45t-EBT High-Impedance Arc Furnace Operation Sequence

45t-EBT High-Impedance Arc Furnace Operation Sequence

EBT EAF stands for Eccentric Bottom Tapping Electric Arc Furnace, meaning eccentric bottom tapping. This design feature of an electric arc furnace allows molten steel to be tapped from an eccentric location at the furnace bottom, rather than the traditional tapping port.

Features of an EBT Arc Furnace:

Eccentric Bottom Tapping: EBT arc furnaces feature an eccentric tapping port at the furnace bottom, which allows for smoother tapping, reduces mixing of molten steel and slag, and improves steel quality.

Efficient Production: The EBT design allows the furnace to complete the tapping process more quickly, accelerating production and improving efficiency.

Reduced Consumption: The EBT arc furnace design helps reduce power and electrode consumption because the long arc ensures stable combustion and allows the use of higher-power transformers.

1. Pre-Furnace Inspection

(1) Check the cooling water pressure; it should be between 0.4 and 0.6 MPa. The water-cooled furnace wall flow rate should be ≥ 200 m²/h, and the water-cooled furnace cover flow rate should be ≥ 150 m²/h.

(2) Inspect all transmission mechanisms and moving points for jams and obstructions.

(3) Inspect all valves and pipe connections (hydraulic, water, oxygen, and compressed air) for leaks.

(4) Inspect the water-cooled components (water-cooled furnace wall, water-cooled furnace cover, water-cooled cross arm, electrode clamp, water-cooled clamp, water-cooled cable, etc.) for leaks. Ensure the return pipe is unobstructed.

Operate the furnace only after confirming that all abnormalities are present.

2. Electric Furnace Operation Sequence

⑴. During normal smelting (including the melting and oxidation phases), the tilting platform must remain free (with the horizontal front and rear supports retracted). The rotating frame must be locked. The furnace can be tilted forward or backward at any time.

⑵. Furnace Lid Raising, Lowering, and Rotating Operations

①. Furnace Lid Raising Operation

a. Interlocking Conditions: High voltage tripped, three-phase electrodes raised to their full height, the tilting platform level, the horizontal front and rear supports locked, and the rotating frame locked. No operator on the furnace roof.

b. Operation Location: Furnace front operating station or main operating station in the control room. When operating from the furnace front operating station, wait until the "Furnace Front Operation Allowed" indicator lights up before operating.

c. The main operating station has an "Operation Selection" knob for selecting operation from either the furnace front or main operating station. Once selected, the furnace lid can be raised using the "Furnace Lid Control" knob from either the furnace front or main operating station in the control room. When the furnace cover reaches its upper limit, the "Furnace Cover Upper Limit" indicator illuminates. Simultaneously, the program controls the rotary frame locking cylinder to release the locking pin, and the "Furnace Cover Lock Pin Extraction" indicator illuminates.

②. Furnace Cover Opening and Reversing Operations

a. After the furnace cover raising operation is completed, the furnace cover can be rotated.

b. Interlocking Conditions: High voltage disconnected, three-phase electrodes raised to their full height, tilting platform level, horizontal front and rear supports locked, and the rotary frame locked in the unlocked position. No operator on the furnace roof. Unobstructed rotation space.

c. Operation Location: Furnace front operating station or main operating station in the control room. When operating from the furnace front operating station, wait until the "Furnace Front Operation Allowed" indicator illuminates before proceeding.

d. From the furnace front operating station or main operating station in the control room, use the "Furnace Cover Rotation" knob to rotate the furnace cover. Once fully rotated, the "Furnace Cover Opening" indicator illuminates. After the furnace cover is fully rotated, scrap steel can be added.

e. After loading is complete, the furnace cover can be reversed. Use the "Furnace Lid Rotation" knob to rotate the furnace lid from the furnace control panel or the main control panel in the control room. Once fully rotated, the "Furnace Lid Rotation" indicator will illuminate. Simultaneously, the program controls the rotary frame locking cylinder to insert the locking pin, and the "Furnace Lid Lock Pin" indicator will illuminate.

③. Furnace Lid Lowering Operation

a. After completing the furnace lid rotation operation, the furnace lid can be lowered.

b. Interlocking Conditions: High voltage disconnected, three-phase electrodes raised to full position, tilting platform level, horizontal front and rear supports locked, and rotary frame locked in the unlocked position. No operator on the furnace roof. Unobstructed rotation space.

c. Operation Location: Furnace Lid Control Panel or the main control panel in the control room. When operating from the furnace control panel, wait until the "Furnace Lid Operation Allowed" indicator illuminates before proceeding.

d. Use the "Furnace Lid Control" knob to lower the furnace lid from the furnace control panel or the main control panel in the control room. Once the furnace lid is fully lowered, the "Furnace Lid Lower Limit" indicator will illuminate.

