A cable tray is a system that is used to support insulated cables for a building's electrical system. Cable trays are most commonly found in commercial and industrial properties and provide an alternative to open wiring or electrical conduit systems. Cable trays are particularly useful in the case where changes to a wiring system are foreseen as new cables can simply be installed by laying them in the cable tray, as opposed to routing them through pipework.
There are many types of cable tray available, including: Wire Mesh, Single Rail, Ladder, Channel, Trough and Solid Bottom. The type of cable tray chosen is dependent upon the layout and type of cable.
Cable trays are manufactured in fibre reinforced plastic, steel and aluminium although around seventy percent of cable trays being used today are made of aluminum.
Cable trays come in a wide range of sizes and therefore will vary depending on the environment. The type of cable tray, ampacity requirements and the type and voltage rating of the cable to be used determines the allowable fill for a cable tray. If a cable tray is overloaded, excessive heat build up in and around live conductors can cause the cable’s insulation to break down, resulting in an electrical short that can easily ignite the cables themselves or other nearby combustible materials.
On top of this when cable trays are overloaded they are at risk of becoming unable to support the weight of the cables they are carrying. Therefore, they are at risk of collapsing, not only putting anyone underneath the tray in danger, but also creating the potential for electric shock or flash/blast events that could result in fire.
Furthermore, cables that are not secured correctly into cable trays can become damaged, also resulting in heat build up or short circuit.
Apart from ensuring that a cable tray has not exceeded its maximum weight and insuring that all cabling has been properly secured it is vital that suitable fire detection is in place to provide adequate warning of fire.
Linear heat detection can provide the ideal solution when protecting cable tray installations from fire. In particular, Eurofyre’s Fyreline linear heat detection system can provide accurate, fast and reliable detection.
FyreLine linear heat detection cable can be laid in a sine wave pattern, on top of all the power and control cables in the tray, and “V” clips can provide support where more than one cable tray needs protection. This provides maximum sensitivity to overheat conditions while minimising obstruction to cables mounted in the tray. However, any additional cable laid in the tray must be laid underneath the heat detection cable. FyreLine heat sensing cable is a capable of detecting heat anywhere along its length and can therefore identify excess heat or fire at any point along the cable tray.
FyreLine Digital heat sensing cable comprises two wires that are coated in a heat sensitive polymer. These cables are twisted together and housed in an outer sheath. When the heat sensitive polymers reach their rated temperature they melt, causing the two wires come into contact with each other. The resulting short sends a signal of fire to the fire alarm control panel.
FyreLine Analogue heat sensing cable is of similar constitution to FyreLine digital, only when the polymer that coats the internal wires reaches its rated temperature it causes the resistance of the cables to change. When a change in resistance is detected, a signal is sent to the control panel. Therefore, FyreLine Analogue heat sensing cable is not only capable of continuously monitoring for changes in heat but can also provide both alarm and pre-alarm warnings.
PVC - is the standard coating and is suitable for most environments.
Nylon - provides suitable protection against UV, is tougher than PVC and is the common choice for when hazardous hydrocarbons such as fuel oils, diesel and kerosene etc. are present.
Polypropylene - is suitable for applications within corrosive environments or where strong acids are present.
Stainless Steel Braid - any of the above cables can be armoured with steel braid to protect them where they may be subject to mechanical abrasion or where there is a risk that they may be accidentally cut.
The recommended cable sheath type for protecting a cable tray will be dependant upon the environment that it is to be installed.
Eurofyre are proud, British manufacturers of specialist fire detection systems. Eurofyre offer a wide range of fire detection systems for both industrial and commercial applications. Our expertise allows us to supply high quality systems and provide a high level of pre- and post-sale technical support.
For more information about the FyreLine Linear Heat Detection System, or to discuss any of the other products that Eurofyre have to offer, please feel free to get in touch either by phone on Call:+44 (0) 1329 835 024, by email to sales@eurofyre.co.uk or via the online enquiry form situated on our contact page.
Michael is the sales manager EMEA at Eurofyre.