Winch Drive Series — Steel & Metallurgical Process Equipment

Winch Drive Planetary Gearbox for Furnace Door Opening

The winch drive gearbox that raises and lowers an electric arc furnace door, reheat furnace door, or ladle furnace door operates within metres of process temperatures exceeding 1,600°C — radiant heat that the gearbox housing absorbs continuously through every charging, tapping, and maintenance cycle. The planetarisk gearkasse med spildrev must maintain stable internal lubrication, seal integrity, and gear tooth contact geometry despite this radiant heat load, while delivering the high-cycle reliability that a steel mill demands from equipment integral to the melting and casting schedule.

2,000 – 15,000 Nm output torque
Radiant heat shield housing
120°C ambient continuous rating
3 million cycle fatigue life

Furnace door drive systems occupy one of the most thermally hostile positions of any winch drive application — mounted on or adjacent to the furnace structure, typically 2 to 5 metres from the door opening through which radiant heat from molten steel, slag, or process gas escapes continuously, especially during charging and tapping operations when the door is open. Electric arc furnace (EAF) doors cycle 15 to 30 times per heat, with 8 to 15 heats produced per day in a high-productivity mill — accumulating well over 100,000 door cycles per year. Reheat furnace doors at rolling mills cycle continuously as billets or slabs enter and exit the furnace on a near-continuous basis during rolling campaigns. Korea Ever-Power supplies planetary winch drive gearboxes engineered specifically for the radiant heat exposure, high-cycle duty, and steel mill environmental contamination (scale, dust, cooling water spray) that furnace door applications impose, across the full range from compact ladle furnace door drives through heavy EAF main door systems.

Furnace Door Applications: EAF, Ladle, and Reheat Furnace Drives

Furnace door opening winch drive planetary gearbox — electric arc furnace door drive system application

Electric Arc Furnace (EAF) Door Drives (5,000–15,000 Nm): The EAF charging door is a heavy refractory-lined steel door that opens for scrap charging via the roof or for oxygen lancing and sampling operations during the melt cycle, and remains closed during electrical melting to contain heat and protect the furnace shell. The door assembly with refractory lining can weigh 3 to 8 tonnes, and the door drive winch must raise and lower this mass through a vertical or pivoting motion at a controlled speed that avoids slamming (which damages the refractory and door frame) while completing the cycle quickly enough to minimise heat loss during charging windows. The winch gearbox is typically mounted on a bracket extending from the furnace shell or an adjacent steel structure, positioning it within direct view of the open door aperture during every charge — meaning the gearbox absorbs significant radiant heat flux during each of the 15 to 30 daily cycles.

Ladle Furnace and Ladle Metallurgy Station Door Drives (2,000–8,000 Nm): Ladle furnace stations use smaller lid or door mechanisms to control atmosphere and heat loss during secondary steelmaking operations — alloy addition, temperature adjustment, and degassing. These doors cycle less frequently than EAF charging doors but operate in close proximity to the ladle, which contains liquid steel at 1,550 to 1,650°C for extended dwell periods of 20 to 60 minutes per heat. The sustained radiant exposure during this dwell period, rather than brief cycle events, is the dominant thermal load on the ladle furnace door drive gearbox.

Reheat Furnace Door Drives (3,000–10,000 Nm): Continuous reheat furnaces in rolling mills maintain a near-constant internal temperature of 1,150 to 1,280°C to bring steel billets, blooms, or slabs to rolling temperature. The charging and discharging doors at each end of the furnace cycle continuously as material moves through on a walking beam or pusher mechanism — in a high-throughput mill, the discharge door may cycle every 30 to 90 seconds around the clock. This continuous high-frequency cycling, combined with sustained proximity to the furnace interior temperature, makes reheat furnace door drives one of the highest-cycle-count winch drive applications in industrial service, while also facing among the highest sustained ambient temperatures.

