SIEMENS QRA4M.U Ultraviolet Flame Sensor Flange Mount

The SIEMENS QRA4M.U Ultraviolet Flame Sensor Flange Mount is a critical component for ensuring safe and reliable combustion control in industrial applications. This sensor boasts rapid flame detection capabilities, a robust design for harsh environments, and seamless integration with Siemens burner control systems. Its core advantages lie in its high sensitivity to UV radiation emitted by flames, its compact and durable construction, and its straightforward flange mounting for easy installation. Key technical parameters include its operating voltage range, response time, and spectral sensitivity, all designed to meet stringent industrial safety standards.

Product Specifications

| Feature               | Specification                               |

| :-------------------- | :------------------------------------------ |

| Product Type          | Ultraviolet Flame Sensor                    |

| Model                 | QRA4M.U                                     |

| Mounting Type         | Flange Mount                                |

| Flame Detection       | Ultraviolet (UV)                            |

| Spectral Sensitivity  | 185-250 nm                                  |

| Response Time         | < 1 second                                  |

| Operating Voltage     | 24 VAC / DC                                 |

| Power Consumption     | Max. 1.5 VA                                 |

| Ambient Temperature   | -40 to +60 °C (-40 to +140 °F)              |

| Protection Class      | IP65                                        |

| Connection Type       | Screw terminals                             |

| Housing Material      | Die-cast aluminum                           |

| Dimensions (approx.)  | 75 mm (diameter) x 95 mm (length)           |

| Weight (approx.)      | 0.4 kg                                      |

Core Features & Market Positioning

The SIEMENS QRA4M.U distinguishes itself through its advanced UV flame detection technology, offering superior reliability compared to less sensitive flame scanners. Its market positioning is firmly rooted in high-performance industrial combustion safety, where rapid and accurate flame failure detection is paramount. The sensor's inherent resistance to nuisance tripping from external light sources, due to its specific spectral filtering, further solidifies its advantage in challenging operational settings. This robustness is a key differentiator, making it a preferred choice for demanding applications where operational continuity and safety cannot be compromised. Its integration within the broader Siemens automation ecosystem also provides a significant advantage for users already invested in Siemens control platforms.

Key Application Scenarios

The SIEMENS QRA4M.U is ideally suited for a wide array of industrial combustion processes. Common applications include its use in industrial boilers, furnaces, thermal oxidizers, and process heaters where reliable flame monitoring is critical for operational safety and efficiency. It is frequently specified for gas and oil-fired burners, ensuring immediate detection of flame loss to prevent fuel buildup and potential explosions. Industries such as petrochemical, power generation, and general manufacturing commonly deploy this sensor to safeguard their combustion equipment. Its flange mount design facilitates integration into burner housings, making it a practical solution for retrofitting or new installations in these varied environments.

Practical System Integration Guidance

Integrating the SIEMENS QRA4M.U into an existing burner management system (BMS) is a streamlined process, primarily due to its standardized output signals and robust connection terminals. The sensor typically connects directly to the flame amplifier or burner controller, such as those within the Siemens LMV series. Wiring involves connecting the power supply (24 VAC/DC) to the appropriate terminals and establishing the signal output connection, which indicates the presence or absence of a flame. For optimal performance, ensuring the sensor's viewing angle is unobstructed and that the UV-transparent quartz window remains clean is crucial. Installation typically involves securely mounting the sensor via its flange to the burner’s combustion chamber, ensuring a tight seal to prevent air ingress.

Operation and Risk Mitigation

The QRA4M.U operates by continuously monitoring the ultraviolet radiation emitted by a flame. Upon ignition, the flame produces UV light within the sensor's detection spectrum, generating an electrical signal. If the flame extinguishes, this UV radiation ceases, and the sensor’s signal changes, alerting the burner control system to shut down fuel flow. Risk mitigation is inherent in its design; a rapid response time minimizes the period during which unburned fuel can accumulate. Essential operational practices include regular visual inspection of the quartz window for sooting or damage and periodic functional testing of the flame detection circuit as part of routine maintenance. Avoiding installation in areas with strong artificial UV light sources that could cause false positives is also a key risk mitigation strategy.

Scalability & Long-Term Value

The SIEMENS QRA4M.U offers significant long-term value through its compatibility with Siemens' comprehensive portfolio of burner control components and automation solutions. This ensures scalability; as combustion systems evolve or expand, the QRA4M.U can be seamlessly integrated into upgraded or new control architectures, including those incorporating advanced digital platforms and Industrial Internet of Things (IIoT) functionalities. Its durable construction and high reliability translate into reduced downtime and maintenance costs over its operational lifespan. Compatibility with established Siemens safety standards and control logic also simplifies system upgrades and ensures adherence to evolving regulatory requirements, providing a secure investment for industrial facilities.

Frequently Asked Questions

What is the primary function of the SIEMENS QRA4M.U flame sensor?

