Product Comparisons

Linear temperature detection is still only specified in many cases for protection of its "traditional" applications: cable tunnels, conveyors, fuel storage tanks, warehouses and road/rail tunnels.

Proven Protection of a much more diverse range of applications - with improved operating sensitivity in many cases compared with other types of detectors - can be viewed within the Typical Applications sections of this website.

ANALOGUE/ANALOG

Description:  An electrical resistance averaging system with design and performance directly related to site ambient temperature and sensor cable length used. Sensor cable MUST be used in conjunction with special interface unit.

Manufacturers Claims:  A recoverable sensing cable and site adjustable alarm temperatures. Alarm point location feature available.
 

FACTS:  ALL incipient fires and overheat conditions are LOCALISED events. Short length sensor cable exposure requires high temperatures to generate the alarm resistance levels required by the "system". Such temperatures exceeding the destruct temperature of the PVC based sensor cable. Alarm temperatures CANNOT be accurately specified unless the EXACT sensor length that will be exposed is known at the system design stage. Similarly, accurate alarm point location is not possible as high temperature rise/short sensor length exposure and lower temperature rise/longer sensor cable length exposure produce identical alarm resistance changes. In order to adjust alarm temperature levels, installed sensor cable length or ambient temperature must first also be adjusted in many cases!!

DIGITAL

Description: A range of 2 conductor "switching" sensor cables, each cable with a different alarm temperature rating which must be specified at time of design/quotation/product ordering. Alarm temperature is fixed and will be the same regardless of 1% or 100% sensor cable length exposure. Sensor cable may be directly connected to a central fire alarm control panel without the requirement for any manufacturer supplied special interface unit. Alternatively, interface units can be supplied with alarm point location indication, multiple site programmable alarm output signalling, RS232/RS485 wiring and loop configured installation arrangements for larger project requirements - PROLINE product range referenced.

Manufacturers Claims: Multi-kms "zone" lengths may be designed and installed as the sensor cable alarm rating specified is not affected by site Ambient temperature fluctuations, RFI or EMI. Up to 50 Ohms resistance of interconnecting cable can be included (where required) without affecting alarm point location accuracy. Section replacement of fire damaged sensor is all that is required after an alarm. A detailed range of PROLINE optional interface units are available to maximise information output from the "system".

FACTS: One of the simplest operating concepts within the linear detection range with a history exceeding 60 years. Applications for "digital" can be restricted by the sensor cable alarm temperature ratings available. Response times from a "digital" sensor cable are further enhanced where the design ambient is closer to the alarm temperature rating - but in excess of the 11C differential recommended by UL to prevent false alarms from "normal" ambient temperature excursions. All Manufacturers Claims indicated above are accurate.

ELECTRONIC PNEUMATIC

Description:  A pressurised tube detection system (non-metallic or metallic) which "ruptures" when exposed to high temperature flames.

Manufacturers Claims:  As a non-electrical system, it is safe for use in any environment. Extinguishing agent can be discharged through the same tube when in alarm state.

FACTS:  A fire - not overheat - detection system which requires use of a high maintenance mechanical pump in order to maintain pressure levels within the sensing tube. The least reliable of the linear detection systems mentioned as long term corrosion or physical damage to the tube -resulting in pressure loss - will generate a false alarm system and cause extinguishing agent discharge.........with costly clean up and repair charges incurred. Maximum "zone" lengths are restricted due to necessity to maintain sensing tube pressures at a specific level.

FIBRE OPTICS

Description: A linear temperature detection system based on Distributed Temperature Sensing (DTS) Technology. The combination of controller and multi mode optical fibre provides the end user with the ability of signalling ( where necessary) a 1-2C change in ambient temperature and of identifying an alarm location to within 1m of its actual position.

NEITHER of the above offer significant advantages when used for fire detection - being more associated and of benefit where minor changes in temperature can have an effect on the economics of the process being monitored (for example power distribution cable control monitoring).    The significantly increased purchase price of fibre optics LHD cannot be justified for an operating concept which has experienced repeated false alarms due to sharp bends in the installed fibre cable and where moderate levels of vibration have been experienced!   Many of the system operating features and benefits can be installed using "digital" linear detection - at a fraction of the cost of fibre optics - including detection with break in sensor cable by loop connection.

Proline can offer fibre optics linear temperature sensing but will only do so where warranted and financially justified.

Manufacturers Claims: System can provide a 1 metre  resolution, +/- 2.0C temperature accuracy,  zone configuration on the fibre connected to the controller in a single or double ended configuration.   Maximum length of fibre cable / single ended channel can be 8kms.   

FACTS: Fibre Systems may be 21 st Century technology but are best focused in areas where minor variances in temperatures can be of greater financial significance ( such as power distribution cable surface temperature monitoring , petro-chemical "downholes" etc). NOT FOR OVERHEAT OR FIRE DETECTION APPLICATIONS!

MEASURING POINT SYSTEM (LIST)

Description: An operating concept which strictly should NOT be classified as a linear detector. Whilst the detection method employs a cable, it is much larger diameter (18mms) than any of the other systems and as a consequence, more difficult/time consuming/costly to handle and install. Of greater importance is that its construction involves the use of "hybrid" electronic circuits installed within the cable at customer specified 1m, 2m, 4m or 8m spacings. It does not therefore have the same advantages of continuous detection at ANY and ALL points along its length - as offered by other linear detection systems.

Manufacturers Claims: A linear heat detection system consisting of sensing cable and electronic measuring device. The electronics provide a cyclic addressing of the sensing cable, reads measured temperature and evaluates data with reference to different alarm criteria.
 

FACTS: A system which potentially would not give the operating sensitivity expected from linear detection concepts. As the complete length of the cable is not a temperature sensor. The two options available are a) a length restrictive maximum 250m cable operating on the "digital" principle and b) 2500m+ zone length capability BUT based on (and with) the operating restrictions already detailed in ANALOGUE / ANALOG above. Additional information output can be obtained but only from additional electronic controller/s. This is not FM approved or UL listed - but does carry Vds approval.