In construction projects, the integrated pipeline corridor, cable trench, cable tray and other parts are the main power supply channels. The cable layout is concentrated and the electrical fire hazards are high. Detectors suitable for this site should be set up.

In construction projects, comprehensive pipeline corridors, cable trenches, cable trays, and other parts are the main power supply channels. The cable layout is concentrated and the electrical fire hazards are high. It is advisable to set up detectors suitable for this site.

According to Article 5.3.3 of the "Design Code for Automatic Fire Alarm Systems" GB50116-2013, cable tunnels, cable shafts, cable mezzanine , and cable trays, cable type temperature sensing fire detectors should be selected.

The reason is that the fire occurs during the process of increasing temperature → heat storage (heating) to generate combustible gas → flue gas → open flame. The above-mentioned places should not use flue gas and open flames to achieve the purpose of detection, so the key to early detection of fire lies in the rising stage of temperature.

cable linear temperature sensing fire detector is an alarm product that responds to the temperature parameters around a certain continuous line. It consists of a signal processing unit (microcomputer modulator), a temperature sensing cable, and terminal box .

a. Signal processing unit (microcomputer modulator)

signal processing unit has a signal processing circuit, including signal acquisition, amplification and conversion circuit, display circuit, ambient temperature testing circuit, etc., to continuously monitor the temperature, alarm the temperature rise, disconnection and short circuit caused by abnormal conditions;

b. Terminal box

terminal box has terminal resistor and diode ;

html l1c. Temperature sensing cable

temperature sensing cable consists of an inner conductor (two cores have no polarity), an insulating layer, and a metal braided layer. Among them, the insulating layer insulating material is a special thermally sensitive material. Therefore, the resistance between the two inner conductors has a negative temperature characteristic. The characteristics of negative temperature coefficient are manifested as a logarithmic function, that is, the detector at room temperature. The resistance will be much greater than the resistance at abnormal temperature;

According to the provisions of " Linear Temperature Sensing Fire Detector " GB16280-2014, different alarm temperature temperature sensing cables can be divided into 60℃, 70℃, 85℃, 105℃, 138℃, 180℃, etc. The conductors inside the analog wire-type temperature sensing cable form a monitoring circuit. When the on-site temperature in the protected place of the temperature sensing cable changes, the resistance value of the monitoring circuit will change significantly. When the microcomputer modulator detects that the resistance value of the front-end temperature sensing cable detection circuit reaches a predetermined alarm value, an alarm signal will be generated and sent to the fire alarm control screen at the back end, thereby causing a fire alarm signal. The input signal at the front end of the microcomputer modulator is the resistance value (analog/analog) generated by the analog linear temperature sensing cable. The output signal at the back end is already a switch signal (digital) that can be recognized by any standard automatic fire alarm control screen. The system diagram is as follows:

Setting principles for linear temperature sensing detectors in different places, "Fire Automatic Alarm System Design Specifications", "Line-type temperature sensing fire detectors", There are relevant provisions in the specification documents such as "Design Specification of Fire Automatic Alarm Systems" and other specifications. Some of the provisions and practices are summarized as follows:

a. When the detector protects cables, stacking and other similar protection objects, it should adopt a contact arrangement;

b. The distance from the linear temperature sensing fire detector placed under the ceiling should be 0.1m.The protective radius of the detector should meet the protection radius requirements of the point-type temperature-sensitive fire detector; the distance between the detector and the wall should be 1m~1.5m;

c. When setting the site linkage requirements of the linear temperature-sensitive fire detector, it is advisable to use the alarm signal combination of two different fire detectors ;

d. The standard alarm length of the cable-type linear temperature-sensitive fire detector should not be greater than 1m;

d. ml1e. The linear temperature sensing fire detector set in the cable tunnel can be connected to the electrical fire monitor;

f. The cable tunnel without external fire source should be equipped with linear temperature sensing fire detector on the upper surface of the cable layer; there is an external If the fire source enters a possible cable tunnel, a linear temperature sensing fire detector should be installed on the upper surface of the cable layer and the top of the tunnel;

g. The linear temperature sensing fire detector should use a contact laying method to detect all power cables in the tunnel; cable-type linear temperature sensing fire The detector should be arranged in a "S" shape on the upper surface of each layer of cable;

The installation diagram of linear temperature sensing detectors in various places is as follows:

a. Lay

b. Lay

b. Lay

c. Lay

d. Warehouse conveyor belt laying

In summary, because of its unique working method, cable-type linear temperature sensing fire detector has good environmental adaptability, can be protected close or close, and can work reliably in various places such as humidity, pollution, and dust. Therefore, it can be widely used in fire detection and alarms in power plants, steel plants, coal preparation plants, power stations, transformers, oil depots, oil tanks, metallurgy, petrochemical plants, warehouses, large memorial halls, exhibition halls, ancient buildings, large shopping malls, airports, shipbuilding, hospitals, subways and other fields.

Attachment: Case sharing, a large-scale commercial street project

. Project overview

The total construction area of ​​this project is about 130,000m2, and the main business formats are large-scale commercial pedestrian streets, e-sports halls, nightclubs, garages, apartments, etc.;

. Setting requirements

Commercial street, apartment, garage distribution room , etc.The alarm signal of the linear temperature sensing detector is required to be connected to the fire automatic alarm system through the fire automatic alarm system signal input module. All linear temperature sensing detectors should have address encoding;

. Set the position

1. substation distribution room cable mezzanine and cable trench;
2. substation distribution room low voltage outlet cable tray;
3. strong electric shaft main cable tray;

. Cable temperature sensing detector selection

1. linear temperature sensing detector selection user internal cable type fixed temperature recovery temperature sensing cable, the outer sheath of the temperature sensing cable should be flame retardant (class B);
2. linear temperature sensing detector operation temperature is 70℃;
3. Each detector should be laid at a length of no less than 10m or more than 200m, and should be laid at a contact type according to sine wave contact type. The cable trench should be laid in layers. Two bridge frame with a width greater than 600mm should be laid at a bridge . The detection signal should be included in the fire alarm system. The schematic diagram is as follows:

. Construction drawing design drawings

1. ml1 system diagram:

1. Laying diagram in the cable trench:

1. Laying diagram in the vertical bridge of the strong shaft:

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