Siemens QRA Series

Series Overview

The Siemens QRA Series is a family of ultraviolet (UV) flame detectors designed for reliable flame supervision in industrial combustion systems. Unlike ionization-based flame rods, QRA detectors monitor ultraviolet radiation emitted by a stable flame, enabling precise flame detection in demanding industrial environments.

The QRA Series is widely used in gas-fired and oil-fired burner systems where fast response time, high detection sensitivity, and stable operation are required.

Why UV Flame Detection?

Industrial burners produce strong ultraviolet radiation during stable combustion. The QRA Series detects this radiation spectrum to confirm flame presence. Compared with ionization probes:

• UV detection is independent of flame conductivity
• Faster flame failure response
• More suitable for high-capacity burners
• Reliable in oil and dual-fuel applications

This makes QRA detectors ideal for industrial combustion systems requiring enhanced safety supervision.

Typical Applications

QRA Series flame detectors are commonly applied in:

• Industrial gas burners
• Oil-fired burners
• Dual-fuel combustion systems
• Industrial boilers and steam generators
• Process furnaces and thermal equipment

They are typically integrated into burner management systems such as Siemens control units and compatible safety controllers.

Core Functional Characteristics

All QRA Series flame detectors share the following principles:

• Ultraviolet radiation detection (approx. 190–270 nm range)
• Rapid flame-on and flame-off response
• Designed for continuous operation
• Compatible with Siemens burner control units
• Robust industrial housing for high-temperature environments

The sensor continuously verifies flame presence and transmits a signal to the burner control unit. In case of flame failure, the system initiates a safety shutdown sequence.

Model Differentiation Within the QRA Series

Although all QRA models are UV-based detectors, variations typically include:

• Detection sensitivity level
• Mounting configuration
• Electrical connection type
• Cable length or connector design
• Environmental protection class

These differences allow proper adaptation to burner size, mounting position, and control system requirements.

Integration & System Compatibility

QRA Series flame detectors are typically integrated with:

• Siemens burner control units
• Burner management systems (BMS)
• Ignition systems and safety relays
• Industrial gas valve control assemblies

Correct electrical configuration and shielded wiring are recommended to ensure signal stability in industrial environments.

Positioning Within Industrial Combustion Safety Systems

Within a complete combustion control architecture:

1. The burner control unit manages sequencing and safety logic.
2. The QRA detector provides real-time flame supervision.
3. Together, they form a closed-loop safety monitoring system ensuring fuel supply is maintained only when stable combustion is present.