SIEMENS QRA55.G27 Ultraviolet Flame Sensor QRA55

The SIEMENS QRA55.G27 Ultraviolet Flame Sensor stands as a critical component in industrial combustion control systems, offering robust flame detection capabilities essential for safe and efficient burner operation. This sensor distinguishes itself through its rapid response time, high sensitivity to ultraviolet radiation emitted by flames, and inherent resistance to interference from incandescent materials or electrical noise. Key technical parameters include its operating voltage range, typically 20 to 30 VDC, and its operational temperature range, often from -40 to +85 °C. The QRA55.G27 is designed for continuous operation and features a durable construction suitable for harsh industrial environments. Its primary advantage lies in its reliable detection of gas, oil, or pulverized coal flames, ensuring immediate shutdown in case of flame failure, thereby preventing dangerous situations and safeguarding equipment.

Product Specifications

| Feature                 | Specification                                   |

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

| Product Type            | Ultraviolet Flame Sensor                        |

| Model                   | QRA55.G27                                       |

| Detection Method        | Ultraviolet (UV) radiation                      |

| Operating Voltage       | 20 to 30 VDC                                    |

| Current Consumption     | Typically < 3 mA                                |

| Operating Temperature   | -40 to +85 °C                                   |

| Storage Temperature     | -40 to +85 °C                                   |

| Response Time           | < 1 second                                      |

| Humidity                | Max. 95 % relative humidity, non-condensing     |

| Ingress Protection      | IP65 (with appropriate connection)              |

| Connection Type         | Terminal block                                  |

| Housing Material        | Die-cast aluminum                               |

| Mounting                | Screw mounting                                  |

| Approvals               | CE, UL, CSA (check specific regional approvals) |

Core Features & Market Positioning

The SIEMENS QRA55.G27 is engineered with a sophisticated UV tube that specifically targets the ultraviolet wavelengths characteristic of combustion flames, minimizing false ignitions caused by other heat sources. This selective detection capability positions it as a superior choice for applications where ambient thermal interference is a concern. Its robust die-cast aluminum housing and IP65 rating ensure resilience against dust, moisture, and mechanical stress, which are common in heavy industrial settings. Unlike simpler flame detectors, the QRA55.G27 offers exceptional reliability and a long operational lifespan, contributing to reduced maintenance costs and enhanced plant uptime. Its integration into broader Siemens burner control systems further amplifies its value, providing a cohesive and intelligent combustion management solution.

Key Application Scenarios

The SIEMENS QRA55.G27 ultraviolet flame sensor finds its primary utility in a wide array of industrial combustion applications. It is extensively deployed in industrial boilers, furnaces, and incinerators to monitor the presence of a stable flame. This includes applications in power generation, chemical processing, and manufacturing plants where consistent and safe combustion is paramount. Furthermore, the QRA55.G27 is instrumental in safeguarding equipment like rotary kilns used in cement production and thermal oxidizers employed for waste treatment. Its ability to reliably detect flames in demanding environments makes it an ideal choice for systems requiring continuous, high-integrity flame supervision.

Practical System Integration Guidance

Integrating the SIEMENS QRA55.G27 into existing combustion control systems is a straightforward process. The sensor connects to the burner control unit via a two-wire connection, requiring a stable 20-30 VDC power supply. Proper wiring is crucial; the sensor's output signal is typically a current that varies with the detected UV intensity. When installing, ensure the sensor's viewing window is unobstructed and pointed directly at the flame to achieve optimal detection. For systems employing Siemens burner controllers like the LMV series, the QRA55.G27 seamlessly integrates, leveraging the controller's diagnostic capabilities to monitor sensor health and flame signal strength. Ensure all connections are made in accordance with local electrical codes and the specific wiring diagrams provided with the burner control unit.

Operation and Risk Mitigation

The QRA55.G27 operates by continuously monitoring the ultraviolet radiation emitted by a flame. When sufficient UV light is detected, it signals the presence of a flame to the connected burner control system. In the event of a flame failure, the sensor ceases to detect UV radiation, prompting the control system to initiate a safety shutdown sequence, thereby preventing the accumulation of unburned fuel and potential explosions. This rapid fail-safe mechanism is critical for risk mitigation in all combustion processes. To mitigate operational risks, regular inspection of the sensor's viewing window for cleanliness and obstructions is recommended. Any signal loss or erratic behavior should be investigated immediately by qualified personnel, referencing the burner control system's error codes for diagnosis.

Scalability & Long-Term Value

The SIEMENS QRA55.G27 is designed for long-term value and compatibility within Siemens' extensive industrial automation portfolio. Its robust construction ensures a considerable lifespan, minimizing the need for frequent replacements. When upgrading combustion control systems, the QRA55.G27 often maintains compatibility with newer Siemens burner controllers, facilitating a phased approach to modernization. For facilities embracing Industry 4.0 initiatives, integrating the QRA55.G27 into digital monitoring platforms is achievable through compatible burner management systems that can relay sensor status and flame data for advanced analytics and predictive maintenance. This ensures that investments in flame detection technology remain relevant and contribute to overall plant efficiency and safety in the long run.

