Introduction
Floating roofs have been essential in the oil industry since their creation in the 1920s. Initially designed to reduce product losses due to evaporation, they have evolved to incorporate high-strength materials, aerodynamic designs, and advanced sealing systems that enhance safety and operational efficiency.
In recent decades, increasing regulatory and environmental pressure has driven innovations such as integrating IoT sensors and lighter, more durable materials, to monitor floating roof in a storage tank.
Floating roofs play a crucial role in reducing volatile organic compound (VOC) emissions by limiting product evaporation and minimizing air exposure. Additionally, they improve operational safety by preventing flammable vapor buildup and contributing to corrosion prevention, thus protecting the tank’s internal structure integrity from adverse weather conditions.
RCM (Reliability-Centered Maintenance) is a systematic approach that identifies and manages failure modes in critical equipment. By leveraging predictive maintenance, potential issues in floating roofs can be anticipated, optimizing operations and reducing environmental risks. This approach extends the lifespan of assets, lowers operational costs, and ensures compliance with safety and sustainability standards.
Basic Principles of floating roofs
What are floating roofs?
Floating roofs are internal structures that move along the surface of the stored liquid in a tank. Their design eliminates the free space where flammable vapors could accumulate, thereby reducing evaporation losses and emissions.
Types of Floating roofs
- External:
- Designed for open tanks exposed to weather conditions.
- Ideal for environments requiring basic emissions control..
- Internal:
- Located inside closed tanks.
- Provide greater protection against weather and superior emission containment efficiency.
Images courtesy of Slideshare LuLopez7 Tanks
Advantages of floating roofs
1. Reduced Product Evaporation:
- Technical Impact: Floating roofs limit contact between stored liquid and air, significantly minimizing evaporation losses.
- Economic Benefit: Lower evaporation translates into less hydrocarbon loss, equating to higher retained product revenues.
- Industrial Applications: Especially valuable for products like gasoline, light crude, and solvents.
2. Improved Hydrocarbon Emission Containment::
- Regulatory Compliance: Facilitates adherence to strict environmental standards, such as those set by the EPA in the U.S. and the European Industrial Emissions Directive.
- Environmental Impact Reduction: Decreases VOC emissions, mitigating their contribution to photochemical smog and climate change.
3. Enhanced Operational Safety:
- Prevents explosions by eliminating flammable vapor accumulation.
- Protects tank walls from corrosion caused by constant vapor contact.
- Protects the structural integrity of the tank by preventing pressure bubble formation and maintaining consistent performance.
4. Adaptability in Different Environments:
- Weather Conditions: Internal roofs offer additional protection in extreme climates, while external roofs suit regions with minimal rain or snow.
- Specific Applications: Suitable for light and heavy hydrocarbons, with customizations for chemical and water storage tanks.
5. Cost and maintenance optimization:
- Preventive Maintenance: Their design facilitates periodic inspections and repairs without halting operations. Predictive maintenance strategies help prioritize necessary interventions, avoiding costly and unnecessary interruptions.
- Energy Efficiency: The integration of IoT sensors reduces the need for forced ventilation or secondary containment systems by enabling precise monitoring, thus lowering associated energy costs.
RCM applied to floating roofs
RCM is a methodology focused on optimizing equipment reliability by identifying critical failure modes and applying specific strategies to prevent or mitigate them. In the context of floating roofs, RCM ensures their continuous and safe performance by prioritizing resources and efforts in high-impact areas.
For tanks with floating roofs, RCM combines failure analysis techniques with IoT sensors and other advanced monitoring tools to ensure operations remain safe and sustainable. This approach centers on maximizing asset availability while incorporating corrosion prevention strategies to minimize the risks of emissions and structural integrity damage.
Key RCM strategies for floating roofs
1. Evaluation of Common Failure Modes:
- Seal Failures: Identifying leaks in primary and secondary seals.
- Structural Degradation: Damage to supports caused by corrosion or mechanical fatigue.
- Wear on Moving Components: Evaluating guides and lift systems that may fail due to prolonged use.
2. Risk Analysis and Prioritized Maintenance:
- Use of FMEA (Failure Mode and Effects Analysis): To identify risks and prioritize inspections.
- Implementation of Maintenance Schedules: Based on actual operating conditions.
3. Integration of Continuous Monitoring Systems:
- Pressure and Level Sensors: Real-time detection of irregularities in roof position.
- Non-Destructive Testing (NDT): Ultrasonic inspections to detect corrosion or damage in critical components. These data feed real-time analysis systems supporting predictive maintenance and ensuring floating roof reliability.
