For a belt conveyor to run safely, the belt must be kept at a certain tension. This is the job of the take-up. Insufficient tension leads to slip on the drive pulley and excessive sag between idlers; excessive tension leads to early fatigue of pulley bearings, belt splices and the belt itself. A correctly chosen and correctly adjusted take-up directly increases belt life and conveyor reliability.
In this guide we cover the types of take-up, how to determine the correct tension, adjustment steps, maintenance points and spare part selection. For general belt conveyor maintenance, see our belt conveyor guide.
Take-Up Types
| Type | How it works | Suitable for |
|---|---|---|
| Screw take-up | The tail pulley bearings are moved forward or back with screw spindles | Short and medium-length conveyors |
| Gravity take-up | A counterweight constantly pulls the take-up pulley downwards | Long conveyors, variable load |
| Horizontal gravity take-up (carriage) | A weight pulls the tail pulley via wire rope and sheaves | Long conveyors with limited vertical space |
| Hydraulic/automatic take-up | Controlled tension by cylinder or winch | Very long, high-capacity conveyors |
A screw take-up is simple and cheap but does not automatically compensate for thermal and elastic stretching of the belt; a gravity take-up keeps tension constant.
How Is the Correct Tension Determined?
- On a loaded belt, sag between carrying idlers should not exceed about 2–3% of the idler spacing (CEMA recommendation).
- There should be no slip on the drive pulley; however, tension should not be increased arbitrarily to prevent slip.
- The required tension is determined by calculation according to the conveyor’s running, starting and stopping conditions.
Adjustment Steps on a Screw Take-Up
- Stop and lock out the conveyor.
- Clean and lubricate the take-up screws.
- Turn the take-up screws on both sides by equal amounts.
- Run the conveyor empty and loaded to check sag and slip.
- If mistracking has occurred, check that the pulley is square to the belt.
- Lock the lock nuts.
Checks on a Gravity Take-Up
- That the take-up carriage moves freely in its guides,
- That the counterweight is not resting on its upper or lower limit (end of travel),
- The condition of the wire rope and sheaves,
- That the safety guarding (fence) around the counterweight area is in place.
Failure Signs
- Slip on the drive pulley,
- Excessive sag between idlers and spillage,
- A take-up screw seizing or bending,
- The carriage sticking on a gravity take-up,
- The belt running to one side (uneven screw adjustment).
Common Mistakes
- Solving slip only by increasing tension,
- Tightening one side only on a screw take-up,
- Not noticing that the gravity take-up travel has run out (the belt has stretched; it needs shortening),
- Going under the counterweight (serious accident risk).
Troubleshooting Table
| Symptom | Possible cause | Solution |
|---|---|---|
| Slip | Low tension, lagging problem | Check tension and lagging |
| Excessive sag | Insufficient tension | Adjust the tension |
| Bearing and splice failures | Excessive tension | Reduce the tension |
| Take-up travel used up | Belt has stretched | Shorten the belt and resplice |
An Example from the Field
On a long stockpile conveyor, belt tension changed markedly between summer and winter: there was slip in winter and excessive tension in summer. The screw take-up was replaced with a gravity take-up; tension stayed constant all year round, and slip and pulley bearing failures decreased.
Pre-Purchase Checklist
- Have the conveyor length, belt type and tension requirement been determined?
- Have the take-up type and travel length been calculated?
- Have the take-up screws, bearings and guides been measured?
Frequently Asked Questions
Can a screw take-up be used on a long conveyor?
On long conveyors belt stretch is greater, so a gravity or automatic take-up is more suitable.
How much take-up travel is needed?
It is calculated according to belt type, length and splicing method; initial stretch of new belts is also taken into account.
How Is Take-Up Travel Calculated?
The take-up travel must be enough to accommodate the belt’s stretch during operation and over time. The main factors determining the travel required are:
- Belt type: Textile carcass (EP) belts stretch much more than steel cord belts, so conveyors with EP belts need longer travel.
- Conveyor length: The longer the belt, the greater the total stretch.
- Elastic stretch: The belt stretches under load because of tension; this stretch changes during starting and stopping.
- Permanent stretch: New belts show some permanent stretch during the initial running period.
- Splice allowance: Extra length may need to be left for belt repairs or resplicing.
When travel is insufficient, a gravity take-up bottoms out and a screw take-up reaches the end of its thread; the belt must then be shortened and respliced.
Detailed Comparison of Take-Up Types
| Criterion | Screw | Vertical gravity | Horizontal gravity | Hydraulic/automatic |
|---|---|---|---|---|
| Constant tension | No | Yes | Yes | Yes (controlled) |
| Space required | Little | Needs vertical height | Long horizontal space | Medium |
| Maintenance | Screw cleaning/lubrication | Guides, rope, counterweight area | Sheaves, rope, carriage | Hydraulic unit |
| Suitable length | Short | Medium to long | Long | Very long |
| Investment | Low | Medium | Medium | High |
Effect of Operating Conditions on the Take-Up
- Temperature changes: Seasonal temperature differences change belt length; on a screw take-up, the adjustment should be checked at the change of seasons.
- Wet operation: Traction falls on the drive pulley; slip should be solved with lagging and cleaning, not tension.
- Frequent starts and stops: The tension peak at start-up moves the carriage on a gravity take-up; clean guides are important.
- Spillage: Material building up on the take-up carriage and guides can prevent movement.
Maintenance Record Form
| Field | Record |
|---|---|
| Take-up type and location | Screw / gravity, tail or intermediate |
| Remaining travel | Weekly measurement |
| Sag measurement | Ratio to idler spacing |
| Slip events | Date, weather, action taken |
| Rope, sheave and guide condition | Monthly inspection notes |
Converting the Take-Up: When Does It Make Sense?
If a conveyor with a screw take-up suffers frequent slip, seasonal changes in tension or a constant need for adjustment, conversion to a gravity take-up can be considered. Before conversion, plan the required travel, counterweight mass, space, guide structure and safety guarding. On long, critical conveyors, conversion can quickly pay for itself by extending belt and pulley life.
Safety Notes
- The gravity take-up area should be fenced so that no one can get under the counterweight.
- Before maintenance, the counterweight should be mechanically secured or supported.
- Wire ropes and sheaves should be checked regularly for the risk of failure.
- When adjusting a screw take-up, the conveyor must always be locked out.
More Questions
How does increasing tension affect belt life?
More tension than necessary creates constantly high stress in the belt carcass and splices, accelerating fatigue; it also shortens the life of pulley bearings and shafts.
How is the counterweight mass determined?
The required take-up force is determined from the conveyor tension calculation, and the counterweight mass is calculated according to the sheave arrangement.
Is a hydraulic take-up always better?
It is advantageous on very long, high-capacity conveyors; on short and medium conveyors a gravity take-up is a simpler, more economical solution.
Spare Parts and Service for Take-Ups
CSP Mühendislik supplies take-up screws, take-up pulleys, gravity take-up carriages and guides for belt conveyors as part of its belt conveyor spare parts range, and provides service support for take-up conversion and adjustment. You can share your conveyor details on WhatsApp.
