IMPROVING COMPRESSED AIR SYSTEM EFFICIENCY AND RELIABILITY WITH SIX SIGMA DMAIC
The six-sigma methodology has been adapted by industry as a business management tool to improve operational capabilities and reduce defects in any process (Mittal et al., 2023). This study aims to present a case study on the implementation of the Six Sigma DMAIC methodology, targeting a 50% reduction in the usage of rental and portable air compressors at a facility. Approximately $824,000.00 per year was spent on compressed air and a good portion of that was wasted on running it inefficiently. Also, the air quality (i.e., oil and water) and equipment reliability impacts the operation of the facility. There was $274,000 spent on portable and rental compressors to keep the plant operational. After implementing some of the Six-Sigma project findings the facility was able to assume an approximate 50% decrease in portable and rental compressor usage, which would yield up to $164,000 per year in cost savings.
List Pull Quote 1: Measurement is the first step that leads to control and eventually to improvement. If you can't measure something, you can't understand it. If you can't understand it, you can't control it. If you can't control it, you can't improve it.
- H. James Harrington, author & management mentor
List Pull Quote 2: If you can't describe what you are doing as a process, you don't know what you're doing.
- W. Edwards Deming, American engineer, statistician, professor, author, lecturer, and management consultant
Industrial air compressors are an essential part of the manufacturing environment. Often called “the fourth utility,” compressed air acts as a reliable, quick, and safe energy source for various industrial applications (Taylor, 2023, para. 1). Compressed air is indispensable for industrial processes, with approximately 10% of industrial electricity consumption dedicated to generating compressed air (Taylor, 2025). A diverse range of industries rely on compressed air systems. Some of these industries are General Manufacturing, Automotive Manufacturing, Food and Beverage, Plastics, Pharmaceutical, Agriculture & Farming, Auto Repair & Body Shops, Construction, Energy Sector, and specifically for this case study, Chemical Manufacturing.
Six Sigma as defined in “The Six Sigma Way” is a comprehensive and flexible system for achieving, sustaining, and maximizing business success. Six Sigma is uniquely driven by close understanding of customer needs, disciplined used of facts, data, and statistical analysis, and diligent attention to managing, improving, and reinventing business processes (Pande et al., 2000). Six Sigma focuses on reducing process variation to reduce errors and defects. One of the primary methodologies of Six Sigma is DMAIC, which is a scientific, fact based, systematic, and closed-loop process for continued improvement (Schwalbe, 2019). DMAIC stands for Define, Measure, Analyze, Improve, and Control. Utilizing DMAIC, the facility set out to reduce portable and rental compressor usage by 50%, aiming for up to $137,000 in annual cost savings.
CASE STUDY/APPLICATION OF DMAIC ON COMPRESSED AIR SYSTEMS
The compressed air system frequently relied on rental portable air compressors to meet the air demand that the installed permanent system could not supply. These rental air compressors were viewed as an unnecessary and avoidable expense for the facility. To address this issue, upper management authorized a Six Sigma project, forming a team of six to eight members that included a newly trained Green Belt, the Operations Manager serving as the project champion, one representative from each operational unit utilizing the portable air compressors, and one Mechanical and Instrument & Electrical Maintenance Engineer. As mentioned previously, the project followed the DMAIC methodology, structured into the following five basic phases:
Define Phase: Define the problem and why it needs to be solved.
Measure Phase: Measure the current performance of the process.
Analyze Phase: Analyze the current situation and opportunities to reduce waste and variation.
Improve Phase: Identifying, implementing, and validating process changes to improve the process.
Control Phase: Control the process with standardized work for sustained results.
DEFINE PHASE
During the Define phase, the project is initiated, the team is formed, and clear targets are established. This phase consists of three essential steps: developing and approving a project charter, which defines the problem and objectives; identifying customer requirements to ensure alignment with their needs; and documenting the process to establish a clear baseline for improvement.
Developing and approving the Project Charter: The first step in the project was to agree on exactly what the project was expected to accomplish, such as problem and objective, and to document this in a Project Charter.
Problem: The facility spent approximately $824,000 per year on compressed air, with a significant amount wasted due to inefficient operations. Furthermore, air quality issues, such as oil and water contamination, along with equipment reliability, affected the facility’s overall performance.
