Consulting

Reliability Availability Maintainability Study

To develop a high level model of the project, utility installations using a Monte Carlo simulation model and determine the expected availability and capacity of the installations and storage facilities.

The objective of the study is:

• Determination of expected availability and the relative contribution of components to the unavailability of the system.

RAM model

The analysis will be carried out at equipment level including all the components which are active (e.g. pump, heat exchanger, turbine, regulating valve, level controller). The possible failure modes of the components will be modelled when this is supported by data and when this is essential for the performance of the installation. Otherwise failure modes are lumped into a single failure state. Maintenance activities will be incorporated only at a high level and do not include definition of specific maintenance skills or resources.

The study will be carried out in a number of phases which are:

• Determination of the modelling basis
• Availability FMEA
• Development of the Reliability Block Diagram (RBD) model
• Determination of data
• Analysis of the installation
• Sensitivity

In the following sections the phases are described in detail.

Determination of the modelling basis

At the start of the modelling essential data is gathered and the basis for the development of the Reliability Block Diagram (RBD) model is determined. Data sources are:

• PFDs
• P&IDs
• Plot plans
• RAM data sheets/information suppliers
• Maintenance policy

The output of this task will be incorporated as a section in the RAM study report

Availability FMEA

Before the development of the RBD model availability dedicated FMEA may be carried out. The function of the availability dedicated FMEA is to identify the typical design features and operational characteristics of the installation (i.e. will the failure of a component lead to complete or partial production loss and is this loss instantaneous or will it develop in time).

In addition, this meeting is to discuss the maintenance logistics and ramping up time once maintenance is carried out.

Development of the Reliability Block Diagram model

The availability and capacity of the power plant will be analysed with a RBD model developed in the Availability Workbench software package provided by Isograph.

In order to asses the performance (availability and capacity) of de design of the installation under review, all equipment that can potentially impact, directly or indirectly the production due to failure or maintenance will be modelled in the RBD model.

The simulation of a system is done by generating, and calculating the effects of, simulated ‘events’ which occur according to the element data in the model. An ‘event’ is anything which can change the state of a model or a group. The possible states for an element are as follows:

• State 1 – Undergoing preventive maintenance
• State 2 – Being repaired following a failure
• State 3 – Failed but not detected (a dormant failure)
• State 4 – Up and passive (available, but not being currently used)
• State 5 – Up and active (being used).

 

Determination of data

One of the essential elements for the analysis is the data used in the analysis. For the RBD model generic data will be used that can be obtained from public available data sources like Oreda unless plant or installation specific RAM data is available. When specific failure and repair rate data for components or sub systems applicable for the project is available, the data will be implemented in the appropriate RBD models.

Random failures which are generically used for the normal operation can be caused by a number of factors; this potentially affects all equipment to a greater or lesser extent. RAM models normally make use of generic reliability and repair data unless specific failure data is available and deemed more appropriate. For this study, the failure rate will be taken from RAM data provided by the client or data will be used from open sources such as OREDA or other historical failure data from industry sources.

Analysis of the installation

Once the RBD model is developed and verified the performance analysis of the installation will be carried out. Based on the results of the analysis the RBD model will be verified once more to determine if the output is realistic for the installation and the components used.

After confirmation that the results reflect the design the results of the RBD model are incorporated in an availability analysis report.

Based on the analysis an interim report will be submitted.

Sensitivity & Options

After review of the RBD model and interim results the model is upgraded where necessary to reflect the design, operation and maintenance. Based on the upgraded model the availability for the base model will be determined and a number of sensitivity evaluations will be carried out. The client to appoint up to 5 items of which the sensitivity will be analysed. The sensitivity analysis is based on a variation of input parameters in the upgraded RBD model.

It is also possible to evaluate options by modifying the RBD model, this is currently beyond the scope of the analysis.

Based on upgraded RBD model and the results of the sensitivity analysis a final report will be submitted.