AT first glance, the heavy-haul export coal line operated by Transnet Freight Rail between South Africa's Highveld coal fields and the massive coal terminal at Richards Bay on the country's eastern seaboard is the perfect railway.
At 588km, the distance between the mines and the port is relatively short and the gradient favours loaded trains which run in rakes of 200 wagons, each carrying 84 tonnes of coal, hauled by new dual-voltage electric locomotives. Gross train weight is 20,800 tonnes.
The privately-owned Richards Bay Coal Terminal (RBCT) is the largest of its kind in the world, with six berths along a 2.2km-long quay where four loaders transfer coal at up to 12,000 tonnes an hour to waiting ships.
As one of Transnet's two crown jewels (the other is the 861km heavy-haul ore line from Sishen to Saldanha), money has been lavished on the coal line as Transnet continues to implement its seven-year market demand strategy which will see Rand 307bn ($US 29bn) invested in rail capacity by 2018.
Yet tension continues to simmer between Transnet and coal mining companies - many of which are shareholders in RBCT - over the railway's inability to keep up with the terminal's capacity. Following its recent Phase V upgrade, completed in 2010, RBCT has the capacity to handle 91 million tonnes per year, whereas Transnet transported only 71 million tonnes of coal to Richards Bay last year.
Tensions boiled over briefly last year when Transnet chief executive Mr Brian Molefe fired a broadside at some of RBCT's shareholders - which include heavyweight mining companies such as BHP Billiton - for not giving smaller companies access to the terminal.
Molefe said he had attended a meeting at BHP Billiton to discuss its refusal to allocate an extra one million tonnes of its annual export allocation to emerging coal mining companies. To redress this, Molefe said Transnet was looking at using some of its own land at the port to build another coal terminal for the "smaller guys."
By "smaller guys" Molefe means the emerging mining companies which have come up under South Africa's Black Economic Empowerment (BEE) programme which aims to reduce historical imbalances by giving black-owned businesses a leg up into the white-dominated economy.
BHP Billiton was not amused. It said Transnet's claims that it was not committed to black economic empowerment were unfounded and that the problem lay not with the mining companies but with Transnet's inability to run more coal trains to Richards Bay.
"The reality is that [Transnet's] rail capacity does not even match the current port capacity of 91 million tonnes per annum, which means that none of the existing RBCT shareholders (including numerous BEE shareholders) have access to their own, nameplate capacity at the port," says BHP Billiton. RBCT exported 70.2 million tonnes last year.
BHP Billiton also noted it had given up 8 million tonnes of its 26-million-tonne share to black-owned mining companies in various deals since 2001.
Much of the extra capacity released by Phase V was allocated to BEE miners, some of whom are now also shareholders in RBCT. Last year, RBCT chief executive Ms Nosipho Siwisa-Damasane told a local mining journal that the entire fifth phase capacity had been allocated to junior miners and seven of the terminal's 19 shareholders were junior or new black-empowered miners.
Transnet has battled over the years to keep up with Richards Bay's expansion. The terminal opened in 1976, four years after the Transvaal Coal Owners' Association won a contract to supply Japanese steel mills with 27 million tonnes of coal over 10 years. Annual capacity was 12 million tonnes but this was raised during subsequent expansion phases to 24 million tonnes in 1979, 44 million tonnes in 1984, 53 million tonnes in 1991, and up to 72 million tonnes in 1999.
To serve the port, the former South African Railways built a dedicated heavy-haul line from the town of Ermelo, on the edge of the coalfields. The line was electrified at 25kV ac and trains were hauled by a fleet of state-of-the-art class 7E and later 11E locomotives. The line is double-track, except for a short section through Overvaal tunnel.
Export coal traffic amounts to 15 200-wagon trains a day but operations are complicated by the presence of other freight trains on the line.
A big problem, however, presents itself at the first milepost. The 25kV ac electrification starts in the vast yard at Ermelo but the wires from there to the mines are energised at 3kV dc. Until the arrival of dual-voltage locomotives last year, coal trains ran first to Ermelo where they were marshalled into longer consists and 25kV locomotives took over. The process added considerable time to the journey.
