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D-LX 201

D-LX 201/721
Optical compact flame monitor

Flexible and selective compact flame monitor for high requirements. For optical monitoring of all fuel flames, including in complex multi-burner plants. 

D-LX 721 for application with


Functionality: Optical flame monitoring

  • Very wide temperature range: Deployable without change, certified and without the need for accessories for insulation, heating or cooling
  • Wide dynamic range: Automatic gain adjustment to the brightness of the flame
  • Consistently dual-channel: Highest safety combined with high availability
  • Ideal support for Functional Safety: Safety chains in high demand mode or low demand mode up to SIL 3
  • Extensive certifications
  • Local display: Operational status, settings and flame intensity visible at a single glance for the entire temperature range for all variants
  • Real-time flame stability information: Optional continuous qualification of flame stability during operation
  • D-LX 201 InformationCentre for logging of the flame signal and parameters as an ideal supplement for commissioning up to six flame monitors simultaneously
  • Safe process control: Even during strong and fast load changes of the combustion plant the process can be controlled safely by the flame stability signal. Reactions in due time are possible
  • Increased load and fuel flexibility: Excellent selective monitoring and information about stability allow operation of the plant in less stable regimes
  • Protection against unscheduled shutdown of the burner: Burner-specific information on stability allows decisions to be made on preventive maintenance of the burner
  • Fulfillment of special requirements: Flexible presettings for different combustion situations and fuels
  • Same technology for different applications: The same product family can be used for plants in the most varied regions and on the basis of a wide range of systems of standards
  • Complex combustion plants including plants with many burners and different fuels
  • Monitoring of burner flames with widely varying fuels
  • Combustion processes with high Functional Safety requirements
  • Combustion processes in continuous operation
  • Technical data
  • Explosion protection
Spectral sensitivityUV, IR
Operating modeIntermittent operation and continuous operation
Functional SafetySelf-monitoring and fail-safe, supports safety chains up to SIL 3 (high demand mode / low demand mode)
Switching thresholdFlame intensity and flicker frequency
Local displayLEDs – always visible at a single glance for all versions, display of flame intensity by flash frequency
Flame failure detection time (FFDT)1, 2, 3, 5 s (separately adjustable for each range)
Flame ON/OFF contact1x NO contact
Ready for operation contact1x NO contact
Switching capacity of relay contactsMax. 24 VDC, 0.5 A
Analogue output0/4 … 20 mA (adjustable), output signal selectable, load max. 750 Ohm
Opening angle6° (D-LX 201)
Real-time informationFlame stability analysis (optional)
Electrical data24 VDC, 5 W, PELV
Ambient conditions-40 … +85 °C
Degree of protectionIP66/IP68, NEMA 4XIP65, NEMA 4X (/MP3)IP66, NEMA 4X (Ex variants)
ConnectionsD-LX 201: Sight tube G 1¼″ or NPT 1¼″, FPurge air G ½″ or NPT ½″, F
DimensionsHousing P2: 80 x 80 x 250 mm Housing M5: 100 x 100 x 260 mm Housing M4: Ø 120 mm, length approx. 310 mm
WeightHousing (without cable):P2: approx. 0.9 kg M5: approx. 1.2 kg M4: approx. 2.8 kg
D-LX 201/721 ../M4/84Exll 2G Ex db llC T6 or T5 Gbll 2D Ex tb lllC T85 °C or T100 °C Db
D-LX 201/721 ../M4/85ExCl. l, Div. 1, Gr. A, B, C, D T6/T5Cl. ll, Div. 1, Gr. E, F, G T6/T5; Cl. Ill
D-LX 201/721 ../M5/86ExCl. l, Div. 2, Gr. A, B, C, D T6/T4Cl. ll, Div. 2, Gr. E, F, G T6/T4; Cl. lll
D-LX 201/721 ../M5/87Exll 3G Ex nA nC llC T6 or T4 Gcll 3D Ex tc lllC T85 °C or T135 °C Dc
  • Real-time analysis of flame stability
  • Mandatory
  • Recommended
  • Optional
D-LL 7xx (for D-LX 721)
D-ZS 033-I - Swivel mount for the alignment of the flame monitor
D-ZS 117-I - Thermal isolator with electrical insulation
D-ZS 133-I - Ball valve for closing the sighting tube
Power supply 24 V - Wide range power supply unit for supply of several D‑LX 201
D-NG 24/05
D-ZS 113 set - Set of orifice plates for insertion in purge air flange
D-ZS 118 - Optical adjustment aid for the alignment of the swivel mount on the sighting tube
D-ZS 140-12 - Terminal box for connecting the flame monitor
D-ZS 141-12 - Terminal box for connecting the flame monitor
D-LX 200 test set - For software supported tests of the compact flame monitors D-LX 200/720 and D-LX 201/721