Repair before failure: vehicle maintenance

Anyone can run a machine to failure. The real skill is judging the optimum time to do a repair before failure, says Stuart Truckel

The waste management industry, like many others, has traditionally repaired machines when they fail. But, in an increasingly competitive world, the knock-on effects of machine downtime on operational efficiency, margins and ultimately profits can be catastrophic.

Transfer stations, material recycling facilities, landfills, incinerators and composting facilities all present unique problems and a demanding environment for machines. And these, without a planned service and maintenance schedule, can have a severely detrimental effect on the total life cost of a machine.

However, the development of a culture of repair before failure as opposed to repair after failure is a difficult undertaking, requiring a significant change in the traditional mindset. As a result, those companies actively planning repairs remain in the minority.

This is unfortunate because, at a time when the waste management sector is faced with increasingly severe performance and profits targets, most continue to run the gauntlet of potential catastrophic failure, which can leave a machine out of production for weeks and even months.

Plan ahead to save time and money
Planning could turn these failures into planned repairs with a consequent saving in both time and money. It is undeniably more expensive to let a machine fail because of potential downtime and loss of production than to plan repairs.

The key is timing, determined by part replacement cycles and key repair indicators, particularly in the drivetrain, where catastrophic failures occur. It is therefore essential to have a repair philosophy that replaces worn-out drivetrain parts before they fail and cause additional downstream damage. However, it must be remembered that certain parts can be reused, ultimately delivering considerable repair cost savings.

For example, on a Caterpillar medium wheel loader - which would typically be used in waste management applications such as transfer stations, composting sites, recycling facilities, and incinerators - the first repair indicator is a machine that has worked about 9,500 hours.

At this point, level one parts, which wear fastest, including anti-friction bearings and seals, must be replaced and cannot be reused. However, level two parts, which include plates, discs, ring gears and final drive gears need checking, but can be reused if there is adequate life left in the part.

Level three parts are capable of lasting the life of a machine up to the expected life expectancy of 24,000 operating hours. These parts will include transmission cases, including shafts, carriers and gears and also final drive cases, hubs and shafts.

Repair indicators
Timing is also determined by two types of repair indicators - namely planned and problem indicators. Planned indicators include machine service meter hours, service history, scheduled oil sampling and diagnostic inspections.
It should also include a full site evaluation, which takes into account site conditions, operator technique, lubrication and maintenance. For example, particularly severe site conditions or the occurrence of water in the fuel tank, which would usually indicate bearing wear, should both determine repair scheduling.

Problem indicators include increased noise, vibration, overheating, oil consumption, leaks, slippage and debris in the filter. These are often identified via operator discussion, which can be invaluable in determining any operational problems, such as noise from the transmission or slippage.

Repairs left beyond the recommended number of operating hours clearly risk machine failure. Equally, repairs commissioned in advance of the recommended hours, and without accurate reading of the repair indicators, risk inflated repair costs for potentially unnecessary work.

Using a typical Caterpillar medium wheel loader as an example, we can demonstrate how all three factors, namely part replacement cycles, planned and problem indicators determine repair timing.

Downtime is costly
Machine A is used for 14,000 hours and repaired after failure. If the failure occurred on a Monday morning, the total number of days lost would typically include five working days and two days at the weekend for a total downtime of seven days. The potential total cost for this repair is likely to be more than £12,500.

Machine B is scheduled for repair at 7,500 hours but the owner fails to read the repair indicators and replaces level two parts that do not require replacement at this stage. Planned maintenance took place on a Friday, which limited downtime to only four days with a resulting cost of more than £3,500.

Machine C was repaired on schedule at 9,500 hours with only the necessary components replaced at this stage. Planned maintenance took place on a Friday afternoon with only four days' downtime for a total cost of less than £3,000.

Monitoring is essential
In order to plan repairs and avoid catastrophic failure, machine condition monitoring is necessary. This should include daily visual inspections including fluid level checks, fuel consumption and leaks. Operational checks should include monitoring of the machine start-up, braking and shut down, in particular transmission and hydraulics.

All of this may sound daunting to companies used to a more finger-in-the-wind approach to machine repairs. However, computer systems, such as Finning's site operations and maintenance adviser system (SOMA) can help plan repair cycles.

The system calculates the estimated life remaining in a machine's engine and transmissions and determines the best time to perform before failure overhaul, taking into account a machine's load factor, operating and maintenance habits.

With systems such as SOMA, repair before failure is a potential win-win solution, allowing companies to plan, schedule and ultimately reduce downtime, while also offering the ability to budget for repairs and know the cost of repairs up front.

Catastrophic failures can be almost totally eliminated if key parts are replaced at the right time, but it will require a culture change on behalf of the waste management industry. As the old proverb says: "What you do not repair, you destroy".

Stuart Truckel
is industry manager for waste & landfill at Finning UK

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