D-LX 201/721


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


  • 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
  • D-LX 721 for application with flexible fibre optic system D-LL 703 / rigid fibre optic system D-LL 704
  • 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


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 4X
IP65, NEMA 4X (/MP3)
IP66, NEMA 4X (Ex variants)
ConnectionsD-LX 201:
Sight tube G 1¼″ or NPT 1¼″, F
Purge 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


DURAG Group products and solutions under its group such as:

  • SMITSVONK (Netherlands-based) for high-energy ignition systems, pilot burners, and ignition burners
  • Hegwein GmbH (Stuttgart-based) for (gas and oil ignition burners and gas burners
  • AP2E (France-based) for ProCeas® lasercem analyzers for gas traces in hydrocarbons via infrared spectrometry online gas analysis, with no need for sample conditioning/heating
  • Grimm Aerosol Technik for detection and analysis of aerosol particles in various fields such as environmental monitoring, occupational safety and research.
  • Mercury Analysers for measuring principle that allows separate determination of elemental and oxidized mercury
  • Dust Monitors and Analysers for measure dust concentrations in dry and wet gases continuously

Approvals And Certifications

  • TÜV certificate (Germany requirement for continuous emission monitoring systems)
  • Compliant to US EPA, QAL 1 Certification, EN 14181, EN 15267, EN 16911-2
  • FM approval (ANSI safety standards)
  • Explosion Proof Certification (IECEx, ATEX, NEPSI, TIIS)
  • CE Marking (conforms with the applicable EU directive)

The DURAG GROUP is a leading provider of intelligent solutions for combustion technology, emissions and ambient air monitoring, multi-gas analysis, tunnel sensors, and environmental and process data management, with more than 70 years of experience.

The company has around 500 specialists who offer modern technology, certified instruments, and reliable services for the individual requirements of customers worldwide.

It provides a comprehensive product portfolio for industrial combustion and flame control technology, visualization and online analysis of thermal processes, gas analysis, as well as the measurement and analysis of emissions and ambient air monitoring.


D-LX 201/721