Radiant Heat Engineering: Protecting the Gearbox from Furnace Proximity

Winch drive planetary gearbox furnace door application — radiant heat exposure steel mill door drive system

A gearbox mounted 3 metres from an open furnace door radiating at 1,400°C internal temperature receives a radiant heat flux that, without protection, would raise the housing surface temperature well beyond the point where standard mineral or even synthetic gear oils maintain adequate lubrication properties. Korea Ever-Power furnace door gearboxes incorporate four engineering measures to manage this thermal exposure:

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Radiant Heat Shield Panel

A polished or ceramic-coated heat shield panel mounted between the gearbox and the furnace door aperture reflects the majority of incident radiant heat away from the gearbox housing. Korea Ever-Power supplies an optional bolt-on heat shield bracket sized to the specific gearbox model, reducing the radiant heat flux reaching the housing surface by 60 to 75% compared to an unshielded installation at typical EAF door mounting distances.

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Water-Cooled Mounting Bracket

For the closest-mounted EAF door drives where radiant flux is most severe, Korea Ever-Power offers a water-cooled mounting bracket that interposes a cooling water circuit between the furnace structure and the gearbox housing, conducting absorbed heat away before it reaches the gear oil. The cooling circuit connects to the furnace cooling water system already present at every EAF installation, requiring no additional plant utility.

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High-Temperature Synthetic Lubricant

Korea Ever-Power furnace door gearboxes are filled with a high-temperature synthetic PAG (polyalkylene glycol) or PAO gear oil with a thermal stability rating to 150°C continuous bulk oil temperature — significantly above the 90 to 100°C upper limit of standard industrial gear oils. This oil maintains its EHL film-forming properties and oxidation resistance at the elevated baseline temperature that radiant heat exposure imposes even after shielding measures are applied.

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High-Temperature FKM Seals

Standard FKM (fluoroelastomer) seal compounds are rated to approximately 200°C continuous service — adequate for most furnace door applications, but Korea Ever-Power offers a high-temperature FFKM (perfluoroelastomer) seal option rated to 260°C continuous for the most extreme close-mounted EAF door installations where standard FKM service life would be unacceptably shortened by sustained thermal exposure.

Korea Ever-Power Furnace Door Drive Selection Guide

ZR75 Winch Drive Planetary Gearbox 2 to 5 stage — ladle furnace door and small reheat furnace door drive unit

Korea Ever-Power planetary winch drive gearboxes for furnace door applications are supplied in the High-Temperature Steel Mill specification — high-temperature synthetic gear oil rated to 150°C continuous, FKM seals as standard with FFKM available for extreme exposure, and 3 million cycle gear tooth fatigue rating for reheat furnace continuous-cycle duty. The ZR75 and 407AW serve ladle furnace and small reheat furnace doors. The 414W3 covers the full EAF main charging door torque range.

All units accept the optional radiant heat shield bracket and water-cooled mounting bracket as bolt-on accessories without modification to the core gearbox design, allowing the thermal protection level to be matched to the specific installation distance and furnace operating intensity without requiring a custom gearbox specification.

Model Udgangsmoment Stadier Forholdsområde Furnace Application Max Continuous Oil Temp Forsegle
ZR75 1,500 – 6,000 Nm 2–5 5.1 – 4,884 Ladle furnace lid, small door 150°C FKM
407AW 2,000 – 10,000 Nm 2–3 50 – 1,200 Reheat furnace door, EAF small 150°C FKM / FFKM
414W3 8,000 – 15,000 Nm 3 100 – 2,500 EAF main charging door 150°C FKM / FFKM

Door Speed Control: Protecting Refractory and Door Seals

407AW Winch Drive Planetary Gearbox Reducer — reheat furnace and small EAF door drive precision speed control unit

Furnace door movement must be controlled precisely to protect both the refractory lining of the door itself and the furnace shell seal interface where the door closes against the furnace opening. A door that closes too fast generates an impact load that cracks refractory and damages the metal-to-metal or rope seal at the closure interface; a door that closes too slowly allows excessive heat loss and slows the production cycle.

