Reliability-centred Maintenance and HAZOP – Is there a need for both?

Our guest blogger is Mr Stephen Young, a Founding Director of The Asset Partnership.

He holds a Bachelor of Engineering (Electro-Mechanical) and Graduate Diploma in Asset Management. 

He is a Chartered Professional Engineer. Stephen has spent more than twenty-five years in field of maintenance and asset management with particular experience in Power Generation and Distribution, Water Utilities, Petrochemicals Food Processing, Brewing, Wine and Spirits, Mining, Defence, Manufacturing, and Printing.

Hazard and operability (HAZOP) analysis has a well-deserved reputation for systematic and thorough evaluation of industrial hazards with the safety, environmental, and economic benefits far outweighing the cost.

Developed by ICI in the 1960s as a form or “what-if” analysis, HAZOP has undoubtedly made the industrial world a safer place by identifying credible incident scenarios that had, or would have had, a significant impact on safety and operational capability.

HAZOP review teams apply an agreed set of ‘guide’ words to identify possible deviations Typical guide words include NONE, MORE, LESS, AS WELL AS, REVERSE, BEFORE, AFTER, EARLY, LATE, etc. Possible causes and consequences of the deviation are identified, along with any safeguards that may exist. Actions that are required (such as design changes, need for procedures, etc) are documented and assigned for action.

The HAZOP review team typically includes operators, designers, technical specialists, and maintainers in addition to the HAZOP facilitator and needs (or must develop) a detailed understanding of the system under analysis.

For most HAZOP studies, 50-60% of the recommendations address product quality or plant operability issues and not safety or environmental concerns. The driving benefit is for engineering design teams to identify potential problems on paper during design rather than in the field during start-up.

Risk management through a HAZOP analysis, is usually through the addition of further technology such as protective devices to initiate some action to avert the consequences but the process does not necessarily address the possibility of the installed projective devices failing to operate as intended. There is no methodology within a HAZOP analysis to develop a rigorous and defensible strategy for managing the reliability of protective devices, or indeed the reliability of the process equipment at all.

The leading maintenance strategy development tool is SAE JA 1011 compliant Reliability Centred Maintenance (RCM), which applies a structured decision logic to the outputs of a Failure Modes and Effects Analysis (FMEA). This technique has been demonstrated to significantly improve plant safety, reliability, and maintenance cost-effectiveness.

RCM was developed in the aviation industry in the late 1960s to address the inability of traditional maintenance programs to effectively manage aircraft reliability. The process is now applied throughout industry.

Today’s RCM uses a multidisciplinary team of people including a facilitator, operators, craftsmen, and other specialists as required to review a defined system.

The team:

• Defines the operating context of the system, including a description of what the system does and a list of the equipment within the system

• Defines all the functions of the system including primary functions, secondary functions (e.g., containment, contamination prevention, protection, economy, efficiency, support, appearance, environment), and protective functions (e.g., alarms, interlocks, devices for relieving abnormal conditions)

• Lists all the failure modes and effects for each function

• Uses a decision diagram to guide decisions on how to best maintain the function of the equipment to minimize the risk of equipment failure or process malfunction.

• For equipment failures which can not be prevented from failing, appropriate strategies are developed to minimize the impact of failure.

As a result, the resultant risk management strategies depend not only on the failure characteristics of the maintainable item, but also on the consequences of the failure in terms of operational performance measured in cost, product quality and customer service but also on safety and environmental impact.

The RCM process is unique in the manner in which it both recognizes and manages hidden failures. Many components, particularly protective devices can fail in such a way that no one knows that the item has failed. These failures, known has hidden failures, have no consequence until some other failure also occurs which requires the device to operate such as a high-high level switch (the process normally never reaches the high-high level, so there is no way to tell if the switch works without testing it)

With the inclusion of appropriate HAZOP guide words into the Functional Failure assessment of an FMEA/RCM analysis, the aims of both analysis processes can be satisfied with the minimum of effort.

SAE JA 1011 compliant RCM rigorously assesses the possibility of protective devices failing to operate as intended and develops functional checks of devices based on a proven algorithm considering the probability and consequences of failure. Further, RCM uses a rigorous, defensible and audit-able process for developing the most appropriate strategy for managing the reliability of assets.

FMEAs can be either component or system based, and the modern evolution of RCM as developed by John Moubray, uses a process based functional FMEA analysis. John Moubray’s RCM 2 clearly identifies the process functions and the failures which can affect the performance of that process. Identified failures include equipment malfunction, equipment degradation, human error and inappropriate or incorrectly designed or installed plant. The RCM 2 process then seeks to find the most appropriate method to manage each one of those risks.

There is a great similarity between the HAZOP and the preliminary stages of an SAE JA1011 compliant RCM analysis. The sequential application of HAZOP and RCM analyses within an organisation therefore wastes precious resources for no benefit. But with a very subtle modification, a robust SAE JA1011 RCM can satisfy the requirements of HAZOP but, a HAZOP in isolation, is unable to generate the same outputs as an RCM analysis.
The Asset Partnership
The Asset Partnership is one of Australia’s leading Asset Management consulting organisations with offices in Sydney, Auckland, Perth. We specialise in partnering with clients make efficient and effective use of their investments in physical assets in the most demanding of environments by:

• Maximising the sustainable capability of existing assets.

• Reducing asset ownership costs and risks

• Optimising capital outlay