Copper is a major metal and an essential element used by man. It is found in ore deposits around the world. It is also the oldest metal known to man and was first discovered and used about 10,000 years ago. And, as alloyed in bronze (copper-tin alloy) about 3000 BC, was the first engineering material known to man.
Today, copper’s uses have expanded to include heating, cooling and refrigeration, electrical wiring, electronics, power generation and transmission, automotive applications, antimicrobial uses and many more.
Copper is essential for modern living. It delivers electricity and clean water into homes and cities and makes an important contribution to sustainable development. Copper retains most of its value when recycled and for this reason, has a relatively high scrap value. In addition, copper can be recycled repeatedly, which means that it is rarely lost from the world’s copper resources and it has important sustainable benefits as a result.
Copper is a major metal and an essential element used by man. It is found in ore deposits around the world. It is also the oldest metal known to man and was first discovered and used about 10,000 years ago. And, as alloyed in bronze (copper-tin alloy) about 3000 BC, was the first engineering material known to man. Today, copper’s uses have expanded to include heating, cooling and refrigeration, electrical wiring, electronics, power generation and transmission, automotive applications, antimicrobial uses and many more
Copper Tubing Africa prides itself on the fact that it only uses virgin metal in the form of cathodes supplied from mines in Zambia and wire supplied from mines in Phalaborwa, Limpopo Province
Copper’s recyclability has meant that only about 1.1 trillion (+/-13.6%) of the world’s total copper resources, estimated at more than 8.1 trillion pounds, have been mined throughout history. In addition, around half the demand for copper in the US is met from recycled material.
Manufacture of copper tubing
Copper Tubing Africa is one of South Africa’s most successful manufacturers of copper tubing and related products. MD Mark Wynn and Technical Director Vladimir Ziserman showed me around the Hospital Street, Cleveland, Gauteng plant, which in essence is a mill that melts virgin copper before casting it into pre determined size ‘rods’ which then go through a pointing process before being drawn.
The production of copper tube begins with raw material. Copper may be either copper scrap, newly refined copper (called cathode copper, or simply cathode) or copper ingots. The choice of raw material depends on economic factors such as cost and availability, and the technical capabilities of the plant’s melting furnace.
Technical Director Vladimir Ziserman and MD Mark Wynn
Copper scrap for tube making is most often in the form of recycled copper wire that has been stripped of its insulation and/or baled copper tube that has been removed from demolished buildings. Another common form of scrap is the so-called “home” or “runaround” scrap generated within the tube mill itself.
Copper Tubing Africa prides itself on the fact that it only uses virgin metal in the form of cathodes supplied from mines in Zambia and wire supplied from mines in Phalaborwa, Limpopo Province.
“Cathode copper gets its name from the way it is made. Cathode is produced in large (football field-sized) electrolytic cells that refine the relatively impure (99+%Cu) blister copper taken from smelting and refining furnaces. In the cells, cast copper anodes (the positively charged pole) approximately one metre square and weighing 80 kilograms, are dissolved in a copper sulphate/sulphuric acid solution under the action of a dc electric current. The copper is immediately re-deposited onto negatively charged cathodes by a simple electroplating process. Cathodes are removed from the cells when they have grown to about 136 kilograms. Cathode copper contains at least 99.95% Cu, making it one of the purest metals in common usage,” explained Vladimir Ziserman, who has been with the company for 23 years and is in charge of the melting and casting processes.
From the holding furnace (or tundish) copper is cast into large “logs” by either the continuous or semi-continuous method
“You can use copper ingots which are cast from remelted cathode or refined scrap. Ingots are mainly used by tube mills that operate small melting furnaces, whose doors are not large enough to accommodate cathodes or large bales of scrap,” continued Ziserman.
“Our eight furnaces are not set up to use ingots, and besides we only use virgin material,” quipped Wynn.
Melting and casting
The charge of raw materials is melted in a furnace, which in a large tube mill, may hold up to 20 tons of metal. In most mills, molten metal is transferred from the melting/refining furnace into a holding furnace or into a tundish, either of which acts as a reservoir for the casting process thereby allowing the melting/refining furnace to begin processing the next charge. The holding furnace/tundish is heated just enough to maintain the molten metal at a constant temperature. To protect the copper from oxidation, the liquid metal surface may be covered with a blanket of graphite powder.
From the holding furnace (or tundish) copper is cast into large “logs” by either the continuous or semi-continuous method.
