Assuming used with a counter mass, potentially for maintenance and or adjustment.

Regards,

Lyle ■

Besides the loop facility mentioned above there is/were/used to be automatic powered tensioning devices using hydraulic, pneumatic or electric prime movers.

Only electric, winches, have general acceptance. For maintenance and adjustment I have only used manual winches.

In an automatic set-up a winch is activated according to pre-set minimum and maximum tensions, rope tensions, with a third over-tension pre-set. A brake is provided to 25% more than the minimum tension. Limit switches are activated at carriage under and over travel as well as rope failure. Fluctuations between max. and min. tensions are ignored to obviate any hunting in the system. Over-tension is limited by a single acting, spring loaded, hydraulic cylinder which 'slips' the brake until the tension becomes acceptable. Winch speed should be fast enough to address full load starting and burden fluctuations. This system was used alongside scoop control couplings.

With the emergence of allegedly sophisticated belt drive controls it might be possible to incorporate this sort of tensioning into the system....but I personally wouldn't try. Not at my time of life. ■

SAFETY of maintenance personnel. Overland conveyors can move at any time from a standstill due to thermal growth and captured tension differentials. Dropping the counterweight highly mitigates this danger.

Belt storage for splice repair, unexpected growth of belt due to tensioning, especially fabrics that iron out, and travel adjustments of carraiges and trolleys as others have noted. ■

My first comment assumed a gravity type take-up. Maybe the enquirer was calling attention to a powered winch controlled (load cell controlled, or other..). In such a case the answer needs to address the selection of a direct electrically powered or hydraulic activated take-up with winch in circuit.

In either case, the answer is too complex for a few word response. Powered winch takeups have many reasons for their selection, including their use on gravity take-ups, not noted above. They can be employed to control difficult dynamics shock wave action during a motor disconnect stop. They can be employed to control excessive take-up motion during a stop and so forth. ■

All responses thus far assume an automatic take-up arrangement be it gravity or reactive to load cell readings. There are powered winches at fixed displacement take-ups all over the brown coal mining system of Germany and else where. Ironically these too adjust to rope tension load cell readings, applying a higher tension during start-up then relaxing to a lower tension after running speed is reached. Beyond this point the take-up position stays fixed.

Joe Dos Santos ■

Motorized winch fixed (displacement) type take-ups are also used at long reversing conveyors when only one drive station and one take-up station are employed.

Joe Dos Santos ■