Locomotive Turbocharger Parts: Wear and Fixes

The turbocharger is one of the hardest-working components on a diesel locomotive. It spins at very high speed, sits in the hot exhaust stream and depends completely on clean oil and clean air. When it starts to fail, the engine loses power, smokes and can suffer secondary damage.

This article looks at how a locomotive turbocharger works, the signs of wear to watch for, common causes of failure, and the parts usually involved in a repair.

How a locomotive turbocharger works

A turbocharger uses exhaust energy to push more air into the engine.

• Exhaust gas leaving the cylinders passes through a nozzle ring and drives the turbine wheel.
• The turbine wheel is on the same shaft as the compressor wheel (impeller) on the cold side.
• The compressor draws in filtered air, compresses it and delivers it, usually through an aftercooler, to the engine's air box or intake manifold.
• The shaft runs in bearings fed with engine lube oil, and seals keep oil out of the air and exhaust passages.

More air means more fuel can be burned cleanly, which is what lets a locomotive engine make its rated power.

Some EMD engines use a turbocharger that is also gear-driven from the engine at low speeds, through an overrunning clutch, so that it supplies enough air before exhaust energy alone is sufficient. That arrangement adds gears and clutch parts to the list of turbo spares.

Signs that a turbocharger is wearing

Turbo problems often start small. Watch for:

• Loss of power or the engine failing to reach full load.
• Black smoke, which points to too little air for the fuel being burned.
• Blue or white smoke, or oil in the exhaust, which can point to leaking oil seals.
• Oil in the intake or air box, another sign of seal or bearing trouble.
• Unusual noise: a change in pitch, a whine, a rub or a rattle.
• Vibration from the turbo area.
• High exhaust temperatures compared with normal for that load.

Any of these deserves investigation before the turbocharger fails completely. A turbo failure in service can send debris into the engine or exhaust system and turn a turbo repair into a much bigger job.

Common causes of turbocharger damage

Turbochargers rarely wear out on their own. The cause is usually somewhere else in the engine's systems.

Lubrication problems

Turbo bearings need a steady supply of clean oil. Contaminated oil, low oil pressure, blocked feed lines or delayed oil supply at start-up all damage bearings quickly. Shutting a hot engine down without the cool-down procedure set out in the maintenance manual can also cook the oil in the bearing housing.

Foreign object damage

Anything that enters the compressor or turbine, such as dirt past a damaged air filter, a loose fastener or a fragment from a failed engine part, can chip blades and unbalance the rotor.

Air filter and intake problems

Blocked filters starve the engine of air; damaged filters let in dust that erodes the compressor wheel.

Imbalance and rub

Once a wheel is damaged or a bearing is worn, the rotor can run out of balance and rub on its housing. Damage then grows quickly.

Exhaust-side problems

Fuel injection faults, high exhaust temperatures or debris from the engine can damage the nozzle ring and turbine wheel.

When you replace turbo parts, find and fix the cause, or the new parts may fail the same way.

Turbocharger parts that are commonly replaced

A turbocharger overhaul or repair typically involves some of the following:

• turbine wheel or turbine blades;
• compressor wheel (impeller);
• rotor shaft;
• nozzle ring;
• bearings and thrust bearings;
• oil seals and air seals;
• gaskets, O-rings and fasteners;
• housings and covers, if cracked or eroded;
• on gear-driven designs, gears and overrunning clutch parts.

Rotating parts are balanced to tight limits. Follow the manufacturer's overhaul instructions on balancing, clearances and the parts that must always be replaced at overhaul.

Repair, exchange or replace?

There are three common approaches when a turbocharger is damaged:

1. Repair the unit by replacing only the damaged parts. This is cost-effective when damage is limited and the core is in good condition.
2. Exchange the unit for an overhauled one, so the locomotive returns to service quickly while the old unit is repaired.
3. Replace with a new unit when the core is badly damaged.

The right choice depends on the extent of the damage, how quickly the locomotive is needed and the availability of parts.

Sourcing turbocharger parts

Turbo parts are part of Deomac's locomotive range. To get an accurate quote:

• give the turbocharger model and part numbers from the parts catalogue or nameplate;
• give the engine model and the locomotive type;
• list the parts needed and quantities, or the findings from the strip report;
• send photos of damaged parts and any markings.

Search the Deomac parts list by drawing number or description, then send your requirement through the contact page. You can see examples of turbocharger housings and rotating parts in the gallery.

Related reading

The turbocharger is only one part of the engine. For the wider picture, see EMD and GE engine spares: a buyer's guide. Turbo oil and air lines are a typical case for the pipework described in CNC tube bending for locomotive pipework.

Summary

A healthy turbocharger needs clean oil, clean air and a sound engine. Watch for loss of power, smoke, oil leaks and noise, find the root cause of any damage, and replace parts as a matched, balanced set according to the manufacturer's instructions. With clear part numbers and photos, sourcing the right turbo spares is straightforward.