8 types of maintenance: a comparison

1. “Run to Failure” or “Reactive”: often where budgets are far outweighed by the available resources, both staff and money. 

Only done in response to an event, i.e. a report from other staff or citizen

Often the only way the Custodian will get to know of an asset “failure” or “suspected failure”

Sometimes Citizen reports initiate jobs, other times it initiates a technical  inspection

Common where the Custodian makes a judgement in the environment of limited funds e.g. Tree Maintenance.  In such cases, Insurance cover represents a “hidden cost”

Can be performed by generic staff using a pre-defined “list of observations” or a locally generated framework.

Often categorised by the Asset Custodian as a “Service request”

The likelihood of the job going ahead sometimes depends on budget and sometimes on Legislation or local service levels

Here, the asset may not have intrinsically failed but the job will “provide a service”, e.g. the service of providing clean streets

Not required in relation to the regular maintenance.  May be performed on an ad-hoc basis in response to an “unusual event”.

Usually comments on the condition of the asset or an event requiring an ad-hoc maintenance action

Pre-planned pattern of jobs based on the domain science and studies made by experts in relevant circumstances.

Examples are Grounds Maintenance, Street Sweeping and Refuse collection.  Sometimes dependent on local budgets and political considerations.

Not required in relation to the regular maintenance.  May be performed on an ad-hoc basis in response to an “unusual event”.

Reports an unusual event as the principle is to maintain 100% availability.

Similar to no 3 the pre-planned pattern of maintenance is based on previous studies by domain or asset experts.

Often used for vehicles, plant and production machinery

Is the basis for this maintenance type.  Sometimes the inspection will be prescribed by Code of Practice or Legislation.

Where received usually initiate a technical inspection.

Jobs collected from Inspections cannot always be executed, due to budget limitations, building up a “Work-bank” or backlog

Roads, Bridges, Play Equipment are all examples of where this is used in the “Municipal” context

An inspection or sensor will take condition readings and, based on readings, jobs are proposed

No usually relevant

Jobs aim to prevent failure and minimise asset “down-time”

Common where maintenance is costly (e.g. Street Lights) and for some types of machinery.

7. “Reliability Centred Maintenance”.  It is generally used to achieve improvements in fields such as the establishment of safe minimum levels of maintenance, changes to operating procedures and strategies and the establishment of capital maintenance regimes and plans. Successful implementation of RCM will lead to increase in cost effectiveness, machine uptime, and a greater understanding of the level of risk that the organization is presently managing.  Common for very high cost assets where reliability has a high consequence, e.g. production line machines, airline engines and so on.

Inspections may be made “on the bench” in the case of “Rotable Assets” or done when machinery is taken out of use on a production line (line switched off or rotable assets within the production line)

Not usually involved, although staff operating these assets will report unusual performance and will usually be trained to act as “non-expert eyes”

Carrying out jobs on assets “on the bench or closed down results in better reliability with high capital cost items.

RCM starts with 7 questions:

What is the item supposed to do and its associated performance standards?

In what ways can it fail to provide the required functions?

What are the events that cause each failure?

What happens when each failure occurs?

In what way does each failure matter?

What systematic task can be performed proactively to prevent, or to diminish to a satisfactory degree, the consequences of the failure?

What must be done if a suitable preventive task cannot be found? 

Can be any mix of machine based, visual or sensor.

Citizens report in non-expert mode so expert inspections usually ensue

Jobs depend on budgets as other options are available: e.g. close a road, restrict bridge width available to vehicles.

Pavement Management is typical and Bridge Maintenance in the UK is heading in that direction with the Bridge Condition Index (BCI).