Pressure on Queensland’s vital timber resource for railway sleepers will be eased significantly with the opening of a $2 million timber preservation plant at Takura, near Maryborough.
The plant, established by Koppers Australia, is the first in Queensland equipped to carry out advanced technology preservation processes suitable for pressure impregnation of sawn hardwood timber sections with creosote/oil-type preservatives.
The demand for hardwood as sleepers is such that at the present rate, timber industry authorities say supplies could be exhausted within 15 years if their use in the untreated form is continued.
However, the existing commercial performance of treated rail timbers and the presence of a preservation plant such as that at Takura, located strategically within the state, is expected to reverse the prospect of a shortfall.
Sleeper replacement is a major track maintenance expenditure faced by Queensland Railways involving 50,000 cubic metres of sawn timber or about one million units annually, the service life of which averages only about 14 years.
The short service life is due to a very high level of premature failure in untreated sleepers caused by weathering, fungal decay and insect attack, the levels in Queensland would be higher than in any other state.
Their replacement by the treated version, estimated to give almost three times the average service life, would ultimately result in major savings in replacement costs and substantially reduced maintenance expenses.
Koppers’ hardwoods division manager Wal Johnson, points out that savings of major proportions are indicated by the service record of treated hardwood sleepers treated by Koppers and used in installation and replacement programs in Tasmania and Western Australia.
According to Johnson, the ultimate benefit of using treated hardwood for railway sleepers in Queensland is that up to 80,000 cubic metres of sawlog could be conserved annually.
The continued depletion of hardwoods available to meet sleeper demand is a growing concern.
Queensland Railways acting state engineer John Casey is “very unhappy” about meeting the immediate need for sleepers but says the establishment of the Takura plant is “on the right track”, giving some hope for the future.
A Queensland Department of Forestry spokesman warns of a decline in the number of private forests and the inaccessibility of some stands.
“The supply from the state forests will not be enough to satisfy demand so that any initiative which extends significantly the life of hardwood now being put to commercial use is to be commended,” he said.
About 20% of the remaining hardwood forest is privately owned; in recent years, about 75% of sleepers have come from this source.
However, according to a report produced by forestry, many private owners are farmers whose primary interest is in land development for agricultural or pastoral pursuits.
Circumstances encourage these owners to sell the entire forest crop and convert the land to other uses, says the report, concluding that the sleepers supply from private lands will decline sharply.
Increasingly, those designers and specifiers throughout Australia who have confirmed timber as a reliable building material also recognise the economic and ecological benefits of preservation technology.
The Takura plant utilises a unique treatment method available only from Koppers in Australia.
The timber, usually at the ‘green’ stage. is first incised by passing it between rollers with protruding knives that puncture it to the required penetration depth and according to a predetermined pattern. The function of incising is to increase the penetration of the preservative and ‘stress relieve’ the surface, thus reducing the extent of checking and splitting during the treatment process and in service.
Next, Sleepers are subjected to a Boulton-type preconditioning involving heating the preservative under reduced pressure conditions. This procedure prepares the wood to accept the preservative, making void spaces in the treatment zone and access to these by removing moisture. Following preconditioning, the preservative is driven into these spaces under pressure.
The final steps are removing surplus preservatives from the process vessel and applying a vacuum from the timber surface.
Incised and Boulton-treated timber is thus given an envelope of penetration in the true wood zone and full treatment of any sapwood present.
The Takura plant is equipped with two massive pressure cylinders, each 29 m long, 2 m in diameter and weighing 40 tonnes, capable of large-scale economic timber impregnation. One is equipped to treat with creosote or oil blends, the other with waterborne Tanalith C.
The installation of a pine debarking machine and other fabrication plants is also planned at Takura to produce fence rails, outdoor furniture, and landscaping products from small pine rounds.
Sid Jensen will manage the Takura plant from Maryborough.
Contracts are already underway for Queensland Railways and the South-East Queensland Electricity Board.
Sugar mills have also shown a strong interest in using treated hardwood sleepers. A recent survey of requirements in the Mackay area showed concern among sugar cane railway operators about the service life and cost of untreated timber tracks due mainly to decay and termite attacks.
Koppers Australia Pty Ltd was formed in 1967 as a joint venture between Koppers Company Inc. of Pittsburgh, USA, and Broken Hill Proprietary Co. Ltd of Australia. The company is structured into three sections – coal tar, timber preservation and engineering divisions. The Takura plant is part of the operations of the timber preservation division.