Reliability, Availability, Maintainability (RAM)
Assets are designed to hardly fail, not hard to source, and easy and cheap when considered for maintenance to achieve harmonization between productivity, supply chain, and maintenance cost by means of Reliability, Availability, and Maintainability analysis with the prime objective of enhanced product quality over the product life cycle. Waste reduction, optimization of profit, and total Life Cycle Cost (LCC).
Reliability is the likelihood of a product or asset to operate without failure within a given time and under certain conditions. It is measurable by means of metrics like – Mean Time Between Failures (MTBF) for repairable items, and Mean Time to Failure (MTTF) for non-repairable items.
Maintainability is the ease and resource requiring asset maintenance would require. It is measurable by means if a metric called Mean Time to Repair (MTTR).
Availability is the probability of an asset being operable within a given time. It combines the parameters of reliability and maintainability. Machine reliability considers fault tolerance mechanisms. The time of maintenance depends on the simplicity of the machine for routine maintenance. Simplifying maintenance instructions like the Operational and Maintenance Manual reduces sign-off and reducing sign-off documents and Increases Preventive Maintenance time. Availability considers Minimum Levels of Service (LOS). RAM is considered throughout the Asset Life Cycle Management stages – planning, acquisition and deployment, operation and maintenance, and disposal.
BENEFITS OF RELIABILITY, AVAILABILITY AND MAINTAINABILITY STUDIES
- Early detection of failures at the design stage. Accurate forecast of asset lifecycle costs as reflections of equipment age, duty cycle, and maintenance efficiency.
- Comparing design alternatives for production. Meeting production requirements at contracting.
- Enhance maintenance scheduling and rich maintenance history.
- Optimize supply chain and logistics management.
- Identify asset maintenance options at failure. Identify problems in the production chain.
- Operational costs are reduced by the reduction of production costs.
- A reduction in the maintenance and spare replacement costs, sustenance, and increase in production levels.
- Prevents loss of business downtime due to any unplanned and planned failures.
- Budgetary economy due to the availability of various alternatives at, plant and enterprise levels.
- Maintenance resources and critical assets balance with revenue generated from production.
ASSET CONDITION MONITORING (ACM) RAM ASSESSMENT: Asset Condition Monitoring (ACM) is a suitable way of checking maintainability and availability based on asset dilapidation and depreciation in cost. Asset conditions in terms of – lubricant or fuel or energy, vibration analysis or stress analysis, infrared thermography, noise, heat and smoke, and failure are adopted in accessing product fatigue and failures. Common types of failures that can be analyzed are tensile yield, creep, crushing, wear, fracture, buckling, torsional twisting, sagging, shearing, corrosion, and burning due to thermal load. A Potential Failures (P-F) Curve, a visualization tool for representing the condition of an asset and its decline towards failure, and Potential Failures (P-F) Interval, a time between the initial detection of potential failures and the actual occurrence of failure are both useful in Asset Condition Monitoring.
FAILURE MODE EFFECTS AND CRITICALITY ANALYSIS (FMEA or FMECA) RAM ASSESSMENT: Failure mode effects and criticality analysis is a reliability evaluation and design technique executed as a bottom-up approach of quantitative failure analysis involving various linkages of potential failures (Failure Modes), impact on the mission (Effects of Failure), and causes of failure (Causes and Mechanisms). FMEA is an extension of failure mode and effects analysis. It has a resemblance to the 5 Why Technique of Root Cause Analysis (RCA). A Failure mode is created, followed by a performance of Critical Analysis. FMEA can be determined by Quantitative or Qualitative techniques.
Quantitative Failure Mode Effects and Criticality Analysis:
Mode Criticality = Item Unreliability x Mode Ratio of Unreliability x Probability of Loss x Time (Life).
Item Criticality = Sum of Mode Criticalities.
Quantitative Failure Mode Effects and Criticality Analysis:
Comparing Failure Modes using the Criticality Matrix, which measures SEVERITY on the horizontal axis against qualitatively derived OCCURRENCE on the vertical axis.
STAGES OF RELIABILITY, AVAILABILITY, AND MAINTAINABILITY IN ENGINEERING
- Preliminary Engineering (Pre-FEED): RAM analysis is applied in comparing various design alternatives through quantification of the production output of each option at design conceptualization. This phase of RAM analysis is good for cost reduction and project schedule management at the early stage of the design.
- Front-End Engineering (FEED): Critical assets or equipment are identified for determining requirements, and optimizing configuration to prevent losses and equipment redundancies in order to increase availability and plan for spares.
- Detailed Engineering: The design alterations, omissions, and errors are identified and corrected to reduce design changes to a minimum. An audit of performance benchmarks that guide design specifications and procurement choices is carried out by the asset owner based on the outcome of the RAM study.
- Process Operation: A RAM study may be conducted on an in-use asset with the aid of an audit of the as-built asset to curtail failures and maintainability.
RAM REFERENCE DOCUMENTS
- P&ID’s.
- Equipment List.
- Equipment Configuration.
- Description of Modes of Operation.
- Maintenance Philosophy.
- Information from RAM Terms of Reference (ToR).
RAM-BASED QUANTITATIVE RISK ANALYSIS (QRA): Assumptions in the Project ToR with data sources from clients, and manufacturers’ documentation are used. A RAM analysis report with facility description, the scope of work, detailed methodology, failure rate data, results of analysis, and recommendations based on results for improving availability are produced. Storing spare parts, additional equipment to enhance redundancy (fail-safe), and factors of safety to enhance safety integrity level may be considered.
Reliability, Availability, and Maintainability are highly recommended for quality controls in engineering, manufacturing, construction, and the built environment. Implementation of RAM improves efficiency and economy in design, procurement, construction, installation, and maintenance projects.
William Nwaogu, Technical Advisor,
SAFETY CONSULTANTS & SOLUTION PROVIDERS LIMITED.
