Process Controller / Programmer
Brief
The 2604 is a highly accurate and stable process controller available in a
single, dual or triple loop format. Can be used to control both furnace temperature, carbon potential and quenching.
Function
Synchronised temperature/carbon profiles
Automatic probe cleaning
Furnace sooting alarm
Probe deterioration alarm
Temperature control of quenching
Comprehensive selection of maths and logic functions
Feature
Setpoint programmer
50 Programs
3 Profiled setpoints/program
500 Segments
16 Event outputs
Furnace Temperature Control
Although the sensor input of the temperature loop can come from the zirconia probe, it is more common for a separate thermocouple to be used. The heat control output can either be connected to gas burners or thyristors. In some applications a cooling output may also be connected to a circulation fan or an exhaust damper.
Furnace Atmosphere Control
In atmosphere loops the controller increases the carbon potential by opening a solenoid valve which allows a carburising gas (ie propane) to enter the furnace. Conversely, to decrease the carbon potential, air or nitrogen is introduced into the furnace. Automatic probe cleaning functions ensure that the reading is accurate, whilst probe health and sooting alarms warn of a deterioration in the probes performance.
Quenching Temperature Control
Steel parts are rapidly cooled (Quenched) from around 850℃to obtain the desired hardness, strength or toughness. Depending on the material being treated, the quench medium is usually oil or water. The quench control loop maintains the quench bath at the desired temperature and provides a quench timer facility.
Sooting Alarm
As well as alarms on the temperature and carbon potential in the furnace the 2604 can trigger an alarm, when the atmospheric conditions are such that carbon will be deposited as soot on all surfaces inside the furnace, including the workpiece. Avoiding sooting protects the furnace lining, maintains the accuracy of the zirconia probe and stops formation of a soot barrier on the workpiece which can prevent carbon diffusion.
Automatic Probe Cleaning
The 2604 has a probe clean and recovery strategy that can be programmed to occur between batches or manually requested by an operator. A short blast of compressed air is used to remove any soot and other particles that may have accumulated on the probe. Once the cleaning has been completed the time taken for the probe to recover is measured. If the recovery time is too long this indicates that the probe is ageing and replacement or refurbishment is due. During the cleaning and recovery cycle, the CP reading is frozen thereby ensuring continuous furnace operation.
Enriching Gas Correction
A gas analyser can be used to determine the CO concentration of the enriching gas. If an analogue output is available from the analyser, it can be fed into the 2604 to automatically adjust the calculated carbon reading. Alternatively, an operator may enter this value manually.
