Guideline For Ram Analysis

Guideline for Reliability, Availability, and Maintainability (RAM) Analysis 1.0 PURPOSE The purpose of this guideline is to establish the requirements for performing a Reliability, Availability and Maintainability (RAM) Analysis. 2.0 SCOPE This guideline applies to all projects involved in performing a RAM analysis. 3.0 RESPONSIBILITIES The following functions have responsibilities guideline:  Client  Project Engineering  Safety & Environmental Engineering  Process  Commissioning  Electrical  Mechanical  Instruments

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4.0 GUIDELINE 4.1 General The RAM analysis assigns failure rates and repair times to the equipment items in the plant design in order to determine the expected frequency and duration of plant production shortfalls for comparison with the target value. 4.2 Define Basis of Analysis Before the analysis begins, the scope of the work must be defined and agreed with the client, the Project Engineer, the Lead Process Engineer, the Project Safety & Environmental Engineer, or other person responsible for executing the RAM study. At least the following issues shall be specified: 4.2.1 The target values for availability and/or throughput for the plant. Such information is likely to be specified in the contract and may form the basis of a performance guarantee. Furthermore, the contract may require a test run to demonstrate that the target values can be met in practice. 4.2.2 References to any national, international, or client standards that are appropriate to the RAM study for the project. 4.2.3 Precise definition of terms such as ‘plant availability’, ‘uptime’, ‘reliability’ and‘throughput’. 4.2.4 Units in which the results are to be presented, e.g., on1/4

stream days per year, total output as percentage of demand. 4.2.5 The software package or method to be used for the study. 4.2.6 The plant configuration to be modelled. 4.2.7 Any items of equipment that are not to be included in the model. 4.2.8 Acceptable data sources. 4.3 Input Data for the RAM Model Input data for the modelling must be specified. The following data types shall be considered: 4.3.1 Process Description The units comprising the facility and how they operate shall be defined from the Process Description, the PFDs, the P&IDs and supplier data. 4.3.2 Failure Modes, Effects, and Criticality Analysis (FMECA) A review of P&IDs shall be carried out to identify those items of equipment whose failure can contribute to plant shortfalls in output. For these items, the potentially critical failure modes shall be noted and the potential output shortfalls determined from the process description and PFDs. 4.3.3 Failure Rate and Repair Time Data For critical components in the FMECA, both failure rate and repair time data shall be obtained. These can come from a number of sources such as generic databases, e.g., OREDA (Offshore Reliability Database), client, or supplier data (usually via Mechanical and Instrument Groups). 4.3.4 Maintenance Schedules Where necessary, for each item of equipment the frequency and duration of maintenance activities shall be obtained. Such data may be obtained from the client or supplier (usually via Mechanical and Instrument Groups). Note: Planned maintenance does not always impact availability as it may be scheduled into periods of no or low demand. 4.3.5 Review Input Data 4.3.5.1 Before setting up the RAM model, the input data may be reviewed and agreed with the functions identified in section 3.0. 4.3.5.2 Agreeing the input data before modelling can save time later because any re-working of the model, due to disputed data, is eliminated. However, this action can be postponed until the reporting stage. 4.4 Construct and Run RAM Model After agreeing with the input data, the modelling process uses the following steps: 4.4.1 Construct RAM Model The determination of plant availability is made by mathematically modelling the plant configuration. Where practical and acceptable to the client, the company will use 2/4

RAMP (Reliability, Availability, and Maintainability of Process Systems), a Monte Carlo simulation computer program for the assessment of the availability, reliability, productivity, and maintainability characteristics of process systems. However, clients sometimes specify other software packages, e.g., MAROS (Maintainability, Availability, Reliability, and Operability Simulator). In this case it may be more economic and/or efficient to contract third party specialists with access to the specific package to perform the work. 4.4.2 Run RAM Model and Analyse Output 4.4.2.1 Utilising failure and repair characteristics and spares availability data the program determines 'up-time' and 'down-time' for each element within a complex system. The program simulates the system over the time period of interest and, on the basis of the results obtained from running numerous such periods, calculates the statistical parameters required to assess system availability, shortfall in throughput, and down-time. 4.4.2.2 Typically, the RAM model of the plant generates the following information:  the total output as a percentage of demand;  the frequency and duration of total loss of output;  the frequency and duration of partial losses of output;  the percentage of time operating at specific outputs;  histograms of shortfall durations;  contribution of equipment items to shortfalls in output. 4.4.2.3 The main factors contributing to the unavailability shall be determined for potential optimisation studies. 4.4.2.4 If the results are below the agreed values, the input data shall be reviewed and/or plant configuration revised to achieve the required target. 4.4.2.5 Some equipment may dominate the unavailability, thus greater attention shall be paid to checking assumptions, source data, plant configuration, and maintenance requirements on such items. 4.5 Issue and Review Report A summary report of the input data, assumptions, model, and results shall be drafted for review by the client and those groups listed in Section 3.0. 5.0 REFERENCES None 6.0 TERMINOLOGY 3/4

Term MAROS

Definition Maintainability, Availability, Reliability, Operability Simulator, a simulation tool from DNV OREDA Offshore Reliability Database, an equipment failure database populated with reliability data from offshore operations, used for quantified risk assessment. RAMP Reliability, Availability, and Maintainability of Process Systems, a simulation tool from W.S. Atkins plc. FMECA Failure, Modes, Effects and Criticality Analysis Supplier Manufacturer, Producer, or Seller of a specific equipment/good.

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