered foam concentrate can be measured by way of a return line. The proportioning rate is calculated from the extinguishing water/foam focus circulate price. No premix is produced; and as the foam concentrate is passed back into the tank, no foam concentrate must be refilled.
Disadvantages are the requirement for an external interruption-free power provide for the froth focus pump and the control system, as nicely as the need for a classy management system and the comparatively higher buying prices. Furthermore, it have to be accepted that a delay occurs between the change of the extinguishing water flow price and the newly adjusted foam concentrate amount. The foam high quality may be compromised when constantly changing operating circumstances as foam discharge units are turned on or off or modified.
Water motor with proportioning pump
The system consists of an atmospheric tank for the froth concentrate, a water motor installed within the extinguishing water circulate line and a foam concentrate pump which is linked directly to the water motor. Water motor and pump type one compact unit. Upon activation of the hearth pumps, rotation in the water motor begins. The direct coupling to the foam-concentrate pump offers immediate foam-concentrate injection into the extinguishing water. If the circulate price adjustments, the quantity of froth focus is adapted immediately.
เกจอาร์กอน of the system is its independence from external energy sources in addition to a precise and instant foam-concentrate proportioning whatever the extinguishing water pressure or move price. If a piston or plunger pump is used, adjustment or calibration after installation just isn’t necessary for the rationale that water motor and the pump are volumetric devices firmly connected to every other. Foam focus refilling during operation is feasible. The system can additionally be capable of proportioning extremely viscous foam concentrates. The system have to be activated for annual testing; however, the delivered foam concentrate may be measured through a return line. The proportioning fee is calculated from the extinguishing water/foam concentrate circulate fee. No premix is generated; and if the froth focus is handed back into the tank, no foam focus must be topped up.
The larger design and the comparatively larger buying costs are an obstacle of the system.
With any system, consideration ought to be taken under consideration for the annual testing prices, which may be appreciable when it comes to substitute foam concentrate, disposal of premix and labour costs.
Mobile extinguishing methods
As the stationary foam discharge equipment can be broken in in depth fires within the tank or in the dyke space and thus lose effectiveness, cellular fireplace screens and foam pipes may be used.
Foam pipes
Foam pipes are usually held by firefighters, making them very versatile. Yet they have solely restricted extinguishing agent move rates and reaches.
Firefighting monitors
Firefighting screens are discharge devices mounted on automobiles or trailers and available in many sizes. The extinguishing agent move fee could be up to 60,000 litres/min and the reach can be as much as 180m if the stress of the fireplace pumps is adequate. They are suitable to discharge foam, e.g., to extinguish a surface fireplace in a tank, or water, to chill down a neighboring tank or the tank wall of a burning tank so as 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 all the time be observed to avoid an overflow of the dyke.
Mobile fireplace displays could be equipped both by the extinguishing water of the stationary fire pumps or by cellular pumps. The injection of the foam concentrate normally takes place by way of mobile proportioners. This clearly factors in path of the benefit of power independence for water-motor-driven proportioning pumps.
The strategic choice for the sizes of mobile models out there as back-ups is shown by the following example for the position of monitors for fireplace extinguishing at tanks which are 45m in diameter and 15m high.
According to NFPA, 32,000 litres of premix per minute are required. This leads to several alternatives for the displays. Generally, foam-concentrate proportioners for no less than 32,000 litres/min are required, which should be succesful of handle varying move charges to ensure flexibility during extinguishing operations. Depending on the native conditions, the screens might 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 is not going to at all times be attainable to place a number of displays around the tank. It should be ensured the monitor has adequate throwing height in relation to the tank height, to ship foam into the within of the tank.
The dimensioning of the whole firefighting system is made following authorized rules as nicely as suggestions by associations like NFPA and isn’t checked out more carefully in the current article.
Fig. 4: Trailer with monitor M4, water motor with proportioning pump FD8000 and foam concentrate tank.
Lessons discovered
As talked about within the introduction to Part One of this article, it seems that evidently many authorities and corporations haven’t realized the necessary lessons from disastrous fireplace incidents of previous years. Tank farm fires in the oil and petrochemical trade don’t happen frequently. When they do, they often have devastating penalties. Let us bear in mind the tank farm fireplace at Deer Park, Texas in March 2019 talked about within the introduction.
The hearth developed after over 30,000 litres butane-enriched naphtha had been leaking from a defective valve for 30 minutes and caught fire for yet unknown reasons. The plant had no gas warning system and no remote-controlled valves to shut off the leaking fluid. In addition, some areas didn’t have fastened extinguishing techniques installed. All 15 tanks had been surrounded by one single dyke. The owner had relied on the native fireplace service, which was on the spot in a short time however couldn’t take control over the hearth with the tools obtainable, partially as a end result of flammable substance was constantly leaking from the tank. Thirty-six hours after the fire had damaged out, a contract was made with an exterior firefighting company to do the extinguishing work. Mobilization of kit and foam focus as well as the preparation of a plan of action took approximately 13 hours. The fireplace was lastly extinguished after 14 hours of firefighting, 63 hours after it initially broke out. Extinguishing attempts had been made over three days, with foam focus and water shortages occurring in the meantime. In whole, over 500,000 litres of froth concentrate have been used. Instead of a fireplace within the dyke area, eleven of the 15 tanks burnt down.
It could be very probable that the fireplace would have been extinguished quickly if the warning systems and valves had worked and a set hearth extinguishing system had existed. It can be possible that the hearth would have been extinguished shortly if the extinguishing operation, which succeeded finally, had been started earlier. Both circumstances would have resulted in notably much less injury.
Summing up, the following factors must be discovered at least. As far as they haven’t yet been applied, or just partly, they want to function a foundation for discussions about one’s personal fire-protection concept:
Have an acceptable fire-protection concept including alternative situations which adapt to the given scenario often.
Always have a adequate variety of cell extinguishing methods as a backup to fastened extinguishing methods.
Stock a suitable foam concentrate.
Ensure adequate foam concentrate provide.
Ensure enough water provide.
Keep well-maintained, rapidly and well-accessible, strategically positioned and functioning extinguishing gear available in a sufficient quantity.
Have skilled personnel obtainable in a sufficient number.
Ensure a quick implementation of an acceptable plan of motion.
For extra data, go to www.firedos.com
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