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Alarm-Line detecting temperature increase (detection cableAlarmline LHD4 )

■max. length:up to300 m

■able to detect temperature increase (at long distances) - resistant tomechanicaland chemical impacts, corrosion, moisture, dust

■ easy to install, economical, easy to maintain, easy to commission

■can be used inexplosive areas

■ admission for operation VdS (No. g 295013), FM, CEGB

Alarm system Alarmline LHD 4 ensurestimely detection of fireor overheating.It can be usedin constrained rooms, under severe conditions,when other safety systems are not enough.The system consists of two elements:detection cableandsignal forming unitAlarmline LHD 4.

Detection cable

Detection cable Alarmlineconsists of fourcopper wires. Each of the wires isenclosed into a jacket made ofcolorfulinsulating materialwith negativetemperature coefficient, andcovered by externalheatproof coating. Metal braid is used to protect the detection cable ifit is applied under severe conditionsand under mechanical impact.The wires are connected as twisted pairisolated at the end of the cable. Both cable sleeves are controlled. Opening of the circuit and short circuitwill result in emerency alarm activation in the signal forming unit. In case of temperature increase the electric resistance between both sleeves changes: resistance will be reduced.This change isdetected by the signal forming unit, and when the setactivation temperature is exceeded the alarm signal is made. If the temperature exceeds 100" and influences the detector for a short period of time, and after the signal is sentitrestores its usual operation mode.If the detection cable is damagedthe signal is sent constantly.

Signal forming unit

The signal forming unit informs aboutany temperature increase wi the help of the detection cable resistance control system. The activation temperature is set by means of a plug-type bonding stripwhich is installed in compliance with the gauge switch position. Two LEDswill illuminate/blink when there is alarm signal of damage. Both messages will block the signal forming unit. Reset will be done by interruption of power supply. The check key allows to carry out power electrical checkout of the system. The electric commutation systemis located in a plastic box(polycarbonate:fire ratingIP55).The unit is connected furtherto fire alarm systemswith the help of volt-free contactsof the relay(2 , 60 ).

Temperature adjustment

The correct temperature is determined by nomogram taking into considerationtwo knownfactors:maximum ambient temperaturein the controlled area. For example:300m long detection cablewith maximum ambient temperatureof 37,5 °. Length parameter of 300mon D scale should be connected with the temperature paramenter of 37,5 ° on scale. The cross pointwill determine the set parameter 7on scale.And scale willdeterminethe temperaturefor alarm signalboth for the whole length andseparate areas of the detection cable:

for 300m lengththe signal will be sent at 49 °

for30m lengththe signal will be sent at73 °

for1 m length the signal will be sent at 114 °Ѡ

Usage in explosive-risk areas

When installed in explosive areas the system should beprovided with internal self-protection. In this casethe signal formng unitshould be installed in the areaclassified as risk-free, and commissioned Zenner barriers (2barriers foreach detection cable)will ensure installation of thedetection cable in the area running less risk. Suitable barriers can bebarriers manufactured byMeasurement Technologyunder nameMTL 761 .

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