Conveyor Gearbox Selection: Sizing a Belt Conveyor Drive

A conveyor gearbox is not a product category in our catalogue — it is a duty, and six of our nine reducer series can perform it. The right way to choose is to start from the belt, not from a series name: belt speed and drum diameter give you the output speed, absorbed power at the drum gives you the torque, and those two numbers point at a frame size. Yanfeng Group Co., Ltd. builds all nine series in Pingyang, Wenzhou, and two of them carry a belt-conveyor worked example printed in the catalogue itself. This guide runs the selection in that order, and every figure below comes from our own gear reducer pages and catalogues.

Key definitions

• Absorbed power: the power the belt actually demands at the drum shaft, which is what the gearbox has to pass. Motor nameplate power is usually larger.
• Output speed (n₂): the drum-shaft speed in r/min. On a belt drive it is fixed by belt speed and drum diameter, not chosen.
• Permissible output torque (T_N): the torque a frame size may carry continuously. It is the figure you compare your calculated torque against.
• Service factors: multipliers for the driven machine (f1), the prime mover (f2) and starting (f3). The catalogue rule is T_N ≥ T₂ × f1 × f2 × f3.
• Thermal capacity (PG1 / PG2): the power a unit can shed as heat without auxiliary cooling (PG1) or with a cooling coil or oil circulation (PG2). It is a second, independent limit on capacity.
• Shaft-mounted (hollow shaft): the gearbox slides onto the drum shaft and is held against rotation by a torque arm, with no coupling and no base frame. A shrink disk clamps the hollow shaft to a plain shaft end.
• Line shaft: one drive distributed along a shaft to several drive points, usually through right-angle gearboxes.

Which series drives a belt conveyor

Series	Shaft layout	Permissible output torque	Power and ratio	Hollow-shaft option	Where it fits on a conveyor
R series coaxial helical	in-line	87–17,700 N·m	0.12–160 kW, ratio approx. 3.37–289.74	no; foot or B5 flange	small drives where motor and drum sit in line
F series parallel-shaft helical	parallel, offset	196–16,800 N·m	0.12–200 kW, ratio approx. 3.77–281.71	yes: YFA, YFAF (B5), YFAZ (B14), YFA…B	the default shaft-mounted belt drive
K series helical-bevel	right angle	156–49,400 N·m	0.18–200 kW, ratio approx. 5.36–197	yes: YFKA, YFKAF, YFKAZ	right-angle drive in a narrow gallery; one load direction only
S series helical-worm	right angle	93–3,990 N·m	0.12–22 kW, ratio approx. 6.8–290	yes: YFSA, YFSAF, YFSAZ	small right-angle drives needing a high ratio in one unit
P series planetary	in-line, or with a bevel, helical or bevel-helical input stage	up to 2,600,000 N·m	0.4–1,293 kW, output 0.19–60 r/min	yes: AZ hollow shaft with shrink disk, AH splined hollow shaft	heavy, slow head drives; carries the catalogue's belt-conveyor example
H/B series industrial gear unit	YFH parallel, YFB right angle	up to 470,000 N·m	2.52–5,366 kW, output 1.7–1,200 r/min	yes: H hollow shaft, D hollow shaft with shrink disk	long-haul and heavy-duty conveyors; carries the second worked example
ZDY / DBY family	ZDY/ZLY/ZSY parallel, DBY/DCY right angle	rated by input power in Tables 1 and 3 rather than by torque	ZDY approx. 5–6,666 kW, ZLY approx. 6.8–6,229 kW nominal input power	yes: K hollow shaft, KD with shrink disc	the catalogue names conveyors first among its applications
T series spiral bevel gearbox	right angle, no motor	rated approx. 11.6–3,499 N·m	ratios 1:1 to 5:1	no	splitting one drive along a line shaft to several drive points

Two readings matter here. First, the torque ranges overlap heavily: a 12,000 N·m drive can be an F series, a K series, an H/B or a ZLY, and the layout, the mounting and the thermal check decide between them, not the torque. Second, the gap between 16,800 N·m (the top of the F series) and 470,000 N·m (the top of H/B) is where most conveyor projects change class — below it you are buying a gearmotor, above it you are buying an industrial gear unit with its own lubrication and cooling decisions.

Sizing a conveyor drive in seven steps

1. Write down the duty before the machine. Belt speed in m/s, drum diameter in m, absorbed power at the drum in kW, daily running hours, starts per hour, and where the unit will stand — enclosed, in a hall, or outdoors. The last item is not a detail; it changes the thermal rating by a factor of about two.
2. Convert belt speed to output speed. n₂ = 60 × v ÷ (π × D). A 1.6 m/s belt on a 0.5 m drum gives about 61 r/min. This is the number the gearbox must deliver; it is not negotiable without changing the drum.
3. Get the required torque from the power. Our catalogues use P = T × n / 9550, so T₂ = 9550 × P ÷ n₂ with P in kW and n₂ in r/min. 30 kW at 61 r/min is about 4,700 N·m.
4. Choose the ratio from the motor speed, then check the actual ratio. Nominal input speeds in the selection tables are 750, 1,000 and 1,500 r/min. A 1,500 r/min motor against 61 r/min asks for about 24.5, and the table will offer a nominal ratio near but not equal to it — the catalogue makes you check the actual ratio against the speed you need, because the difference lands on belt speed.
5. Apply the service factors. Determine f1 for the driven machine, f2 for the prime mover and f3 for starting from the load type, the daily running time and the starting frequency, then require T_N ≥ T₂ × f1 × f2 × f3. For the P and H/B series the selection pages add three further checks: peak torque, permissible additional radial force on the output shaft, and a safety factor on nominal power.
6. Pick the layout and the mounting. In-line, parallel-offset or right-angle is set by the geometry of the gallery, not by preference — see the next section.
7. Check the thermal balance last, and separately. Mechanical capacity and thermal capacity are two different limits, and a unit can pass one and fail the other. The answer to a thermal failure is usually cooling, not a bigger frame.