Objective: The project aims to reduce the facility’s reliance on portable and rental compressors by 50%, achieving an estimated cost savings of up to $137,000 per year.
Identify customer requirements: Every process exists to serve a customer. Thus, it is vitally important to begin a project by defining value from the customer’s point of view and understanding their requirements. To achieve this, the customer requirements were identified based on the Voice of the Customer as detailed in Table 1 and Critical Customer Requirements shown in Table 2.
Documenting the process: To establish process boundaries, identify input and output variables, and become familiar with the process, the team developed the Suppliers, Inputs, Process, Outputs, and Customers (SIPOC) diagram shown in Figure 1.
Citation: Performance Improvement Journal 63, 5; 10.56811/PIJ-25-0015
MEASURE PHASE
The measure phase involves identifying waste and variation by mapping and measuring the process. Building on our Six Sigma Lean training, the project team further refined these steps into five detailed actions: clearly and accurately describing the process, developing a measurement strategy, collecting data, graphically analyzing the process, and identifying key focus areas.
Describe the process clearly and accurately: To do any work on improving processes, the team first had to create an accurate description of how the process worked. Using the SIPOC previously created in the Define Phase and expert judgement and knowledge of the current plant system they created the Plant Air Flow Chart presented in Figure 2.
Develop a measurement strategy: After completing the basic process mapping, the team created the Issue Diagram show in Figure 3 to determine what should be measured to fully describe the process and identify improvement opportunities. Following the creation of both the Flow Chart and Issue Diagram, the team quickly recognized several challenges. While some data could be collected, they lacked an accurate measurement system for determining airflow to each unit. Additionally, they were unable to track when and why rental compressors were being utilized.
Collect data: To begin collecting basic flow data for each department and usage data of the rental air compressors, the Project Manager (PM) collaborated with each department and the I&E Maintenance group to enhance the existing pressure and flow instrumentation setups. New wireless flowmeters were installed at each potential plant air rental compressor location. This was a significant challenge, primarily due to a lack of interest from the departments in improving or installing these instruments. Many departments were reluctant to measure and document their air flow usage, and there was unexpected resistance from the maintenance department. Specifically, some Instrument Technicians were opposed to the installation of wireless devices, preferring traditional wired instrumentation. The effort to upgrade the instrumentation took over 2 years. Once completed, all data was integrated into the plant’s DCS system for tracking and monitoring purposes.
Graphically analyze the process: This is the process of making sense of the data, determining if it is adequate, and representing it in a way that informs and highlights key information. The deep analysis of data takes place in the Analyze phase, but the team needed to limit the areas where they will want to do a deeper dive. Creating a visual representation of data was a powerful first step in understanding. Figure 4 displays some of the graphical analysis used to determine what the team would limit the areas into which they would take a deeper dive.
Identify focus areas: It is important to identify the focus areas and provide a storyboard to explain the team’s logic to the Stakeholders. Using all the tools previously discussed the team determined the six items displayed in the Focus Area Storyboard shown in Table 3 would be the Focus Areas of the project. On the right side of the table, you can see the data supporting the interest in each Focus Area.
Citation: Performance Improvement Journal 63, 5; 10.56811/PIJ-25-0015
Citation: Performance Improvement Journal 63, 5; 10.56811/PIJ-25-0015
Citation: Performance Improvement Journal 63, 5; 10.56811/PIJ-25-0015
ANALYZE PHASE
In this phase, the team examines each focus area to identify and verify sources of waste, defects, and ideally, root causes. Three key steps were utilized: Explore, Generate Hypothesis, and Verify Causes. The team reviewed data from both past and current occurrences, including graphical data, to identify potential root causes for instances of rental compressor usage. This review included logbooks, contractor service reports, and the “Why” Sheet created specifically for this project. Additionally, the team discussed rental procedures, the requirements for rentals in the plant, and examined past air leak surveys, current preventative maintenance practices, and the process for determining when and how refueling occurs.
The data collected were analyzed using various tools such as Pareto Analysis, Run Charts, Histograms, Cause-and-Effect (Fishbone) Diagrams, Pie Charts, 5 Whys, and a comparison of historical data. These analyses helped identify major defects and their root causes, providing a foundation for process improvement. The identified Root Causes are displayed on in Table 4 below.
