Stationary installations and fire extinguishing systems. The main goal of fighting a fire is to quickly bring it under control and extinguish it, which is only possible if the fire extinguishing agent is delivered to the fire quickly and in sufficient quantities.
This can be achieved using fixed fire extinguishing systems. Some of the fixed systems can apply extinguishing agent directly to the fire without the participation of crew members.
Fixed fire extinguishing systems are in no way a substitute for the necessary structural fire protection of a ship. Structural fire protection provides sufficiently long-term protection of passengers, crew and critical equipment from fire, which allows people to evacuate to a safe place.
Fire fighting equipment is designed to protect the ship. Ship fire extinguishing systems are designed taking into account the potential fire danger, existing in the room, and the purpose of the room.
Usually:
water is used in stationary systems protecting areas in which solid flammable substances are located - public areas and corridors;
foam or fire extinguishing powder is used in fixed systems protecting areas where class B fires may occur; stationary systems are not used to extinguish fires involving flammable gases;
carbon dioxide, gallon (freon) and the corresponding fire extinguishing powder are included in systems that provide class C fire protection;
There are no fixed systems for extinguishing Class D fires.
Ships flying the Russian flag are equipped with nine main fire extinguishing systems:
1) water fire;
2) automatic and manual sprinkler;
3) water spray;
4) water curtains;
5) water irrigation;
6) foam extinguishing;
7) carbon dioxide;
8) inert gas system;
9) powder.
The first five systems use liquid extinguishing agents, the next three use gaseous agents, and the last uses solids. Each of these systems will be discussed below.
Water fire system
Water fire system- This is the primary means of protection against fire on a ship. Its installation is required regardless of what other systems are installed on the vessel. Any crew member, according to the alarm schedule, can be assigned to a fire post, so each crew member must know the principle of operation and start-up of the ship's water supply. fire system.
The water fire system ensures the supply of water to all areas of the vessel. It is clear that the supply of water in the sea is unlimited. The amount of water supplied to the location of the fire is limited only by the technical data of the system itself (for example, pump performance) and the influence of the amount of water supplied on the stability of the vessel.
The water fire system includes fire pumps, pipelines (main and branches), control valves, hoses and trunks.
Fire hydrants and pipelines
Water moves through pipelines from pumps to fire hydrants installed at fire stations. The diameter of the pipelines must be large enough to distribute the maximum required amount of water from two pumps operating simultaneously.
The system water pressure should be approximately 350 kPa at the two furthest or highest fire hydrants (whichever produces the greatest pressure difference) for cargo ships and other vessels, and 520 kPa for tankers.
This requirement provides sufficient choice large diameter pipelines so that the pressure developed by the pump does not decrease due to friction losses in the pipelines.
The pipeline system consists of a main line and branches of smaller diameter pipes extending from it to fire hydrants. No pipelines are allowed to be connected to the water fire system, except those intended for fire fighting and deck washing.
All areas of the water fire system on open decks must be protected from freezing. To do this, they can be equipped with shut-off and drain valves, allowing water to be drained during the cold season.
There are two main schemes of the water fire system: linear and circular.
Linear diagram. In a linear water fire system, one main line is laid along the ship, usually at the level of the main deck. Due to horizontal and vertical pipes, departing from this highway, the system branches throughout the vessel (Fig. 3.1). On tankers, the water fire main is usually laid in the center plane.
The disadvantage of this scheme is that it does not make it possible to supply water beyond the point where serious damage to the system has occurred.
Rice. 3.1. Typical linear diagram of a water fire system:
1 - highway; 2 - branches; 3 - shut-off valve; 4 - fire station; 5 - shore connection; b - kingston; 7 - fire pumps
Ring diagram. The system, made according to this scheme, consists of two parallel lines connected at the extreme bow and stern points, thereby forming a closed ring (Fig. 3.2). Branches connect the system to fire stations.
In a ring circuit, the area where the rupture occurred can be disconnected from the main, and the main can continue to be used to supply water to all other parts of the system. Sometimes isolation valves are installed on the main line behind fire hydrants. They are designed to control the flow of water when a rupture occurs in the system.
In some single-circuit systems, isolation valves are provided only on the aft and forward decks.
Shore connections. At least one water main connection to the shore must be installed on each side of the vessel. Each shore connection should be located in an easily accessible location and be equipped with shut-off and control valves.
A ship on international voyages must have at least one portable shore connection on each side. This makes it possible for ship crews to use shore-mounted pumps or resort to the services of shore fire brigades in any port. Some ships have the required international shore connections permanently installed.
Fire pumps. This is the only means of ensuring the movement of water through the water fire system when the ship is at sea. The required number of pumps, their performance, location and power sources are regulated by the Register Rules. The requirements for them are briefly outlined below.
Quantity and location. On cargo and passenger ships with a capacity of 3,000 gross tons or more, performing international voyages, two fire pumps with autonomous drives must be installed. All passenger ships with a gross tonnage of up to 4,000 tons must be equipped with at least two fire pumps, and on ships with a gross tonnage of more than 4,000 tons, three fire pumps, regardless of the length of the ship.
If the vessel requires installation of two pumps, they must be located in various rooms. Fire pumps, seacocks and power sources should be located so that a fire in one room does not disable all pumps, thus leaving the ship unprotected.
The crew is not responsible for installing the required number of pumps on the ship, for their correct placement and the availability of appropriate energy sources. The vessel is designed, built and, if necessary, re-equipped in accordance with the Register Rules, but the crew is directly responsible for maintaining the pumps in good condition. In particular, the responsibilities of mechanics include Maintenance and testing of ship fire pumps to ensure they reliable operation in case of an accident.
Water consumption. Each fire pump must supply at least two jets of water from fire hydrants having a maximum pressure drop of 0.25 to 0.4 N/mm 2 for passenger and cargo ships, depending on their gross tonnage.
On passenger ships of less than 1,000 gross tonnage and on all other cargo ships of 1,000 gross tonnage and more, a stationary emergency fire pump must be installed. The total flow of stationary fire pumps, except for emergency ones, may not exceed 180 m^/h (except for passenger ships).
Safety. A safety valve and pressure gauge may be provided on the discharge side of the fire pump.
Fire pumps may be connected to other fire extinguishing systems (for example, a sprinkler system). But in this case, their performance must be sufficient so that they can simultaneously serve the water fire and second fire extinguishing systems, providing water supply under appropriate pressure.
Use of fire pumps for other purposes. Fire pumps can be used for more than just supplying water to the fire main. However, one of the fire pumps should be kept ready for its intended use at all times. The reliability of fire pumps increases if they are used from time to time for other purposes and are properly maintained.
If control valves that allow the use of fire pumps for other purposes are installed on the manifold next to the pump, then by opening the valve to the fire main, the operation of the pump for another purpose can be immediately interrupted.
If it is specifically stated that fire pumps may be used for other purposes, such as deck and tank washing, such connections shall only be provided at the discharge manifold at the pump.
Fire hydrants. The purpose of the water fire system is to supply water to fire hydrants located throughout the ship.
Placement of fire hydrants. Fire hydrants must be located so that the water jets supplied from at least two fire hydrants overlap each other. Fire hydrants on all ships must be painted red.
If the ship carries deck cargo, it must be stowed so as not to obstruct access to fire hydrants.
Each fire hydrant must be equipped with a shut-off valve and a standard quick-closing type connection head in accordance with the requirements of the Register Rules. According to the requirements of the SOLAS-74 Convention, the use of threaded connecting nuts is allowed.
Fire hydrants should be placed at a distance of no more than 20 m indoors and no more than 40 m on open decks.
Sleeves and trunks (refer to fire-fighting supplies).
The hose should have a length of 15+20 m for cranes on open decks and 104-15 m for cranes on premises. An exception is for hoses installed on the open decks of tankers, where the length of the hose must be sufficient to allow it to be lowered over the side, directing a stream of water along the side perpendicular to the surface of the water.
A fire hose with an appropriate barrel must always be attached to the fire hydrant. But in heavy seas, hoses installed on the open deck can be temporarily detached from the fire hydrants and stored nearby in an easily accessible place.
The fire hose is the most vulnerable part of the water fire system. If handled incorrectly, it is easily damaged.
Dragging the sleeve along the metal deck, it is easy to damage it - tear it external cladding, bend or split the nuts. If the hose is not drained of all water before installing it, the remaining moisture can cause mold and rot, which in turn will cause the hose to rupture under water pressure.
Laying and storing sleeves. In most cases, the hose for storage at the fire station should be laid in a coil.
In this case, you must do the following:
1.Check that the water is completely drained from the hose. A damp sleeve cannot be laid.
2. Place the hose in the coil so that the end of the barrel can be easily brought to the fire.
3. Attach the barrel to the end of the sleeve.
4. Place the barrel in the holder or place it in a sleeve so that it does not fall.
5. The rolled sleeve should be tied so that it does not lose its shape.
Trunks. On merchant marine vessels, combination barrels with a locking device are used. They must be permanently attached to the sleeves.
Combined barrels must be equipped with a control that allows you to turn off the water supply and regulate its flow.
River fire trunks must have nozzles with holes of 12, 16 and 19 mm. In residential and office premises there is no need to use nozzles with a diameter of more than 12 mm.
Centrifugal Fire Pump Vacuum System Designed for pre-filling the suction line and pump with water when drawing water from an open water source (reservoir). In addition, using a vacuum system, it is possible to create a vacuum (vacuum) in the housing of a centrifugal fire pump to check the tightness of the fire pump.
Currently, two types of vacuum systems are used on domestic fire trucks. The first type of vacuum system is based on gas jet vacuum apparatus(GVA) with a jet type pump, and based on the second type - vane vacuum pump(volumetric type).