The output of those seven steps is a complete model designation. Our catalogues print one worked example each: YFP3N-AZ-17-225-B500-96 on the planetary side and YFB 2 S H -10 -12.5 -A -CW as the H/B designation pattern, where the fields are series, stages, output-shaft design, mounting, size, nominal ratio, assembly design and input rotation. The ZDY family uses YFD B Y K 160 14 III S, which encodes the final-stage centre distance rather than a frame number.

Shaft-mounted or foot-mounted

Shaft mounting removes three things from the installation: the coupling, the base frame, and the alignment work that goes with them. What it adds is a torque arm to stop the casing turning, and a load path through the drum shaft that someone has to check. The hollow-shaft options across the range are the F series YFA, YFAF and YFAZ types, the hollow-shaft K and S types, the P series AZ hollow shaft with shrink disk and AH splined hollow shaft, the H/B series H and D output shafts, and the ZDY family K and KD types. On the P series the reaction hardware is ordered as part of the designation: add-on code 75 is a torque reaction arm on one side, 76 on both sides, 77 a torsion shaft support, and 96 a gear housing base for foot mounting instead.

Foot mounting with a coupling is the better answer in three cases: when the drum shaft cannot carry the gearbox weight and the overhung load, when the drive has to be inspected or exchanged without disturbing the drum, and when the unit is big enough that forced lubrication and cooling pipework need a fixed base anyway. Mounting position is part of the order either way — M1 to M6 on the R, F, K and S series, with the breather, oil sight glass and drain plug relocated for each position; B500–B556 horizontal and V100–V130 or V300–V330 vertical on the P series; H horizontal with feet, M horizontal without feet and V vertical on the H/B series.

The thermal check, and when a fan is not enough

Unit	Standard lubrication	Thermal capacity as printed	Cooling options
P series YFP2N, horizontal	dip lubrication	PG1 21–437 kW in a small confined space; 29–619 kW in a large hall or workshop; 39–838 kW in the open	forced lubrication on request; an oil pump is required on larger vertical arrangements to lubricate the input bearings
H/B series	dip (splash) lubrication when horizontal	separate thermal-capacity tables for four conditions: no auxiliary cooling, fan cooling, cooling coil, and fan plus coil	forced lubrication (standard on vertical units), cooling fan, cooling coil; oil-supply factor f9 is 1.0 horizontal and 1.05 with forced lubrication
ZDY / ZLY cylindrical	oil-bath lubrication	PG1 13–1,020 kW with no auxiliary cooling, by frame size 80–560 and ambient air velocity (≥0.5, ≥1.4, ≥3.7 m/s); PG2 43–1,780 kW with a cooling coil or oil circulation	fan, cooling coil, oil-pump circulation

The pattern is the same in all three tables and it is the one thing most enquiries leave out: the same gear unit in the same duty has a different rating depending on the air around it. A ZLY sized on its open-air figure and then installed in a closed transfer house can be thermally undersized without a single mechanical number changing, and on the ZDY family the fix — a coil or oil-pump circulation — roughly doubles the rating from PG1 to PG2 without changing the frame.

The two conveyor examples in our own catalogues

The P series catalogue works through a belt conveyor drive: 75 kW at 1,500 r/min, ratio 227, and lands on YFP3N-AZ-17-225-B500-96 — a three-stage planetary unit, standard structure, hollow shaft with shrink disk, size 17, nominal ratio 225, horizontal mounting B500, on a gear housing base. Note the ratio: the required 227 against a nominal 225, which is exactly why the catalogue makes you check the actual ratio in step 4.

The H/B series catalogue works through a blast-furnace feed conveyor drive — a heavy, continuous, dusty duty, and the case where the thermal tables and the f9 oil-supply factor do the deciding. Between them the two examples bracket most of what a conveyor project asks for: one at 75 kW on a shaft-mounted planetary unit, one at industrial-gear-unit scale with cooling to specify.

Our recommendation

Size in the order above and the series chooses itself. Below about 16,800 N·m, shaft-mount an F series unit on the drum shaft and fit a torque arm; that covers the majority of belt drives and the fewest parts are involved. Where the drive must turn a corner, use the K series and state the rotation direction when ordering, because the spiral-bevel set bears load in one direction only. Above that torque, move to the H/B industrial gear unit or, where output speed is very low and torque very high, the P series planetary unit — and in both cases settle the thermal check and the cooling hardware before the frame size. For several drive points from one motor, keep the reducer at the motor and distribute with T series bevel gearboxes along a line shaft.

For the series-by-series comparison behind this table, see our industrial gear reducer round-up and the R, F, K and S selection guide; for how to check a supplier's factory and machining, see the manufacturer verification guide and our production capacity page. The full catalogues are on each series page: P series, H/B series and ZDY / DBY series.

Send us belt speed, drum diameter, absorbed power, daily running hours, starts per hour and where the unit will stand through the enquiry form. Our Reducer Sales department returns a frame size, a ratio, a mounting arrangement, a complete model designation and the thermal rating for that installation. Office hours are Monday to Saturday 08:00–17:30 and Sunday 09:00–17:30, China Standard Time (UTC+8).