Maintenance, inspection, and testing error

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What are maintenance, inspection and testing?

Maintenance, inspection and testing error in the 10 Human and Organisational Factors

Maintenance is when preventative work is undertaken on plant to maintain it in sound operating condition. It includes inspection and testing of plant to ascertain the current condition of, or quality of repairs to, plant, and informs what maintenance is required.

In addition to preventative work, there is reactive or breakdown maintenance for repair of plant that has failed. The scale of this work covers a multitude of items from simple fuse changes to major process plant shutdowns, and can involve removing or disabling safety systems.

In major hazard industries, maintenance work may also involve isolating process streams of dangerous substances, then dismantling and rebuilding a system.

As maintenance requires human labour, its quality – and thus the safety of the plant maintained – depends upon the performance of the people who carry out the work. Ensuring the quality of maintenance, inspection and testing activities involves managing human error and supporting human performance.

Human error in maintenance, inspection and testing activities

When performing maintenance, even experienced, highly-trained people can make errors, potentially returning equipment or systems to service in an unsafe state. However, these errors are often predictable and can be identified and managed.

Maintenance failures due to human error include incorrect reassembly, wrong specification of replacement items, omission of a task step, re-commissioning errors, safety features left disconnected, instrument set-points incorrectly set and leaving tools inside plant.

It is essential that factors that increase the likelihood of error during maintenance are considered to design, manage and improve safe maintenance, inspection and testing activities.

Reducing maintenance, inspection and testing error

A human error in maintenance processes can lead directly to an injury or introduce a fault into the plant which can then malfunction at a later date, potentially leading to a catastrophic incident such as a loss of containment of dangerous substances. Such undetected faults are known as ‘unrevealed errors’ and can be reduced by performing adequate inspection and testing. Plant failure can expose people to many hazards as plant is often an integral part of higher order controls such as isolation.

The incident on the Piper Alpha oil platform in 1988 is a well-known example of a catastrophic incident following a maintenance error within the petroleum industry. There are many examples of disasters in other industries where maintenance errors were the root cause. To help avoid such disasters, it is essential that organisations establish a maintenance system of work with clearly defined roles and responsibilities.

Considerations to support human performance


  • Provision of adequate resourcing (people, tools, parts etc.) to make tasks achievable.
  • Planning and scheduling maintenance activities to ensure tasks can be performed safely.
  • Clear task-specific and role-specific competency requirements.
  • Clear task, role and work group supervision requirements.
  • Provision of role clarity for all people involved in maintenance activities.
  • Identification of environmental factors that may impede workers or maintenance operations (e.g. temperature extremes, lighting, atmospheric contaminants or oxygen levels).
  • Defined contingency plans; for example, if a job looks like it might run overtime or if emerging problems arise along the way.
  • Structured change management (how to deal with changes that arise during maintenance activities, changes to maintenance schedules or changes as a result of plant modifications).


  • Clear means to identify plant that is to be isolated/maintained.
  • Set methods for how equipment will be maintained to specified requirements.
  • Defined processes to identify and assess error potential in safety critical maintenance tasks.
  • Provision of clear accept/reject criteria with respect to plant condition prior to being put back into service, or allowed to continue in service.
  • Integrated quality assurance into the process to minimise the risk of unrevealed errors.

Communication and consultation

  • Provision of all necessary information, including written instructions, permits, diagrams and other paperwork, as well as ensuring labels are clear and up-to-date.
  • Provision of reliable and transparent means and opportunities for information to be communicated; particularly so that so that maintenance crews (and others who might be affected by maintenance) know what and where work has been done (this is especially important at shift handover).
  • Involvement of all relevant maintenance personnel in plant & equipment design, job design, task analysis, writing procedures etc.


Human factors: Maintenance, inspection and Testing (MIT)

Common Topic 2: Maintenance error

Human factors: Maintenance error

These resources by the UK Health and Safety Executive (HSE) cover various aspects of maintenance, inspection and testing, and provide resources to support workplaces to reduce human failure.

Incident summary: Piper Alpha case history

This report published by the Centre for Chemical Process Safety of the American Institute of Chemical Engineers, summarises events and key findings of the Piper Alpha incident in 1988.

Hazard Register – Injuries 2011 to 2017

Hazard Register – Fatalities 2000 to 2018

These documents by DMIRS, summarise findings from 65 serious injury or incident investigations in the WA mining industry from 2011 to 2017 and 71 fatal mining accident investigations in the WA mining industry from 2000 to 2018. Updated annually.