Conclusion on the issue: Modern brands of fire trucks use various vacuum systems.
Gas jet vacuum systems
This vacuum system consists of the following main elements: a vacuum valve (gate) installed on the fire pump manifold, a gas-jet vacuum apparatus installed in the exhaust tract of the fire truck engine, in front of the muffler, a GVA control mechanism, the control lever of which is located in the pump compartment, and a pipeline , connecting the gas-jet vacuum apparatus and the vacuum valve (gate). Schematic diagram vacuum system is shown in Fig. 1.
Rice. 1 Diagram of the vacuum system of a centrifugal fire pump
1 – body of a gas-jet vacuum apparatus; 2 – damper; 3 – jet pump; 4 – pipeline; 5 – hole to the cavity of the fire pump; 6 – spring; 7 – valve; 8 – eccentric; 9 – eccentric axis; 10 – eccentric handle; 11 – vacuum valve body; 12 – hole; 13 – exhaust pipe, 14 – valve seat.
The housing of the gas-jet vacuum apparatus 1 has a damper 2, which changes the direction of movement of the exhaust gases of the fire engine engine or to jet pump 3, or into the outlet pipe 13. The jet pump 3 is connected by a pipeline 4 to the vacuum valve 11. The vacuum valve is installed on the pump and communicates with it through hole 5. Inside the vacuum valve body, springs 6 press two valves 7 to the seats 14. When moving the handle 10 with axis 9, eccentric 8 presses valves 7 from their seats. The system works as follows.
In the transport position (see Fig. 1 “A”), damper 2 is in a horizontal position. The valves are pressed to the seats by 7 springs 6. The engine exhaust gases pass through housing 1, exhaust pipe 13 and are released into the atmosphere through the muffler.
When drawing water from an open water source (see Fig. 1 “B”), after connecting the suction line to the pump, press the bottom valve down using the vacuum valve handle. In this case, the pump cavity through the cavity of the vacuum valve and pipeline 4 is connected to the cavity of the jet pump. Damper 2 is moved to a vertical position. The exhaust gases will be directed to the jet pump. A vacuum will be created in the suction cavity of the pump, and the pump will be filled with water under atmospheric pressure.
The vacuum system is turned off after filling the pump with water (see Fig. 1 “B”). By moving the handle, press the upper valve away from the seat. In this case, the lower valve will be pressed against the seat. The suction cavity of the pump is disconnected from the atmosphere. But now pipeline 4 will be connected to the atmosphere through hole 12, and the jet pump will remove water from the vacuum valve and connecting pipelines. This is especially necessary to do in winter to prevent water from freezing in pipelines. Then the handle 10 and the valve 2 are placed in their original position.
Rice. 2 Vacuum valve
(see Fig. 2) is designed to connect the suction cavity of the pump with a gas-jet vacuum apparatus when drawing water from open reservoirs and removing water from pipelines after filling the pump. The valve body 6, cast from cast iron or aluminum alloy, contains two valves 8 and 13. They are pressed by springs 14 to the saddles. When the handle 9 is positioned “away”, the eccentric on the roller 11 pushes the upper valve away from the seat. In this position the pump is disconnected from the jet pump. Moving the handle toward you, we press the lower valve 13 away from the seat, and the suction cavity of the pump is connected to the jet pump. With the handle in a vertical position, both valves will be pressed against their seats.
In the middle part of the body there is a plate 2 with a hole for connecting the connecting pipeline flange. In the lower part there are two holes, covered with eyes 1 made of organic glass. The body of 4 light bulbs is attached to one of them. The filling of the pump with water is monitored through the peephole.
On modern fire trucks, in the vacuum systems of fire pumps, instead of a vacuum valve (gate), ordinary plug water taps are often installed to connect (disconnect) the suction cavity of the fire pump with a jet pump.
Vacuum valve
Gas jet vacuum apparatus designed to create a vacuum in the cavity of the fire pump and suction line when they are pre-filled with water from an open water source. On fire trucks with gasoline engines, single-stage gas-jet vacuum apparatus is installed, the design of one of which is shown in Fig. 3
Housing 5 (distribution chamber) is designed to distribute the exhaust gas flow and is made of gray cast iron. Inside the distribution chamber there are lugs processed for the seats of the rotary valve 14. The housing has flanges for attaching to the engine exhaust tract and for attaching a vacuum jet pump. The valve 14 is made of heat-resistant alloy steel or ductile cast iron and is secured to the axis 12 using a lever 13. The valve axis 12 is assembled with graphite lubricant.
Using the lever 7, the axis 12 rotates, closing either the housing hole 5 or the cavity of the jet pump with a damper 14. The jet vacuum pump consists of a cast iron or steel diffuser 1 and a steel nozzle 3. The jet vacuum pump has a flange for connecting a pipeline 9 that connects the vacuum chamber jet pump with fire pump cavity through a vacuum valve. When the damper 14 is in a vertical position, the exhaust gases pass into the jet pump, as shown by the arrow in Fig. 3.25. Due to the vacuum in vacuum chamber 2, air is sucked out of the fire pump through pipeline 9 with the vacuum valve open. Moreover, the greater the speed of passage of exhaust gases through nozzle 3, the greater the vacuum created in vacuum chamber 2, pipeline 9, fire pump and suction line, if it is connected to the pump.
Therefore, in practice, when operating a vacuum jet pump (when drawing water into a fire pump or checking it for leaks), the maximum engine speed of the fire truck is set. If the valve 14 closes the hole in the vacuum jet pump, the exhaust gases pass through the body 5 of the gas jet vacuum apparatus into the muffler and then into the atmosphere.
On fire trucks with a diesel engine, two-stage gas-jet vacuum devices are installed in vacuum systems, which resemble single-stage ones in design and operating principle. The design of these devices is capable of ensuring short-term operation of a diesel engine when back pressure occurs in its exhaust tract. A two-stage gas-jet vacuum apparatus is shown in Fig. 4. The vacuum jet pump of the device is flanged to the housing 1 of the distribution chamber and consists of a nozzle 8, an intermediate nozzle 3, a receiving nozzle 4, a diffuser 2, an intermediate chamber 5, a vacuum chamber 7, connected to the atmosphere, through a nozzle 8, and through an intermediate nozzle - with receiving nozzle and diffuser. In the vacuum chamber 7 there is a hole 9 for connecting it with the cavity of the centrifugal fire pump.
Scheme of operation of the electric pneumatic drive for switching on the GVA
1 – gas-jet vacuum apparatus; 2 – pneumatic cylinder of the GVA drive; 3 – drive lever; 4 – EPC inclusion of GVA; 5 – EPC for turning off GVA; 6 – receiver; 7 – pressure limitation valve; 8 – toggle switch; 9 – atmospheric outlet.
To turn on the vacuum jet pump, it is necessary to turn the valve in the distribution chamber 1 by 90 0. In this case, the damper will block the exit of diesel exhaust gases through the muffler into the atmosphere. Exhaust gases enter the intermediate chamber 5 and, passing through the receiving nozzle 4, create a vacuum in the intermediate nozzle 3. Under the influence of vacuum in the intermediate nozzle 3, atmospheric air passes through the nozzle 8 and increases the vacuum in the vacuum chamber 7. This design of the gas-jet vacuum apparatus allows for efficient the jet pump can operate even at low pressure (velocity) of the exhaust gas flow.
Many modern fire trucks use an electro-pneumatic GVA drive system, the composition, design, principle of operation and operating features of which are outlined in the chapter.
Rice. 4 Two-stage gas jet vacuum apparatus
The procedure for working with a vacuum system based on GVA is given using the example of tank trucks model 63B (137A). To fill a fire pump with water from an open water source or check the fire pump for leaks, you must:
- make sure that the fire pump is tight (check that all taps, valves and valves of the fire pump are closed tightly);
- open the lower valve of the vacuum seal (turn the vacuum valve handle toward you);
- turn on the gas-jet vacuum apparatus (use the appropriate control lever to use the damper in the distribution chamber to block the release of exhaust gases through the muffler into the atmosphere);
- increase speed idle move engine to maximum;
- observe the appearance of water in the sight glass of the vacuum valve or the reading of the pressure and vacuum gauge on the fire pump;
- when water appears in the inspection eye of the vacuum valve or when the pressure-vacuum gauge shows a vacuum in the pump of at least 73 kPa (0.73 kgf/cm2), close the lower valve of the vacuum seal (set the vacuum valve handle to a vertical position or turn it away from you), reduce engine speed to minimum idle speed and turn off the gas-jet vacuum apparatus (use the appropriate control lever to shut off the flow of exhaust gases to the jet pump using the damper in the distribution chamber).
The time for filling a fire pump with water at a geometric suction height of 7 m should be no more than 35 s. A vacuum (when checking a fire pump for leaks) within 73...76 kPa should be achieved in no more than 20 s.
The control system for a gas-jet vacuum apparatus can also have a manual or electro-pneumatic drive.
The manual drive for switching on (rotating the damper) is carried out by lever 8 (see Fig. 5) from the pump compartment, connected through a system of rods 10 and 12 to the lever of the damper axis of the gas-jet vacuum apparatus. To ensure a tight fit of the damper to the saddles of the distribution chamber of the gas-jet vacuum apparatus during operation of the fire truck, periodic adjustment of the length of the rods is required using appropriate adjustment units. The tightness of the damper in its vertical position (when the gas-jet vacuum apparatus is turned on) is assessed by the absence of exhaust gases passing through the muffler into the atmosphere (if the damper itself is intact and its drive is in good working order).
Conclusion on the issue:
Electric Vane Vacuum Pump
Currently, in vacuum systems of centrifugal fire pumps in order to improve technical and performance characteristics install vane vacuum pumps, incl. ABC-01E and ABC-02E.
