For Unreliable Machine: Which Failed First, the Machine or the Machine’s Design?
MOHAMED IBRAHIM, VA CAT IV, API-SIRE, CLS, MLE, MLAIII, MLTII, VIM, VPR, ARP-E, CRL, CMRP
Senior Mechanical Engineer at Qatar Energy, Member of ICML technical committee , Certified vibration Analyst CAT IV and ARP-E from Mobius, certified Machinery Lubrication Engineer and Machinery Lubrication Analyst III
?Introduction
In the world of industrial machinery, rotating equipment such as pumps, compressors, turbines, and motors are critical components that require high reliability. When these machines fail, it’s essential to determine whether the failure was due to the machine itself or its design. This lecture will explore the factors contributing to the reliability of rotating equipment and analyze whether it is the machine or the design that typically fails first.
1. Understanding Rotating Equipment Failures
Failures in rotating equipment can manifest in various forms, such as bearing failures, seal leaks, misalignments, or shaft breakages. These failures can be attributed to multiple causes, including material fatigue, improper maintenance, operational errors, and inherent design flaws.
2. Machine vs. Design: Defining the Terms
- Machine: Refers to the physical equipment and its components, including bearings, seals, shafts, and casings.
- Design: Refers to the engineering principles, specifications, and plans used to create the machine, including material selection, structural layout, and intended operational parameters.
3. Factors Leading to Machine Failures
- Operational Overloads: Running equipment beyond its design limits, such as higher speeds, loads, or pressures, can lead to premature failure.
- Improper Maintenance: Lack of routine maintenance, improper lubrication, and failure to replace worn-out components can degrade machine performance.
- Environmental Factors: Exposure to harsh conditions, such as extreme temperatures, corrosive environments, or contamination, can accelerate wear and tear.
- Human Error: Mistakes during installation, operation, or maintenance can introduce faults that lead to equipment failure.
4. Factors Leading to Design Failures
- Inadequate Design Specifications: Incorrect assumptions or miscalculations during the design phase can result in a machine that is not fit for its intended purpose.
- Material Selection: Using materials that cannot withstand operational stresses or environmental conditions can lead to early failures.
- Insufficient Testing: Failure to conduct comprehensive testing and validation during the design phase can leave potential issues undetected.
- Design Complexity: Overly complex designs may introduce unnecessary points of failure and make maintenance difficult.
5. Root Cause Analysis (RCA)
To determine whether a failure is due to the machine or its design, a thorough Root Cause Analysis (RCA) must be conducted. RCA involves:
- Data Collection: Gathering data on the failure, including operational records, maintenance logs, and environmental conditions.
- Failure Mode Analysis: Identifying how the failure occurred and what components were involved.
- Comparison to Design Specifications: Evaluating whether the machine was operated within the design specifications and whether those specifications were appropriate for the operational conditions.
6. Case Studies and Examples
- Case Study 1:
Bearing Failure in a Pump
- Observation: Frequent bearing failures.
- Analysis: Bearings were not rated for the operational load and speed.
- Conclusion: Design failure due to incorrect bearing specification.
??- Case Study 2:
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Seal Leakage in a Compressor
- Observation: Seal failures and leaks.
- Analysis: Improper installation and maintenance practices.
- Conclusion: Machine failure due to human error and inadequate maintenance.
- Case Study 3:
Shaft Breakage in a Turbine
- Observation: Shaft broke during operation.
- Analysis: High-stress concentration points due to design flaws.
- Conclusion: Design failure due to poor structural layout.
7. Preventing Failures
- Design Phase:
? - Conduct thorough design reviews and simulations.
? - Select appropriate materials and components.
? - Implement rigorous testing and validation protocols.
??- Operational Phase:
? - Ensure proper installation and alignment.
? - Adhere to OEM recommended operational limits.
? - Implement condition monitoring and predictive maintenance programs.
- Maintenance Phase:
? - Follow preventive maintenance schedules.
? - Use OEM recommended lubricants and parts.
? - Train personnel on proper maintenance practices.
8. Conclusion
Determining whether a failure is due to the machine or its design requires a comprehensive analysis. While both machine and design can contribute to failures, many issues can be traced back to design flaws that set the stage for operational problems. By focusing on robust design practices, proper maintenance, and rigorous testing, the reliability of rotating equipment can be significantly improved.
By understanding the interplay between machine performance and design integrity, we can better address the root causes of failures and enhance the reliability of rotating equipment in industrial operations.
References
1. [Machinery Failure Analysis Handbook](https://www.reliabilityweb.com/ )
2. [Engineering Design Principles](https://www.engineering.com/ )
3. [Plant Engineering – Maintenance Best Practices](https://www.plantengineering.com/ )
4. [Reliabilityweb.com – Maintenance and Reliability Resources](https://www.reliabilityweb.com/ )