Maintenance, Inspection and Thorough Examination of Mobile Cranes

4.0 Approaches to Maintenance
4.1 Maintenance System Elements
The introduction to this Best Practice Guide has emphasised the need to ensure that
equipment is maintained, as required by PUWER, so that its performance does not
deteriorate to the extent that it puts people at risk. Many people have a part to play in this
from the mobile crane operator carrying out daily and weekly checks, through the user
reporting defects to the crane owner, to the maintenance personnel. Adequate
maintenance can only be achieved by establishing an effective maintenance
management system which should include
� A statement of maintenance policy (e.g. Planned Preventive Maintenance,
backed up by breakdown repairs and supplemented by Predictive Maintenance or
in combination);
� Definition of roles and responsibilities of persons involved in the maintenance
activities;
� Systems for the assessment of individual competencies;
� A maintenance plan/schedule;
� Written maintenance procedures;
� Maintenance records;
� A review and audit plan to ensure that the maintenance is suitable and sufficient.
4.2 Types of Maintenance Management
There are three main types of maintenance management that may be applied to the
maintenance of machines, including mobile cranes: breakdown maintenance, preventive
maintenance and predictive maintenance. Not all of these are appropriate for the
effective maintenance of mobile cranes, as explained below.
4.3 Breakdown Maintenance
Breakdown or “run-to-failure” maintenance management has a simple and
straightforward logic. “If it ain’t broke, don’t fix it” is often seen as a way of limiting
expenditure on maintenance and keeping costs low. The problem with this approach for
mobile cranes is that any failure could present an immediate and unacceptable risk.
Additionally repair costs may well be very high when the machine does break down, often
at the most inconvenient moment, with considerable downtime whilst repairs are carried
out.
4.4 Planned Preventive Maintenance
All planned preventive maintenance systems are time driven. In other words,
maintenance tasks are carried out at intervals that are based on actual hours of operation
or on an interval of time that equates to an average number of operating hours or number
of operational cycles. The maintenance interval is based on experience of breakdowns or
the mean-time to failure (MTTF) as illustrated in Figure 1. The MTTF or bathtub curve
indicates that a newly purchased machine has a higher probability of breakdown due to
teething problems in the first few weeks of operation. Following this initial period, the
probability of failure is relatively low for an extended period until wear and deterioration
means that the probability of breakdown/failure increases sharply with elapsed time.
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