In continuous casting, metal is poured into horizontally oriented, cylindrical graphite molds, which are water-cooled to force the copper to freeze quickly. As the copper in the chilled moulds solidifies, gripping devices withdraw it in short, 25mm steps. At the same time, more molten copper flows into the mould from behind. Slowly, a solid log of pure copper is formed. These logs can vary in diameter up to approximately 300mm, depending of the requirements of each mill. A moving saw cuts the log into sections as it emerges from the casting machine. These sections are known as billets.
Copper Tubing Africa uses wire supplied from mines in Phalaborwa, Limpopo Province
When the casting process is done vertically, it is often called semi-continuous casting because the process has to be interrupted when the length of the log reaches the depth of the pit beneath the moulds. In this process, the moveable, water-cooled floor of the mould cavity (or a dummy block) seals the mould until the first volume of copper freezes. Molten metal is then added to the mould at the same rate that the floor is withdrawn downward. When the resulting logs reach the desired length, the mould is withdrawn upward, allowing the logs to be removed from the pit.
In a modification of the process practiced by some tube makers, the casting moulds contain a central water-cooled core, and the log emerges as a very thick-walled pipe called a tube round.
The next step is to reheat the billets to approximately 835°C to make the copper pliable. A pointed rod called a piercing mandrel is then driven lengthwise through the center of the billets to create what will eventually become the inside wall of the plumbing tube. Obviously, this step is not needed if the billets are cast as tube rounds. Piercing can take place either immediately before, or concurrent with extrusion.
Extrusion is often quite accurately compared with squeezing toothpaste from a tube. During extrusion, the billet, heated to the proper hot-working temperature, is placed in the chamber of an extrusion press. The horizontally mounted chamber contains a die at one end and a hydraulically driven ram at the other. The face of the ram is fitted with a dummy block that is slightly smaller in diameter than the billet. The ram may also be fitted with a piercing mandrel, or, if the billets are hollow, with a rod that matches the diameter of the cast hole in the billet but is slightly smaller than the hole in the die at the opposite end of the chamber. As the ram moves forward, the copper is forced over the mandrel and through the hole in the die, causing a long hollow tube, about 70mm in diameter and 26 metres long to squirt out of the extrusion press (the length can vary depending of the capabilities of each mill). Just like toothpaste, only hollow.
One of the eight furnaces that Copper Tubing Africa uses in its melting department
Metal near the surface of the billet extrudes backwards over the undersized dummy block, forming a shell. This shell contains copper oxide and is therefore removed and recycled to the refining furnace. As the extruded tube emerges from the die, rollers carry it along on a long run-out table so that it remains straight until it is cool enough to handle. The tube is then cleaned to remove surface oxide scale in preparation for the next stage in the tube-making process.
Drawing simply involves pulling the hollow tube through a series of hardened steel dies to reduce its diameter. Before each step of the drawing process, the tube is pointed at one end to fit through the next die, whereupon it is gripped by automatic jaws attached to a rotating drawing machine called a bull block.
All the copper “logs” have to be pierced on the end pieces so extrusion and drawing can take place
A tapered plug mandrel, which may be either fixed or floating depending on the process used, is placed inside the tube. (Floating plugs are used with bull blocks. Stationary mandrels are used for relatively short lengths of tube that are drawn on linear drawbenches.) As the tube is drawn onto the spinning bull block, the mandrel and die act together to reduce both the tube’s outside diameter and its wall thickness. The mandrel also imparts a smooth surface to the tube’s inside surface. The tube is drawn in several stages until the desired diameter and wall thickness is attained. Drawing work-hardens the copper, and the tube is now quite stiff.
Tube that is to be sold in the soft condition, generally as coils, is next passed through a continuous annealing furnace operating at 704°C. The furnace is essentially a long heated box filled with a protective atmosphere to prevent the copper from oxidizing. In plants that are not equipped with continuous annealing furnaces, annealing is done in batches in what are aptly called bell furnaces. These furnaces look very much like large cylindrical church bells, the open bottoms of which can be sealed to keep air out. Coils of tube to be annealed are stacked under the bells and heated in a protective atmosphere. Annealed tube can be visually distinguished from hard-drawn tube by its matte surface finish. Aside from their appearance and stiffness, however, annealed and hard-drawn tubes have the same qualities and, in general, act identically when in contact with properly treated drinking water.
