African HFO stations add their own challenges: dust, heat, variable fuel quality and long distances to workshops and parts. This guide sets out a practical service routine for turbochargers on these sites.
Why HFO is hard on turbochargers
Heavy fuel oil contains more ash, sulphur and heavy compounds than distillate. Combustion products deposit on the turbine nozzle ring and blades, gradually reducing gas flow and turbine efficiency. Sulphur compounds can cause corrosion, and vanadium and sodium in some fuels produce hard, corrosive deposits at high temperatures.
Fuel treatment upstream makes a large difference. Well maintained separators and filters remove water and solids that would otherwise reach the engine and its turbocharger. Our guide to HFO separator maintenance covers that side.
Compressor and turbine washing
Most turbochargers on HFO engines are designed for regular washing in service. Compressor washing with water removes dust and oil deposits from the air side. Turbine washing, using water or a dry method with granules, removes combustion deposits from the turbine side. The method and frequency depend on the turbocharger maker’s instructions and the fuel in use.
Keep a log of each wash with the engine load, exhaust temperatures and charge air pressure before and after. The trend shows whether washing is keeping up with fouling.
What to monitor every day
Turbocharger speed, charge air pressure, exhaust gas temperatures before and after the turbine, air filter differential pressure and lube oil pressure and temperature should all be recorded daily. Changes in these values often give early warning of fouling, filter blockage, bearing wear or leaks.
Compare readings at the same load. A rise in exhaust temperature or a fall in charge air pressure at a given load is a sign that something needs attention.
Bearings and lubrication
Turbochargers on medium-speed engines may use plain bearings lubricated from the engine oil system or rolling element bearings with their own oil supply, depending on the model. Clean oil at the right pressure and temperature is essential. Dirty oil or a pressure drop can destroy bearings very quickly at turbocharger speeds.
Check oil filters, pressure and temperature routinely, and follow the maker’s guidance on bearing replacement intervals. Many turbochargers have a defined bearing life in running hours.
Fouling, surging and loss of power
A fouled compressor or turbine reduces air delivery, raising exhaust temperatures and limiting output. Severe fouling or a blocked intake can make the compressor surge, a rapid, noisy reversal of airflow that stresses blades and bearings. Surging may also come from a dirty charge air cooler or from operating outside the matched range.
If surging appears, reduce load and investigate before continuing. Clean filters, coolers and the turbocharger, and check that the engine is running within its normal envelope.
Dust and heat on African sites
Dusty seasons load air filters quickly and erode compressor wheels if dust gets through. Use filters suited to the site, monitor their differential pressure and replace them before restriction rises too far. In hot climates, high intake temperatures reduce air density and raise exhaust temperatures, so the margin to temperature limits is smaller.
Ventilation in the engine hall matters as much as filtration. If the turbocharger draws hot hall air, output falls and component life shortens.
Inspection and overhaul intervals
Turbocharger makers specify inspection and overhaul intervals in running hours, often with different intervals for bearings, nozzle rings and rotating parts. On HFO, inspections usually show deposits and wear that need cleaning and part replacement. Plan overhauls with the engine’s own maintenance so the unit is stopped only once.
Our page on HFO engine overhauls in Africa explains how the larger engine work is planned.
Spare cartridges and exchange units
Many turbocharger types allow the rotating assembly, sometimes called the cartridge, to be replaced as a unit. Keeping a spare cartridge or a complete exchange turbocharger on site can turn a long outage into a short one, especially where a workshop is far away.
Store spares correctly, protected from moisture and with rotating parts supported, and record their condition and history.
Field or workshop overhaul
Some turbocharger work can be done on site with the right tools and trained staff. Balancing the rotor, repairing blades and refurbishing nozzle rings usually needs a specialist workshop. On remote sites, plan transport and turnaround time, and consider an exchange unit to cover the period.
Mobilising a team and tools for a remote site needs planning. Our article on mobilising for a remote site overhaul sets out the steps.
Charge air coolers and the air path
A turbocharger can only perform as well as the air path around it allows. Charge air coolers foul on the air side with dust and oil mist and on the water side with scale, raising charge air temperature and pushing exhaust temperatures up. Include the cooler in the washing and inspection plan, check its pressure drop and water temperatures, and inspect the intake ducting for cracks or loose clamps that let unfiltered air bypass the filters and reach the compressor wheel.
Training and records
Train operators to read turbocharger trends, carry out washing correctly and recognise surging and abnormal noise. Keep a record of every wash, inspection, part change and overhaul, with the running hours at each event.
These records support warranty claims, help predict when parts will be needed and show whether the fuel and air systems are protecting the turbocharger.
About our HFO service team
This guide was written by our HFO service engineers, who maintain medium-speed engines and their turbochargers on stations across Africa. USP&E carries out that O&M work as the contractor of record, not as a broker, with 24+ years in the field, 150+ power projects in 45+ countries and 25,000 MW contracted since 2002. Our service model is set out on the operations and maintenance page.
Offices: Colorado Springs (1755 Telstar Dr, Suite 300), Knoxville (800 S Gay St, Suite 700), London (162-168 Regent Street), Johannesburg (22 Kildoon Rd, Bryanston), Cape Town (31 Brickfield Road, Woodstock) and China (No. 1 Ningzhou Road, Wuxi). Regions: USA | AFRICA | UK | UAE | CHINA. ISO 9001 and ISO 45001 certified.
HFO turbocharger service questions
How often should an HFO engine turbocharger be washed?
As often as the turbocharger maker specifies for the fuel and load, adjusted by trends in exhaust temperature and charge air pressure. Log each wash to see whether it keeps fouling under control.
What causes turbocharger surging?
Usually fouling, a blocked air filter, a dirty charge air cooler or operation outside the normal range. Reduce load and investigate before continuing.
Can turbochargers be overhauled on site?
Some work can be done on site with the right tools and training. Rotor balancing and blade repair usually need a specialist workshop.
Is a spare turbocharger worth keeping?
On remote sites, a spare cartridge or exchange unit can shorten outages greatly, because workshop turnaround and transport can take a long time.
Plan turbocharger support
Send the engine and turbocharger models, running hours and recent trends, and our engineers will propose a service routine and spares plan.
Phone +27 10 822 2324 during office hours, or write to info@uspeglobal.com at any time; the service enquiry form also routes straight to our project engineers. Engines and station equipment are listed in our equipment inventory.