112 / 116
110
M
arch
/A
pril
2007
With level-wound coils, however, the set
temperature cannot be attained inside the
coil, as is apparent in the charts. This results
in grain size and hardness variations. With
the Otto Junker high-convection technology
the temperature of the furnace chamber
at the end of the annealing cycle is almost
identical with the outside and inside coil
temperature. This means extremely uniform
annealing quality.
3.2 Equipment options
Following are three typical designs
presented from the multitude of roller hearth
system configurations.
A high-convection multi-tier roller hearth
furnace is used for bright annealing of level wound coils (LWC and
pancakes), with a vacuum lock chamber.
The equipment is made up of the following units:
• Loading table
• Entry vacuum lock chamber
• Entry vestibule
• High-convection furnace – indirectly gas-fired or indirectly
electrically heated
• High-convection cooling zone
• Exit vacuum lock chamber
• Unloading table
• Tray return track with cross conveyor, stacker and destacker
• Electrical equipment control and temperature control by PLC
• Visualisation and data logging by PC
A multi-purpose single-tier high-convection roller hearth furnace is
used for the bright annealing of level-wound coils, pancakes and
straight copper tubes up to 2.5m long. It has vacuum lock chambers
and is up to 6m long in continuous operation.
Figure 14 shows a multi-purpose high-convection roller hearth
furnace for the bright annealing of level-wound coils, pancakes and
straight copper tubes with a throughput capacity of about 2t/h.
Design is similar to the furnace just described, with vacuum
chamber, furnace and cooling zone and indexing conveyor
system. A special feature of this furnace, in addition to the vacuum
chamber, is entry and exit lock chambers with curtains for sealing
the furnace ends. The curtains are used for annealing of straight
tubes exceeding the length of the vacuum chamber. In this mode
of operation the vacuum chamber is not in use. The furnace is then
sealed only by the curtains that are lowered in position in the entry
and exit lock chambers when this mode of operation is used. For
continuous operation of the line all drive sets, in this case thirteen,
are equipped with servo motors enabling them to be run together at
a slow speed.
A high-convection roller hearth furnace is used for bright annealing
of level-wound coils, pancakes and straight copper tubes up to 6m
long. As you will see from figure 15 this furnace is similar to that
of the first example. However, this furnace line has entry and exit
vacuum chambers about 6m long. This line can anneal up to 5t/h
of copper tube, either straight, pancakes or level-wound coils, with
vacuum lock chambers.
3.3 Innovations
The Otto Junker Copper Tube Purging (CTP)
system with connection to one end
of the tube coils
This system produces clean, high-quality copper tubes by expelling
the lubricant vapours from the tube bore as they form during heat-
up in the furnace. This reduces the carbon and lubricant deposits
on the inside surface of the heat-treated tube.
›
Figure 13
:
Longitudinal view of the furnace
›
Figure 15
:
High convection roller hearth furnace
€
Figure 14
:
Multi-purpose
high-convection
roller hearth
furnace
€
Figure 16
:
The Otto Junker copper
tube purging system