Technical Blog
The Importance of Flare Studies: Addressing Key Challenges & Optimizing Safety
Flare systems play a vital role in industrial safety, particularly in the oil, gas, and chemical sectors, not only by handling relief fluids from overpressure events but also by managing excess gas during process upsets, depressurizing events, and specific modes of operation such as startup and shutdown, among others. Designed to safely combust excess gases during potentially hazardous events, flare systems protect equipment and personnel from potentially catastrophic failures. However, these systems can face significant challenges that, if left unaddressed, may compromise safety, compliance, and operational efficiency.
In this post, we explore the importance maintaining an up-to-date flare system design basis, the top challenges in the industry, highlight a real-world example from a recent flare study, and provide several points to consider when optimizing flare system design and performance.
The Importance of Flare Studies:
Although flare systems are critical for protecting facilities from potentially hazardous events, without regular evaluation (which should ideally occur during the Management of Change process when modifications are made to the flare system), they may fail to meet essential safety and regulatory standards. Flare studies provide detailed evaluations of a flare system’s capacity and integrity, ensuring it can handle both routine and emergency situations.
Key reasons for conducting flare studies include:
- Ensuring Safety: Flare studies help identify and address potential risks such as high backpressure, poor system design (including inadequate flare system capacity), and improper routing. These studies ensure facilities are aware of any issues that could compromise safety and efficiency.
- Regulatory Compliance:Compliance with industry standards and environmental regulations is a major driver for flare studies. These studies help facilities meet safety requirements while ensuring proper design and capacity.
- System Optimization: Flare studies also present opportunities to optimize system performance, reduce emissions, and implement cost-effective solutions, such as flare gas recovery systems.
Key Challenges in Flare Systems
Despite their importance, flare systems face significant challenges that can compromise their effectiveness if not addressed. The three common challenges are:
- Backpressure: Properly addressing backpressure in a flare system is critical to ensure that relief devices function effectively during an emergency. Excessive backpressure can result from inadequate system design, such as undersized headers, and may cause relief valves to malfunction. This can lead to mechanical damage or failure to relieve pressure, posing serious safety risks.
- Acoustic and Flow-Induced Vibrations (AIV/FIV): High-velocity gas flows can cause acoustic and flow-induced vibrations (AIV/FIV) in the flare system piping. These vibrations, if left unchecked, lead to fatigue and potential failure of the piping system over time. AIV/FIV is a particular concern in segments with high Mach numbers, which indicate excessive velocities and pressures.
- Low-Temperature Stress: During relief events, the temperature within flare headers can drop significantly, sometimes below the minimum design metal temperature (MDMT) of materials like carbon steel. Operating under these low-temperature conditions without the proper materials can lead to brittle fractures, compromising the system’s structural integrity.
Real-World Example: Gas Plant Flare Study
In a recent flare study, we identified several key issues in a gas plant’s flare system related to backpressure, vibrations, and low temperatures. Specifically:
- Backpressure Issues: Backpressures on multiple relief valves were found to exceed allowable backpressure limits during various flaring scenarios. In some cases, the backpressure exceeded the valve’s setpoint, potentially resulting in improper operation, which could lead to mechanical damage during a relief event.
- Vibration Concerns: Several piping segments in the flare system showed Mach numbers above generally accepted values, indicating a high risk of AIV and FIV. Without intervention, these vibrations could cause long-term fatigue damage to the piping system.
- Low-Temperature Exposures: Several flare header segments were shown to experience temperatures below the Minimum Design Metal Temperature (MDMT) of carbon steel, raising concerns about the material’s integrity during low-temperature relief events.

Solutions to Flare System Challenges
- Optimizing Backpressure Control: To address backpressure issues, it’s essential to reassess relief valve sizing and configuration. This can involve switching to different types of relief valves, such as balanced bellows or pilot-operated valves, which can handle higher back pressures. In some cases, modifying the flare header’s design to reduce backpressure through strategic piping adjustments may be necessary. Preventing excessive backpressure through proper piping and valve design ensures that relief devices function reliably during emergency scenarios.
- Reducing Vibrations Through Piping Design and Stress Analysis: Acoustic and flow-induced vibrations can be mitigated by redesigning piping systems to reduce velocities and Mach numbers, which are key contributors to AIV/FIV. Performing stress analysis on the flare header can help identify at-risk segments and inform targeted reinforcement. Additionally, using thicker piping and better supports can reduce vibrations, prolonging the system’s life and maintaining its integrity.
- Upgrading Materials for Low-Temperature Scenarios: When flare systems are exposed to temperatures below the MDMT, upgrading to materials with better low-temperature tolerance is crucial. For example, replacing carbon steel with low-temperature alloys like stainless steel can prevent brittle fractures. Additionally, evaluating the thermal profile of the flare system and ensuring adequate heat tracing or insulation in vulnerable segments can further protect the system from low-temperature stress.
Flare systems are vital components of industrial safety, but they come with challenges—particularly with backpressure, mitigating vibrations, and ensuring material integrity at low temperatures. By maintaining up-to-date process safety information, including a comprehensive flare design basis, facilities can address these challenges and ensure that flare systems remain safe, compliant, and efficient. Optimizing relief valve configurations, reinforcing piping against vibrations, and upgrading materials to withstand low temperatures are critical steps toward maintaining the long-term reliability of flare systems.
Investing in maintaining up-to-date process safety information and adopting proactive solutions not only ensures compliance with safety regulations but also optimizes overall system performance, helping facilities reduce risks, improve safety, and enhance operational reliability.
Meet the Author
Timothy Threatt, P.E. – Technical Manager – Pressure Relief Systems
Timothy is an experienced chemical engineer with a background in pressure relief analysis, process simulation, and process safety management. His pressure relief experience includes identification of overpressure scenarios, pressure relief device sizing, hydraulic calculations, and identification of deficiencies.
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