The QRA4M.U's main purpose is to detect the presence of a flame. It does this by sensing the ultraviolet radiation emitted by combustion. This detection is vital for safe burner operation and immediate shutdown if the flame fails.

This sensor ensures rapid flame monitoring. It plays a critical role in preventing hazardous conditions like fuel accumulation. Its design focuses on reliable and prompt flame signal generation for control systems.

Its UV detection capability makes it highly specific to actual flames. This reduces false alarms from other light sources. It is a key safety component in many industrial combustion processes.

How does the QRA4M.U detect a flame?

It uses a UV-sensitive photocell to detect specific wavelengths of UV light. This light is characteristic of burning fuel. When a flame is present, UV photons strike the cell, generating a signal.

When the flame disappears, UV emission stops, and the signal is interrupted. This change is what signals the burner control to initiate a shutdown sequence. The response time is very fast.

The sensor is designed to be sensitive to the 185-250 nm UV range. This specific band is strongly associated with flame radiation, ensuring accurate detection.

What are the typical installation considerations for the SIEMENS QRA4M.U?

Installation involves securely mounting the sensor via its flange to the burner housing. A proper seal is essential to prevent air leaks. The sensor should be positioned to have a clear view of the flame.

Ensure the viewing window remains clean and unobstructed. Avoid directing it towards strong external UV light sources. Proper wiring to the flame amplifier or burner controller is crucial.

The sensor requires a stable 24 VAC or DC power supply. Follow the wiring diagrams provided by Siemens for correct connection to the control system.

Can the QRA4M.U be used with any type of burner?

This sensor is primarily designed for gas and oil-fired burners. Its UV detection is most effective for flames producing UV radiation. It is suitable for many industrial boilers and furnaces.

It is important to check compatibility with the specific burner type and the associated control system. The QRA4M.U integrates well with Siemens LMV series controllers. Consult system documentation for specific approvals.

While versatile, it may not be ideal for all combustion types. For instance, some very low-temperature flames might not emit sufficient UV.

What is the spectral sensitivity range of the QRA4M.U?

The sensor is sensitive to ultraviolet light within a specific range. This range is from approximately 185 to 250 nanometers. This is a key characteristic for accurate flame detection.

This spectral sensitivity allows it to distinguish flame-generated UV from other light sources. It is a critical parameter for its reliable performance. It focuses on the UV output of combustion.

By focusing on this narrow UV band, the sensor minimizes false ignitions. This enhances safety and operational stability. It is engineered for this specific detection window.

How does the QRA4M.U handle environmental conditions?

The QRA4M.U is built for harsh industrial environments. It has an IP65 protection class, meaning it is dust-tight and protected against water jets. This ensures durability.

It can operate reliably across a wide temperature range, from -40 to +60 °C. This makes it suitable for both very cold and hot operational settings. Its housing is die-cast aluminum for robustness.

The robust construction protects the internal components from physical damage and environmental exposure. This ensures long-term performance and reliability.

What are the power requirements for the QRA4M.U?

The QRA4M.U operates on a low voltage power supply. It can accept either 24 VAC or 24 VDC. This flexibility aids integration into various power systems.

Its power consumption is quite low, with a maximum of 1.5 VA. This makes it an energy-efficient component in combustion control systems. It does not impose a significant load.

Ensure the power supply is stable and within the specified voltage range for optimal sensor performance. Incorrect voltage can affect its functionality.

What is the response time of the SIEMENS QRA4M.U?

The response time of the QRA4M.U is exceptionally fast. It can detect flame failure in less than one second. This rapid response is critical for safety.

This speed ensures that the control system is alerted almost instantly when a flame goes out. This minimizes the risk of dangerous situations developing. It is designed for immediate action.

A fast response time is a key feature for preventing fuel blow-back and explosions. It guarantees that fuel is shut off promptly if the flame is not established or is lost.

How does the QRA4M.U differ from infrared flame sensors?

UV sensors like the QRA4M.U detect ultraviolet radiation. Infrared sensors detect heat signatures (IR radiation). UV sensors are generally faster to respond to flame ignition.

UV sensors are also less prone to false tripping from hot surfaces or steam. IR sensors might be better suited for very smoky flames. The QRA4M.U's UV focus is its primary differentiator.

The choice depends on the specific application and combustion characteristics. The QRA4M.U is ideal when rapid UV detection is the priority.

What are common troubleshooting issues with UV flame sensors like the QRA4M.U?

A common issue is a dirty or obstructed viewing window, which can prevent flame detection. Ensure the quartz window is kept clean. Incorrect wiring is another frequent problem, leading to no signal.

False tripping can occur if the sensor is exposed to strong external UV sources. Check the installation environment for such interference. Ensure the sensor is correctly connected to the flame amplifier.

If the sensor fails to detect a flame, verify the power supply and signal connections. Always consult the SIEMENS technical documentation for specific fault codes and advanced troubleshooting.