FLOOD SYSTEMS

Description of the DI.MARCA FIRE system

DI. M.A.R.C.A. Service makes flood systems, that are fixed fire prevention systems that flood the area with water under pressure through a piping system and open sprinkler nozzles. The pipes are empty and remain so until the flood valve is activated by an activation system that can be triggered hydraulically, pneumatically or electrically.

APPLICATIONS

The flood system is normally used to protect high risk areas, through the formation of water barriers, that have a cooling effect and prevent the deformation and collapse of structures. Typical examples are flammable deposits, fast spreading areas of fire, tanks containing fuel, transformers, etc. Calculation and dimensioning of the installation must always be carried out by qualified and experienced engineers so the best use can be made of the equipment used, according to the criteria dictated by law.

FUNCTIONING

The flood valve prevents water from entering the pipes until the entire system is activated. It is kept closed by the pressurised chamber (membrane chamber) associated with the valve. The pressure inside is in turn maintained by a restriction on the load line. This chamber is also connected to the detection line. When the pressure falls in the upper chamber of the valve through the detection line, the clapper valve rises due to water pressure under the clapper. At this point the water escapes and reaches the nozzle network, triggering the audible alarm.

EMERGENCY MANUAL CONTROL

Every flood system can be operated manually by an emergency control. This is installed at any point on the pilot line of a system and can be activated hydraulically, pneumatically or electrically. When the emergency control lever is lowered, the activation line is released and the valve operates due to falling pressure in the system and, therefore, in the pressurised chamber of the flood valve.

HYDRAULIC ACTIVATION SYSTEMS

The detectors are connected to the diaphragm chamber of the flood valve by a common activation line. When a pilot sprinkler head breaks, or the emergency manual control is activated, water escapes from the diaphragm chamber of the flood valve faster than the water that simultaneously enters through the initial loading line, as it has to pass through a reduced orifice, depressurising the system. The flood valve opens and the water pressure thus reaches the system. The system will remain in this state until manual intervention blocks the water supply to the valve.

DIAGRAM OF A FLOOD SYSTEM WITH HYDRAULIC ACTIVATION

Flood system

A - Flood valve body

B - Flood valve trim components

1-Drain valve NC

2-Alarm test valve NC

3-Alarm valve NA

4-Automatic ball drip valve

5-Flood valve chamber supply valve

6-Manometer and upstream pressure gauge

7-Filter 

8-No return valve

9-Calibrated orifice diameter

C - Alarm components

10-Water motoralarm 

11-Alarm pressure switch


D - Detection and control line 

12-Manualemergency control 

13-Manometer and diaphragm chamber pressure control gauge 

14-Supervision switch


E - Main shut-off valve 

NC: Normally Closed

NA: Normally Open

PNEUMATICALLY ACTIVATED SYSTEMS

This system requires a supply of dry air or nitrogen at a pressure between 20 and 40 PSI (1.38 and 2.76 Bar), which passes through a restricted orifice. The detection line is then dry pressurised and is connected to the upper chamber of the flood valve as for the previous system, the only difference being the intervention of the Pneumatic Actuator. This is a three-way device constructed to have a pressure differential for air/water of 8 to 1 to allow a use of low air pressure in the face of high pressure from the water supply. When a detector is activated, or the emergency control is activated, the air in the detection line comes out much faster than it can be replaced by its source due to the reduced orifice. When the pressure reaches approximately 7 PSI (0.48 Bar), the Pneumatic Actuator opens, the water is discharged from the upper chamber of the flood valve through the third way; the water pressure is not always made up because it is supplied through a reduced orifice. The flood valve opens and the water pressure reaches the system; from this point on it functions like the hydraulic system.

DIAGRAM OF FLOOD SYSTEM WITH PNEUMATIC ACTIVATION

A - Flood valve body


B - Flood valve trim components 

1 - Drain valve NC

2 - Alarm test valve NC

3 - Alarm valve NA

4 - Automatic ball drip valve

5 - Flood valve supply valve

6 - Manometer and upstream pressure control gauge

7 - Filter 8 - Non-return valve

9 - Calibrated orifice diameter

10 - Pneumatic actuator


C - Alarm components

11 - Water motor alarm with filter and/or

12 - Alarm pressure switch

 

D - Control and detection line 

13 - Emergency manual control NC

14 - Diaphragm chamber gauge

15 -Compressed air line output

16 - Low air pressure alarm switch

17 - Detector air line gauge

18 - Air loading and maintenance

19 - Air outlet

20 - Compressed air tank 

21 - Supervisory switch


E - Main shut-off valve 

NC: Normally Closed

NA: Normally Open

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SYSTEMS WITH ELECTRICAL ACTIVATION

This system requires the use of an electrical detection system, alternating or direct current, closed or open circuit, with an electrical control panel. The side chamber (diaphragm chamber) of the flood valve is kept pressurised by means of a solenoid valve that is normally closed. When an electrical detector sounds an alarm, the solenoid valve excitation signal is sent from the control panel causing the valve to open instantly. The water flows out from the flood valve lateral chamber faster than it is simultaneously replaced by the initial supply line that has to pass through a reduced orifice, thus depressurising the system. The flood valve opens and the water pressure reaches the piping; the process from this point is the same as that for the systems already described in points 1.5 and 1.6. In the event that the solenoid valve closes, either by mistake or deliberately controlled from the Control Panel, the system will NEVER revert: in fact, the flood valve shutter will remain in the open position until the valve itself is manually reset.

DIAGRAM OF FLOOD SYSTEM WITH ELECTRICAL ACTIVATION

Diagram of flood system with electrical activation

A - Flood valve body


B - Flood valve trim components 

1 - Drain Valve NC

2 - Alarm test valve NC

3 - Alarm valve NA

4 - Automatic ball drip valve

5 - Flood valve supply valve

6 - Manometer and upstream pressure control gauge

7 - Filter

8 - Non-return valve

9 - Calibrated orifice diameter

10 - Diaphragm chamber manometer and pressure control valve

11 - Solenoid valve NC C


C- Alarm components

12- Water motor alarm

13- Alarm pressure switch


D- Command and control line 

14- Manual

emergency control 15-Supervisory switch

16- Control panel


E- Main valve 

NA Normally Open

NC Normally Closed

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