After the furnace cover is lowered, smelting operations can begin.

⑶. Furnace Tilt Operation

a. Interlocking Conditions: The tilting platform must remain free (both the horizontal front and rear supports are retracted); at the same time, the rotating frame lock must be locked.

b. Operation Location: The furnace front operating station, the furnace rear operating station, or the main operating station in the control room. When operating from the furnace front operating station, wait until the "Furnace Front Operation Allowed" indicator illuminates before proceeding. When operating from the furnace rear operating station, wait until the "Tilting Furnace Operation Allowed" indicator illuminates before proceeding.

The main operating station has an "Operation Selection" knob for selecting operation from the furnace front, furnace rear, or main operating station. When "Main Station" is selected, operations are only permitted at the main control station. When "Furnace Front" is selected, operations are only permitted at the furnace front control station, and the "Furnace Front Operation Allowed" indicator will illuminate for operations at the furnace front control station. When the knob is in the middle position, operations are only permitted at the furnace rear control station, and the "Furnace Tilt Operation Allowed" indicator will illuminate for operations at the furnace rear control station.

①. Slag Discharge Operation

a. Slag discharge operations are only permitted at the furnace front control station or the main control station in the control room. When operating at the furnace front control station, wait until the "Furnace Front Operation Allowed" indicator illuminates before proceeding.

b. Turn the "Furnace Tilt" knob to the "Forward" position to perform slag discharge. The furnace will then slowly tilt in the direction of slag discharge, with a maximum tilt angle of 15°. Tilt can be stopped at any time as needed. After slag discharge is complete, turn the "Furnace Tilt" knob to the "Back" position, and the furnace will slowly return to 0° and automatically stop tilting. 

②. Furnace Shaking Operation

a. Furnace shaking is necessary to reduce melting time and prevent the scrap from collapsing automatically after drilling. This operation is only permitted at the furnace control panel. The "Furnace Operation Allowed" indicator light is on before operation begins.

b. The furnace control panel is equipped with a spare three-position knob that only tilts the furnace (toward the tapping direction) from 0° to 5°.

Turning the knob to the left allows the furnace to tilt in the tapping direction, automatically stopping at 5°. This protects the water-cooled furnace walls and prevents molten steel from eroding them. Turning the knob to the left allows the furnace to tilt back toward 0°, automatically stopping at 0°.

③. Tapping Operation

a. In addition to meeting the interlocking conditions in ④a, the tapping car must be at the tapping position, the high-voltage switch must be disconnected, the three-phase electrodes must be raised approximately 1000mm above the molten steel, and the EBT taphole must be open. b. Tapping operations are only permitted at the rear operating platform. This operation is only permitted when the "Tilt Operation Allowed" indicator on the rear operating platform illuminates.

c. Turn the "Furnace Tilt" knob on the rear operating platform to the "Back" position to begin tapping. When the tilt reaches 15°, the "Furnace Back Limit" indicator illuminates, and an audible and visual alarm sounds. (The normal tapping tilt angle is 15° to ensure proper steel retention.) At this point, the operator should stop tilting according to the ladle capacity. If complete tapping is required, the furnace will automatically stop tilting when the backward tilt reaches 20°. After tapping is complete, promptly turn the "Furnace Tilt" knob to the center position and press the "Furnace Quick Return" button to achieve rapid return tilting. Pressing the "Furnace Quick Return" button automatically stops the furnace when it returns to 0°.

d. During tapping operations, both horizontal front supports must be extended to ensure that the furnace returns to the horizontal position during rapid return after tapping, preventing over-tilting. After the tapping operation is complete, the next cycle can proceed.

⑷. EBT Taphole Operation

①. EBT Taphole Opening

After the smelting operation (including the melting and oxidation periods) is completed and the ladle car has reached the tapping position, the EBT taphole opening operation can be performed. This operation is performed manually on a small platform in the eccentric area of the furnace. First, remove the locking pin, lift the rotary handle, and quickly rotate the handle to open the EBT taphole. Lower the rotary handle into the notch and insert the locking pin. This completes the EBT taphole opening operation.

