Siemens Flame Sensor QRA 50M

ENERGY COMBUSTION,Ahmedabad importer and suppliers of siemens make flame sensor. The Siemens QRA50M is a high-durability, self-checking ultraviolet (UV) flame detector designed for continuous operation. It is an older, specialized model that is often considered "obsolete" or legacy in many regions, but it remains a critical component in industrial settings where it is paired with the LFE50 UV flame safeguard system. Full Technical Specifications Feature Specification Detection Type Ultraviolet (UV) Spectral Sensitivity 190 to 240 nm Operating Voltage AC 220–240 V (for the shutter motor) Operating Mode Continuous Operation (Self-Checking) Protection Rating IP54 (Dust and splash-proof) Sensitivity Normal Internal UV Cell Siemens Part No. 4 502 4268 0 Self-Check Mechanism Rotating shutter (approx. 3 interruptions per second) Operating Temperature -20 °C to +60 °C Weight Approx. 0.75 kg Connection Flange for viewing tube mounting (1" internal thread) Key Features & Design Shutter Mechanism: The QRA50M contains a rotating cylindrical shutter driven by a synchronous motor. This shutter interrupts the UV radiation reaching the cell 3 times every second. This constant "on-off" cycle allows the control unit (LFE50) to verify that the UV cell has not failed in a "permanently on" state (simulated flame), which is a vital safety requirement for burners running longer than 24 hours. Cooling Air Connection: The mounting flange includes a 3/8" tapping on the side. This allows for the connection of cooling air, which is necessary if the detector is mounted in high-heat areas or if there is a risk of soot buildup on the lens. Rugged Housing: The head is made of die-cast alloy and features a quartz-glass lens to seal the unit from the combustion chamber pressure (up to 500 mbar). Comparison: QRA50M vs. QRA51M You will often see these two listed together. The primary difference is the Protection Rating: QRA50M: Rated IP54 (better protection against water splashes and dust). QRA51M: Rated IP40 (more open design, typically for cleaner environments). Installation & Wiring The QRA50M typically uses a 5-core cable if the distance is under 30 meters. For longer distances (up to 200m), a specific wiring configuration using a 2-core and a 3-core cable is recommended to reduce electrical interference. Maintenance Tip: The internal UV cell has an expected life of approximately 10,000 hours. If the burner control unit (LFE50) triggers a lockout during the startup check, it is often due to the UV cell losing its "quenching" ability, meaning it needs to be replaced.