Constru C tion site maintenan C e strategies

The importance of construction site maintenance strategies cannot be overemphasized. Imagine a project for a noncommercial building just months away from crossing the finish line when a tower crane topples and causes four floors to collapse into rubble. Luckily no one is hurt, but the penalty clause from the contract is activated, and the construction site must remain closed while the authorities investigate the cause of the disaster. After two months of uncertainty and frayed nerves, the result from the investigation finally reveals mechanical failure as the cause: no maintenance recorded on the crane for the last five months.

Below are some construction site maintenance strategies to guide the decisionmaking process: preventative, conditionbased, predictive, and reliability-centered maintenance.

Preventative Maintenance (PM)

Preventative maintenance (PM) is a systematic approach that involves regularly scheduled inspection, repairs, replacements, or any other task that minimizes wear and tear of an asset. On a construction site, preventative maintenance can be time-based, usage-based, or predictive. A cut-off-saw is an example where both time-based and usage-based maintenance are appropriate.

Advantages of Preventative Maintenance

Fewer expensive repairs; Reduces downtime due to unplanned maintenance; Longer lifespan of asset; Improved reliability and availability of asset; Cheaper than CMB, PdM, and RCM to implement and; Does not require a large amount of data to implement

Disadvantages of Preventative Maintenance

Does not consider the critical function of an asset; Is not necessarily an optimized maintenance strategy; Requires in-depth planning and a critical analysis of an asset; Routine maintenance may be unnecessary leading to inefficient use of time and higher spending and; Does not consider the optimum lifespan of a component

Condition-based Maintenance (CBM)

Condition-based monitoring uses tests, visual inspections, operational performance, and other equipment information as a “listening ear” to determine the real-time condition of an asset. Different algorithms later use the data acquired to detect, diagnose, and perform a prognosis for an asset’s failure modes.

Advantages of CBM

Maintenance performed on an as-needed basis; Lowers expenses on maintenance by minimizing time spent to maintain an asset; Lowers the risks associated with unscheduled downtime; Optimizes maintenance intervals; Increases the lifespan of an asset; Better time management due to predefined scheduled intervals and; Longer useful life for parts

Disadvantages of CBM

Relies on specific indicators that may lead to asset modification; requires specific knowledge to choose the type of measurement equipment; Expensive to install and time-consuming to perform database analysis; CBM does not detect all types of failures and; Resistance to change is an obstacle

Predictive Maintenance (PdM)

Predictive maintenance uses conditionmonitoring strategies to identify and asset’s performance and establish a future date for maintenance. This approach closely intertwines data collected from sensors, environmental measurements, maintenance history, machine operations, and other suitable parameters with algorithms. These algorithms then use the collected data with other variables to predict when failure occurs according to the criteria established in a predictive maintenance model.

The answers to two crucial questions below provide essential information about the applicability of predictive maintenance for an asset: Does the asset perform a critical function that can negatively impact the project if it fails unexpectedly? Is it possible to cost-effectively monitor the failure modes of the asset? If the answer is “YES” to both questions, then the next step is selecting the components/ systems on a construction site to monitor. Vibration of bearings, overloads in electrical panels, temperature differences of electrical components, spikes in motor amperages, motor oil insulation resistance, and overloads are just some examples to monitor on a construction site.

Advantages of PdM

Increases asset availability due to less downtime; Reduces maintenance costs by making it possible to acquire spare parts promptly and possibly for a lower cost; Better customer satisfaction and employee productivity which are direct results of better maintenance planning and reduced downtime

Disadvantages of PdM

Misinterpretation of data from sensors and other measuring devices can lead to prediction error; High setup costs and careful analysis to determine which assets perform a critical function can be timeconsuming and; requires more time to develop compared to other methods

Reliability-centered Maintenance (RCM)

Reliability-centered maintenance (RCM) is an empirical approach that focuses on the reliability and availability of an asset as opposed to its optimized functionality. The failure mode, effect, and criticality analysis (FMECA) concept is an important tool that elaborates on the goals, principles, and approach in RCM with the final aim of identifying an optimal maintenance program anchored on various maintenance strategies. RCM considers an acceptable level of risk, and consequently, not all failure modes are immediately maintained; only those deemed critical.

Advantages of RCM

Increases equipment availability as a result of reduced downtime; Reduces maintenance costs by lowering corrective and preventative maintenance costs; Better planning for spare parts availability and consequently lower costs; Better risk awareness and maintenance optimization strategies; Reduces the likelihood of sudden equipment failure and associated probability and; Involves root cause analysis in methodology approach

Disadvantages of RCM

Cost reduction is only evident over the long term; Management interested in shortterm saving results may, therefore, resist the change; High start-up costs to buy equipment, allocate resources, implement strategies and train personnel; does not consider ownership costs and; requires good understanding of failure modes at the system level

The construction industry relies heavily on building and industrial maintenance strategies to ensure optimal functionality of assets and reduced downtime. A single maintenance strategy cannot achieve this due to the wide range of components/ systems, the numerous failure modes, and the differing degrees of criticality assigned to each.

Construction projects are also case-specific with unique design and legal requirements that play an essential role in defining equipment usage, building specifications, and work practices. Cost-effectiveness, available resources, manufacturer’s product guidelines, the criticality of a particular component/system, and long-term maintenance plans are essential deciding factors for choosing a combination of different optimal maintenance strategies.