Alarm-Line detecting temperature increase (detection cableáAlarmline LHD4 )
■áááááááááámax. length:áup toá300 m
■ááááááááááable to detect temperature increase (at long distances) - resistant toámechanicalááand chemical impacts, corrosion, moisture, dust
■ááááááááá easy to install, economical, easy to maintain, easy to commission
■áááááááááácan be used ináexplosive areas
■ááááááááá admission for operation VdS (No. g 295013), FM, CEGB
Alarm system Alarmline LHD 4 ensuresátimely detection of fireáor overheating.áIt can be usedáin constrained rooms, under severe conditions,áwhen other safety systems are not enough.áThe system consists of two elements:ádetection cableáandásignal forming unitáAlarmline LHD 4.
áDetection cable Alarmlineáconsists of fourácopper wires. Each of the wires isáenclosed into a jacket made ofácolorfuláinsulating materialáwith negativeátemperature coefficient, andácovered by externaláheatproof coating. Metal braid is used to protect the detection cable ifáit is applied under severe conditionsáand under mechanical impact.áThe wires are connected as twisted pairáisolated at the end of the cable. Both cable sleeves are controlled. Opening of the circuit and short circuitáwill 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.áThis change isádetected by the signal forming unit, and when the setáactivation temperature is exceeded the alarm signal is made. If the temperature exceeds 100"Đ and influences the detector for a short period of time, and after the signal is sentáitárestores its usual operation mode.áIf the detection cable is damagedáthe signal is sent constantly.á
Signal forming unit
áThe signal forming unit informs aboutáany temperature increase wi the help of the detection cable resistance control system. The activation temperature is set by means of a plug-type bonding stripáwhich is installed in compliance with the gauge switch position. Two LEDsáwill 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 systemáis located in a plastic box(polycarbonate:áfire ratingáIP55).áThe unit is connected furtheráto fire alarm systemsáwith the help of volt-free contactsáof the relayá(2 └, 60 ┬).á
The correct temperature is determined by nomogram taking into considerationátwo knownáfactors:ámaximum ambient temperatureáin the controlled area. For example:á300ám long detection cableáwith maximum ambient temperatureáof 37,5 °Đ. Length parameter of 300ámáon D scale should be connected with the temperature paramenter of 37,5 °Đ on ┬ scale. The cross pointáwill determine the set parameter 7áon └ scale.áAnd Đ scale willádetermineáthe temperatureáfor alarm signaláboth for the whole length andáseparate areas of the detection cable:
for 300ám lengtháthe signal will be sent at 49 °Đ
forá30ám lengtháthe signal will be sent atá73 °Đ
forá1 m length the signal will be sent at 114 °Đá
Usage in explosive-risk areas
When installed in explosive areas the system should beáprovided with internal self-protection. In this caseáthe signal formng unitáshould be installed in the areaáclassified as risk-free, and commissioned Zenner barriers (2ábarriers foráeach detection cable)áwill ensure installation of theádetection cable in the area running less risk. Suitable barriers can beábarriers manufactured byáMeasurement Technologyáunder nameáMTL 761 └Đ.