HFO Power Station Auxiliary Systems: What Sits Around the Engines

Fuel reception, storage and heating

HFO arrives by truck, rail or ship and is stored in heated tanks, because at ambient temperature it is too viscous to pump. Tank heating, by steam or thermal oil coils or electric tracing, keeps it fluid. Transfer pumps move fuel to settling tanks, where water and heavy sediment separate out over time.

Diesel or light fuel storage is also needed, for starting, flushing the engines before a long stop and running when HFO is not available.

Separation and booster units

Centrifugal separators remove water and solids, including catalytic fines that can rapidly wear injection pumps and liners. Clean fuel goes to the day or service tanks, then to a booster unit that raises pressure and heats it to the viscosity required at the engine inlet.

Separator capacity and maintenance are common bottlenecks on older stations. If the separators cannot keep up, fuel quality at the engine drops and wear rises.

Lube oil and cooling systems

Each engine has a lube oil system with pumps, filters, coolers and often its own separator, because HFO combustion contaminates the oil faster than diesel. Cooling is usually split into high-temperature and low-temperature circuits, with radiators or cooling towers rejecting the heat.

Where water is scarce, as at many mines, radiators are preferred. Their sizing must allow for the hottest days at the site.

Starting air and instrument air

Medium-speed engines are usually started with compressed air from receivers charged by compressors. A separate, dried supply serves the instruments and pneumatic valves. Losing compressed air can stop a whole station, so compressors and receivers are normally duplicated.

Exhaust, heat recovery and emissions

Exhaust passes through silencers and stacks, and on some stations through waste heat boilers that produce steam for fuel heating. That saves fuel and electricity in the auxiliaries. Stack height and emissions controls depend on local rules and the project’s lenders.

Common auxiliary problems on older HFO stations

On older stations the engines are often in better shape than the auxiliaries. Separators that have not been overhauled lose capacity, tank heating coils leak, and booster units run with failed viscosity controllers in manual. Each of these quietly raises engine wear and fuel use.

A focused auxiliary audit, looking at fuel treatment, lube oil cleaning, cooling performance and compressed air, is one of the quickest ways to improve the reliability of an existing HFO station. It usually costs far less than an engine overhaul and can show where the station is losing output on hot days.

Electrical auxiliaries and waste

Station auxiliaries draw a noticeable share of the gross output, so the auxiliary switchboard, motor control centres and station transformer must be reliable. A black-start diesel set allows the station to restart after a total shutdown.

HFO stations also produce sludge from the separators and tanks, which has to be stored and disposed of under environmental rules. Our page on diesel station balance of plant and our guide to converting a diesel station to HFO go further.