Condition data keeps ageing rolling stock on the right track

THERE COMES a point with older rolling stock when knowing the age of the train only tells a maintenance engineer part of the story. A vehicle might have been in service for more than 30 years, but few of its components will likely share that history. Wheelsets may have been overhauled relatively recently, while components like bearings, gearboxes and bogie components could have been replaced or refurbished at different points.

While the fleet gets older, the maintenance picture becomes more mixed. Engineers need to know the condition of the equipment in front of them, how it has been operating and whether there are signs something is beginning to change. This is where condition monitoring helps to fill in the gaps.

Looking for changes, not waiting for an interval

Lubricants are a useful source of information because they can reveal what is happening inside equipment that would otherwise be difficult to assess.
Oil analysis can identify water ingress and other contamination, changes in the condition of the lubricant and wear particles that may indicate abnormal wear within a gearbox or other lubricated equipment. Instead of waiting for a problem to become apparent, engineers have another opportunity to spot something may be changing.

There is also a key difference between taking an occasional sample and building up a history. One test provides a snapshot, while regular samples allow the latest result to be compared with previous ones. This makes trends easier to identify, which is particularly useful in rail, where apparently similar pieces of equipment don't necessarily experience the same working life. There will be significant variations in load, operating hours, temperatures, duty cycles and environments.

Oil analysis is only one part of that picture. On gearboxes, it can sit alongside vibration monitoring, while with axle box bearing condition monitoring, vibration and temperature measurements might be considered alongside grease analysis. None of these replaces an established maintenance regime, but they give the engineer more evidence when deciding where attention is needed.

And catching deterioration in the depot is very different from dealing with a failure out on the network. Once a train has stopped in service, particularly somewhere difficult to recover it from, the implications can extend well beyond the failed component. Other services may be affected, and recovery becomes part of the problem. The cost of the component itself can quickly become the smallest consideration.

Getting reliable information in the first place

Condition data is useful only when engineers can trust how it has been obtained. In the case of vibration analysis, the measurement needs to be dependable if a maintenance decision is going to be based on it. The same applies to temperature probes, thermal imaging equipment and pressure instruments. Calibration can sometimes feel like another administrative requirement, with dates to track and equipment unavailable while checks are carried out. In practice, its purpose is much more immediate and confirms whether the engineer can trust the reading.

Torque wrenches are one tool used widely across rail maintenance. If a wrench is out of calibration, a fastening could be under or over-torqued. Excessive torque can overstress the fastener. The issue becomes more significant when equipment is being kept in service for longer. If condition information says a component remains healthy and can continue operating, the quality of the measurement behind that decision matters.

Oil sampling can also be compromised by something as simple as a dirty container or sampling point. Water or dirt appearing in a sample doesn't automatically mean the lubricant arrived in that condition, although sometimes it does. Contamination could have been introduced during storage, transfer or sampling. This means where lubricant drums are stored, how clean transfer equipment is, how oil is moved from its container to the machine and how are samples are taken can all make a significant difference. That puts depot best practice at high priority.

Correct lubricant selection is equally important. Oils and greases are formulated for particular duties rather than being interchangeable products. Load, speed and temperature all have a bearing on selection, alongside the equipment itself and the contaminants it might encounter. In heavily loaded rail applications, a significant change in temperature can affect how the lubricant behaves. Keeping equipment running for longer makes getting those details right much more important.

Making evidence-based maintenance decisions

There is another reason for understanding lubricant condition: oil doesn't necessarily need replacing simply because a predetermined interval has been reached.
Sometimes it will because, as lubricants degrade, additives become depleted and contamination can make continued use inappropriate. Analysis, however, gives maintenance teams evidence on which to make that call. Where the lubricant itself remains suitable, but contamination is the problem, filtration or other oil-conditioning processes may offer an alternative, depending on the application and the equipment manufacturer's requirements.

That can avoid unnecessary lubricant changes and the associated cost of buying replacement oil and dealing with the waste. This offers numerous environmental benefits: lower oil consumption, less waste and keeping a usable resource in service for longer. This fits with the move towards more circular use of materials.
Environmental targets should never take precedence over engineering judgement. Oil should be changed if necessary. The point is the decision can be based on its condition rather than the calendar alone. The same principle runs through the wider maintenance of ageing rolling stock.

There will come a point where components become uneconomic to overhaul or obsolete. In the meantime, engineers must keep the equipment they have safe, available and reliable.

A train's age cannot tell them everything they need to know about that equipment. Condition data can tell them considerably more, provided the lubricant has been handled correctly, samples have been taken properly and the instruments and tools producing the measurements can be trusted. For fleets continuing to work beyond the intended life, those details increasingly matter.

Rob Webster is head of onsite condition monitoring for RS Maintenance Solutions

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