Maintenance Types
Maintenance involves activities that help keep assets in good working order, so they will operate as intended. Proactive maintenance activities are those that are carried out in a planned fashion. Proactive maintenance categories include:
Routine or Planned Maintenance Examples:
An example of this type of activity is a planned sewer cleaning program. The system may decide to clean 1 mile of sewer every month, and a plan can be developed to move through the sewer system to get this work completed.
Cleaning the forebay after a rain event is another example of a planned maintenance activity.
Predictive Maintenance Examples:
Machine vibration is continually monitored through sensors that are attached to the machine. The sensors gather data to assess and monitor machine health quickly and accurately. Sensors are used to quantify and report how smooth or rough the machine is running. Vibration analysis and monitoring can be used to discover and diagnose a wide range of problems related to rotating equipment.
Another example is close-circuit televising (CCTV) of sewer line or placing a condition monitor insied a pipeline to determine wall thickness or the presence of holes in the pipe.
Preventive Maintenance Example:
For example, if the system examines a sewer with a camera and it shows significant corrosion of a concrete pipe, the system may wish to add a chemical to reduce sewer gas build up. Another example is a pump that is showing signs of wear in the bearings. The system can replace the bearings before they fail so that the work may be performed when it is advantageous for the system (e.g., during business hours, when an operator is on duty, and when spare parts can be ordered ahead of time.) Watering plants at the beginning of the asset’s life in a green infrastructure project could also be considered preventive maintenance.
Warranty-Related Maintenance Example:
Warranty maintenance is often the systems responsibility. However, in the case of Johnson County, KS the contractor has to sign a maintenance bond for the first three years and then responsibility is turned over to the city. Before the maintenance can be turned over, it needs to be certified that it is working by an engineer.
Reactive maintenance activities are those that are completed after the asset fails to meet the desired level of service or fails to function at all. Reactive maintenance categories include:
Corrective/Reactive Maintenance
When a water line breaks, staff must repair the line immediately to avoid as much water loss and disruption of services as possible.
Backlog Maintenance
During a weather event, routine maintenance can get behind schedule. Use additional time to get caught up on repair or preventative maintenance to ensure assets are running at optimal levels.
Different types of assets need different ratios of proactive and reactive maintenance. For gray assets, there is enough historical information to establish a best management practice of 80 percent planned maintenance (including the categories of planned, preventive, and warranty-related) and 20 percent reactionary (corrective) maintenance. For green infrastructure, data is still needed to define best management practices. However, for both green and gray assets, the type of asset, its risk level, and its replacement cost must be considered when optimizing maintenance funds.
Risk should be a factor in determining how much to invest in maintenance for each asset. The maintenance needs for green assets are often highly dependent on the specific location, rather than the asset type, whereas gray assets maintenance planning may rely on asset type, amount of use, and location.
For low-risk gray assets, the most economical option might be to allow the asset to fail. This allows the full life span of the asset to be achieved. This management strategy is called “run to failure,” or managed failure. In this case, the operations staff are choosing to let the asset run until it fails, at which time it is repaired, rehabilitated, or replaced. In contrast, green assets can become more self-sustaining over time, so staff might be able to reduce the frequency of planned maintenance.
A companion activity to maintenance is monitoring, which includes inspection. Monitoring can help determine when maintenance should be performed. Monitoring can:
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- Be ongoing and permanent using continuous read equipment
- Be intermittent, such as inspections
- Allow the asset’s operation and maintenance to be adjusted and improved over time
- Assess specific condition attributes to forecast asset failure
- Evaluate variables of assets such as temperature, vibration, oil quality, etc.
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Monitoring and inspection can support adjustments to operation and maintenance plans by using data collected to inform utility staff of attention that assets may need. For example, if a gray asset is leaking oil, that could impact the frequency in which the asset is maintained. Additionally, if a rain garden is growing faster than anticipated, maintenance activities may be able to become more infrequent.
To know the best way to maintain the asset, it is important to collect maintenance data. This data should include the costs for any maintenance activities conducted. Maintenance data can aid informed decision-making. Data can also be used to improve decision-making after failures.
WRF’s Asset Management Framework for Forested and Natural Assets provides example of maintenance activities required for natural assets as shown below.
WRF‘s Asset Management Framework for Forested and Natural Assets provides example of maintenance activities required for natural assets as shown below.
Natural Asset Type
Asset Stressor or Hazard
Maintenance Activities
Prescribed burns
Purpose
Predictive and preventative maintenance – Jim Smith, Director, Infrastructure Planning, Louisville Water Company, Louisville, KY
The importance of maintenance – David Montgomery, SCADA Manager, Albuquerque Bernalillo County Water Utility Authority, Albuquerque, NM