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reliability and maintainability

The risk to project is significantly influenced by failure of key component or systems.

For example for a plant:

  • Failure of key component contributes to down time and thus productivity; where as
  • Failure of a safety system can significantly increase the safety risk.

Chilworth Group has assessed Reliability, Availability and Maintainability (RAM) of systems in the management of risk. Chilworth Group applies the relationship between RAM and risk by systematically modelling the inter-dependency of different elements of a system. These models can be developed in either dynamic or static RAM model, where the selection of the modelling depends upon the risk contributors to be investigated, and the level of risk it may pose on a project.

Chilworth Group has helped its clients in performing the following key services:

  • Failure Mode, Effects and Criticality Analysis (FMECA);
  • Reliability Assessment of Instrumented Protection Systems such as Overpressure Protection Systems;
  • Reliability Assessment of a High Integrity Protection Systems (HIPS);
  • RAM assessment of the production plants on off-shore installations;
  • RAM assessment of the on-shore plants;
  • Safety Integrity Level (SIL) Assessment.
  • Instrumented Protection Function (IPF) Assessment.

FMECA

FMECA provides a structured and meticulous approach to identify possible failure modes, their preceding events, the resulting effects and opportunities to design out these eventualities. In identifying potential failure scenarios, the FMECA provides proactive planning opportunities. In essence, it provides the following benefits:

  • A tabulation of all operating equipment at a facility;
  • Identification and documentation of failure modes of each equipment;
  • The resulting effects of such failure modes on the failure potential of the overall system; and
  • Development of a criticality ranking for each failure mode, which provides the basis for establishing preventive maintenance and sparing philosophies as well as redundancy configurations.

Overpressure Protection System & HIPPS

An Instrumented Protection System (IPS), for example at the specification-break where a pipeline enters a processing facility, will reduce the 'calculated' risk of over pressure only if there is confidence in its ability to respond. Chilworth Group designs such systems based on a detailed understanding of the transient behaviour of the system, rigorous reliability assessment of the components and proof of the proposed configuration. The resulting benefits include:

  • Protection of downstream equipment and systems from potential pressure surges upstream;
  • Provision of an extremely reliable protection mechanism, with reliability expectations two orders of magnitude higher than conventional process plant relief systems;
  • Redundancy and diversity of components comprising the HIPS.
  • Cost effective, safe solution to protect plant integrity and minimise potential environmental effects;
  • Achieve good system reliability-to-availability balance;
  • Achieve high input integrity due to reduced downtime and production losses.

RAM

Dynamic RAM is an efficient method for reducing design, operations and contractual cost of projects by means of the following:

  • It ensures that return on investment is as per expectations by ascertaining the design requirements to meet contractual productivity target;
  • It assesses the changes in CAPEX required for different levels of redundancy and sparing, and trade this off against the OPEX costs develop maintenance and sparing strategies;
  • It confirms the redundancy of different system elements;
  • It predicts productivity shortfall;
  • It can help assess and develop make-up strategies upon expected shortfall in productivity;
  • It can determine operational constraints;
  • It can define spares locations, supply logistics and storage cost;
  • It can develop commonality of spares and help reduce investment in spares holding;
  • It can define resource allocation and hence help assess resource requirement to meet target productivity;
  • It can define maintenance schedules in line with the target or contractual productivity; and
  • It can include cost of maintenance and repairs in the model to help assess cost profile over the life of a facility.

SIL

The integrity of a facility/system can be evaluated in terms of the adequacy of its control measures and safeguards in place. This is the principle behind the SIL assessment which allows a facility/system to be assessed and graded according to different classifications. SIL classes can then provide the basis for determining if additional measures are required (in light of the criticality of a system) or conforms to the stipulated level of safety. The resulting benefits from such an assessment include:

  • Consistent evaluation of each system based on the SIL classification;
  • Derivation of individual SIL classes for each system;
  • Integration and derivation of individual SIL classes to obtain the overall SIL class for the facility;
  • Demonstration of the SIL class in light of compliance requirements.

IPF

Control systems form a crucial component for smooth and safe operations of any facility. The inability for a control system to perform as required could result in cascading effects on other control systems and the facility at large. In order to foresee such eventualities and prevent them, the IPF provides an approach that is both comprehensive and thorough. The resulting benefits from such an assessment include:

  • Detailed examination of each control loop at a facility/system;
  • Identification of potential control loop failures and resulting cascading effects;
  • Provision of safeguards to eliminate such failures and preserve the integrity of the overall control system
  • All of this directly translates to higher productivity and efficiency.

Maintenance

Interest in Reliability Centred Maintenance (RCM) is growing but the preservation of reliability through maintenance may be unnecessary if the risk arising from failure is acceptable. A rigorous maintenance strategy is therefore an essential foundation on which to build an RCM system. Defining a maintenance strategy for the components of a facility based on risk provides a real cost reduction opportunity. Chilworth Group can develop a risk based maintenance strategy based on the QRA. This approach can also be applied to existing facilities, e.g. a large scale risk model was provided to a client operating ageing facilities which allowed maintenance and replacement budgets to be targeted to give maximum risk reduction.