According to its composition and functional characteristics vacuum pump ABC-01E is an autonomous vacuum water filling system for a centrifugal fire pump. ABC-01E includes the following elements: vacuum unit 9, control unit 1 with electrical cables, vacuum valve 4, vacuum valve control cable 2, filling sensor 6, two flexible air ducts 3 and 10.
Rice. 4 Vacuum system kit АВС-01Э
The vacuum unit (see Fig. 4) is designed to create the vacuum necessary for filling water in the fire pump cavity and suction hoses. It is a vacuum pump 3 of a vane type with an electric drive 10. The vacuum pump itself consists of a housing part formed by a housing 16 with a sleeve 24 and covers 1 and 15, a rotor 23 with four blades 22 mounted on two ball bearings 18, a lubrication system (including an oil tank 26, tube 25 and nozzle 2) and two pipes 20 and 21 for connecting air ducts.
Working principle of a vacuum pump
The vacuum pump works as follows. When the rotor 23 rotates, the blades 22 are pressed against the sleeve 24 under the action of centrifugal forces and thus form closed working cavities. The working cavities, due to the rotation of the rotor occurring counterclockwise, move from the suction window communicating with the inlet pipe 20 to the outlet window communicating with the outlet pipe 21. When passing through the area of the suction window, each working cavity captures a portion of air and moves it to the exhaust a window through which air is discharged into the atmosphere through an air duct. The movement of air from the suction window into the working cavities and from the working cavities into the exhaust window occurs due to pressure differences that are formed due to the presence of eccentricity between the rotor and the sleeve, leading to compression (expansion) of the volume of the working cavities.
The rubbing surfaces of the vacuum pump are lubricated by engine oil, which is supplied to its suction cavity from the oil tank 26 due to the vacuum created by the vacuum pump itself in the inlet pipe 20. The specified oil flow rate is ensured by a calibrated hole in the nozzle 2. The electric drive of the vacuum pump consists of an electric motor 10 and traction relay 7. Electric motor 10, designed for voltage 12 V direct current. The rotor 11 of the electric motor at one end rests on the bushing 9, and the other end, through the centering bushing 12, rests on the protruding shaft of the vacuum pump rotor. Therefore, turning on the electric motor after disconnecting it from the vacuum pump is not allowed.
Torque from the engine to the rotor of the vacuum pump is transmitted through pin 13 and a groove at the end of the rotor. Traction relay 7 ensures switching of the contacts of the “+12 V” power circuit when the electric motor is turned on, and also moves the cable strand 2, leading to the opening of the vacuum valve 4, in systems where it is provided. The casing 5 protects the open contacts of the electric motor from accidental short circuit and from water getting on them during operation.
The vacuum valve is designed to automatically shut off the cavity of the fire pump from the vacuum unit at the end of the water filling process and is installed in addition to the vacuum seal 5. 2, attached to rod 7, is connected to the cable core from the traction relay of the vacuum unit. In this case, the cable braid is fixed with a sleeve 4, which has a longitudinal groove for installing the cable. When the traction relay is turned on, the cable core pulls the rod 6 by the earring 2, and the flow cavity of the vacuum valve opens. When the traction relay is turned off (i.e. when the vacuum unit is turned off), rod 6, under the action of spring 9, returns to its original (closed) position. With this position of the rod, the flow cavity of the vacuum valve remains blocked, and the cavities of the centrifugal fire pump and vane pump remain separated. To lubricate the rubbing surfaces of the valve, a lubricating ring 8 is provided, into which oil must be added through hole “A” when operating the vacuum system.
The filling sensor is designed to send signals to the control unit about the completion of the water filling process. The sensor is an electrode installed in an insulator in top point internal cavity of a centrifugal fire pump. When the sensor is filled with water, it changes electrical resistance between the electrode and the housing (“ground”). The change in sensor resistance is recorded by the control unit, which generates a signal to turn off the electric motor of the vacuum unit. At the same time, the “Pump full” indicator on the control panel (unit) turns on.
The control unit (remote control) is designed to ensure operation of the vacuum system in manual and automatic modes.
Toggle switch 1 “Power” serves to supply power to the control circuits of the vacuum unit and to activate light indicators about the state of the vacuum system. Toggle switch 2 “Mode” is designed to change the operating mode of the system – automatic (“Auto”) or manual (“Manual”). Button 8 “Start” is used to turn on the motor of the vacuum unit. Button 6 “Stop” is used to turn off the engine of the vacuum unit and to remove the lock after the “Not normal” indicator lights up. Cables 4 and 5 are designed to connect the control unit, respectively, to the vacuum unit motor and the filling sensor. The remote control has the following light indicators 7, which serve to visual control on the state of the vacuum system:
1. The “Power” indicator lights up when toggle switch 1 “Power” is turned on;
2. Vacuuming – signals that the vacuum pump is turned on when button 8 “Start” is pressed;
- Pump full – lights up when the fill sensor is triggered when the fire pump is completely filled with water;
- Not normal – records the following malfunctions of the vacuum system:
- the maximum time of continuous operation of the vacuum pump (45...55 seconds) has been exceeded due to insufficient tightness of the suction line or fire pump;
- poor or missing contact in the vacuum unit traction relay circuit due to burnt relay contacts or broken wires;
- The vacuum pump motor is overloaded due to clogging of the vane vacuum pump or other reasons.
On the ABC-02E model and the latest ABC-01E models, the vacuum valve (item 4 in Fig. 3.28) is not installed.
The ABC-02E vacuum pump ensures that the vacuum system operates only in manual mode.
Depending on the combination of the position of the “Power” and “Mode” toggle switches, the vacuum system can be in four possible states:
- Inoperative The “Power” toggle switch should be in the “Off” position, and the “Mode” toggle switch should be in the “Auto” position. This position of the toggle switches is the only one in which pressing the “Start” button does not turn on the electric motor of the vacuum unit. Indication is disabled.
- In automatic mode(main mode) the “Power” toggle switch should be in the “On” position, and the “Mode” toggle switch should be in the “Auto” position. In this case, the electric motor is turned on by briefly pressing the “Start” button. The shutdown is performed either automatically (when the filling sensor or one of the types of electric drive protection is triggered), or forcedly by pressing the “Stop” button. The indicator is on and reflects the state of the vacuum system.
- In manual mode The “Power” toggle switch should be in the “On” position, and the “Mode” toggle switch should be in the “Manual” position. The engine is turned on by pressing the “Start” button and runs as long as the “Start” button is held down. In this mode, the electronic protection of the drive is disabled, and the readings of the light indicators only visually reflect the water filling process. The manual mode is designed to allow operation in the event of failures in the automation system or false alarms. Control of the moment of completion of the water filling process and shutdown of the vacuum pump motor in manual mode is carried out visually using the “Pump full” indicator.
- To ensure the completion of a combat mission during a fire in the event of an electronic unit failure, when the system does not work in automatic mode, and in manual mode the light indicators do not reflect the actual processes taking place, there is emergency mode, in which the “Power” toggle switch must be turned off, and the “Mode” toggle switch must be moved to the “Manual” position. In this mode, the electric motor is controlled in the same way as in manual mode, but the indication is turned off, and the moment of completion of the water filling process and shutdown of the vacuum pump motor is monitored based on the appearance of water from the exhaust pipe. Systematic operation in this mode is unacceptable, because can lead to serious damage to vacuum system components. Therefore, immediately upon returning to the fire station, the cause of the control unit malfunction should be identified and eliminated.
Air ducts 3 and 10 (see Fig. 3.28) are designed, respectively, to connect the cavity of the centrifugal fire pump with the vacuum unit and to direct the exhaust from the vacuum unit.
Operating a Vacuum System with a Vane Pump
Operating order of the vacuum system:
- Checking the fire pump for leaks (“dry vacuum”):
a) prepare the fire pump for testing: install a plug on the suction pipe, close all taps and valves;
b) open the vacuum seal;
c) turn on the “Power” toggle switch on the control unit (remote panel);
d) start the vacuum pump: in automatic mode, the start is made by briefly pressing the “Start” button; in manual mode, the “Start” button must be pressed and held down;
e) evacuate the fire pump to a vacuum level of 0.8 kgf/cm 2 (at in good condition vacuum pump, fire pump and its communications, this operation takes no more than 10 seconds);
f) stop the vacuum pump: in automatic mode, the stop is forced by pressing the “Stop” button; in manual mode, you need to release the “Start” button;
g) close the vacuum valve and use a stopwatch to check the rate of decrease in vacuum in the cavity of the fire pump;
h) turn off the “Power” toggle switch on the control unit (remote panel), and set the “Mode” toggle switch to the “Auto” position.
- Automatic water intake:
b) open the vacuum seal;
c) set the “Mode” toggle switch to the “Auto” position and turn on the “Power” toggle switch;
d) start the vacuum pump - press and release the “Start” button: in this case, simultaneously with the vacuum unit drive turning on, the “Vacuuming” indicator lights up;
e) after the completion of water filling, the drive of the vacuum unit is switched off automatically: in this case, the “Pump is full” indicator lights up and the “Vacuuming” indicator goes out. In the event of a leak in the fire pump, after 45...55 seconds the vacuum pump drive should automatically turn off and the “Not normal” indicator should light up, after which the “Stop” button must be pressed;
g) turn off the “Power” toggle switch on the control unit (remote panel).
As a result of a failure of the filling sensor (this can happen, for example, if a wire is broken), the automatic shutdown of the vacuum pump does not work and the “Pump full” indicator does not light up. This situation is critical, because After the fire pump is filled, the vacuum pump does not turn off and begins to “choke” with water. This mode is immediately detected by the characteristic sound caused by the release of water from the exhaust pipe. In this case, it is recommended, without waiting for the protection to operate, to close the vacuum shutter and forcefully turn off the vacuum pump (using the “Stop” button), and upon completion of work, detect and eliminate the malfunction.
