Method and control system for starting crushing in a gyratory crusher

1. Method for determining a start-up crushing gap width for a crushing operation in a gyratory crusher, the crusher comprising a crushing head fastened on a shaft and provided with first and second crushing shells arranged to form a crushing gap to receive material to be crushed, the width of the crushing gap being adjustable, and a driving device arranged to cause the crushing head to execute a gyratory pendulum movement, the method comprising the steps of:

A. activating the driving device to cause the crushing head to initiate a gyratory pendulum movement, with the crushing gap set at a first start-up width;

B. commencing a feed of material into the crushing gap to initiate crushing;

C. measuring a load on the crusher resulting from the crushing;

D. adjusting the width of the crushing gap to cause the load to approach a selected value, and obtaining a measure representative of the adjusted gap width;

E. calculating a subsequent start-up width in accordance with the obtained measure of step D; and

F. setting the width of the crushing gap to correspond to the calculated subsequent start-up width of step E prior to repeating step A for a subsequent crushing operation;

wherein step B includes starting a countdown of a predetermined time period beginning with the start of the supply of material into the crushing gap; step D including determining whether the width adjustment has occurred within the predetermined time period; and step E being performed only if the width adjustment has occurred within the predetermined time period.

2. The method according to claim 1 wherein the predetermined time period is in the range of 3-30 seconds.

3. The method according to claim 1 wherein when a plurality of adjustments occur within the predetermined time period, step D comprises obtaining a measure that is representative of the crushing gap width following the first width adjustment that was made.

4. The method according to claim 3 wherein the predetermined time period is in the range of 3-30 seconds.

5. The method according to claim 1 wherein step E comprises determining a ratio between the adjusted width of step D and a constant-operation reference width, and calculating the subsequent start-up width in accordance with the ratio.

6. The method according to claim 5 further comprising performing steps A-F for a plurality of crushing operations, calculating a mean value of the ratios determined in step E for the plurality of crushing operations, and calculating the next subsequent start-up gap in accordance with the mean value.

7. The method according to claim 6 wherein the plurality of crushing operations is in the range of 3 to 10.

8. Method for determining a start-up crushing gap width for a crushing operation in a gyratory crusher, the crusher comprising a crushing head fastened on a shaft and provided with first and second crushing shells arranged to form a crushing gap to receive material to be crushed, the width of the crushing gap being adjustable, and a driving device arranged to cause the crushing head to execute a gyratory pendulum movement, the method comprising the steps of:

A. activating the driving device to cause the crushing head to initiate a gyratory pendulum movement, with the crushing gap set at a first start-up width;

B. commencing a feed of material into the crushing gap to initiate crushing, and starting a countdown of a predetermined time period at the start of the supply of material into the crushing gap;

C. measuring a load on the crusher resulting from the crushing,

D. adjusting the width of the crushing gap to cause the load to approach a selected value, and determining whether the width adjustment has occurred within the predetermined time period; and

E. setting a gap width for a subsequent crushing operation to be the same as the first gap width, when the width adjustment of step D occurs after the predetermined time period.

9. Apparatus for determining a start-up crushing gap width for a crushing operation in a gyratory crusher which comprises a crushing head fastened on a shaft and provided with first and second crushing shells arranged to form a crushing gap to receive material to be crushed, the width of the crushing gap being adjustable, and a driving device arranged to cause the crushing head to execute a gyratory pendulum movement, the apparatus comprising:

activating means for activating the driving device to cause the crushing head to initiate a gyratory pendulum movement in a crushing operation, with the crushing gap set at a first start-up width;

measuring means for measuring a load on the crusher resulting from the crushing;

adjusting means for adjusting the gap width to cause the load to approach a selected value;

obtaining means for obtaining a measure representative of the adjusted gap width;

calculating means for calculating a subsequent start-up width for a subsequent crushing operation in accordance with the obtained measure; and

a clock for counting down a predetermined time period beginning with the supply of material to the gap, wherein said calculating means is operable to calculate the subsequent start-up width only if the width adjustment is made within the predetermined time period.