The Importance of Alarm in Fire Fighting System

The alarm valve is one of the important components in the fire fighting system, to give an alarm signal when there is a problem.

1. What is an alarm valve?

1.1 Concept of alarm valve

Alarm check valve is basically a check valve that includes an alarm output van báo động. The main purpose of an alarm valve is to sound a mechanical bell or what is known as a water-activated mechanical bell.

1.2 Alarm valve function

The main function of the alarm valve is to alarm when a fire occurs. In addition, this valve helps keep system pressure stable and reduces the possibility of false alarms.

1.3 Composition:

1.3.1 Alarm valve:

Alarm security consists of 2 main components: valve body, valve leaf phụ kiện ren. To choose the right alarm valve, it is necessary to pay attention to the following parameters:

– Size: There are many sizes to choose from DN65, DN100, DN150 and DN200 depending on design requirements. The body of the alarm valve usually comes with a trim valve set.

– Connection type:

+ Flange x Flange

+ Coupling x Coupling

+ Flange x Coupling

– Installation type: Vertical or horizontal installation

– Rated working pressure: not less than 12 bar (TCVN 6305-2:2007).

1.3.2 Composition of wet system using alarm valve:

– Pressure Gauges

Pressure gauge on alarm valve

Pressure gauge on alarm valve

Measure the supply water pressure and system working pressure.

Characteristics: The system working pressure gauge will have a higher value than the water supply meter. The two meters will be valid together immediately after a supply water pressure surge until normal again. If the system working pressure gauge falls down with the value to check the valve valve is not in the correct position and needs to be serviced.

– Water bell:

Operates on hydraulic actuators that emit audible alarms in an area when water flows through the alarm valve.

Is a device to detect the state of water flow in the automatic sprinkler fire fighting system, alarm valve, overflow valve system … Send alarm signal to the fire alarm system in the area.

– Delay jar:

The volumetric delay mechanism is designed to minimize false alarm signals caused by sudden surges and fluctuations in the water supply to the spinkler system.

1.3.3 Components of dry system using alarm valve

Used in dry pipeline system, designed in low temperature, below +4oC to prevent the risk of freezing in the pipeline system, works on air and nitrogen pressure.

– Dry alarm valve accelerometer

– Equipment to maintain air pressure

This device is designed to regulate the pressure of the system

1.4 Principle of system operation

1.4.1 Under normal conditions:

The valve leaf of the alarm valve is closed, the alarm output is locked, the pressure in the system is maintained, the water of the sprinkler system does not flow back to the water supply.

1.4.2 In case there is a nozzle that breaks off when there is a fire:

When there is a large pressure difference between the system pressure and the supply water pressure (shown by 2 pressure gauges), the valve leaf is open to allow the supply water to flow into the alarm port and the tank. delay the start of water accumulation. If this is due to a surge in the water supply, the retard tank will only be partially filled. The pressure switch that does not reach the trigger threshold (preset) will not send a signal to the fire alarm system to avoid false alarms.

In case the nozzle bursts when there is a fire, the water supply flowing into the alarm port activates the water bell to sound the alarm, the delay tank is now filled. The pressure switch that reaches the trigger threshold sends a signal to the fire alarm system for monitoring.

1.5 Classification

Function classification:

– Alarm valve used for wet system

– Alarm valve used for dry system

Type of installation:

– Vertical installation alarm valve: Use connection device (trim) for vertical installation.

– Horizontal installation alarm valve: Use a horizontal connection device (trimmer).