- Manual water intake:
a) prepare the fire pump for water intake: close all valves and taps of the fire pump and its communications, connect the suction hoses with a mesh and immerse the end of the suction line into the reservoir;
b) open the vacuum seal;
c) set the “Mode” toggle switch to the “Manual” position and turn on the “Power” toggle switch;
d) start the vacuum pump - press the “Start” button and hold it pressed until the “Pump full” indicator lights up;
e) after filling the water (as soon as the “Pump is full” indicator lights up), stop the vacuum pump - release the “Start” button;
f) close the vacuum valve and start working with the fire pump in accordance with its operating instructions;
g) turn off the “Power” toggle switch on the control unit (remote panel), and set the “Mode” toggle switch to the “Auto” position.
In the event of a pressure failure, it is necessary to stop the fire pump and repeat operations “c” – “e”.
- Features of work in winter:
a) After each use pumping unit it is necessary to blow out the air lines of the vacuum pump, even in cases where the fire pump supplied water from a tank or hydrant (water may enter the vacuum pump, for example, through a loose or faulty vacuum seal). Purge should be done by briefly (3÷5 seconds) turning on the vacuum pump. In this case, it is necessary to remove the plug from the suction pipe of the fire pump and open the vacuum seal.
b) Before starting work, check the vacuum valve for freezing of its moving part. To check, you need to make sure that its rod is mobile by pulling the earring 2 (see Fig. 3.30), to which the cable core is connected. In the absence of freezing, the earring together with the vacuum valve rod and the core cable should move with a force of approximately 3–5 kgf.
c) To fill the oil tank of the vacuum pump, use winter grades of motor oils (with reduced viscosity).
Conclusion on the issue: In vacuum systems of centrifugal fire pumps, vane vacuum pumps are installed in order to improve technical and operational characteristics.
Maintenance
At simultaneously with checking the fire pump for leaks, check the operability of the gas-jet vacuum apparatus, the vacuum valve and carry out (if necessary) adjustment of the drive rods of the gas-jet vacuum apparatus.
TO-1 includes daily maintenance operations. In addition, if necessary, dismantling, complete disassembly, lubrication, replacement of worn parts and installation of a gas-jet vacuum apparatus and vacuum valve are carried out. To lubricate the damper axis in the distribution chamber of a gas-jet vacuum apparatus, graphite lubricant is used.
At TO-2, in addition to TO-1 operations, the performance of the vacuum system is checked on special stands at the technical diagnostic station (post).
To ensure constant technical readiness of the vacuum system, the following types are provided: Maintenance: daily maintenance (ETO) and first maintenance (TO-1). The list of works and technical requirements for carrying out these types of maintenance are given in table.
List of works during maintenance vacuum system ABC-01E.
| View Maintenance |
Contents of work | Technical requirements (methodology) |
| Daily Maintenance (DTO) | 1. Check for the presence of oil in the oil tank. | 1. Maintain the oil level in the tank at least 1/3 of its volume. |
| 2. Checking the functionality of the vacuum pump and the functioning of the lubrication system of the vane pump. | 2. Carry out the test in the fire pump leak test mode (“dry vacuum”). When the vacuum pump is turned on, the oil supply tube must be completely filled with oil up to the nozzle. | |
| First maintenance | 1. Check the tightness of fasteners. | 1. Check the tightness of the fasteners of the components of the vacuum system. |
| 2. Lubricate the vacuum valve rod and control cable. | 2. Place a few drops of engine oil into hole A of the vacuum valve body. Disconnect the cable from the vacuum valve and place a few drops of engine oil into the cable. |
|
| 3. Checking the axial play of the vacuum valve control cable braid at the point of its connection with the traction relay of the vacuum pump electric drive. | 3. Axial play is allowed no more than 0.5 mm. Determine the play by moving the cable braid back and forth. If there is a discrepancy, eliminate the play. | |
| 4. Checking the correct position of the vacuum valve earring 2. | 4. Check the gap sizes: — Gap “B” — when the electric drive is not working; — Gap “B” — with the electric drive running. The gap sizes “B” and “C” must be at least 1 mm. If necessary, the gaps should be adjusted. To adjust, disconnect the cable from the vacuum valve, loosen the lock nut and set the earring to the required position; tighten the locknut. |
|
| 5. Checking oil consumption. | 5. Average oil consumption per operating cycle of 30 seconds. must be at least 2 ml. | |
| 6. Cleaning the working surfaces of the fill sensor. | 6. Unscrew the sensor from the housing, Clean the electrode and the visible part of the housing surface down to the base metal. |
Conclusion on the issue: Maintenance is necessary to maintain vacuum systems in working condition.
Malfunctions of vacuum systems
When operating a vacuum system as part of a pumping unit, the most typical malfunction of the vacuum system is: the pump does not fill with water (or the required vacuum is not created) when the vacuum system is turned on. This malfunction, if the engine of the fire truck is working properly, can be caused by the following reasons:
- The damper does not completely block the exit of exhaust gases through the muffler into the atmosphere. The reasons may be the presence of carbon deposits on the damper and in the GVA housing, violation of the adjustment of the control rod drive, wear of the damper axis.
- The diffuser or nozzle of the vacuum jet pump is clogged.
- There are leaks in the connections of the vacuum valve and fire pump, the vacuum system pipeline or cracks in it.
- There are deformations or cracks in the GVA housing.
- There are leaks in the exhaust tract of a fire truck engine (as a rule, they occur due to burnout of the exhaust pipes).
- The vacuum system pipeline is clogged or water freezes in it.
Possible malfunctions of the ABC-01E vacuum systemand methods for eliminating them
| Name of failure, its external signs | Probable Cause | Elimination method |
| When you turn on the “Power” toggle switch, the “Power” indicator does not light up. | The control unit fuse has blown. | Replace the fuse. |
| Open circuit in the power supply circuit of the control unit. | Eliminate the break. | |
| When operating in automatic mode, after drawing water, the vacuum pump does not automatically turn off. | Open circuit from the electrode or from the fill sensor housing. | Repair open circuit. |
| Reduced electrical conductivity of the housing surface and the fill sensor electrode | Remove the fill sensor and clean the electrode and the surface of its housing from dirt. | |
| Insufficient supply voltage at the control unit. | Check the reliability of contacts in electrical connections; Provide a supply voltage to the control unit of at least 10 V. | |
| In automatic mode, the vacuum pump starts, but after 1-2 seconds. stops; The “Vacuum” indicator goes out and the “Not normal” indicator lights up. In manual mode the pump operates normally. | Unreliable contact in the connecting cables between the control unit and the electric drive of the vacuum pump. | Check the reliability of contacts in electrical connections. |
| The wire tips on the contact bolts of the traction relay are oxidized or the nuts securing them are loose. | Clean the ends and tighten the nuts. | |
| Large (more than 0.5 V) voltage drop between the contact bolts of the traction relay during operation of the electric motor. | Remove the traction relay and check the ease of movement of the armature. If the armature moves freely, then clean the relay contacts or replace it. | |
| The vacuum pump does not start either automatically or manually. After 1-2 seconds. after pressing the “Start” button, the “Vacuum” indicator goes out and the “Not normal” indicator lights up | It is difficult to move the strand of the vacuum valve control cable. | Check the ease of movement of the cable core, if necessary, eliminate a strong bend in the cable or lubricate its core with engine oil. |
| It is difficult to move the vacuum valve stem. | Lubricate the valve through hole A. In winter, take measures to prevent freezing of the vacuum valve parts. | |
| Open power supply circuit | Repair open circuit. | |
| The position of the vacuum valve earring is broken. | Adjust the position of the earring. | |
| Electrical break circuits in the cable connecting the control unit to the electric drive of the vacuum unit. |
Repair open circuit. | |
| The contacts of the traction relay are burnt. | Clean the contacts or replace the traction relay. | |
| The electric motor is overloaded (the vane pump is blocked by frozen water or foreign objects). | Check the condition of the vane pump. In winter, take measures to prevent mutual freezing of vane pump parts. | |
| When operating the vacuum pump, it is noted that the oil consumption is too low (on average less than 1 ml per operating cycle) | The lubricating oil is of the wrong grade or is too viscous. | Replace with all-season motor oil in accordance with GOST 10541. |
| The metering hole of jet 2 in the oil line is clogged. | Clean the dosing hole in the oil line. | |
| There is air leakage through the joints of the oil pipeline. | Tighten the oil pipe fastening clamps. | |
| When the vacuum pump is running, the required vacuum is not provided | Air leakage in suction hoses, through open valves, drain taps, through damaged air ducts. | Ensure the vacuum volume is sealed. |
| Air leakage through the oil tank (in the complete absence of oil). | Fill the oil tank. | |
| Insufficient supply voltage to the electric drive of the vacuum unit. | Clean the contacts of the power cables, the pole terminals of the battery; Lubricate them with technical petroleum jelly and tighten securely. Charge the battery | |
| Insufficient lubrication of the vane pump. | Check oil consumption. |
Conclusion on the issue: Knowing the structure and possible malfunctions of vacuum systems, the driver can quickly find and eliminate the malfunction.
Lesson conclusion: The vacuum system of a centrifugal fire pump is designed to pre-fill the suction line and pump with water when drawing water from an open water source (reservoir), in addition, using the vacuum system, you can create a vacuum (vacuum) in the body of the centrifugal fire pump to check the tightness of the fire pump.
