DIGITAL lINEAR HEAT dETECTION

Overview of LHD

FyreLine linear heat detection provides early warning of fire or  overheating equipment. Heat sensing cables are capable of detecting heat  anywhere along their length and designed for use in commercial and  industrial applications.

Linear heat detection is highly cost-effective and can be easily  installed with, or in place of, conventional heat detectors where  traditional style detection may be difficult to install or maintain or  is too expensive.

How Does Linear Heat Detection Work?

There are two types of heat sensing cable available, fixed temperature (Digital) and analogue:

FyreLine Digital (Fixed Temperature) Heat Sensing Cable

FyreLine fixed temperature heat sensing cable is available in four different temperature ratings; 68°C, 88°C, 105°C or 185°C.

FyreLine linear fixed heat sensing cable is  constructed using two twisted and tensioned, tri-metallic conductors.  Each of the conductive cables are coated in a heat sensitive polymer  which, when heated to its rated temperature, melts, causing the the two  cables to touch. The resulting short sends a signal to the fire alarm  control panel, indicating that a fire (or excessive heat) has been  detected.

Once a fire has been detected the damaged length of cable is easily replaceable.

An Digital Input Monitor Module (DiMM) can be used in conjunction with digital heat sensing cable to  provide an accurate location of the point at which the alarm is  triggered along the detection cable.

Overview of DLHD

FyreLine Digital Linear Heat Detection Systems provide a  cost-effective and reliable fixed temperature heat detection solution  that is suited to a wide range of applications.

FyreLine Digital Heat Sensing Cable is comprised of two tri-metallic  conductors that are covered with advanced temperature sensitive  polymers. The two conductors are twisted together and a protective outer  sheathing is wrapped around them.

Once the temperature sensitive polymer reaches its rated temperature  it melts, causing the two conductors to come into contact. The resulting  short circuit signals to the fire alarm control panel that a fire (or  extreme heat) has been detected.

Once a fire has been detected, or if the detection cable becomes  damaged, the affected length of cable can be easily replaced; the  damaged section can be removed and new section spliced in its place.

Fyreline Digital Linear Heat Sensing Cable is available with temperature ratings of 68°C, 88°C, 105°C or 185°C.

Fire Alarm System Integration

The digital linear heat detection cable can be directly connected to a  single zone of a conventional fire alarm control panel, or, easily  interfaced to an addressable loop using an addressable zone/switch  monitor.

Sensing Cable Construction

 FyreLine linear fixed heat sensing cable is  constructed using two twisted and tensioned, tri-metallic conductors.  Each of the conductive cables are coated in a heat sensitive polymer  which, when heated to its rated temperature, melts, causing the two  cables to touch. The resulting short sends a signal to the fire alarm  control panel, indicating that a fire (or excessive heat) has been  detected. Once a fire has been detected the damaged length of cable is  easily replaceable.

Digital Product Range

PVC Coated Sensing Cable

The standard coating used on Digital cables  is made from PVC and is suitable for most environments. However, PVC  should not be used when the cables are directly exposed to UV (sunlight)  or hazardous chemicals (eg. hydrocarbons) for long periods, or for  applications where they may be exposed to regular mechanical abrasion.

Where the standard PVC is not recommended other materials/sheaths are available to provide a suitable solution.

Nylon Coated Sensing Cable

A Nylon coated cable is the common choice  when hazardous hydrocarbons such as fuel oils, diesel, kerosene etc. are  present. Nylon cables are coloured black and provide suitable UV  protection when used in direct sunlight. Nylon is much tougher than PVC  and therefore provides additional mechanical protection.

Stainless Steel Braid Coated Sensing Cable

Any of the above cables can be armoured by  placing stainless steel braiding over the outside of the cable. This  provides the ideal solution for areas where the cable may be  accidentally cut or where it may be subject to mechanical abrasion.

High Temperature Coated Sensing Cable

The High Temperature coated linear heat cable  is manufactured from two different types of nylon, with the outer  sheath being a chemical resistant material. Commonly used in high  temperature areas, hazardous and safe areas where chemicals such as  hydrocarbon fuel oils, diesel, kerosene etc. are present.

Digital Interface Monitor Module

The Digital Interface Monitor Module (DiMM)  is a dual zone module for monitoring up to two zones of Digital Linear  Heat Detection (DLHD) Cable.

If an overheat or fire situation triggers  either zone of the Digital LHD cable, the unit automatically calculates  and displays the distance along the cable, in feet and metres, to the  alarm point. The two zones can operate independently of each other, or  in interlock mode and a separate alarm and normally conducting fault  output are provided for each zone.

The unit is intended to be installed between  the FyreLine Digital Linear Heat Detection cable and a conventional or  addressable fire alarm control panel. It has power, fault and alarm  lights, as well as volt free outputs for fault and alarm, corresponding  to each zone. It may also be connected to an industrial process control  system using the two wire RS-485 Modbus RTU output.

Wiring Configurations

Conventional fire alarm systems

When used in conjunction with a conventional  fire alarm control panel, FyreLine Digital (fixed temperature) linear  heat detection cable should be connected to the initiating device  circuit.

If the area to be protected is some distance  away from the fire alarm control panel, leader cable may be used between  the beginning of the heat sensing cable and the control panel. However,  a junction box must be used to connect the leader cable to the heat  sensing cable in order to establish a secure, waterproof electrical  connection.

Addressable fire alarm systems

When FyreLine Digital heat sensing cable is  used as part of an addressable system, the heat sensing cable should be  connected to the addressable loop using a switch or zone monitor. If the  protected area is some distance away, leader cable may be used between  the beginning of the heat sensing cable and the addressable switch or  zone monitor. Again, when connecting the leader cable to the heat  sensing cable, a junction box must be used to ensure a secure and  waterproof electrical connection.

When using FyreLine Digital heat sensing  cable in conjunction with an addressable fire alarm system, external  power is not required for the cable.

Digital Interface Monitor Module

The Digital Interface Monitor Module (DiMM)  can be used to provide the location of the point along the cable at  which an alarm was triggered, giving an accurate a measurement in metres  and feet.

Leader cable can be used between the DiMM and  the control panel or addressable switch/zone monitor and between the  DiMM and the heat sensing cable. As always a junction box must be used  to maintain a secure and waterproof electrical connection.

When using a DiMM it is essential to map the  system to associate distances along the detection cable to locations  within the building to help determine the area where an alarm has been  triggered easily.