This page explains what availability means, what drives it on an HFO plant, and how a mine should measure it in an O&M contract.
Availability and reliability are not the same
Availability is the share of time a unit or plant is able to produce power, whether or not it is asked to. Reliability is how often it fails unexpectedly. A plant can have good availability with many short failures, or poor availability with few failures that take a long time to fix. A mine needs both, measured at the plant level against the load it must carry.
Driver 1: the number of units
An HFO plant for a mine is usually built from several medium-speed engines in parallel. If the plant has one more engine than the peak load needs (N+1), one unit can be in maintenance or fail without the mine losing load. Many mines choose N+2 for large plants or when one engine is often in a long overhaul. Unit count is decided at design, which is why availability starts with the EPCM design for mines, not with the operator.
Driver 2: fuel treatment
HFO must be heated, separated and filtered before it reaches the engines. Poor separation lets catalytic fines and water through, which wears injection pumps, injectors, liners and rings, and turns planned overhauls into unplanned ones. Separator maintenance, fuel testing on delivery and sludge handling are among the highest-value tasks on an HFO plant. Our page on HFO fuel systems explains the treatment train.
Driver 3: planned maintenance
Medium-speed engines follow maintenance schedules based on running hours, from routine inspections to major overhauls. Planning those overhauls so that only one engine is out at a time, with parts on site before the engine is opened, is the difference between a planned outage of days and an unplanned one of weeks.
Driver 4: spares and people
Remote mines cannot wait for parts to clear customs. A critical spares store sized for the plant, with cylinder heads, injection pumps and turbocharger parts ready, keeps repairs short. So does a stable operating team trained on the plant, with clear shift handovers and work permits.
What an O&M contract should measure
| Measure | Why it matters |
|---|---|
| Plant availability against contracted capacity | Tells the mine whether its load can be carried |
| Forced outage hours | Shows reliability separately from planned work |
| Load shed events | Measures what the mine actually felt |
| Fuel and lube oil consumption | Tracks efficiency and engine condition |
| Maintenance backlog | An early warning of future failures |
Contracts that pay or penalise on these measures align the operator with the mine. On plants we operate, availability is reported monthly with the evidence behind it, and our case studies show 95% availability as an achieved figure.
From HFO today to gas later
Many mines plan to add solar and batteries, or to move to gas when it becomes available. A well-run HFO plant does not stand in the way of that; it becomes the firm base around which the hybrid is built. See adding solar and batteries to an HFO plant.
HFO plants built and run by one team
USP&E builds and operates HFO power plants for mines and utilities under EPC, EPCM and O&M contracts. We have delivered 150+ power projects in 45+ countries and contracted 25,000 MW since 2002, and we work by Speed with Excellence and Extreme Ownership. Read our HFO power station EPC and O&M guide for the full picture.
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HFO plant availability FAQ
What availability can an HFO power plant achieve?
A well-designed and well-run HFO plant with spare units can achieve high availability. Our case studies report 95% availability as an achieved figure.
What is the biggest cause of lost availability on HFO plants?
Poor fuel treatment and unplanned engine work are common causes. Separator maintenance and planned overhauls with parts on hand prevent much of it.
How many spare engines does a mine HFO plant need?
At least one more engine than the peak load needs (N+1); large plants or those with long overhauls often use N+2.
How should a mine measure its power plant operator?
By plant availability against contracted capacity, forced outage hours, load shed events, consumption and maintenance backlog, reported monthly.
Need firm power for a mine?
We can design, build and operate an HFO plant around your mine’s load, or review availability on a plant you already run.
An engineer will reply if you email info@uspeglobal.com, call +27 10 822 2324 or fill in the HFO project team. HFO engines and sets we hold are in the USP&E inventory.