Cable Trays - Fire and/or Overheat Detection
As a combined cable and detector designed for the protection of capital investments and human lives LINEAR TEMPERATURE SENSOR CABLES provides rapid LOCALISED detection of abnormal temperature rises - pre combustion because of its ability to be installed at the exact point of risk.
Overheat conditions can be generated from overloading of high voltage power cables, short circuits on the same cables, cable joint overheats and fires generated by extraneous sources - local maintenance work (i.e. soldering tools, halogen lights etc. carelessly located on/adjacent to the trays and cables) or ignition of rubbish left on the tray or under the bottom tray on multi-tier tray installations.
Today, linear detection systems are regularly specified by end users, consultants, Fire engineering Companies etc. throughout all the major continents across the globe. With literally thousands of installations now also protecting cable trays at petro-chemical plants, airports, railway stations - above and below ground -, hospitals, shopping centres, office blocks - to name but a few!
The dirty, damp, humid, dusty, abrasive, corrosive environmental conditions found at the above sites plus potential high levels of RFI and/or EMI do not physically affect linear sensor cable operating reliability, sensitivity, required annual maintenance, anticipated life time ...which should exceed 20 years....and will not generate unwanted alarm signals. The installation of the heat sensor cable above the tray it is protecting allows access, without obstruction, to the tray for power cable repair, replacement or addition of new cables by site engineers.
System design procedures that should be adopted for linear detection include:
- Zoning 1 - use of fire barriers or fire doors in tunnels to provide easily identified zone locations
- Zoning 2 - Detection and Extinguishing zones should protect identical areas.
- Cable Tray width - a single run of heat sensor cable for protection of trays up to 600mm width. A second run of sensor cable for wider trays.
- Always install a sensor cable run beneath the bottom tray - the incidence of rubbish fires are MUCH greater than many believe.
- Alarm Temperature selection - A minimum of 11C should be allowed between the specified maximum ambient temperature and minimum linear heat detection alarm temperature - UL recommended
- Use non heat sensitive/short term fire-proof Inter-connecting cabling for connection of risk area installed linear sensor cable to remotely located interface unit/s.
A.) Multi-Tier Cable Trays - International Design for Protection - Parallel Runs
B.) Multi-Tier Cable Trays - U.S.A. Design for Protection = "Sine Wave " on Tray
Direct contact between sensor and cables can present obstruction to site engineers and the "heat sink" effect of cable or metallic surfaces can slow the alarm response times of linear sensor cables.