Transnet hopes its new dual-voltage class 19E locomotives will go some way to alleviating that bottleneck. Last July, it began running "Shongololo" trains - named after a large millipede - which run as two 100-wagon trains with distributed traction from mine to port behind the same power. The Shongololos are able to bypass Ermelo and have cut the cycle time by between eight and 10 hours.
Although the coal trains still run at a maximum speed of 80km/h, they are able to achieve higher average speeds which have cut the journey time from the mines to the port to 17 hours.
Transnet invested Rand 3.3bn in the 110 new locomotives and 696 hopper wagons and says its plans are well advanced to boost capacity on the line to 81 million tonnes a year, a target it plans to reach by 2017.
"We can do it," says Transnet. "The rolling stock, the human resources are in place, the money is there, but it requires small capital projects to get it to consistent, sustainable levels."
To be fair to Transnet, there are other mountains to climb. Export coal from the developing Waterberg coalfields in the far northwest also moves down the coal line to Richards Bay, traffic that is expected to top 28 million tonnes a year in the next few years.
Transnet also hopes to transport more general freight to the port by rail. A Rand 15bn initiative called the Eastern Catchment Integrated Corridor Strategy seeks to boost the port's attractiveness to shippers of other bulk commodities such as timber, chrome and ferrochrome, magnetite, fertilisers, chemicals and containers. Richards Bay already handles 23 million tonnes a year of other cargo and Transnet National Ports Authority would like to boost that to 59 million tonnes by 2040.
If it is not to travel by road - and there is a good deal of pressure from government to move freight from road to rail - all that extra traffic will have to come down the coal corridor or along the north-south corridor running through Swaziland to link the Maputo Corridor with the country's second city, Durban.
To alleviate some of the future pressure, Transnet is pushing ahead with a new line running eastwards from South Africa into Swaziland. The rail link will run from an existing branch line railhead at the logging town of Lothair and cross mountainous country to reach the Swaziland border.
From there the contractors may build a new track on the bed of a long-abandoned ore line from Ka Dake to Sidvokodvo, or follow an entirely new route from the border to a junction on the north-south line.
Transnet's capacity troubles are not the only problem in the supply chain. In January, train service was halted for nine days following a power failure at the main sub-station that feeds the coal terminal. While trains were running normally within 10 days, RBCT dropped its export target for 2014 from 75 million tonnes to 73 million tonnes.
It is against this backdrop that the rumblings continue at Richards Bay. Transnet has promised to lift capacity on the coal line to 95 million tonnes by 2018.
Meanwhile, RBCT's shareholders are to go ahead with a sixth expansion phase which will raise capacity by 19 million tonnes to 110 million tonnes. The expansion would require another tippler and one more ship loader as well as a bigger stockpile area and more conveyors and silos.
There was a brief spat earlier this year over who would install new capacity at the port. In January Transnet said it was investigating the possibility of building a new terminal, even as RBCT was wooing Transnet as its partner for the phase six expansion.
Then RBTGrindrod, another contender, waded into the fray as it sought Transnet's hand in a plan to build more capacity for junior miners.
As the established operator, RBCT clearly has the advantage over any potential newcomers which it would be able to beat on capital cost alone. It has also said it would allocate the extra 19 million tonnes to junior miners.
However, the junior miners will be unable to access that extra capacity until Transnet is able to rail the full amount of coal to Richards Bay.
In March, Transnet's ports authority announced that it would not build a separate coal terminal but would instead expand the port's existing Dry Bulk Terminal.
Transnet is not sitting on its hands. The Shongololo service has improved turnaround times with locomotives now running in 41-hour cycles instead of 58 hours and wagons turning around in 48 hours instead of 63.
Transnet and RBCT personnel also collaborate on train movements and a bypass within the port allows some coal trains to go straight to waiting ships instead of the stockpile. As RBCT knows which vessels are waiting to load which type of coal it is able to coordinate train arrivals.
Transnet is currently dispatching 14 to 15 trains - or 230,000 tonnes of coal - every day to Richards Bay. To meet the terminal's 91 million tonne capacity, it needs to send 16 trains - or 250,000 tonnes of coal. One more train a day and there will be smiles all round.