IMPROVE PHASE
During the Improve phase of the Six Sigma DMAIC methodology, the team generated a variety of potential solutions. These solutions were then refined and selected for implementation after a comprehensive review with key stakeholders at a scheduled quarterly project review meeting. This collaborative approach ensured the most impactful solutions were chosen to address the primary causes and enhance the process effectively. It is important to note that some of these solutions were implemented prior in previous phases of the project, because they were deemed valuable contributors to not only improving the system but to helping determine some of the root causes.
Lack of Awareness
Create a Plant Air Overview Screen to be displayed to Operators and Engineers
Add specific air compressor’s status and data to the plant DCS System and display on the Plant Air Overview Screen
Create a procedure for Operators to document “when” and “why” rental compressors are being hooked up and used in the plant to eliminate unnecessary rental, usage and refueling.
“Why” Rentals Are Running
Install an Automatic Pressure Control Valve (PCV) at the powerhouse to remove operator chain valve.
Determine a Preventative Maintenance interval to pull and check aftercooler tubes for plugging (Water Quality)
Add Motors Taps to Quarterly Preventative Maintenance of #1/#2 Dry Air (DA) Compressors (#2 DA – Motor Issues)
Tie in #2 Instrument Air Compressor to Plant Air System (#3 Compressor Out of Service)
Yielded $94,000 in Cost Avoidance (Purchase and Installation of a new #3 Compressor)
Purchase Spare Universal 1500 PA Aftercooler for fixed assets (Aftercooler)
Replace Well Water Piping and Install Strainer Baskets (#1 DA – Water Quality)
Unnecessary Rental Cost
Use Westlake owned – Portable Diesel Compressor to reduce rental cost
Install another permanent Air Compressor at Caustic to help alleviate the necessity to run the rental at Caustic (Engineering Department and Operations to Evaluate)
Excessive Leaks
Create & Implement an Air Leak and Bleed Management Program
The leak survey conducted in 2023 found approximately $166,000 in air leaks. This is over double the amount ($78,909) found in 2017.
Plant standard to move to oil-free compressors with sufficient aftercooler units
Preventative Maintenance Issues
Improve Preventative Maintenance procedures and documentation in SAP and Document Management System
Establish an Engineering Standard to make every attempt to Replace with Like-in-Kind Compressors
Refueling Labor
Daily automated email for a runtime/refueling report
Natural Reduction in round time when rentals are not in place.
High-Impact Solutions Selected:
1b. Add specific air compressor's status and data to the plant DCS System and display on the Plant Air Overview Screen.
1c. Create a procedure for Operators to document “when” and “why” rental compressors are being hooked up and used in the plant to eliminate unnecessary rental, usage and refueling.
2a. Install an Automatic Pressure Control Valve (PCV) at the powerhouse to remove operator chain valve.
4a. Create & Implement an Air Leak and Bleed Management Program.
5a. Improve Preventative Maintenance procedures and documentation in SAP and Document Management System.
CONTROL PHASE
The Control phase aims to establish methods for maintaining a process that is stable, predictable, and meets client requirements. Key activities performed during this phase included:
Regularly updating the plant overview screen for accurate reflection of current field conditions.
Revising outdated procedures and documents to align with current practices.
Training operators on the new automatic pressure control valves installed in the Powerhouse.
Continuously refining and standardizing Preventative Maintenance procedures.
Encouraging operators to diligently record the usage of rentals and portables in the Logbook, noting the “When” and “Why.”
Developing and implementing an Air Leak and Bleed Management System to ensure efficient operation.
These initiatives are instrumental in sustaining process integrity and performance. Figure 5 below presents a bar chart illustrating the percentage of rental compressor usage per year, comparing data from before and after project initiation.
Citation: Performance Improvement Journal 63, 5; 10.56811/PIJ-25-0015
RESULTS AND DISCUSSION
The Six Sigma Compressed Air System Project successfully met its overall scope by reducing rental compressor usage by 50% and achieving approximately $164,000 in savings during its execution, excluding the additional $94,000 in cost avoidance from the #2 Instrument Air (IA) System tie-in and savings from the leak survey fixes.