- Predictive Software: Real-time data analysis to predict failures before they occur.
4. Long-Term Resource Optimization:
- Reduction of Unscheduled Downtime: Through predictive strategies.
- Extension of Roof Lifespan: Through effective and tailored maintenance. Predictive maintenance plays a vital role in RCM, focusing on proactive interventions based on real data analysis.
Failure modes in floating roofs and common causes
Corrosion and factors contributing to it
Corrosion is one of the most frequent problems in floating roofs, especially in aggressive environments where humidity and chemicals in the stored liquid accelerate oxidation processes.
- High Humidity: Water accumulation in joints, supports, or guides creates ideal conditions for corrosion.
- Chemical Exposure: Volatile products like light hydrocarbons can react with roof materials, weakening them over time.
- Poor Coating: Lack of protective coatings undermines corrosion prevention efforts and intensifies susceptibility to damage.
Structural damage and most common causes
Structural integrity can be compromised due to mechanical interactions between the floating roof, the stored liquid, and external loads such as wind or pressure.
- Overload Impacts: Excess product stored or debris accumulation on the roof.
- Extreme Movements: Rapid changes in liquid levels or turbulence inside the tank can be tracked using IoT sensors to prevent wear on guides and structural supports.
- Material Fatigue: Prolonged operational cycles without proper maintenance.
Seal and Joint Failures
Seals and joints are critical components to maintaining tightness, ensuring structural integrity, and limiting emissions.
1. Specific Damage Mechanisms:
- Wear: Constant roof movement and exposure to abrasive particles deteriorate the seals.
- Crushing or Deformation: Occurs when seals are subjected to excessive pressure.
- Chemical Incompatibility: Seals made with unsuitable materials for the stored products.
2. Leaks and Tightness Problems
- Impact on Efficiency and Safety:
- Economic losses due to product evaporation.
- Increased VOC emissions, affecting compliance with environmental regulations.
- Higher risk of explosion due to the accumulation of flammable vapors in confined spaces.
Inspection and monitoring of floating roofs
Recommended inspection techniques
Periodic inspections in storage tanks are essential to preserve the structural integrity of floating roofs and identify problems before they escalate into critical failures.
- Detecting corrosion, deformations, or damage in visible components.
- Observing the condition of primary and secondary seals.
2. Pruebas no destructivas (NDT):
- Ultrasound: Useful for measuring metal thickness, detecting internal corrosion, and enhancing corrosion prevention through early detection.
- Radiography: Identifying internal cracks or discontinuities in the material.
- Thermography: Detecting temperature variations that may indicate leaks or active corrosion points.
3. Real-Time Monitoring
The integration of advanced technologies allows for the detection of anomalies in real-time, optimizing resources and improving safety.
- IoT sensors are used to monitor critical parameters such as pressure, liquid level, roof position, and vibrations, enabling real-time data collection and analysis..
- Allow early detection of leaks or structural failures.
- Analyze real-time data to predict failures and schedule preventive maintenance.
- Automated alerts enable quick decision-making.
Floating roof seals: Key Components for efficiency and safety
Purpose of floating roof Seals
- Emission Reduction: Seals minimize the release of VOCs into the environment, contributing to operational sustainability.
- Contamination Prevention: Prevent water, dirt, or other contaminants from entering the tank, preserving the quality of the stored product.
Types of seals and their characteristics
- Primary Seals:
- Provide the initial level of containment to prevent vapor leaks.
- Made from foam or flexible elastomers to adapt to roof movement.
- Secondary seals:
- Act as an additional barrier over the primary seal.
- Increase tightness and further reduce emissions.
- Made of materials resistant to abrasion and chemicals.
Common damage mechanisms in seals
- Mechanical wear: Caused by constant contact with the tank walls.
- Corrosion: Accelerated deterioration due to exposure to volatile products or corrosive atmospheres.
- Extreme temperatures: Accelerated deterioration due to exposure to volatile products or corrosive atmospheres.
- Physical Impacts: Damage during maintenance operations or sudden movements of the floating roof.
Seal inspection and maintenance
- Visual methods: Inspect for cracks, deformations, or visible signs of wear.
- Non-Destructive Testing (NDT): Utilize ultrasound or thermal imaging to evaluate seals that are not directly visible.
- Scheduled replacements: Plan seal replacement according to the manufacturer’s recommended lifecycle.
