A RAM analysis (Reliability, Availability and Maintainability) is used to estimate the availability of a system. There are several methods and tools that can be applied for RAM analyses; each method has its strengths and weaknesses.
When considering a production or process plant which may have several output levels the RAM analysis is often denoted Production Availability Analysis or Production Performance Analysis. The latter term is used in ISO20815.
Production Availability Analysis
A process plant may be complex with several production levels and a number of different products. We perform production performance studies to evaluate the operational performance of a process plant. This type of study is often called RAM analyses (Reliability, Availability and Maintainability) which describe the important parameters in production performance.
The results from a RAM analysis typically include the availability of the systems, i.e. the uptime, as well as the main contributors to unavailability. Our studies help clients to design, construct, operate and maintain processes and systems to achieve the optimum reliability and availability. These studies are high focus areas through all phases in a field development project, as they provide valuable input to process designers, economic evaluations (LCC analyses) and decision-making. The results can be used to find the most favorable balance between process configuration/redundancy, spare parts/repair resources and investment/operating cost.
A RAM analysis of a process plant – a production performance analysis – requires an advanced method and a correspondingly advanced software tool. Lilleaker Consulting has been an active participant in the development of the software package Miriam RAM Studio which is developed for evaluating the production performance of continuous process plants. In Miriam RAM Studio Monte Carlo simulation is applied to a flow network. System configuration, failure and repair data, different operational modes, spare parts and repair resources are only some of elements that can be included in the simulation model.
Production Assurance Programme
In order to spend your reliability efforts in a systematic and efficient manner, a Reliability Management Programme or a Production Assurance Programme is an essential first step. A Production Assurance Programme is a mandatory deliverable for compliance with ISO 20815. The most important objectives of the programme are to define any reliability performance objectives and requirements, identify activities necessary to fulfil the objectives and meet the requirements, and plan how those activities will be carried out.
Fault tree analysis
Fault tree analysis is used to analyse undesired states of a system, i.e. failure to perform its intended function. The analysis is a top down approach where lower level events are combined. The method can be used to understand how systems can fail, investigating combination of events resulting in a failure. The output includes probability of failure, total failure frequency or availability, component importance and list of cut sets. Fault tree analysis may be applied to a variety of systems. Typical uses are for safety systems and other systems which primarily have just two states; functioning/failed, on/off, etc. Lilleaker Consulting uses a software tool for designing the fault trees doing the calculations.
Failure Modes, Effect (and Criticality) Analysis
A Failure Mode, Effect and Criticality Analysis (FMECA) is a simple analytical method to;
- Identify potential failure modes of an equipment unit or a system
- Predict the effect and criticality of a failure on sub-system and system
The method is inductive; it only deals with one component/subsystem at a time and examines the consequences of failure. The criticality part of the FMECA consists of an evaluation of the frequency and the consequence of the end event or global effect.
A FMECA is normally performed as a multi discipline workshop where the participants contribute with their knowledge. To ensure a systematic analysis a special worksheet is used. A FMECA worksheet will vary depending on the nature of the task.
The benefits of performing a FME(C)A includes:
- Improved reliability
- Improved safety
- Improved quality
The analysis can be used to identify critical equipment or equipment parts, and the results can be used in a number of applications:
- input to maintenance planning (Reliability Centered Maintenance, RCM)
- input to production performance analysis,
- evaluation of design of equipment or processes
Example of FME(C)A worksheet. The worksheet is customized depending on the objective of the analysis.
Reliability Centered Maintenance (RCM)
Reliability Centered Maintenance (RCM) is a structured methodology for determining a maintenance strategy. The RCM process focuses on preventive maintenance of equipment most likely to fail, or where failures have the most severe consequences. RCM is often referred to as a means to establish the safe minimum levels of maintenance. Implementing this methodology may both increase equipment reliability and reduce maintenance costs.
The FMECA is normally used as basis for RCM analyses. Through the RCM process, the criticality, risk and root causes of equipment failures are investigated to identify maintenance tasks (preventive or corrective maintenance).