Chapter 12 - Stationary emergency fire pumps
1 Application
This chapter sets out the specifications for emergency fire pumps required by chapter II-2 of the Convention. This chapter does not apply to passenger ships of 1,000 gross tonnage or more. For the requirements for such vessels, see regulation II-2/10.2.2.3.1.1 of the Convention.
2 Technical specifications
2.1 General provisions
The emergency fire pump must be a stationary pump with an independent drive.
2.2 Component requirements
2.2.1 Emergency fire pumps
2.2.1.1 Pump flow
The pump flow must be not less than 40% of the total fire pump flow required by regulation II-2/10.2.2.4.1 of the Convention and in any case not less than the following:
2.2.1.2 Pressure in taps
If the pump supplies the quantity of water required by paragraph 2.2.1.1, the pressure at any tap shall not be less than the minimum pressure required by Chapter II-2 of the Convention.
2.2.1.3 Suction lifts
Under all conditions of list, trim, roll and pitch that may occur during operation, the total suction lift and the net positive suction lift of the pump must be determined taking into account the requirements of the Convention and this chapter with respect to pump flow and tap pressure. A vessel in ballast when entering or leaving a dry dock may not be considered to be in service.
2.2.2 Diesel engines and fuel tank
2.2.2.1 Starting the diesel engine
Any diesel engine driven power source powering the pump must be capable of being easily manually started from a cold state at temperatures down to 0°C. If this is not practicable or if lower temperatures are expected, consideration should be given to the installation and operation of heating means acceptable to the Administration to ensure rapid start-up. If manual starting is impracticable, the Administration may permit the use of other means of starting. These means must be such that the diesel engine driven power source can be started at least six times within 30 minutes and at least twice within the first 10 minutes.
2.2.2.2 Fuel tank capacity
Any fuel supply tank must contain sufficient fuel to ensure that the pump can operate at full load for at least 3 hours; Outside the machine room of category A there must be sufficient fuel reserves to ensure that the pump can operate at full load for an additional 15 hours.
Damn the internet is evil.Our dear Nina, of course, the PKF itself understands everything and displays what is needed and how it is needed and will transmit it to the security post (the signal is displayed as a “malfunction” or “Accident”, it doesn’t matter what you call it, and
Signaled by simply opening dry contacts No. 5 and No. 6). From the passport for the PKF, I concluded that it can only control two power supply inputs (i.e. main and backup), and if something goes wrong,
Switch the power supply to the pump from one input to another (AVR, so to speak). IN general point SP.513130.2009
12.3.5 "... It is recommended to give a short-term sound signal: ... , 0 .... when the voltage disappears at the main and backup power supply inputs of the installation..." Done.
But I (and you too) needed a signal that the control of the power cabinet is in automatic mode, in order to avoid the situation that everything is ready, only the “manual” mode of operation is on the switchboard or
Generally "0" (disabled). Or is there no such switch on their shields? :)
You give a signal, but you and I (you) just make a fuss, the power shield won’t work. We are screaming, swearing, what is it, how can it be, everything is already on fire, the APS gave a signal, I have already started it 100 times myself! Where is the WATER? I scream in convulsions
:). Of course, competent installers will not allow this to happen and will control it, but this is already a classic in projects, removing this signal from the panel.
I called Plazma-T. I was told that PKF controls this (which I don’t believe; from the diagrams I don’t see how it does this). Let's say he controls. Let's imagine we are sitting at a post and then a general signal comes
"MALFUNCTION". And it is not clear what is there, i.e. without decryption. In general, you sit and see “Fault” on the central information center. And Uncle Fedr was doing something there and switched the installation to manual mode and forgot to switch it back.
You call the service that serves you, they will come to you now, for the urgency you will be charged two rubles. All you had to do was go and turn the switch. Resigned himself to this, that there is a weak point in
My system. And until they convince me (where I can find an explanation, they will write it in my passport, you will enlighten me) that he actually controls, I will refrain from using their equipment in the future.
Perhaps they answered me wrong, but I can assume that the author. the mode is controlled by the start circuit itself (terminals PU X4.1 and so on), and not by the PCF. That if the circuit is not broken, then everything is normal and therefore “auth.
Mode." But then a signal will come or "NOT AUTO. MODE" or "LOCK OF LINE", again twenty-five. I don’t know, there’s no time to figure it out now, while the project is frozen for a while (a more urgent one has been superseded). Then I’ll probably call
And I torment Plasma-T. And this is normal equipment.
Has anyone seen the SHAC fire safety shields, they meet the condition
Quote SP5.13130.2009 12.3.6
12.3.6 The premises of the pumping station should provide light alarm:
...
b) on disabling the automatic start of fire pumps, metering pumps, drainage
pump;
...Did the plasma help?
There is no project to do. If they do, answer for them later :).
After reading the documentation, I called them and interrogated them with torture :) (I’m joking about torture) about the capabilities of their equipment, in general I asked, can they do it? do they do this? and so on. only by their equipment.
I don’t like their passports, as it is written there, everything seems to be, but somehow clumsily. It needs to be polished so that it can be read and understood immediately. Because of her, there were questions for them.
Quote Nina 12/13/2011 18:56:31
--End quote------But let the hairdresser do the APS, I’ll scratch my turnips :).
Andorra1 Not everything is so simple.
The sensor has setting limits of 0.7-3.0 MPa. If you do not penetrate into the return zones (Max and min values), the sensor can be configured (i.e. set) to operate in the range of 0.7-3.0 MPa, i.e. your 0.3 and 0.6 MPa, something is wrong here. Either the skis don't work or I'm stupid. These return zones Min and Max somehow set the range of response accuracy. It seems like if they set a setting of 2.3 MPa, then when the pressure increases, the device will work in some range from 2.24 to 2.5, guaranteed, and not exactly at 2.3 MPa. In general, who the hell knows.
What fixed fire extinguishing systems are used on ships?
Fire extinguishing systems on ships include:
●water fire extinguishing systems;
●low and medium expansion foam extinguishing systems;
●volumetric extinguishing systems;
●powder extinguishing systems;
●steam extinguishing systems;
●aerosol extinguishing systems;
Ship premises, depending on their purpose and the degree of fire hazard, must be equipped with various fire extinguishing systems. The table shows the requirements of the Rules of the Register of the Russian Federation for equipping premises with fire extinguishing systems.
Stationary water fire extinguishing systems include systems that use water as the main extinguishing agent:
- fire water system;
- water spray and irrigation systems;
- flooding system for individual rooms;
- sprinkler system;
- deluge system;
- water mist or water mist system.
Stationary volumetric extinguishing systems include following systems:
- carbon dioxide extinguishing system;
- nitrogen extinguishing system;
- liquid extinguishing system (using freons);
- volumetric foam extinguishing system;
In addition to fire extinguishing systems, fire warning systems are used on ships, such systems include an inert gas system.
What are design features water fire protection system?
The system is installed on all types of ships and is the main one for extinguishing fires, as well as a water supply system for ensuring the operation of other fire extinguishing systems, general ship systems, washing tanks, tanks, decks, for washing anchor chains and hawses.
Main advantages of the system:
Unlimited supplies of sea water;
Cheapness of fire extinguishing agent;
High fire extinguishing ability of water;
High survivability of modern UPS.
The system includes the following main elements:
1. Receiving seawalls in the underwater part of the vessel for receiving water in any operating conditions, incl. roll, trim, roll and pitch.
2. Filters (dirt boxes) to protect pipelines and system pumps from clogging with debris and other waste.
3. Non-return valve, which does not allow the system to empty when the fire pumps are stopped.
4. Main fire pumps with electric or diesel drives for supplying sea water to the fire main to fire hydrants, fire monitors and other consumers.
5. Emergency fire pump with an independent drive for supplying sea water in the event of failure of the main fire pumps with its own seacock, valve, safety valve and control device.
6. Pressure gauges and pressure-vacuum gauges.
7. Fire cocks (end valves) located throughout the vessel.
8. Fire main valves (shut-off, non-return shut-off, secant, shut-off).
9. Fire main pipelines.
10. Technical documentation and spare parts.
Fire pumps are divided into 3 types:
1. main fire pumps installed in machinery spaces;
2. emergency fire pump located outside the machinery spaces;
3. pumps permitted as fire pumps (sanitary, ballast, bilge, general use, if they are not used for pumping oil) on cargo ships.
The emergency fire pump (AFP), its seacock, the receiving branch of the pipeline, the discharge pipeline and shut-off valves are located outside the machine access. The emergency fire pump must be a stationary pump with an independent drive from a power source, i.e. its electric motor must also be powered from an emergency diesel generator.
Fire pumps can be started and stopped both from local posts at the pumps and remotely from the navigation bridge and control room.
What are the requirements for fire pumps?
Vessels are provided with independently driven fire pumps as follows:
●passenger ships with a gross tonnage of 4000 and more must have at least three, less than 4000 - at least two.
●cargo ships of 1000 gross tonnage and more - at least two, less than 1000 - at least two pumps driven by a power source, one of which has an independent drive.
The minimum water pressure in all fire hydrants when two fire pumps are operating should be:
● for passenger ships with a gross tonnage of 4000 and more 0.40 N/mm, less than 4000 – 0.30 N/mm;
● for cargo ships with a gross tonnage of 6000 and more – 0.27 N/mm, less than 6000 – 0.25 N/mm.
The flow rate of each fire pump must be at least 25 m/h, and the total water supply on a cargo ship must not exceed 180 m/h.
The pumps are located in different compartments; if this is not possible, then an emergency fire pump must be provided with its own power source and seacock located outside the room where the main fire pumps are located.