②. EBT Taphole Closing

After tapping is completed, the furnace body is quickly tilted back to the horizontal position. The EBT taphole should be free of residual steel and slag before closing. First, remove the locking pin, lift the rotary handle, and rotate the handle in the opposite direction to close the EBT taphole. Lower the rotary handle into the notch and insert the locking pin. This completes the EBT taphole closing operation. 

(5). Electrode Release and Tightening Operations

①. Interlocking Conditions: The high-voltage trip switch and the crane hook can effectively control the electrode raising and lowering.

②. Operation Location: Main console in the control room.

③. To release the electrode, first turn on the "Electrode Clamping Allow" key button on the main console in the control room. Then, in coordination with the operator on the furnace top, operate the three-phase "Electrode Release" self-reset knobs. When the operator on the furnace top requests tightening, release the "Electrode Release" self-reset knobs to automatically tighten the electrode.

④. After the operation is completed, turn off the "Electrode Clamping Allow" key button on the main console and remove the key to prevent accidental operation.

⑹. Furnace Door Opening and Closing Operations

Furnace door opening and closing operations can be performed by operating the "Furnace Door Control" knob from the furnace front console or the main console in the control room.

⑺. Horizontal Front and Rear Support Operations

①. Horizontal front and rear supports lock the cradle platform horizontally. They are necessary for raising, lowering, and rotating the furnace cover and are also required before shutting down the furnace or replacing the furnace shell. 

②. Operation Location: Furnace Front Control Station, Furnace Back Control Station, or Main Control Station in the Control Room. When operating from the furnace front control station, wait until the "Furnace Front Operation Allowed" indicator light is on before operating.

③. Operate the "Front Support" and "Rear Support" knobs to the "Insert" and "Unplug" positions, respectively, to extend and retract the horizontal front and rear supports.

⑻. Water Spray Operation

①. Water spray operation is essential to reduce electrode consumption and prevent overheating of the electrode chuck during the smelting process.

②. Interlocking Condition: Electrode heating and arcing.

③. Operation Location: Main Control Station in the Control Room.

④. After the electrode is heated and arcing, and the exposed portion of the electrode turns red, operate the "Stop - Spray" knob on the main control station to the "Spray" position to spray the electrode with water. To stop electrode heating, immediately turn the knob to the "Stop" position.

⑤. Adjust the shutoff valves on the three-way solenoid valve path on the water tank to adjust the water flow rate for the water spray. 

⑼. Furnace Top Charging Operation

From the back-of-furnace operation panel, operate the "Furnace Top Charging Valve" knob to the "Open" or "Close" position to open and close the pneumatic gate valve for the furnace top charging.

⑽. Back-of-furnace Charging Operation

Back-of-furnace charging operations must be performed after the ladle car has reached the tapping position.

From the back-of-furnace operation panel, operate the "Back-of-furnace Charging Valve" knob to the "Open" or "Close" position to open and close the pneumatic gate valve for the furnace back-of-furnace charging.

⑾. Tap Car Travel Operation

The tap car travel operation is performed from the back-of-furnace operation panel. Operating the "Tapping Car" knob to the "Forward" position moves the tap car toward the electric furnace. Operating the "Tapping Car" knob to the "Reverse" position moves the tap car toward the refining furnace. Operating the "Tapping Car Electric" self-reset knob can be used to jog the tap car. 

⑿. Cooling Water Operation for Water-Cooled Furnace Cover and Water-Cooled Furnace Walls.

①. Commissioning

a. Check that the total inlet water pressure reaches 0.4-0.6 MPa and the total inlet water temperature is ≤37°C.

b. Open the main inlet water valve.

c. Tilt the furnace toward the tapping point and the furnace door (to facilitate air release).

d. Open each air valve and release air for a few seconds until water flows out.

e. Check that the water flow rate for the water-cooled furnace wall is ≥200 m²/h and the water flow rate for the water-cooled furnace cover is ≥150 m²/h.

f. Check that there are no leaks in all areas.

g. Check that the protective refractory materials and center cover are intact.

h. Normal Operation

i. When the furnace is hot, adjust the flow rate based on the return water temperature display at each location to ensure that the return water temperature is ≤55°C. Check this regularly during operation.

j. Check the refractory protection before each charging and after each tapping. 

②. Shutdown

a. Ensure the water-cooled furnace cover and walls are completely cooled before closing the main water inlet valve.

b. During a power outage or furnace shutdown due to an emergency, emergency water supply should be connected with a flow rate of ≥ 90 m²/h for the water-cooled furnace cover and ≥ 110 m²/h for the water-cooled furnace walls, and maintained for at least 30 minutes.