Planetary Gearbox Conveyor Drive Selection —
Belt, Chain, Roller and Screw Conveyor Guide

Conveyors represent the single largest application category for the planetary gearbox conveyor drive in Korean industry in Korean industry — food processing, logistics, steel manufacturing, automotive assembly, and chemical processing all depend on conveyors running continuously in three shifts. Despite this volume, conveyor gearbox selection is frequently under-engineered: the torque is estimated rather than calculated, the startup condition is ignored, and the operating environment is treated as standard when it is actually hostile.

The four major conveyor types in Korean industry each have a distinct dominant specification that governs gearbox selection. Applying the wrong priority — backlash for a conveyor that needs startup torque, or rated torque for a screw that needs self-locking — produces predictable failures:

The full torque calculation for a belt conveyor drive gearbox requires four components: the effective belt pull to move the loaded material, the belt tension losses, the incline gravity component, and the startup factor. Omitting any one of these produces an undersized gearbox.

Worked example — Korean steel mill slab conveyor: Material mass 8,000 kg on belt, belt mass 600 kg, incline θ=5°, pulley radius r=0.25 m, belt friction μ=0.04, drive efficiency η=0.96.

Service Factor Selection — Korean Conveyor Applications

The most common Korean conveyor gearbox failure mode is not wear or fatigue under normal running — it is shear failure or tooth overload on the first start of the day, or after a power outage that leaves the belt fully loaded. Engineers who select gearboxes based on steady-state running torque are selecting for the easiest operating condition, not the hardest.

The startup torque on a loaded conveyor differs from the running torque in three ways. First, static belt tension is higher than dynamic tension — the belt and material must be accelerated from rest against the belt’s static coefficient of friction, which is 20–50% higher than its kinetic coefficient. Second, inertia of the loaded belt, material, and rotating pulleys must be accelerated from zero speed. Third, on cold Korean mornings, material adhesion and belt stiffness further increase the peak breakaway torque.

The practical resolution: specify the gearbox on T_rated = T_running × SF using the appropriate service factor from the table above. Do not attempt to calculate the exact startup torque — the service factor already encapsulates the typical startup peaks for each conveyor category. Only for unusual applications (very long belts, frozen material handling, high-frequency starts) should a detailed startup torque calculation replace the service factor approach.

For Korean conveyor installations replacing existing worm gear reducers with the EP-BPG energy-saving planetary series: the SF selection should account for the same startup conditions as the original worm unit. The planetary’s higher efficiency means a smaller motor can deliver the same output torque — but the motor must still be sized for the startup peak, not just the running power at ≥97% efficiency.

Chain conveyors — including slat conveyors, drag conveyors, and plate chain systems — transmit drive forces through discrete chain engagement events. Each time a chain link engages the drive sprocket, there is a small but measurable velocity change in the driven system — a periodic impulse load at the drive shaft. At high chain speeds, these impulses merge into a nearly continuous load. At low chain speeds (below 0.5 m/s, common in heavy-load Korean steel and automotive conveyors), the impulses are distinct mechanical shocks at the gearbox output shaft.

The dynamic service factor for chain conveyors (KA in DIN standards) ranges from 1.25 for smooth uniform-pitch chain on smooth-running equipment to 2.5 for highly irregular chain engagement with shock loading. In Korean food processing, stainless steel drag chain running at 0.3 m/s through a chilled protein processing tunnel requires KA=1.75 minimum — the chain stiffness at cold temperature increases the impulse magnitude, and the food-safe lubricant-free chain generates higher friction variation than a lubricated industrial chain.

Screw conveyors — horizontal augers for grain/powder/pellet transfer, vertical screw elevators, and inclined mixing augers — present a unique combination of requirements for the drive gearbox. Very low output speed (typically 20–150 rpm), high continuous torque from material shear resistance, and for inclined or vertical installations, the need to hold position when the motor is de-energised.

The position-holding requirement: When a vertical screw elevator stops, the material column above the screw applies a gravitational torque that attempts to back-drive the screw — rotating it in reverse and allowing material to slide back down the tube. For a planetary gearbox, this back-drive torque is transmitted directly to the motor shaft through the gearbox (which is back-drivable). If the motor servo brake or VFD holding torque is insufficient, or if a power failure disables the motor, the screw will rotate backwards.

Korean food processing and grain handling facilities address this through one of two methods: a downstream self-locking stage (worm gear) that physically prevents back-drive regardless of motor state, or an electromagnetic spring-set brake on the motor shaft that engages on power-off (fail-safe: spring force holds the brake closed, power is required to release it). For vertical screw elevator gravity load holding where a power failure would allow material to uncontrollably slide back and create a hazard, the self-locking worm stage is the preferred safety solution — it provides passive holding that requires no electrical power to maintain.

For horizontal screw conveyors where position holding is not required, the planetary gearbox provides advantages over the worm reducer that has historically dominated this application: ≥97% efficiency versus 55–70% for the worm at typical 20:1–60:1 single-stage ratios, sealed maintenance-free grease versus worm oil bath requiring periodic changes, and lower motor sizing. The EP-AH New Line series covers the high-torque, moderate-ratio requirements of heavy Korean grain and mineral screw conveyors up to 9,585 N·m.

Motorised roller conveyors for logistics, e-commerce fulfilment, and automotive parts sortation use individually powered roller zones — each zone driven by its own small gearbox unit whose output shaft couples directly to the roller end. The physical envelope constraint is severe: the gearbox must fit between the roller and the conveyor frame side rail, typically within 60–100 mm of total axial space, with the output shaft coaxial to the roller centreline.