Two-Speed Profile: Korea Ever-Power furnace door gearboxes support a two-speed VFD control profile as standard — fast travel speed for the majority of the door stroke, and a slow creep speed for the final approach to the fully open or fully closed position. This profile, combined with sub-10 arcminute backlash in the gearbox, provides smooth, controlled door seating without the impact that a single fixed speed would generate at final closure.

Position Feedback for Seal Compression Control: Where the furnace door uses a compressible refractory rope seal to maintain atmosphere control when closed, the final closing motion must compress the seal to a specific, repeatable depth — too little compression allows atmosphere leakage, too much accelerates seal wear. Korea Ever-Power furnace door gearboxes include an absolute encoder mounting provision on the motor input shaft, enabling the furnace control system to position the door to a precise, repeatable final closure depth on every cycle, maintaining consistent seal compression across the seal service life.

Emergency Open Function: Furnace operations require a rapid emergency door open capability in the event of an abnormal furnace condition — excessive internal pressure, detected equipment malfunction inside the furnace, or operator-initiated emergency response. Korea Ever-Power furnace door gearboxes are rated for the higher torque and speed combination required for emergency rapid-open operation as a duty cycle exception to the normal controlled-speed operation, without exceeding the gear tooth shock rating during this infrequent but operationally critical event.

Steel Mill Contamination: Scale, Dust, and Cooling Water Spray

Winch Drive planetary gearbox furnace door installation — steel mill electric arc furnace charging door drive system

Beyond the radiant heat challenge, furnace door gearboxes operate in the broader steel mill environment, which presents additional contamination sources that the gearbox sealing and housing design must address:

Mill Scale and Refractory Dust: Reheat furnace and EAF operations generate continuous fallout of mill scale (iron oxide flakes shed from hot steel) and refractory dust (from door and furnace lining wear). This material settles on every horizontal surface near the furnace, including the gearbox housing, and infiltrates any seal gap. Korea Ever-Power furnace door gearboxes use the same FKM floating face cassette seal specification used for marine and mining applications — excluding mill scale and dust ingress at the shaft penetrations.

Cooling Water Spray Exposure: EAF furnace shells and door frames use water-cooled panels to manage the intense heat load, and these cooling circuits occasionally develop minor leaks or experience spray from cooling water connections during maintenance. The furnace door gearbox must tolerate occasional water spray exposure without IP rating compromise — Korea Ever-Power furnace door gearboxes are rated IP66 as standard, providing protection against powerful water jets in addition to the dust exclusion already required for the mill environment.

Thermal Cycling Stress on Housing Castings: The furnace door gearbox experiences significant thermal cycling — radiant heat exposure during each door open event, followed by cooling during the closed dwell period between cycles. Over years of service, this thermal cycling imposes fatigue stress on the gearbox housing casting at geometric stress concentrations. Korea Ever-Power furnace door gearbox housings are stress-relieved after casting and machining to remove residual stresses that would otherwise combine with thermal cycling stress to accelerate housing crack initiation, particularly at mounting bolt bosses and ribbing intersections.

Testing for High-Temperature, High-Cycle Furnace Door Service

Korea Ever-Power gearbox testing centre — furnace door drive high-temperature and cyclic load testing facility

Planetary gearbox processing details — high-temperature seal and gear manufacturing for furnace door drive units

Korea Ever-Power furnace door drive gearboxes are tested against the specific thermal and cyclic demands of steel mill door duty:

Elevated Temperature Load Test: The gearbox is heated to 120°C external housing temperature in a thermal chamber — simulating sustained radiant heat exposure — and operated at rated load for 4 hours while internal oil temperature and bearing temperature are monitored. Verification that the high-temperature synthetic oil maintains adequate viscosity and the FKM seals maintain sealing integrity at this elevated baseline temperature is the primary objective of this test.

