Siemens Ultraviolet flame detector QRA2(1)

This Siemens ultraviolet flame detector, catalogue SKU QRA2(1) (also article 884.208.005), belongs to the category of flame sensors. It uses a UV cell to sense ultraviolet radiation from combustion, with a quartz lens focusing the radiation onto the cell. The detector is designed for gas, liquid fuel, and dual-fuel burners and is compatible with Siemens burner controls. It provides continuous flame presence monitoring and signals the control system when the flame is lost.

When selecting a replacement of this type, compare the detection principle (ultraviolet), spectral response range, response time, cable length and connector type, and the mounting sleeve, as these must match the existing installation. Verify the mounting arrangement and cable termination against the original before ordering. The sensor must have a direct line of sight to the flame; position it accordingly in the mounting sleeve. No compatibility with specific burner models is implied beyond the class of oil and industrial burners that require UV detection.

Typical failure modes for this class of sensor are a contaminated or fogged quartz window, an aged UV cell with weakened signal output, and a broken or cracked sheath. When the sensor does not confirm flame, the burner control initiates a lockout during the safety check. Inspect the quartz window for contamination or fogging, check the cable and sheath for damage, and validate the sensor's output against the expected UV response.