The expertise of fire detection solutions provider Patol in the manufacture of linear heat detection cable (LHDC) systems has been recognised in a project to help protect the Hinkley Point B Nuclear Power Station.
Placed by site licensee and operator, EDF Energy - one of the largest suppliers of energy to homes and businesses throughout the United Kingdom - the order was for the supply, installation and commissioning of the LHDC fire detection system. The system is now installed to protect cable flats and risers in the power station.
The nuclear power station, located on the coast of the Bristol Channel in south west England, near Bridgwater, Somerset, comprises of two operating Advanced Gas-Cooled Reactors (AGR) that became operational in 1976. The station is capable of producing a net power output of 945 MW and thus supplying 1.5 million homes, representing around one percent of the UK’s total power output.
Patol is primarily concerned with the provision of all kinds of safety related equipment and systems. Giving early detection of hazards at temperatures well below flame point, its LHDC comprises a coaxial cable inside a protective sheath. The core of each cable is tinned copper coated steel with resistive negative temperature coefficient polymer insulation. The insulation is formulated so that the polymer starts to conduct as temperature rises. When this happens, the controller compares the signal and triggers an alarm.
The technology has been applied at the Hinkley B facility to replace an original system installed in the 1990’s which required 140 local zone monitoring units dispersed throughout the cable flats. The new system offers significant technological advances, employing control modules grouped into five distributed swing frame control cabinets with 19 inch rack-mounted LHDC monitoring and actuation control modules. This makes identification and location of a potential incident much easier, with each control module monitoring the existing zonal length of analogue re-settable LHDC. The modules feature a two stage alarm output, activated when a short length of the cable is elevated in temperature above the pre-defined trip points. The alarm signals from the modules are sent to the site’s fire alarm system and also to 600 zonal metron actuated sprinklers located throughout the cable flats. If the second stage of the two stage alarm is reached, the relevant sprinklers are automatically activated to quickly extinguish the fire in the affected zone.
A further benefit is easy access for maintenance, with the control cabinets located outside the cable flat and riser areas, thereby eliminating the need to work in confined spaces.
Patol’s LHDC system is suitable for installations in ducts, cable risers, mezzanine floors or in tunnels, to trigger alarms for any hot spot occurring on even the smallest sections of the overall cable length. The cable is particularly suited to applications such as road or rail tunnels where harsh environmental conditions preclude the use of other forms of detection. It is versatile in that it can both provide an alternative to point heat detectors in conventional (space) protection situations and it may also be readily installed in very close proximity to monitored hazards.