High-Cycle Endurance Test: For reheat furnace door applications, a sample unit is cycled 50,000 times at rated torque on an accelerated test bench, simulating approximately 1.5 years of continuous reheat furnace door operation. Backlash and gear tooth surface condition are verified before and after the endurance run.

IP66 Verification: Standard water jet and dust chamber testing per IEC 60529, conducted on every production unit before shipment for furnace door applications, given the criticality of sealing integrity in this contamination-prone environment.

Common Furnace Door Drive Failures and Prevention

Fejltilstand Grundårsag Detection Prevention
Oil carbonisation — radiant heat Standard mineral or low-temperature synthetic oil exceeding oxidation limit from sustained radiant heat absorption — carbon deposits forming on gear surfaces Dark, varnished oil at sample; reduced lubrication film causing accelerated gear wear Specify high-temperature PAG or PAO oil rated to 150°C; fit radiant heat shield if oil temperature trending upward at routine checks
FKM seal hardening — extreme heat Standard FKM seal exceeding its 200°C continuous rating at very close EAF door mounting positions — seal cracking and losing sealing force Oil weeping at output shaft; visible seal cracking at inspection Specify FFKM high-temperature seal for close-mounted applications; verify mounting distance against the heat shield protection rating
Door slam — closure damage Single-speed control without creep approach — door impacting closed position at full speed, cracking refractory or damaging seal Refractory cracking pattern at door edge; audible impact at closure; accelerated seal wear Implement two-speed VFD profile with creep approach to final 50 to 100 mm of travel; verify encoder feedback for consistent seating depth
Gear tooth fatigue — high-cycle reheat door Reheat furnace door cycling every 30 to 90 seconds exceeding the calculated fatigue life faster than standard maintenance interval anticipates Gear noise increase tracked against cycle counter; micro-pitting at borescope inspection during planned shutdown Track actual cycle count against the 3 million cycle rating; schedule replacement at 80% of calculated fatigue life
Housing crack — thermal cycling fatigue Repeated thermal expansion and contraction at mounting bosses without stress relief after casting — fatigue crack initiation over years of cycling Visible crack at mounting boss or rib intersection at annual inspection; oil weeping from crack location Specify stress-relieved housing castings; annual visual and dye-penetrant inspection of mounting boss areas on close-mounted EAF door units

Why Steel Mill Engineers and Furnace OEMs Choose Korea Ever-Power

Korea Ever-Power manufacturing workshop — furnace door winch drive gearbox high-temperature precision production

Korea Ever-Power quality certifications — furnace door drive high-temperature testing and steel mill compliance

150°C

Continuous oil temperature rating — high-temperature synthetic PAG and PAO formulations maintaining EHL film at sustained radiant heat exposure

260°C

FFKM high-temperature seal option for extreme close-mounted EAF door installations beyond standard FKM service limits

3M cycles

Gear tooth fatigue rating — verified by accelerated 50,000-cycle endurance bench test for reheat furnace continuous-cycle duty

60–75%

Radiant heat flux reduction from optional bolt-on shield bracket, reducing gearbox housing thermal load at close EAF door mounting positions

Korea Ever-Power application engineers provide free thermal exposure assessment and gearbox sizing for furnace door projects, evaluating mounting distance, furnace internal temperature, door cycle frequency, and refractory weight to recommend the appropriate combination of gearbox model, lubricant grade, seal material, and heat protection accessories. Contact us with your furnace type, door cycle frequency, mounting distance, and door mass for a free application review within 48 hours.

Source Your Furnace Door Winch Drive Planetary Gearbox

Whether you are specifying door drives for a new electric arc furnace, ladle furnace, or reheat furnace build programme, or sourcing replacement gearboxes for an operating steel mill furnace fleet — Korea Ever-Power delivers radiant-heat-rated, high-cycle planetary winch drive gearboxes built for the thermal and cyclic demands of furnace door duty. Send us your furnace type, door mass, mounting distance, and cycle frequency for a free thermal exposure assessment and gearbox specification within 48 hours.

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