Korean logistics hub roller conveyors typically run at 1–3 m/s with 20–100 kg package loads per zone. The required output torque per zone is modest — typically 5–25 N·m — and the reduction ratio is in the range i=10–50 from a 3,000 rpm motor to achieve the target roller surface speed. Backlash grade is irrelevant: these zones are speed-controlled open-loop drives.

For the compact axial space requirement, the ซีรี่ส์ EP-ABR มุมฉาก places the motor perpendicular to the roller axis — the motor extends sideways rather than axially, freeing the axial space constraint. This is the dominant installation layout for Korean motorised roller conveyors in fulfilment centres. The EP-ABR042 and EP-ABR060 frames (42 mm and 60 mm body diameter) fit within standard conveyor frame roller-to-frame clearances. P2 grade is the standard specification — backlash is irrelevant for speed-only zone control.

Korean conveyor manufacturers increasingly specify variable-frequency drives (VFDs) on belt conveyor systems to allow soft-start (reducing the startup torque peak) and variable speed operation (matching conveyor speed to upstream production rate). VFD integration changes the gear ratio selection logic compared to direct-on-line starts.

How VFD affects service factor selection: A VFD provides controlled acceleration — instead of a direct-on-line motor applying full torque instantly, the VFD ramps the motor up over a programmable acceleration time (typically 3–10 seconds for conveyors). This controlled ramp dramatically reduces the peak startup torque: a conveyor that requires SF=2.0 for direct-on-line start typically requires only SF=1.25–1.5 with VFD soft-start. The gearbox can therefore be specified at a smaller size.

How VFD changes ratio selection: Without a VFD, the gearbox ratio must be selected to produce the target belt speed at the motor’s fixed rated speed (typically 1,450 or 2,900 rpm). With a VFD, the motor speed is variable — the VFD can run the motor at 50%–120% of rated speed. This flexibility means the gearbox ratio can be selected for the mid-speed operating point rather than the maximum speed, and the VFD trims to the required speed. The practical benefit is that a standard catalogue ratio (e.g. i=25) can be used for an application that would otherwise require a non-standard ratio (e.g. i=22.5) without a VFD.

คิว
Our existing conveyor uses a worm reducer rated at 200 N·m. We want to replace it with a planetary. What size EP-BPG do we order?

Do not order a 200 N·m planetary unit directly. The worm reducer was likely selected at rated torque without a service factor — or was oversized precisely because the service factor was unknown. First, calculate the actual running torque from the conveyor parameters: belt weight, material load, belt speed, pulley radius, and incline. Then apply the appropriate service factor (typically 1.5–2.0 for food belt conveyors). If the calculated T_rated = running torque × SF is, for example, 280 N·m, then select an EP-BPG frame covering ≥280 N·m. Korea Ever-Power’s application team can calculate this from your conveyor specifications and confirm the correct BPG frame size, including checking that the output shaft and flange dimensions match the existing worm reducer mounting.

คิว
My Korean outdoor belt conveyor is used at a port facility. What are the specific concerns for winter operation?

Korean port facilities in Incheon, Busan, and Pohang experience winter ambient temperatures of −5 to −12°C. Three concerns apply: (1) Grease viscosity — EP planetary sealed grease is rated to −10°C minimum operating temperature, covering most Korean port locations. Verify your minimum ambient against this limit; if your site reaches −12°C, discuss a low-temperature grease option with Korea Ever-Power. (2) Startup torque — as discussed, cold-start SF=2.5 for loaded outdoor belts is the conservative specification for Korean winter conditions. (3) Belt and material stiffening — the gearbox torque capacity must cover the elevated starting torque from cold belt rubber and frozen material adhesion, not just the summer running condition. Select gearbox frame at T_rated = T_running_warm × 2.5 for robust Korean outdoor port specification.

คิว
Can a planetary gearbox replace a worm reducer on a food facility vertical screw elevator?

Only if position holding on power-off is addressed separately. A planetary gearbox delivers better efficiency and longer service life than the worm reducer, but it cannot self-lock — the material column in a vertical screw elevator will back-drive a planetary gearbox when the motor is off. The replacement configuration requires either: (a) a spring-set electromagnetic brake on the servo or induction motor — this is fail-safe (brake engages on power loss) and allows the planetary gearbox to handle the running drive; or (b) retaining a worm stage as the final stage downstream of the planetary — the planetary handles the speed reduction and efficiency, and the worm stage provides the self-lock. Option (b) is used for very tall elevators where the back-drive torque is large and a reliable brake with sufficient torque is impractical.

คิว
How does the pulley overhang distance affect gearbox bearing selection for belt conveyor head drives?

Belt conveyor head drums are typically mounted with a shaft projecting from the gearbox output and the pulley located some distance from the gearbox face. The belt tension creates a radial force at the pulley that acts as a bending moment on the gearbox output shaft — the magnitude of this bending moment increases linearly with the distance from the gearbox face to the pulley centre (the overhang distance). Korea Ever-Power EP series gearbox specifications include a permissible radial force at a reference overhang distance from the shaft face. For installations where the pulley is mounted further from the gearbox than this reference, the permissible radial force must be de-rated — or the EP-AF high-rigidity shaft series must be substituted, whose enlarged shaft diameter provides significantly higher bending stiffness and bearing load capacity at the increased overhang. Always confirm the actual overhang distance and belt tension when specifying a head drum drive gearbox — these two parameters determine whether a standard shaft series is adequate or high-rigidity shaft is required.