Noteworthy seal manufacturers
- HMT is a leader in designing and manufacturing seals for floating roofs, offering advanced solutions that ensure emission reduction, efficient vapor containment, and protection of tank contents. Their products include primary seals like the Scissor Shoe and SealMaster, as well as secondary seals like the Flex-A-Seal and Seal King®, which maximize emission reduction and hydrocarbon containment. HMT also incorporates sustainability-enhancing technologies, such as emission reduction systems and continuous monitoring accessories, meeting the industry’s highest standards.
- Mesa ETP manufactures a wide variety of seals for floating roofs, including primary and secondary seals with advanced designs that comply with EPA regulations and international standards. Their product line includes mechanical, foam-filled, and liquid-mounted seals, along with customizable options for reduced emissions and resistance to extreme conditions.
- Storage Tech is a manufacturer of advanced storage technology, specializing in external floating roofs and sealing systems designed to maximize operational efficiency and safety. Their innovations in floating roof seals, such as the Pantagraph type seal and the Scissor type seal, stand out for their robust and adaptable design. These Storage Tech solutions not only meet strict environmental standards but also adapt to the specific needs of various industries. Their commitment to innovation and sustainability positions Storage Tech as a benchmark in the design of advanced sealing systems and floating roofs.
Watch the following video to see how their solutions redefine the quality standard in industrial storage, courtesy of Storagetech.
External Floating Roof Storage Tank Mechanical Seals.
Economic and environmental benefits of the RCM approach
The Reliability-Centered Maintenance (RCM) approach offers substantial benefits from both operational and environmental perspectives.
Operational cost optimization through predictive maintenance
- Reduced Repair Costs: By identifying potential failures before they occur, predictive maintenance prevents unplanned shutdowns and costly major repairs.
- Improved Resource Efficiency: Scheduling inspections and maintenance based on real-time data minimizes unnecessary labor and material use.
- Extended Asset Life: Continuous monitoring of floating roofs and their components maximizes durability, delaying the need for replacements.
Environmental risk reduction and regulatory compliance
- Emission control: Real-time monitoring quickly detects hydrocarbon leaks, minimizing environmental impact and ensuring compliance with regulations like the EPA in the United States and European standards.
- Disaster prevention: Early identification of structural risks mitigates critical incidents such as spills or explosions.
- Sustainable operations: Adopting technologies aligned with international standards reinforces corporate environmental responsibility.
Positive impact on the longevity of floating roofs and components
- Structural preservation: Regular inspections and proactive maintenance support corrosion prevention and reduce exposure to mechanical wear.
- Seal and joint conservation: RCM ensures these critical components are replaced before failure, guaranteeing continuous performance.
- Reduced replacement costs: Extending the service life of floating roofs lowers investment in new equipment.
Case studies and best practices
Case 1: Phillips 66 – Emission reduction and maintenance optimization
Phillips 66 implemented RCM principles in its refineries to reduce emissions and optimize operations in storage tanks. Enhancing floating roof integrity achieved a significant 17% reduction in Scope 1 and 2 emissions related to manufacturing. Efforts included advanced methane management strategies and integrating monitoring technologies to detect and mitigate leaks. Additionally, the company collaborated with partners to adopt low-carbon technologies, such as green hydrogen, to replace fuel gas, further reducing environmental impact.
Case 2: Petronas – Tank asset management program
Petronas applied RCM techniques to improve the performance and reliability of floating roofs in storage tanks. By focusing on predictive maintenance and real-time monitoring, they significantly reduced unplanned downtime and extended tank component lifespans. This program included detailed failure mode analysis of floating roof seals and structural components, improving safety and operational efficiency. The success highlights RCM’s critical role in large-scale oil and gas operations.
Conclusions
Reliability Centered Management (RCM) is critical to optimize efficiency, safety and sustainability in floating storage tank roofs. By integrating advanced technologies such as IoT sensors, continuous monitoring and state-of-the-art seals, it transforms traditional management into a proactive model that prevents failures and minimizes risks.
RCM contributes to the control of emissions and the prevention of critical incidents, aligning with global environmental sustainability goals. The optimization of resources and the extension of the useful life of components guarantee a significant economic return, positioning companies that adopt these strategies at the forefront of the industry, ready to face the regulatory and environmental challenges of the future.
References
- API Standard 650: “Welded Tanks for Oil Storage” – Guidelines on the design, construction and inspection of tanks.
- OSHA Regulations – “Oil Storage Tank Safety” and “Hydraulic Fracturing Site Safety”
- IEC 60812:2006 – “Analysis techniques for system reliability” on the analysis of failure modes in industrial assets.
- IAM (Institute of Asset Management) – RCM Manual and best practices in critical asset maintenance.
- SMRP – Guidelines for the application of RCM in the oil and gas industry
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