Modern Production Methods for High
Volume Copper Tube Manufacturing
by
Dr. Rainer Hergemoeller
Copper Tube Machinery Specialist of Schumag AG
INTRODUCTION
Schumag Group supply equipment and machinery to the global copper tube industry.
Most of the well-known manufacturers of copper tube, throughout the world, are customers, and current users of Schumag Group Machinery, which stands out due to its superior design, build quality and high volume productivity.
Copper tube products made on Schumag equipment are generally: -
- Sanitary tubes: drawn in hard or half-hard condition
- Industrial tubes: smooth or with an inner grooved pattern
in the form of: -
- Straight lengths
- Pancake Coils
- Bunch coils
- Level Wound Coils (LWC).
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Complete Copper Tube Drawing Facility supplied by Schumag Group
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SCHUMAG GROUP PRODUCT RANGE FOR COPPER TUBE PRODUCTION
Schumag's specialist product range for the production of copper tubes revolves around the areas of drawing, finishing and handling: -
Tube Drawing
- Break-down drawing equipment (Cascade) starting with larger sized mother tubes
- Spinner Blocks
- Combined Drawing Machines for finishing
- Half-hard drawing equipment with integrated inductive annealer
Tube finishing
- Tube straightening and cutting lines
- Re-sawing and deburring machines
- Pancake coilers
- Level winders
- Equipment to make inner grooves
- Eddy current testing lines
Tube Handling
- Complete Factory Layouts
- Systems to transport and feed straight length tubes
- Tube storage for straight lengths up to, typically, but not limited to, 120 mtrs
- Recoilers and pay-offs for mother tubes
- Tube preparation stations, including Crush Pointing Machines
- Basket storage and conveyor systems
- Basket loading and unloading devices
- Coil Transportation Systems
- Tube cutting equipment
- Bundle loader and tube separation devices
- Bundling De-Scrambling Machines
In summary, Schumag Group can offer the complete equipment range, after mother tube production.
MOTHER TUBE PRODUCTION
The processing of copper tubes, using Schumag Equipment, begins with a larger diameter mother tube, manufactured by different methods. Irrespective of the type of mother tube and its production process, the breakdown passes take place on Schumag Cascades, in straight drawing, to a more efficient and suitable size of coiled tube for the MRB Schumag Spinner Blocks.
Nowadays, the three common processes used to produce the mother tube, to draw seamless copper tube are, Extrusion with Cold Pilgering, High Ratio Extrusion and CAST AND ROLL™. Each has its specific characteristics, as well as advantages and disadvantages. In principle, the highest possible piece weight minimising manufacturing losses, is sought because, simply, the greater the coil weight, the more efficient the subsequent processing becomes.
In the case of Extrusion with Cold Pilgering and High Ratio Extrusion, cast billets are sawn into lengths and, prior to being pressed are reheated to the appropriate extrusion temperature (approximately 880ºC). Manufacturers of copper tubes, who do not have a foundry, generally outsource the raw material in billet form.
Low Ratio Extrusion with Cold Pilgering
This method has been used for many years, as, it is possible to process extruded tubes of significant weight through the cold pilgering process. A typical extruded shell cross section is dia. 85 x 13mm wall thickness and hence the extrusion can be done with a relatively low force (low ratio extrusion).
The extruded shell is reduced to mother tube size on the Pilger Mill. Smaller pilgered tubes, eg, dia. 40 x 1.8mm, can be re-drawn directly onto Spinner Blocks, however, this can restrict the potential overall productivity of the plant.
The thick-walled shell has proportionally low eccentricity values and the pilgering process improves the concentricity.
One disadvantage is the inconsistency in productivity levels between the Pilger Mill (approximately 10,000 t/yr), the press itself, and modern production capacities, which can achieve upwards of 20,000 t/yr. Capacity can be increased with larger diameter pilgered tube, but in this case a Schumag Cascade is recommended. Nowadays, piece weights can easily be in the region of 500 kg. Moreover, the capacity of the extrusion press is often several times greater than that of a pilger mill, thus rendering the pilger mill as a potential bottleneck area.
It is possible for the pilger mill to work from a buffer stock of shells, and similarly so after the appropriate modification, the extrusion press can accommodate other products, eg, differing materials and profiles.
In order to increase tube production capacity, additional pilger mills have to be used. The investment costs for a pilger mill are relatively high and from experience and market feedback, maintenance can be intensive and expensive.
High Ratio Extrusion
A modern High Ratio Tube Extrusion Press can produce thin-walled mother tubes of significant weight with good concentricity. Large extrusion presses can make tubes of up to approximately 500 kg capacity. However, this size of press will have up to and in excess of 100,000 t/year capacity, which is rarely fully utilised. It is therefore also possible to use the extrusion press to make other special products in addition to the copper mother tube.
Smaller examples of the High Ratio Extrusion Press can produce up to 50,000 t/year which if used for copper tube only, allows expansion capacity. The affect of the smaller press and force is smaller piece weights, i.e. between approximately 250kgs and 350kgs. However, this disadvantage is often compensated with modern production facilities and automated equipment.
This method of mother tube production allows for flexibility and good utilisation of the overall plant capacity and investment. The combination of High Ratio Extrusion Press and subsequent drawing on Schumag Equipment produces high quality copper tubes.
CAST AND ROLL™
This relatively new process, has increased in popularity since its launch in 1992 by Outokumpu Castform.
The process offers compact design of the equipment, from smelting, tube casting, right through to the rolling of a mother tube and consequently, it is very definitely suited for new copper tube production facilities with projected capacity requirements of between approximately 10,000 to 18,000 t/year.
The soft rolled tube is reduced on a Schumag Cascade and subsequently processed as a hard tube on MRB Schumag Spinner Blocks. The coil weights can be up to 700 kg, which is ideally suited to downstream efficient production.
To further expand production capacity, the dimensions of the rolled mother tube can be increased or a complete CAST AND ROLL™ Line installed to operate in parallel with the existing facility.
There has been an Industry trend since its introduction to the market place, to use the CAST AND ROLL™ technique. This has been particularly apparent in greenfield applications, but is also useful for expansion of an existing, fully utilised copper tube plant. Its inherent characteristics allow for a self sufficient process from casting to final product, however, conversion to and production of other materials and alloys is not easily achievable.
Due to the size of the rolled mother tube (approximately dia. 48 - 54mm), it is only possible to produce final products with a maximum diameter range of approximately dia. 35 - 42mm.
These sizes do however, cover the majority of the global product range and requirements for sanitary and industrial tubes.
SUMMARY
The three processes described above are the most frequently used, more often than not followed by Schumag Cascade, in various formats, MRB Schumag Spinner Blocks and Schumag Finishing Lines.
Other processes, of mother tube production have been introduced to the market place over recent years, but are not nearly as apparent in high volume production environments.
As the Single Source Supplier for all drawing, finishing and handling systems, Schumag and MRB Schumag considers it a fundamental task to maintain close contact and technical collaboration with all our existing and potential Customers and Project Partners worldwide.
Our aim is to have the most advanced technology to meet customer requirements.
Further information :
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