The capacity of the emergency fire pump must be at least 40% of the total capacity of the fire pumps, and in any case not less than the following:
● on passenger ships with a capacity of less than 1000 and on cargo ships with a capacity of 2000 or more - 25 m3/h; And
● on cargo ships with a gross tonnage of less than 2000 – 15 m/h.
Schematic diagram of a water fire system on a tanker
1 – Kingston highway; 2 – fire pump; 3 – filter; 4 – kingston;
5 – water supply pipeline to fire hydrants located in the aft superstructure; 6 – water supply pipeline to the foam fire extinguishing system;
7 – double fire hydrants on the poop deck; 8 – deck fire main; 9 – shut-off valve for disconnecting the damaged section of the fire main; 10 - double fire hydrants on the forecastle deck; 11 – non-return shut-off valve; 12 – pressure gauge; 13 – emergency fire pump; 14 – clinker valve.
The system construction scheme is linear, powered by two main fire pumps (2) located in the MO and an emergency fire pump (13) APZhN on the tank. At the inlet, the fire pumps are equipped with a kingstone (4), a line filter (dirt box) (3) and a clinker valve (14). A non-return shut-off valve is installed behind the pump to prevent water from draining from the main when the pump stops. A fire valve is installed behind each pump.
From the main line through clinker valves there are branches (5 and 6) into the superstructure, from which fire hydrants and other consumers of sea water are supplied.
The fire main is laid on the cargo deck and has branches every 20 meters to dual fire hydrants (7). On the main pipeline, secant fire mains are installed every 30-40 m.
According to the Maritime Register Rules, portable fire nozzles with a spray diameter of 13 mm are mainly installed in interior spaces, and 16 or 19 mm on open decks. Therefore, fire hydrants (hydrates) are installed with D of 50 and 71 mm, respectively.
On the forecastle and poop decks in front of the wheelhouse, twin fire hydrants (10 and 7) are installed on the side.
When the ship is moored in port, the fire water system can be supplied from the international shore connection using fire hoses.
How do water spray and irrigation systems work?
The water spray system in special category rooms, as well as in machine rooms of category A of other ships and pumping rooms, must be powered by an independent pump, which automatically turns on when the pressure in the system drops, from the water fire main.
In other protected premises, the system may only be powered from the fire water main.
In special category spaces, as well as in machinery spaces of category A of other ships and pumping rooms, the water spray system must be constantly filled with water and be under pressure up to the distribution valves on the pipelines.
Filters must be installed on the receiving pipe of the pump feeding the system and on the connecting pipeline with the water fire main to prevent clogging of the system and nozzles.
Distribution valves must be located in easily accessible places outside the protected area.
In protected rooms with permanent occupancy, remote control of distribution valves from these rooms must be provided.
Water spray system in the machine and boiler room
1 – roller drive bushing; 2 – drive roller; 3 - drain valve of the impulse pipeline; 4 – upper water spray pipeline; 5 – impulse pipeline; 6 – quick-acting valve; 7 – fire main; 8 – lower water spray pipeline; 9 – spray nozzle; 10 – drain valve.
Sprayers in protected areas must be placed in the following places:
1. under the ceiling of the room;
2. in the mines of machinery spaces of category A;
3. on equipment and mechanisms whose operation involves the use of liquid fuel or other flammable liquids;
4. over surfaces on which liquid fuel or flammable liquids may spread;
5. over stacks of bags of fishmeal.
Sprayers in the protected area must be located in such a way that the coverage area of any sprayer overlaps the coverage areas of adjacent sprayers.
The pump may be driven by an independent internal combustion engine, located so that a fire in the protected space does not affect the air supply to it.
This system allows you to extinguish a fire in the Ministry of Defense under the slans using lower water spray nozzles or, at the same time, upper water spray nozzles.
How does a sprinkler system work?
Passenger ships and cargo ships are equipped with such systems according to the IIC protection method for signaling a fire and automatic fire extinguishing in protected premises in the temperature range from 68 0 to 79 0 C, in dryers at temperatures exceeding maximum temperature in the Podvolok area no more than 30 0 C and in saunas up to 140 0 C inclusive.
The system is automatic: when the maximum temperature in the protected premises is reached, depending on the area of the fire, one or more sprinklers (water spray) are automatically opened, fresh water is supplied through it for extinguishing, when its supply runs out, the fire extinguishing will continue with sea water without the intervention of the ship’s crew.
General scheme sprinkler system
1 – sprinklers; 2 – water main; 3 – distribution station;
4 – sprinkler pump; 5 – pneumatic tank.
Schematic diagram of a sprinkler system
The system consists of the following elements:
Sprinklers grouped into separate sections of no more than 200 each;
Main and sectional control and signaling devices (KSU);
Block fresh water;
Sea water block;
Panels for visual and audio signals when sprinklers are activated;
Sprinklers – these are closed-type sprayers, inside of which are located:
1) sensitive element - a glass flask with a volatile liquid (ether, alcohol, gallon) or a low-melting Wood's alloy lock (insert);
2) a valve and diaphragm that close the hole in the sprayer for supplying water;
3) socket (divider) for creating a water torch.
Sprinklers must:
Trigger when the temperature rises to preset values;
Be resistant to corrosion when exposed to sea air;
Installed in the upper part of the room and placed so as to supply water to the nominal area with an intensity of at least 5 l/m2 per minute.
Sprinklers in residential and service premises must operate in the temperature range of 68 - 79 ° C, with the exception of sprinklers in drying and galley rooms, where the response temperature can be increased to a level exceeding the temperature at the ceiling by no more than 30 ° C.
Control and alarm devices (KSU ) are installed on the supply pipeline of each sprinkler section outside the protected premises and perform the following functions:
1) sound an alarm when sprinklers are opened;
2) open water supply paths from water supply sources to operating sprinklers;
3) provide the ability to check the pressure in the system and its performance using a test (bleed) valve and control pressure gauges.
Fresh water block maintains pressure in the system in the area from the pressure tank to the sprinklers in standby mode when the sprinklers are closed, as well as power supply to the sprinklers fresh water during the start-up of the sprinkler pump of the seawater unit.
The block includes:
1) Pressure pneumatic hydraulic tank (HPHC) with a water meter glass, with a capacity for two water reserves equal to two capacities of the sprinkler pump of the seawater unit in 1 minute for simultaneous irrigation of an area of at least 280 m2 at an intensity of at least 5 l/m2 per minute.
2) Means to prevent seawater from entering the tank.
3) Means for supplying compressed air to the NPGC and maintaining such air pressure in it that, after using up the constant supply of fresh water in the tank, would provide a pressure not lower than the operating pressure of the sprinkler (0.15 MPa) plus the pressure of the water column measured from the bottom tanks to the highest located sprinkler system (compressor, pressure reducing valve, compressed air cylinder, safety valve, etc.).
4) A sprinkler pump to replenish the supply of fresh water, which turns on automatically when the pressure in the system drops, before the constant supply of fresh water in the pressure tank is completely used up.
5) Pipelines made of galvanized steel pipes located under the ceiling of the protected premises.
Sea water block supplies sea water to the sprinklers that open after the sensitive elements are activated to irrigate the premises with a spray jet and extinguish the fire.
The block includes:
1) Independent sprinkler pump with pressure gauge and piping system for continuous automatic feeding sea water to sprinklers.
2) A test valve on the discharge side of the pump with a short outlet pipe having an open end to allow water flow at the pump capacity plus the water column pressure measured from the bottom of the pumping station to the highest sprinkler.
3) Kingston for independent pump.
4) A filter for cleaning sea water from debris and other objects in front of the pump.
5) Pressure switch.
6) Pump start relay, which automatically turns on the pump when the pressure in the sprinkler power system drops before the constant supply of fresh water in the NPGC is completely consumed.
Visual and audio panels about the activation of sprinklers are installed on the navigation bridge or in the central control room with a constant watch, and in addition, visual and audio signals from the panel are output to another location to ensure that the crew immediately receives a fire signal.
The system should be filled with water, but small outdoor areas may not be filled with water if this is a necessary precaution in freezing temperatures.
Any such system must always be ready for immediate operation and be activated without any intervention by the crew.
How does the deluge system work?
Used to protect large areas of decks from fire.
Diagram of the deluge system on a RO-RO vessel
1 – spray head (drenchers); 2 – highway; 3 - distribution station; 4 – fire or deluge pump.
The system is not automatic; it irrigates large areas at the same time with water from deluges at the choice of the team, uses sea water for extinguishing, and is therefore in an empty state. Drenchers (water sprayers) have a design similar to sprinklers but without a sensitive element. It is supplied with water from a fire pump or a separate deluge pump.
How does the foam extinguishing system work?
The first fire extinguishing system using air-mechanical foam was installed on the Soviet tanker Absheron with a deadweight of 13,200 tons, built in 1952 in Copenhagen. On the open deck, for each protected compartment, the following was installed: a stationary air-foam barrel (foam monitor or monitor barrel) of low expansion, a deck main (pipeline) for supplying the foam concentrate solution. A branch equipped with a remotely controlled valve was connected to each trunk of the deck main. The foaming agent solution was prepared in 2 foam extinguishing stations bow and stern and supplied to the deck main. Fire hydrants were installed on the open deck to supply the PO solution through foam hoses to portable air-foam nozzles or foam generators.
foam extinguishing stations
Foam extinguishing system
1 – kingston; 2 – fire pump; 3 – fire monitor; 4 – foam generators, foam barrels; 5 – highway; 6 – emergency fire pump.
3.9.7.1. Basic requirements for foam extinguishing systems. The performance of each monitor must be at least 50% of the design capacity of the system. The length of the foam jet must be at least 40 m. The distance between adjacent monitors installed along the tanker should not exceed 75% of the flight range of the foam jet from the gun in the absence of wind. Twin fire hydrants are evenly installed along the ship at a distance of no more than 20 m from each other. A shut-off valve must be installed in front of each monitor.
