First impressions can be deceiving. A meticulously designed compressed air system may appear flawless on paper, boasting powerful compressors, advanced dryers, and strategic storage solutions. However, delving deeper often reveals hidden challenges and opportunities for enhancement. In this blog post, we embark on a journey through a comprehensive case study, dissecting a seemingly robust compressed air system to uncover underlying issues, explore potential improvements, and emphasize the critical role of root cause analysis in optimizing system performance and reliability.
The system in question boasts an impressive array of components:
- Four large, fixed-speed 300 hp oil-flooded rotary screw compressors: With one serving as a backup, these compressors ensure a steady supply of compressed air.
- Operating pressure: Set at 150 psig to ensure optimal performance at the point of use.
- Desiccant dryers: Two large, heated blower purge desiccant dryers are employed to reduce compressed air consumption compared to standard heatless cold regenerative desiccant dryers.
- Storage receivers: Four 3000-gallon storage receivers, comprising two wet and two dry, are strategically placed to maintain adequate air supply and support station controls.
- Piping: Utilizing 6” aluminum piping as the main header in both the compressor room and the new facility.
- Master controller: The system includes a master controller to regulate pressure and optimize efficiency. This controller also helps balance operating hours for the compressors and streams and stores valuable data for future analysis.
- Component breakdown: The P&I diagram provides clarity on the component configuration, ensuring proper installation and component placement.
While this system appears robust on paper, there's always room for improvement, as we'll explore further.
Accompanying the detailed specifications is a Process and Instrumentation (P&I) diagram, offering a visual representation of the system's layout and components.
Even with an exemplary system in place, there are opportunities for enhancement. Potential areas for improvement may include:
- Energy Efficiency: Assessing the energy consumption of the compressors and exploring options for efficiency improvements as well as energy recovery systems.
- Maintenance Optimization: Implementing predictive maintenance techniques and leveraging data from the master controller for proactive servicing.
- Air Quality Management: Fine-tuning the dryer system to minimize energy consumption while maintaining optimal air quality.
- System Integration: Exploring opportunities for automation and integration with other plant systems for seamless operation.
Root Cause
As with any case study, there's often more to the story than meets the eye. Following the installation and full commissioning of the compressed air system and plant operation, an unexpected issue arose: broken pipe hangers causing a safety concern for all parties. At first glance, it might seem straightforward to attribute the problem to insufficiently designed hangers. While this possible cause among many other possibilities were fully investigated, upon closer inspection, the true cause became apparent.
Further investigation revealed that the point-of-use piping was inadequately supported. While there was a pipe hanger at the top of the point of use drops from the ceiling, there was no support for the pipe at the point of use, leading to pipe movement. During operation, high demand events at the point-of-use caused the point-of-use pipe to sway, setting off a chain reaction that fatigued the pipe hangers further upstream.</</body>
Cascading Effects
The movement of the piping not only led to broken hangers but also resulted in fluctuating pressure within the compressor room. Despite the master controller's efforts to maintain pressure within a preset range, the system occasionally fell below the preset control range due to the pulsations in demand, as evidenced by the fluctuating pressure graph.
Analyzing Compressor Operations
Delving deeper into the data provided by the master controller revealed insights into compressor operations. Despite the design intending one compressor to serve as a backup, all compressors were frequently loading and unloading, indicating inefficiencies in the system's response to demand fluctuations.
Connecting the Dots
The journey from broken pipe hangers to pressure fluctuations to over cycling compressors underscores the interconnected nature of the system and highlights the importance of addressing root causes rather than symptoms.
Implementing Solutions
To address the issues identified, several solutions were required in conjunction to ensure safe and efficient operation:
- Rigidly Mount Piping: Ensure proper support and minimize vibration by rigidly mounting the piping and utilizing flexible connections where necessary.
- Buffer Tanks: Introduce buffer tanks at the point-of-use to handle high-demand events, coupled with flexible hoses to accommodate fluctuations and minimize vibration transfer from the point of origin.
- Sizing Considerations: Select buffer tank sizes based on event duration, recovery time, and acceptable pressure differentials. Consider metering this storage to further minimize station fluctuations.
- Adaptation and Best Practices: Emphasize the importance of completing a root cause analysis, especially when considering safety, continuously monitoring system performance, adapting to changes, and implementing best practices, including considerations for heating, ventilation, condensate management, and efficient piping and storage solutions.
The case study serves as a reminder that root cause analysis of compressed air systems requires attention to detail beyond the compressor room. By analyzing data, evaluating the entire compressed air system, and implementing targeted solutions, industrial operations can optimize their compressed air systems for enhanced performance and reliability. As systems evolve, it's crucial to remain vigilant, adapt, and uphold best practices to ensure ongoing success.
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