Frequently Asked Questions

What is the primary function of the SIEMENS QRA55.G27?

The SIEMENS QRA55.G27's main role is to detect the presence of a flame in industrial combustion processes. It specifically senses ultraviolet radiation emitted by flames. This detection is vital for safe burner operation.

It serves as a critical safety component, triggering immediate shutdown if a flame is lost. This prevents dangerous fuel accumulation and potential explosions. Its UV sensitivity ensures reliable operation even in dusty or hot environments.

The sensor provides a signal to the burner control unit, confirming a stable flame or indicating its absence. This allows for precise control over the combustion process, optimizing efficiency and preventing hazardous conditions.

What type of flame does the SIEMENS QRA55.G27 detect?

This sensor is designed to detect flames that emit ultraviolet (UV) radiation. This includes flames from natural gas, propane, oil, and pulverized coal. It effectively senses the characteristic UV spectrum of combustion.

It is particularly well-suited for applications where other heat sources might emit visible or infrared light. The UV detection capability minimizes false alarms from non-flame sources. This ensures a highly reliable flame signal.

The QRA55.G27's sensitivity is tuned to the specific UV wavelengths produced by burning fuel. This allows for precise and dependable flame monitoring in diverse industrial settings.

How is the SIEMENS QRA55.G27 installed?

Installation involves mounting the sensor securely in a location with a clear view of the flame. It connects to the burner control unit using a two-wire system. Power is supplied via a 20-30 VDC source.

Ensure the sensor's viewing window is clean and unobstructed to guarantee optimal detection performance. Adhere to all local electrical codes and wiring diagrams for safe and correct setup.

The sensor typically screws into a mounting bracket or flange, allowing for precise alignment with the combustion zone. Proper sealing is important to maintain its IP65 rating.

What are the power requirements for the SIEMENS QRA55.G27?

The SIEMENS QRA55.G27 operates on a DC power supply ranging from 20 to 30 volts. It requires a stable voltage within this specified range for reliable function. Low power consumption is a key design feature.

The sensor draws a minimal current, typically less than 3 mA, which allows for integration into systems with limited power budgets. This efficiency contributes to its suitability for various industrial applications.

Proper power connection is essential for accurate flame signal transmission. Fluctuations outside the specified voltage range may lead to incorrect readings or sensor malfunction.

What is the operating temperature range of this flame sensor?

The QRA55.G27 can operate reliably within a wide temperature range, typically from -40 °C to +85 °C. This broad operational window makes it suitable for extreme industrial environments.

This extensive temperature tolerance ensures consistent performance regardless of ambient conditions. It is designed to withstand both very cold and very hot operational settings.

When specifying for an application, verify the exact temperature limits in the product datasheet. However, its standard rating provides excellent flexibility for most industrial uses.

Can the SIEMENS QRA55.G27 be used in dusty environments?

Yes, the SIEMENS QRA55.G27 is designed for use in demanding industrial settings, including dusty environments. Its robust construction and sealing contribute to its durability.

With an appropriate connection, the sensor achieves an IP65 ingress protection rating. This means it is protected against dust ingress and low-pressure water jets.

Regular cleaning of the sensor's viewing window may still be necessary to maintain optimal performance in extremely dusty conditions. This ensures the UV sensor can clearly "see" the flame.

What is the response time of the SIEMENS QRA55.G27?

The SIEMENS QRA55.G27 offers a rapid response time, typically less than one second. This quick detection capability is crucial for safety interlocks.

When a flame fails, the sensor detects the absence of UV radiation almost instantly. This allows the burner control system to react swiftly.

A fast response time is essential for preventing the buildup of unburned fuel in the combustion chamber, significantly enhancing operational safety.

How does the SIEMENS QRA55.G27 differentiate from other flame sensors?

Its primary differentiation lies in its high sensitivity to specific ultraviolet wavelengths, minimizing false detections. It uses a specialized UV tube for selective flame sensing.

The QRA55.G27's robust construction and IP65 rating ensure exceptional durability in harsh industrial conditions. It is built for long-term reliability and minimal maintenance.

It offers seamless integration with Siemens burner control systems, providing a comprehensive and intelligent combustion management solution. This synergy enhances overall system performance and diagnostics.

What maintenance is required for the SIEMENS QRA55.G27?

Routine maintenance primarily involves visually inspecting the sensor's viewing window. This ensures it is free from soot, dirt, or other obstructions that could impair flame detection.

Periodic checks of electrical connections for tightness and corrosion are advisable to ensure uninterrupted signal transmission. Refer to the burner control system's diagnostics for any sensor status alerts.

While the sensor itself is highly reliable and designed for long life, adherence to recommended inspection schedules will maximize its operational lifespan and ensure continuous safety.

Is the SIEMENS QRA55.G27 compatible with older burner control systems?

Compatibility depends on the specific older system's capabilities and input requirements. The QRA55.G27 is designed for modern burner control units.

It utilizes a standard two-wire UV sensing principle, which may be adaptable to some older systems if they support such inputs and the required voltage. However, optimal performance is achieved with compatible Siemens controllers.

For older systems, consulting the original equipment manufacturer or Siemens technical support is recommended to confirm interoperability and any necessary interface modifications.