To increase the survivability of the system, cutting valves are installed on the main pipeline every 30–40 meters, with the help of which the damaged section can be disconnected. To increase the tanker's survivability in case of fire in the cargo area, two fire monitors are installed on the deck of the first tier of the aft deckhouse or superstructure and dual fire hydrants are installed to supply solution to portable foam generators or guns.
The foam extinguishing system, in addition to the main pipeline laid along the cargo deck, has branches into the superstructure and into the main building, which end with fire foam valves (foam hydrants), from which portable air-foam nozzles or more efficient portable foam generators of medium expansion can be used.
Almost all cargo ships combine two water fire extinguishing systems and a foam fire extinguishing pipeline in the cargo area by laying these two pipelines in parallel and branches from them to the combined foam-water fire monitors. This significantly increases the survivability of the ship as a whole and the ability to use the most effective fire extinguishing agents depending on the class of fire.
Stationary foam extinguishing system with main consumers
1 - fire monitor (on the VP); 2 - foaming heads (indoors); 3 - medium-expansion foam generator (at the VP and indoors);
4 - manual foam barrel; 5 - mixer
The foam extinguishing station is an integral part of the foam extinguishing system. Purpose of the station: storage and maintenance of foam concentrate (FO); replenishment of supplies and unloading of software, preparation of a foaming agent solution; flushing the system with water.
The foam extinguishing station includes: a tank with a reserve of software, a sea water supply pipeline (very rarely fresh water), a software recycling pipeline (mixing software in the tank), a software solution pipeline, fittings, instrumentation, and a dosing device. It is very important to maintain a constant percentage
PO – water ratio, because The quality and quantity of foam depends on this.
What are the steps to use the foam station?
| LAUNCH OF FOAM STATION 1. OPEN VALVE “B” 2. START THE FIRE PUMP 3. OPEN VALVES “D” and “E” 4. START FOAM AGENT PUMP (BEFORE CHECKING THAT VALVE “C” IS CLOSED) 5. OPEN THE VALVE TO THE FOAM MONITOR (OR FIRE HYDRANT), AND START STEWING FIRE. | EXTINGUISHING BURNING OIL
1. Never direct the foam jet directly at burning oil, as this may cause burning oil to splash and spread the fire. 2. The foam jet must be directed so that the foam mixture “floats” onto the burning oil layer by layer and covers the burning surface. This can be done by taking advantage of the prevailing wind direction or the slope of the deck where possible. 3. You need to use one monitor and/or two foam barrels |
Foam extinguishing station fire monitor
Stationary volumetric foam extinguishing systems are designed to extinguish fires in military buildings and other specially equipped premises by supplying them with high-expansion and medium-expansion foam.
What are the design features of a medium-rate foam extinguishing system?
Medium expansion foam extinguishing uses several medium expansion foam generators permanently installed in the upper part of the room. Foam generators are installed above the main sources of fire, often at different levels of the fire department, in order to cover as much as possible more area extinguishing. All foam generators or their groups are connected to a foam extinguishing station located outside the protected premises by pipelines of the foam concentrate solution. The principle of operation and design of the foam extinguishing station is similar to the conventional foam extinguishing station discussed earlier.
Disadvantages of the dyna system:
Relatively low expansion rate of air-mechanical foam, i.e. less fire extinguishing effect compared to high expansion foam;
Higher foam concentrate consumption; compared to high expansion foam;
Failure of electrical equipment and automation elements after using the system, because the foaming agent solution is prepared using sea water (the foam becomes electrically conductive);
A sharp decrease in the foam expansion rate when hot combustion products are ejected by a foam generator (at a gas temperature of ≈130 0 C, the foam expansion rate decreases by 2 times, at 200 0 C – by 6 times).
Positive indicators:
Simplicity of design; low metal consumption;
Use of a foam extinguishing station designed to extinguish fires on the cargo deck.
This system reliably extinguishes fires on mechanisms, engines, spilled fuel and oil on floors and under them, but practically does not extinguish fires and smoldering in the upper parts of bulkheads and on the ceiling, thermal insulation of pipelines and burning insulation of electrical consumers due to the relatively small layer of foam.
Diagram of a medium volumetric foam extinguishing system
What are the design features of a volumetric fire extinguishing system with high expansion foam?
This fire extinguishing system is much more powerful and efficient than the previous medium-extinguishing system, because uses more effective high-expansion foam, which has a significant fire extinguishing effect, fills the entire room with foam, displacing gases, smoke, air and vapors of combustible materials through a specially opened skylight or ventilation closures.
The foaming solution preparation station uses fresh or desalinated water, which significantly improves foaming and makes it non-conductive. To obtain high-expansion foam, a more concentrated solution of PO is used than in other systems, approximately 2 times. To obtain high-expansion foam, stationary high-expansion foam generators are used. Foam is supplied into the room either directly from the generator outlet or through special channels. The channels and the outlet from the supply cover are made of steel and must be hermetically sealed to prevent fire from entering the fire extinguishing station. The lids open automatically or manually simultaneously with the supply of foam. Foam is fed into the MO at platform levels in places where there are no obstacles to the spread of foam. If there are fenced-off workshops or storerooms inside the MO, then their bulkheads must be designed in such a way that foam gets into them, or it is necessary to connect separate valves to them.
Schematic diagram for obtaining thousandfold foam
Schematic diagram of volumetric fire extinguishing with high-expansion foam
1 - Fresh water tank; 2 - Pump; 3 - Tank with foaming agent;
4 – electric fan; 5 - Switching device; 6 - Skylight; 7 - Foam supply blinds; 8 - Upper closure of the channel for releasing foam onto the deck; 9 - Throttle washer;
10 - Foaming mesh for high-expansion foam foam generator
If the area of the room exceeds 400 m2, then it is recommended to introduce foam in at least 2 places located in opposite parts of the room.
To check the operation of the system, a switching device (8) is installed in the upper part of the channel, which diverts the foam outside the room to the deck. The supply of foam concentrate for replacing systems must be five times to extinguish a fire in largest room. The performance of foam generators should be such that it fills the room with foam in 15 minutes.
High-expansion foam is produced in generators with forced air supply to a foam-forming mesh wetted with a foaming agent solution. Used to supply air axial fan. To apply the foam solution to the mesh, centrifugal sprayers with a swirl chamber are installed. Such sprayers are simple in design and reliable in operation; they have no moving parts. Generators GVPV-100 and GVGV-160 are equipped with one sprayer, other generators have 4 sprayers each installed in front of the tops of pyramidal foam-forming meshes.
Purpose, design and types of carbon dioxide extinguishing systems?
Carbon dioxide fire extinguishing as a volumetric method began to be used in the 50s of the last century. Until this time, steam extinguishing was very widely used, because most of the ships were with steam turbines power plants. Carbon dioxide fire extinguishing does not require any type of ship's energy to operate the installation, i.e. it is completely autonomous.
This fire extinguishing system is designed to extinguish fires in specially equipped, i.e. protected premises (MO, pump rooms, paint storerooms, storerooms with flammable materials, cargo rooms mainly on dry cargo ships, cargo decks on RO-RO ships). These rooms must be sealed and equipped with pipelines with sprayers or nozzles for supplying liquid carbon dioxide. In these premises, sound (howlers, bells) and light (“Go away! Gas!”) warning alarms are installed to indicate the activation of the volumetric fire extinguishing system.
System composition:
Carbon dioxide fire extinguishing station, where carbon dioxide reserves are stored;
A minimum of two launch stations for remote activation of the fire extinguishing station, i.e. for the release of liquid carbon dioxide into specific room;
A ring pipeline with nozzles under the ceiling (sometimes at different levels) of the protected premises;
Sound and light alarms warning the crew when the system is activated;
Elements of the automation system that turn off the ventilation in this room and shut off the quick-closing fuel supply valves to the operating main and auxiliary mechanisms to stop them remotely (for MO only).
There are two main types of carbon dioxide fire extinguishing systems:
High pressure system - storage of liquefied CO 2 is carried out in cylinders at a design (filling) pressure of 125 kg/cm 2 (filling with carbon dioxide 0.675 kg/l of cylinder volume) and 150 kg/cm 2 (filling 0.75 kg/l);
Low pressure system - the estimated amount of liquefied CO 2 is stored in a tank at an operating pressure of about 20 kg/cm 2, which is ensured by maintaining the temperature of CO 2 at about minus 15 0 C. The tank is served by two autonomous refrigeration units to maintain negative temperature CO 2 in the tank.
What are the design features of a high-pressure carbon dioxide extinguishing system?
CO 2 extinguishing station is a separate heat-insulated room with powerful forced ventilation located outside the protected premises. Double rows of 67.5 liter cylinders are installed on special stands. The cylinders are filled with liquid carbon dioxide in an amount of 45 ± 0.5 kg.
The cylinder heads have quick-opening valves (full flow valves) and are connected by flexible hoses to the manifold. The cylinders are grouped into batteries of cylinders using a single manifold. This number of cylinders should be enough (according to calculations) to extinguish a certain volume. In a CO 2 extinguishing station, several groups of cylinders can be grouped to extinguish fires in several rooms. When the cylinder valve is opened, the gaseous phase of CO 2 displaces liquid carbon dioxide through the siphon tube into the collector. A safety valve is installed on the manifold, releasing carbon dioxide when the maximum CO 2 pressure is exceeded outside the station. A shut-off valve for supplying carbon dioxide to the protected area is installed at the end of the collector. This valve is opened either manually or by compressed air (or CO 2 or nitrogen) remotely from the starting cylinder (the main control method). Opening the valves of CO 2 cylinders into the system is done:
The valves of the heads of a number of cylinders are opened manually using a mechanical drive (outdated design);
With the help of a servomotor, which is able to open a large number of cylinders;
Manually by releasing CO 2 from one cylinder into the launch system of a group of cylinders;
Remotely using carbon dioxide or compressed air from a launch cylinder.
