Semi – Continuous Brazing Furnaces for Aluminum
In Short: A semi-continuous CAB furnace brazes aluminum heat exchangers in medium or smaller production volumes. It is designed for part-time operation. The furnace heats from ambient to brazing temperature and reaches the right atmosphere in a very short time.
- Part-time operation: Quick start-up from ambient temperature.
- Variable heating and cooling rates: Set by the indexing times.
- Wide product range: Brazes the widest variety of heat exchangers when total production requirements are lower.
CAB Furnace Designs
The following furnace designs are available to produce a variety of parts in medium or smaller volume production runs:
Active Only Convection CAB Furnace
Our Active Only Convection CAB furnaces work in a multi-step indexing cycle. The product runs horizontally through these positions:
- Load table
- Dry-off oven
- Entrance purge chamber
- Patented convection preheating and brazing chambers
- Air-jacketed cooling / exit purge chamber
- Airblast chamber
Key features:
- Adjustable dwell time: Infinitely adjustable, based on hearth load and load configuration.
- Work zone thermocouple: Monitors recovery time when the load runs intermittently.
- Load thermocouples: Predict the actual product temperature and control the required heating time for each heat exchanger type.
- Patented convection muffle: Ensures uniform preheating of the product.
- Fast cold-to-hot transport: Keeps temperature uniform even for large products such as HVAC units and battery coolers.
Vertical Brazing CAB Furnace
The Vertical Brazing CAB furnace is a uniquely designed version of an Active Only indexing furnace where the brazed elements are positioned horizontally. For some types of heat exchangers such orientation provides benefits as the cladding melts. Vertical positioning of the heat exchanger allows the joints to be evenly filled on a horizontal plane, preventing the brazing alloy from accumulating on one side of the heat exchanger.
Additionally, semi-continuous configured furnaces utilize vacuum purging. This solution limits nitrogen consumption and improves furnace-atmosphere cleanliness. Due to vacuum flushing in the furnace vestibule, air is removed not only in the chamber but also from the internal openings of the heat exchanger. Furnaces of this type may be used in the production of some types of heat exchangers (such as PLATE & BAR), which previously required more expensive vacuum-brazing furnaces.
Ecology and energy efficiency options:
- Thermal afterburner: Reduces VOC emissions from degreasers.
- Activated alumina scrubber: Reduces hydrogen fluoride (HF) emissions generated during brazing.
- Energy recovery for gas heating: A heat exchanger links the afterburner and degreasers. Exhaust gases from the preheat chambers and brazing furnace also support dryer heating. This cuts gas consumption and CO2 emissions.
- Electric heating: Replaces gas heating, also in existing equipment, to reduce CO2 emissions.
- Microporous insulation: Optional high-performance insulation reduces heat losses and energy consumption.
- Heated inlet tunnel: Limits the temperature drop of the belt and load. Re-heating is shorter and net energy use is lower.
- Common conveyor belt: One belt for the dryer (or TTBB) and furnace avoids double heating.
- Heat recuperation: Energy from the cooling chamber and dryer supports plant heating.
- Non-emission cooling: Air jacket cooling instead of a closed water circuit.
- IDLE and WEEKEND modes: The control system lowers the temperature or turns the furnace off during production breaks.
For gas-heated furnaces, each energy saving also means lower CO2 emissions.
Frequently Asked Questions
What is a semi-continuous CAB furnace?
It is a controlled atmosphere brazing (CAB) furnace for aluminum heat exchangers, designed for part-time operation. It heats from ambient to brazing temperature in a very short time and suits medium or smaller production volumes.
What CAB furnace designs are available for semi-continuous production?
SECO/WARWICK offers the Active Only Convection CAB furnace with horizontal product flow and the Vertical Brazing CAB furnace, where heat exchangers are brazed in a vertical position.
Why braze heat exchangers in a vertical position?
When the cladding melts, vertical positioning lets joints fill evenly on a horizontal plane. This prevents the brazing alloy from accumulating on one side of the heat exchanger.
What are the benefits of vacuum purging in a CAB furnace?
Vacuum purging limits nitrogen consumption and improves furnace atmosphere cleanliness. It removes air also from the internal openings of the heat exchanger, so some PLATE & BAR types can be brazed without more expensive vacuum brazing furnaces.
How can a CAB line reduce energy use and emissions?
Options include a thermal afterburner for VOC, an activated alumina scrubber for hydrogen fluoride, energy recovery, electric heating, microporous insulation, air jacket cooling and IDLE/WEEKEND operating modes.
