When a locomotive needs a part, the buyer usually has more than one option. The original equipment manufacturer (OEM) may still supply it. Aftermarket manufacturers may offer an equivalent. Used or reconditioned stock may be available, and in some cases the part can be re-engineered and made to order.
Each option has its place. This guide sets out the differences between OEM and aftermarket locomotive parts, the questions worth asking about each, and how to decide which is right for a given part.
What we mean by OEM and aftermarket
OEM parts are made by, or for, the company that built the locomotive or the subsystem, such as the engine, brake system or traction equipment. They are supplied under the OEM's part number and usually carry the OEM's documentation.
Aftermarket parts are made by other manufacturers to fit and perform like the original. Quality varies widely, from parts made to the original drawings and specifications by experienced manufacturers to low-cost copies with little evidence behind them.
Deomac supplies both. Through our global trade service we source diesel locomotive spares, OEM or aftermarket, through reliable partners around the world, and we supply quality replacement parts for EMD, GE, WABCO, CSR and Bombardier equipment.
The case for OEM parts
OEM parts are often the default, and for good reason:
- Known specification. The part matches the original design, including materials and tolerances.
- Documentation. Certificates and traceability are usually straightforward to obtain.
- Approvals. Many operators' engineering standards already accept OEM parts without further review.
- Warranty alignment. Where a locomotive or subsystem is still under a support agreement, OEM parts may be required.
The drawbacks are usually cost and availability. As fleets age, OEMs rationalise their ranges, lead times stretch and some parts are discontinued altogether.
The case for aftermarket parts
A good aftermarket part can be the better choice:
- Availability. Aftermarket suppliers often stock parts that are slow or impossible to get from the OEM.
- Cost. Competition can bring prices down, which matters on high-volume wear items.
- Improvements. Some aftermarket parts address known weaknesses of the original, such as a better material for a part that wears quickly.
The risk is inconsistency. Two parts sold under the same description can differ in material, heat treatment or finish. The way to manage that risk is evidence.
Questions to ask about any part
Whichever route you take, these questions help separate a sound part from a gamble:
- What is it made from? Ask for the material grade and, for critical parts, a material certificate.
- How was it made and treated? Forging, casting or machining from solid, and any heat treatment or plating, all affect performance.
- How was it inspected? A dimensional report against the drawing is reasonable for critical parts.
- Is it traceable? Can the supplier link the part to a batch, a material certificate and an inspection record?
- Has it been used before? Experience of the same part in similar service is valuable evidence.
- What does your engineering team need? Many operators require approval before an alternative part is fitted to a safety-critical system.
Matching the choice to the part
Not every part deserves the same level of scrutiny. A practical approach is to group parts by how critical and how specialised they are.
Safety-critical parts
Brake components, running gear, couplers and similar items affect safe operation. For these, follow your organisation's approval process strictly. OEM parts may be the simplest path; well-documented aftermarket or re-engineered parts can also be approved, but plan for the paperwork. Our brake parts buyer's guide covers this area in more detail.
Performance-critical parts
Engine, compressor and turbocharger components affect reliability and fuel use. Quality evidence matters here too, and the cost of a failure in service usually outweighs any saving on the part. See our article on locomotive air compressor parts for an example.
General wear and consumable items
Gaskets, seals, filters, fasteners and simple bushes are often well suited to good aftermarket supply, provided the specification is right.
When neither option is available
Sometimes the OEM no longer makes the part and no aftermarket equivalent exists. That is where re-engineering comes in: a replacement is designed and manufactured from a sample, drawing or part number. Our article on re-engineering obsolete locomotive parts explains how it works, and our in-house capabilities in CNC turning, milling, welding and fabrication are listed on the services page.
Total cost, not unit price
The cheapest part on the quote is not always the cheapest part in service. When comparing options, consider:
- Downtime. A part that arrives weeks sooner can be worth far more than its price difference.
- Service life. A part that lasts twice as long halves the labour spent replacing it.
- Failure consequences. A failure in service can mean a failed train, recovery costs and disruption well beyond the part itself.
- Approval effort. Engineering time to approve a new source is a real cost, but it is usually a one-off.
How Deomac can help
We work with maintenance teams to find the right source for each part, whether that is OEM supply, a proven aftermarket part or a re-engineered component made to order. Search our parts list for items we supply, or contact our Australian office with a part number, drawing or photo and we will advise on the options.
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- aftermarket parts
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