Overview of Reliability

Reliability is a special attribute that describes the dependability of a component. This means that the component consistently performs a desired function under certain conditions for a certain period of time in order to meet business goals and customer needs. Theoretically, reliability can be described as:

Reliability = 1 - Probability of Failure

Thus, the lower the probability of failure, the greater the reliability of the system. However, there are many factors that can contribute to the uncertainty involved with any new design and capital project including variations in materials, manufacturing plants, shipping, storage, and use.

Another way of thinking about reliability is the quality of the component over time. A common term used in a reliability engineering context is mean time between failures (MTBF). MTBF is a metric that describes the average time it takes for a specific component to failure. MTBF does not measure the time when a component is waiting for repair or being repair; rather, it measures the time only when the component is operating. This is an important parameter to consider in the decision-making process when investing in new equipment. The higher the MTBF the higher the reliability of the product.

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Reliability Engineering

The responsibility of a reliability engineer is to increase the dependability and safety of a component in service. Additionally, reliability engineers work together with design, inspection, and maintenance individuals to identify failures and their causes. Common tools reliability engineers use across the entire equipment lifecycle include:

Risk analysis techniques
Exploratory experiments
Accelerated life testing
Modeling
Process control techniques
Product and process testing
Root cause analysis
Failure modes and effects analysis
Field data analysis¹

Furthermore, reliability engineers are expected to be able to align equipment performance with business goals, identify risks and failure modes, estimate remaining life and performance, and minimize variability.

Common Responsibilities of a Reliability Engineer

Reliability engineers are expected to:

Notify management of upcoming inspections and recommendations, deficiencies in processes, and corrective actions.
Use probability and statistic tools for risk and process hazard assessments.
Comply with standards and specifications defining requirements for design, construction, inspection, testing, decommissioning, and integrating new components with aging infrastructure.
Analyze and interpret reliability data and provide recommendations on how the data can be used to measure and improve performance and reliability.
Understand the value of reliability and how to build a business case
Establish testing, inspection, and maintenance priorities and recommend frequency in which these procedures should be performed.
Develop strategies for planning, inspecting, and maintaining the reliability of assets throughout the equipment’s lifecycle.
Measure and report key performance indicators.
Understand the value of investing in reliability and how to build a business case to present to the owners of the company.
Lead change (i.e., change in processes, strategies, etc.).
Stay informed about new and developing processes.
Maintain equipment history and inspection and maintenance records. Data should be stored in a centralized computer maintenance management system. Changes to data can only be done so in a master database system.

Certification and Training

A certified reliability engineer is one who aims for performance improvement and manages asset safety, reliability, and maintenance throughout the component’s life cycle.² A combination of professional work experience and education are considered for certification. The following outline provides an overview of specific topics that a reliability engineer should be familiar with for certification. A detailed list of the minimum necessary knowledge and skills can be found in the Body of Knowledge document.³

Reliability Management
Probability and Statistics for Reliability
Reliability in Design and Development
Reliability Modeling and Predictions
Reliability Testing
Maintainability and Availability
Data Collection and Use

Equipment Reliability

Strategy for Optimizing Equipment Reliability

Equipment reliability is measured in terms of quality, performance, and productivity. The goal of an equipment reliability program is to effectively monitor equipment, procedures, and data covering the life of equipment. Advantages of a reliability program include eliminating unexpected shutdowns, reducing production losses that occur between start-up and operation, and extending the life of the asset. Additionally, company’s typically experience a reduction in costs of repair and maintenance, reduction in delay, and increases in safety.

Methods to Ensure Reliability of Equipment

Besides the engineering practices described above, there are three other essential components to equipment reliability: maintenance, inspection, and technology.

1) Maintenance

Maintenance can be divided into three categories, preventive, predictive, and corrective maintenance. Preventive measures are taken to eliminate unnecessary inspection and repair tasks. Predictive maintenance generally involves nondestructive inspection techniques to monitor the serviceability of the equipment. Corrective maintenance involves repairing or replacing components to restore equipment back to its operating conditions. Collectively, these tasks should be managed in a well developed reliability centered maintenance program.

2) Inspection

Nondestructive testing (NDT) techniques are used extensively throughout the lifecycle of equipment to locate and monitor damage mechanisms. Furthermore, inspection plays a major role in any equipment reliability program. Some common NDT methods used in the petroleum and chemicals industries include radiographic testing, ultrasonic testing, electromagnetic testing, and many more. When selecting an NDT method several considerations should be taken into account including the type of damage, where the damage is located (external or internal), and the size, shape, and orientation of the damage.

Additionally, there are two other types of inspection that provide information on the reliability and remaining life of equipment. These include risk-based inspection (RBI) and fitness-for-service (FFS) assessments. Put simply, the purpose of RBI is to identify and understand risk in order to reduce uncertainty about the condition of equipment. FFS assessments are performed to determine if a component is suitable for continued service.

3) Technology

New advancements in technology, such as sensors, will be able to greatly improve the overall reliability of the system. Sensors can provide data on the performance and condition on the equipment in real-time to make better decisions for preventive, predictive, and corrective maintenance.

References

Schenkelberg, Fred. “Introduction to Reliability Engineering Management.” Inspectioneering Journal, vol. 21, no. 1, 2015.
Reliability Engineer Certification offered by the American Society for Quality (ASQ)
ASQ Certified Reliability Engineer (CRE) Body of Knowledge

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