The hottest season of the year has arrived. Faced with 40 °C or higher temperature in the heat treatment workshop, equipment is prone to many problems. For maintenance team, the equipment stability is their greatest expectation, so that they can stay in the office to enjoy the coolness of air conditioning. In fact, spend 1-2 hours every day on proper daily check for the equipment, you will have your carburizing furnace running smoothly.
Here are the instructions of daily inspection and maintenance of carburizing furnaces:
1. Equipment cooling water supply
The cooling water system cools down the heating chamber fan, oxygen probe and furnace wall and ensures the temperature of these key parts. Therefore, stable supply of cooling water is essential for the equipment, requiring the operator to check pressure and flow every 30 minutes. The cooling water pressure must be between 0.15-0.3 MPa, and flow rate depends on return water temperature, which should be between 40°C-45°C. If the water pressure is too low, water filter should be cleaned up. If the water pressure drops due to the failure of the cooling water station, switch to emergency water supply before repairing the cooling water station.
2. Electric heating system
The electric heating system, important for equipment stability and process, controls the heating power, thus controls temperature of heating chamber. Heating current of the inner and outer heaters should be checked every 30 minutes. The three-phase current should be basically the same, and the indicated current is proportional to the heating control output power.
3. Gas panel media supply
Stable media supply on gas panel is essential for process control. They affect directly quality of products. Inspect the pressure and flow of each medium every 30 minutes that all readings are within correct range. Adjust or repair media pipes for leaks and other issue.
4. Compressed air
Compressed air provides power to cylinders on equipment. Compressed air pressure should be between 0.6 and 0.8 MPa. adjust pressure if actual pressure exceeds the range.
5. Oxygen probe reference gas, purge gas
Oxygen probes or Carbon Sensor measures in furnace atmosphere oxygen potential (the potential difference between the oxygen in furnace and that in the air), based on which carbon potential can be calculated according to the temperature and CO content in furnace gas. Oxygen probes require stable feeding of reference air, and the flow rate of the reference gas is controlled at 20 ml/min.
Oxygen probes typically work in high-carbon environments, forming carbon deposit on the tip of the probe. Therefore, purging air should be introduced every 90-120 minutes. 60 seconds every time, burning carbon soot thus cleaning the oxygen probe. The flow rate of the purge gas is 80 ml/min.
6. Outer door flame curtain
If there is flammable gas in the furnace, flame curtain must be ignited before opening furnace door, in order to ignite and burn out flammable gas. Furnace is exposed to risk of explosion if manually force the door open without igniting flame curtain.
Since the flame curtain is very important, The flame curtain controller must be checked every shift, the electronic ignition probe should be 2 to 2.5 mm clear away from flame curtain, and flame sensor should be 5 to 8 mm away from the flame. Clean up oil and smoke stains on the probe after check.
7, Exhaust head igniter
In order to ensure the activity of the furnace atmosphere, gas should be continuously injected and discharged to replacement of the furnace gas. Discharged furnace gas contains mainly nitrogen, hydrogen and carbon monoxide, the latter two must be burned through the exhaust port before discharged. Therefore, a long open flame igniter is installed at the exhaust port that continuously burns for 24 hours, flame length about 120mm, and, once ignited, generating mV with an internal thermocouple locking up the control SV coil so that the igniter will always burn. A flame monitor is installed to detect the state of the igniter: a green light on the flame monitor is on if it’s working properly, otherwise the green light will be off and an alarm will be triggered.
8. Heating chamber fan motor coolant
The heating chamber circulation fan motor works constantly at high temperature. To protect its bearings and windings, the motor cap flange is cooled by coolant. There motor can be cooled by air or water.
Water-cooled motor:Cooling water is injected into the cooling jacket to cool down bearings and shaft. In order to ensure the cooling effect, the water outlet temperature should be checked every 30 minutes, and maintained between 40 and 50 ° C. Increase water flow immediately if the temperature goes too high.
Air-cooled fan:：air instead of water is blowed into the cooling jacket to cool down bearings and shafts of the motor. In order to ensure cooling effect, check the outlet temperature every 30 minutes that the temperature is between 40℃ and 50℃, clean up the filter of blower periodically.
9. Oil level Indicators
The oil level indicator should be between low and high limit. If it is out of limits, then oil level is too low or too high, refill or pump out oil.
There is an oil overflow elbow at the bottom of the heating chamber. When the quenching oil level is too high and parts are quenched, quenching oil will overflow to the chain guide groove of the heating chamber furnace chain. In order to ensure the sealing, a liquid level gauge is installed, oil in the gauge should reach the 2/3 position, if not, unscrew the top cover of the level gauge and then add the quenching oil to the level gauge.
10. Signal light
Press the "light test" button, then all the signal indicators will be on, inform electrician to replace the damaged signal light.