HIGH-pressure hydraulic equipment of a type typically used in the factories, mines, workshops and building sites of the Asia-Pacific region is lending itself to a more elegant purpose in Papua New Guinea.
The 700 bar (10,000psi) Enerpac precision hydraulics are being used to streamline stamping processes by a gold refiner producing about 120,000 bars of the precious metal a year, mainly for the local and Asian jewellery markets.
The operation is now being expanded to include the striking of decorative medallions.
Metal Refining Operations in Port Moresby uses two Enerpac 9-tonne bench presses to stamp the one-kilogram bars with PNG's international gold mark, the company's identification, the source of the gold and sometimes a number as well. Each bar is worth more than $US8,000.
Simplicity and reliability are the keynotes of the operation, which replaced the stamping of the gold bars by hand using a hammer.
According to operations manager Michael Hyland, the conversion to Enerpac presses has meant standardisation of the process, which can now be carried out by relatively unskilled workers under the eye of trained operators.
One operator was trained by Enerpac in Sydney last year and, along with supervising staff, now leads the maintenance team that services the presses.
The two bench presses involved, equipped with single-acting 9-tonne cylinders, are each activated by a PAT-1102N foot-operated Enerpac air hydraulic Turbo pump, which recycles its own exhaust gases to increase speed of actuation and power. The stamping operation requires about six tonnes.
"The correct pressure was originally reached by trial and error, but now we have clock gauges installed and the workers stamp to the desired pressure," Mr Hyland said.
Gold bars are pressed in batches of a few thousand at a time. Metal Refining Operations buys crude gold bullion from major mines as well as individual prospectors, either as metallic gold or in mineralised form.
The metal is refined up to marketable quality, with nearly all the product being sold to Asian markets, largely for jewellery manufacture.
The company has now progressed to the striking of gold and silver decorative medallions, which are pressed out of metal sheets and the waste remelted.
For making 10mm diameter gold medallions, the existing 9-tonne Enerpac presses are used, but silver - a much harder metal - requires a substantially larger press.
At present the company is using a borrowed press that is capable of the desired 38-42 tonnes, but is planning to upgrade to an Enerpac 180-tonne press to do the job.
The silver and gold medallions are used as mementos or commemorative medals or are worked by craft jewellers into necklaces, bracelets or earrings. A typical necklace may include 10-15 small medallions, while a bracelet may have 3-6.
Some medallions have markings, which are pressed into the metal. A typical marked medallion has a bird of paradise on one side with the words Metals Refining Operations around the edge, while the other side features a lakatoy, which is a sailing boat with a reed sail that is the emblem of PNG's Central Province that surrounds Port Moresby.
The company produces gold in three qualities. The purest form, 99.999 per cent pure, is mainly for the electronics industry where it is used in circuit boards and pin connectors.
The next grade is 99.99 per cent pure and is used for jewellery, for precious metal plating, or simply for personal gold stocks. This gold is sold in 1kg bars.
The third grade produced by the company is 99.9 per cent pure, alloyed with copper that gives it a slightly reddish tint that is often required by the jewellery trade, which will commonly alloy it further. It is sold in 116-gram bars.
Enerpac North Queensland and Papua New Guinea territory manager Pat Molloy says the Metal Refining Operations application of standard Enerpac product demonstrates the power, precision, versatility and labour-saving potential of high-force hydraulics. Applied Power Australia 02 9743 8988.