Conveyor drive unit: motor, fluid coupling, reducer and backstop on a drive base

01

Control the belt start with a fluid coupling

Voith's constant-fill fluid couplings sit between motor and reducer and transmit torque through oil (or water, on demand) moved from a pump wheel to a turbine wheel; at nominal operation a small speed difference, the nominal slip, remains and only the torque the driven machine needs is transmitted. Voith lists load-free start and run-up of the motor, torque limitation during start-up, shock damping, overload protection and load compensation for multi-motor drives among the coupling's properties. [1]

The TV type adds a delay-fill chamber that holds part of the fluid at standstill so a reduced torque is transmitted while the motor runs up; the TVV enlarges that chamber, and the TVVS adds an annular chamber that further reduces starting torque and was designed originally for conveyor belt drives. [1] Voith states that the TVVS suits medium and long belt conveyors with start-up times up to 45 seconds, and that multi-motor drives can be switched on in a staggered sequence to limit current demand; in one project its couplings served belt conveyor drives of 200 to 800 kW. [2]

Size changes the package: in Voith's table, size 562 is 634 mm in diameter and 162 kg as a TVV, and 660 mm and 185 kg as a TVVS, with weights including the connecting coupling and maximum oil fill. [1] Editorial note: ask the supplier for the coupling's start-up torque curve and the belt's start-up time at full and empty load, not only the coupling size.

Give the supplier the conveyor length, lift, belt speed, capacity, pulley diameter and shaft size, number and position of drives, motor power and starting method, required start-up time, whether the conveyor is inclined, and the drive base and guarding required.

02

Size the backstop on stalled motor torque

U.S. Tsubaki states that a conveyor backstop must be sized for the breakdown or stalled torque of the drive motors, not average loads, and lists service factors of 1.30 for motors with 175% or 200% stalled torque, 1.67 for 250% and 2.00 for 300%. [3]

Its single-drive example takes a 125 HP motor, a 43.75 RPM head shaft and a 250% stalled-torque motor: 125 × 5,250 × 1.67 / 43.75 = 25,050 ft·lb, met by a backstop rated 32,500 ft·lb. [3] Editorial calculation: that is about 93.2 kW and 33,960 N·m required against about 44,060 N·m rated.

For two backstops on one head shaft, Tsubaki applies a load-sharing factor of 1.7 rather than 2; for tandem drives, the backstop on the primary drive unit is sized for the sum of the primary and secondary motors and the secondary backstop for the secondary motor alone. [3]

03

Tsubaki's worked backstop selections for single, dual and tandem drives

U.S. Tsubaki works four conveyor arrangements through the same formula (motor HP × 5,250 × service factor ÷ head-shaft RPM, in ft·lb) and picks a backstop rated above the result. [3]

Editorial calculation: the twin-backstop case divides by 1.7 instead of 2, so each backstop carries about 59% of the total rather than 50% (1 ÷ 1.7 ≈ 0.59).

04

Data for a conveyor drive enquiry

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Conveyor: [length; lift; belt speed; capacity]
Pulley: [diameter; shaft size; RPM]
Drives: [single, dual, tandem; motor power]
Start-up: [coupling type; start-up time; starting method]
Backstop: [inclined; stalled torque %; service factor]
Base: [bedplate or swing base; hand]
Site: [ambient; supply; protection]

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