The CO 2 extinguishing station must have a device for weighing cylinders or instruments for determining the liquid level in the cylinder. By level of liquid phase CO 2 and temperature environment you can determine the weight of CO 2 from tables or graphs.
What is the purpose of the launch station?
Launch stations are installed outdoors and outside the CO 2 station. It consists of two starting cylinders, instrumentation, pipelines, fittings, and limit switches. Launch stations are mounted in special cabinets that are locked with a key; the key is located next to the cabinet in a special case. When the cabinet doors are opened, the limit switches are activated, which turn off the ventilation in the protected room and supply power to the pneumatic actuator (the mechanism that opens the CO 2 supply valve to the room) and to the sound and light alarm. The scoreboard lights up in the room "Leave! Gas!" or the blue flashing lights come on and an audible signal is given by a bellow or loud bell. When the valve of the right starting cylinder is opened, compressed air or carbon dioxide is supplied to the pneumatic valve and the CO 2 supply to the corresponding room is opened.
How to turn on a carbon dioxide fire extinguishing system for a pumpmain and engine rooms.
| 2. ENSURE THAT ALL PEOPLE LEAVE THE PUMP COMPARTMENT, PROTECTED BY THE CO2 SYSTEM. 3. SEAL THE PUMP COMPARTMENT. 6. SYSTEM IN WORK. | 1. OPEN THE DOOR OF THE START CONTROL CABINET. 2. ENSURE THAT ALL PERSONS HAVE LEFT THE ENGINE ROOM PROTECTED BY THE CO2 SYSTEM. 3. SEAL THE ENGINE COMPARTMENT. 4. OPEN THE VALVE ON ONE OF THE STARTING CYLINDERS. 5. OPEN VALVES No. 1 And No. 2 6. SYSTEM IN WORK. |
3.9.10.3. COMPOSITION OF THE SHIP SYSTEM.
Carbon dioxide extinguishing system
1 – valve for supplying CO 2 to the collecting manifold; 2 – hose; 3 - blocking device;
4 – non-return valve; 5 – valve for supplying CO 2 to the protected area
Diagram of the CO 2 system of a separate small room
What are the design features of a low-pressure carbon dioxide extinguishing system?
Low pressure system - the calculated amount of liquefied CO 2 is stored in a tank at an operating pressure of about 20 kg/cm 2, which is ensured by maintaining a CO 2 temperature of about minus 15 0 C. The tank is served by two autonomous refrigeration units (cooling system) to maintain a negative CO 2 temperature in the tank.
The tank and the sections of pipelines connected to it filled with liquid carbon dioxide are thermally insulated to prevent the pressure from increasing below the setting safety valves within 24 hours, the field is without power to the refrigeration unit at an ambient temperature of 45 0 C.
The tank for storing liquid carbon dioxide is equipped with a remote liquid level sensor, two control valves for the liquid level of 100% and 95% of the calculated filling. The emergency warning system sends light and sound signals to the control room and mechanics' cabins in the following cases:
When the maximum and minimum (at least 18 kg/cm 2) pressures are reached in the tank;
When the CO 2 level in the tank decreases to the minimum permissible 95%;
In case of malfunction in refrigeration units;
When starting CO 2.
The system is started from remote posts from carbon dioxide cylinders, similar to the previous high-pressure system. The pneumatic valves open and carbon dioxide is supplied to the protected area.
How does a volumetric chemical extinguishing system work?
In some sources, these systems are called liquid extinguishing systems (LES), because The principle of operation of these systems is to supply the fire extinguishing liquid halon (freon or freon) to the protected premises. These liquids evaporate at low temperatures and turn into gas, which inhibits the combustion reaction, i.e. are combustion inhibitors.
The freon supply is located in steel tanks of the fire extinguishing station, which is located outside the protected premises. In protected (guarded) premises, under the ceiling there is a ring pipeline with tangential type sprayers. Sprayers spray liquid refrigerant and, under the influence of relatively low temperatures in the room from 20 to 54 o C, it turns into gas, which easily mixes with the gaseous environment in the room and penetrates into the most remote parts of the room, i.e. is also able to combat the smoldering of flammable materials.
The freon is forced out of the tanks using compressed air stored in separate cylinders outside the extinguishing station and the guarded room. When the refrigerant supply valves are opened, a sound and light warning alarm is triggered. You must leave the premises!
What is the general structure and operating principle of a stationary powder fire extinguishing system?
Vessels intended to carry liquefied gases in bulk must be equipped with dry chemical powder extinguishing systems to protect the cargo deck, as well as all loading areas at the bow and stern of the ship. It should be possible to supply powder to any part of the cargo deck using at least two monitors and (or) hand guns and hoses.
The system is activated inert gas, as a rule, nitrogen, from cylinders located near the place where the powder is stored.
It is necessary to ensure the presence of at least two independent, autonomous powder extinguishing installations. Each such installation must have its own controls, gas supply high pressure, pipelines, monitors, and hand guns/sleeves. On ships with a capacity of less than 1000 r.t., one such installation is sufficient.
Protection of the areas around the loading and unloading manifolds should be provided by a monitor, either locally or remotely controlled. If from its fixed position the monitor covers the entire area protected by it, then it does not require remote targeting. At least one hand sleeve, gun or monitor should be provided at the rear end of the cargo area. All arms and monitors should be capable of being actuated on the arm reel or monitor.
The minimum permissible feed for the monitor is 10 kg/s, and for the hand sleeve - 3.5 kg/s.
Each container must contain enough powder to supply all monitors and hand arms connected to it for 45 seconds.
What is the principle of working withAerosol fire extinguishing systems?
The aerosol fire extinguishing system refers to volumetric fire extinguishing systems. Extinguishing is based on chemical inhibition of the combustion reaction and dilution of the flammable environment with a dust aerosol. Aerosol (dust, smoke fog) consists of tiny particles suspended in the air, produced by the combustion of a special discharge of a fire extinguishing aerosol generator. The aerosol floats in the air for about 20 minutes and during this time affects the combustion process. It is not dangerous to humans, does not increase the pressure in the room (a person does not receive a pneumatic shock), and does not damage ship equipment and electrical mechanisms that are under voltage.
The ignition of the fire extinguishing aerosol generator (for igniting the charge with a squib) can be set manually or when feeding electrical signal. When the charge burns, the aerosol exits through the cracks or windows of the generator.
These fire extinguishing systems were developed by JSC NPO "Kaskad" (Russia), they are new, fully automated, do not require large installation and maintenance costs, and are 3 times lighter than carbon dioxide systems.
System composition:
Fire extinguishing aerosol generators;
System and alarm control panel (SCUS);
A set of sound and light alarms in a protected area;
Ventilation and fuel supply control unit for MO engines;
Cable routes(connections).
When detecting signs of fire in the premises, automatic detectors send a signal to the control panel, which issues a sound and light signal to the central control room, control center (bridge) and to the protected room, and then supplies power to: stop ventilation, block the fuel supply to the mechanisms to stop them and ultimately to activate fire extinguishing aerosol generators. Apply different types generators: SOT-1M, SOT-2M,
SOT-2M-KV, AGS-5M. The type of generator is selected depending on the size of the room and the materials being burned. The most powerful SOT-1M protects 60 m 3 of space. Generators are installed in places that do not prevent the spread of aerosol.
AGS-5M is manually activated and thrown indoors.
To increase survivability, the control panel is powered from different power sources and from batteries. The control panel can be connected to a unified computer fire extinguishing system. When the control panel fails, the generators self-start when the temperature rises to 250 0 C.
How does a water mist extinguishing system work?
The fire extinguishing properties of water can be improved by reducing the size of water droplets .
Water mist extinguishing systems, called “water mist extinguishing systems,” use smaller droplets and require less water. Compared to standard sprinkler systems, water mist extinguishing systems have the following advantages:
● Small diameter of pipes, facilitating their installation, minimal weight, lower cost.
●Requires lower capacity pumps.
●Minimum secondary damage associated with the use of water.
● Less impact on vessel stability.
More high efficiency in an aqueous system operating using small droplets, it is ensured by the ratio of the surface area of the water droplet to its mass.
Increasing this ratio means (for a given volume of water) increasing the area through which heat transfer can occur. Simply put, small water droplets absorb heat faster than larger ones and therefore have a greater cooling effect on the fire zone. However, excessively small drops may not reach their destination because they do not have enough mass to overcome the warm temperatures generated by the fire. air flow. Water mist extinguishing systems reduce the oxygen content in the air and therefore have an asphyxiating effect. But even in enclosed spaces, such action is limited, both due to its limited duration and due to the limited area. With very small droplet sizes and high heat content of the fire, resulting in rapid education significant volumes of steam, the suffocating effect is more pronounced. In practice, water mist extinguishing systems provide extinguishing primarily through cooling.
Water mist extinguishing systems should be carefully designed, should provide uniform coverage of the protected area, and, when used to protect specific areas, should be located as close as possible to the relevant potential hazard area. In general, the design of such systems is the same as the previously described sprinkler system design (with “wet” pipes), except that water mist extinguishing systems operate at a higher operating pressure, in the order of 40 bar, and they use specially designed heads that create drops of the required size.
Another advantage of water mist extinguishing systems is that they provide excellent protection to people because the fine water droplets reflect thermal radiation and bind flue gases. As a result, personnel involved in extinguishing the fire and ensuring evacuation may move closer to the source of the fire.