The tube is now almost ready for shipping. It may be cleaned to remove any traces of drawing lubricants or other contaminants. This is particularly important for special-use products, such as tube that is intended to carry medical gases and refrigerants for cooling applications. In all cases, however, samples of the finished tube are taken at regular intervals to ensure that it meets all requirements of size, wall thickness and quality as required under applicable standards.
Recent business-sector changes—copper cost increases, globalisation, technology advances, and rapidly changing consumer tastes—have had big effects on copper producers and extruders, and have led to profound changes in the industry. Change isn’t necessarily bad; it brings both risk and opportunity. Changes must be sensed, interpreted, and acted on. Charles Darwin said, “It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.” This applies to industry today.
Although large size and global coverage can make an organisation powerful, power isn’t the only ingredient for success. Flexibility, innovation, and speed to market are still important competitive assets.
Copper “logs” ready for further beneficiation
Since its inception in 1988 Copper Tubing Africa, known in the industry as CTA, has shown that it is a flexible company, one that innovates and prides itself on getting its product to market on time.
History tells us that Woollfe Matchet opened a structural steel fabrication and erection company, Matchet Engineering in the 1940’s. In the early 1950’s Matchet acquired Aerys & Heuberger, a manufacturer of washers and earth clips, and subsequently changed the company name to SW Products. The company is still an integral part of the group but has changed its product mix to manufacturing lugs and ferrules, with a zinc coated finish.
Copper Tubing Africa was established in 1988 when it was registered to manufacture copper tubing of all shapes and sizes. Influential in this decision was Woolfe’s son Dave Machet.
Matchet had no formal engineering training, but was schooled through experience in the family business. After his father’s passing, he worked with his mother to keep the family business alive. He continued to run the business until late 2009 before taking up a position as MD of The Copper Development Association, Africa (CDAA) in 2010.
During his reign as CEO of CTA Matchet developed the company into a leading manufacturer and supplier of domestic, medical, refrigeration, air conditioning and general industrial copper tube.
Matchet was also instrumental in the development of multi-channel tubing in 2005, an exciting venture and a world first at the time. International research and development agencies were unable to perfect the process, using copper. When CTA heard that attempts internationally were proving unsuccessful, they put their R&D team on it and were able to produce prototypes within a few months. Their experience and unique method of producing copper tubing for the local plumbing, electrical and refrigeration industries afforded them the opportunity to approach production differently with successful results.
Drawing taking place to produce copper tubing
CTA formed a joint development agreement with Mitsubishi Materials Corporation, Japan, and the multi-channel copper tube has had an enormous impact internationally on the refrigeration and heat exchange industry.
New owners: Medu Capital
In 2008 CTA brought Medu Capital on board as a strategic financial partner. Medu Capital is a majority black-owned and managed private equity focused business. They acquired 41.3% of CTA’s shares in a deal that afforded them the opportunity to play a role in the continued development and growth of CTA’s business.
In 2014 Medu Capital subsequently purchased the remaining of Matchet’s shares in CTA and appointed Mark Wynn as MD.
2014 also saw CTA patent an anti microbial shower mat, a product that Matchet had developed through his own experience and his research into the antimicrobial properties of copper and its potential ability to kill bacteria, fungi and viruses.
Corroborating the theory
Machet said at the time that as a long-distance runner he suffered from athlete’s foot and struggled to get it under control for at least three years. After hearing the statement about the antimicrobial properties of copper, Machet started doing some research and found that 70 percent of the world’s population suffers from athlete’s foot. After hearing about these natural properties found in copper, he went into the factory and produced a pure copper duckboard for his bathroom at home. Machet started using the duckboard in the shower and two months later his athlete’s foot problem was cured and, according to Matchet, he hasn’t suffered since.
“Obviously, the fungi couldn’t survive on the copper bathroom mat and the cycle of re-infection was broken – personal proof that copper is antimicrobial and can kill bacteria and fungi,” said Machet.
Facts and figures
Copper Tubing Africa produces approximately 300 tons of copper tubing every month in various diameters, from 4mm up to 108mm. Besides the eight furnaces, it also has 16 double sided drawing machines. It currently employs 216 staff and is SABS ISO 9001 certified.
The company has been progressive in developing other products than the manufacture of tube. These include the previously mentioned multi-channel tubing and anti microbial shower mat as well as chaplets for use in furnaces. Currently it is developing a mechanical solar panel that will be maintenance free because of the use of its primary material, copper.
For further details Contact Copper Tubing Africa on TEL: 011 615 7193 or visit www.coppertubing.co.za