While the project excelled in scope and cost, meeting two of the triple constraints, it fell short in the time constraint. Initially projected to take one year for implementation and another for control, the project extended several years beyond its expected completion. By the project’s end, only a quarter of the original team remained, with the Project Sponsor role having changed hands four times. The implementation phase coincided with COVID, necessitating a shift to a hybrid remote-work schedule, which posed challenges for a team accustomed to on-site collaboration and face-to-face interactions.
Moreover, despite support from top management and stakeholders, not all were aligned with the changes being implemented. Resistance stemmed from reluctance to alter established procedures, adopt modern technologies, or being held accountable for changes perceived as irrelevant to their unit’s financial results. These challenges required careful management to ensure the project’s efficient completion.
For future projects, it may be beneficial to incorporate lessons learned from this experience, such as the importance of clear communication, stakeholder alignment, and flexibility in project management to adapt to unforeseen circumstances.
CONCLUSION
Quality Management and Stakeholder Management are crucial components of project management, particularly in relation to the Triple Constraint of scope, time, and cost. Schwalbe (2019) defines Six Sigma as “an operating philosophy that is customer-focused and strives to drive out waste, raise levels of quality, and improve financial performance at breakthrough levels” (p. 345). While it demands considerable effort, the results validate its effectiveness.
SIPOC of Compressed Air System
Process Flow Diagram of the Plant Air System
Issue Diagram
Graphical Analysis
Before/After Bar Chart
Contributor Notes
SYED ADEEL AHMED holds a BS in Electronics & Communication Engineering from Osmania University (India) and two MS degrees from the University of New Orleans, in Electrical Engineering (MSEE) and Engineering Management (MSENMG). He is a Microsoft Certified Professional and Business Strategy Game Champion. Dr. Ahmed was awarded his PhD in Engineering & Applied Sciences in 2006 from the University of New Orleans.
Dr. Ahmed has been in the teaching and research profession for over 20 years. He has taught math, physics, engineering, business and computer science courses at the undergraduate and graduate level at Tulane University, the University of New Orleans, Xavier University, Southern University of New Orleans, Dillard University, Delgado Community College, and Nunez Community College. Additionally, he is a PhD Degree, Master’s Degree and Bachelor’s Degree advisor for several graduate & UG students.
He has many research and teaching interests, including Usability analysis of interfaces in Virtual Reality, Electro-Optics-Polarization Optics, Lasers, Engineering Management, Service Operations Management, MIS, Sustainability, TQM, Decision Sciences, Technology Entrepreneurship & Statistical Process Control/Quantitative Methods.
He also serves in the following professional and civic roles: Examiner for the Louisiana Quality Foundation; Management Consultant for the City of New Orleans; member of the online advisory board at Xavier University; and member of the board of the Islamic School of Greater New Orleans. As an Editorial Board Member of the Universal Journal of Electric and Electronic Engineering, Dr. Ahmed is an investigator on multiple interdisciplinary grants and global collaborative research projects through multi-university research initiatives. He serves on Climate Reality, Interfaith and CLEP research boards. He can be reached at sahmed1@xula.edu.
MIA T. JACKSON is a seasoned Electrical Engineer with over 15 years of experience specializing in process control, instrumentation, energy efficiency, and regulatory compliance in the chemical manufacturing industry. She currently serves as a Process Control Engineer in which she is responsible for maintaining and optimizing distributed control systems (DCS), enhancing automation processes, and supporting maintenance teams with technical guidance.
Her professional background spans a variety of engineering roles, including Energy Engineer, Instrument and Electrical Maintenance Engineer and Planner, and Compliance Coordinator. She has led cross-functional initiatives to improve system reliability, streamline energy usage, and ensure environmental compliance. Her work has included site-wide energy assessments, capital project planning, emissions monitoring implementation, and integration of process data systems.
Prior to her engineering career, she served as a Special Agent in the U.S. Air Force Office of Special Investigations, where she conducted criminal and counterintelligence investigations. This experience honed her analytical and leadership skills, which she continues to apply in high-stakes industrial environments.
She holds a Bachelor of Science in Electrical Engineering from Tuskegee University, where she graduated summa cum laude and is currently working on her Master of Science in Engineering Management from University of New Orleans. Her technical expertise includes platforms such as Aspen Process Explorer, SAP, Meridium, and Foxboro control systems. She is also an active mentor in professional development programs and community outreach initiatives, including the American Corporate Partners Mentoring Program. She can be reached at mjacks19@my.uno.edu.
