A crane is being used to lift pallets of concrete blocks onto the upper floor of...

  

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A crane is being used to lift pallets of concrete blocks onto the upper floor of a multi storey building under construction. Each pallet holds 500 blocks. The ground crew load the crane at ground level and another crew (upper crew) help unload on an upper floor. There is currently only one sling on site. The whole operation has been measured in a work study exercise and the information is shown in the table below. The pallets are moved to the same loading bay at the upper level. Elements of the process Standard time (minutes) 1.5 A. Ground crew secures sling around pallet. B. Ground crew attach sling to the crane hook. C. Crane raises hook, rotates jib and lands pallet. D. Upper crew unhooks sling. E. Upper crew removes sling from pallet. 0.5 2.5 0.5 1.0 0.5 1.0 H. Upper crew supervise the removal of the blocks from the loading bay ensuring the area is clear for the next delivery. 1.0 F. Upper crew connects empty sling to crane hook. G. Crane hook and sling is lowered to ground level. (you must include this as an "upper gang" activity in your chart, however you should ignore others at the upper level who may be part of this activity i.e. fork lift driver to lift and transport pallet to another part of the upper floor) I. Ground crew unhooks sling. Part 1 16 marks 0.5 (a) Construct a multiple activity chart to represent the total operation. Please draw at least 3 cycles. Note any assumptions made. (b) Determine the cycle time, and utilisation of the crane and each of the gangs, after the cycle has continued long enough to overcome start-up effects. (c) A total of 30,000 blocks need to be delivered. How long will this take using the described operation? Assume no break. (d) Comment on the efficiency of the operation and make suggestions for improving the utilisations. Part 2 20 marks (a) Draw a new multiple activity chart representing the best improvement you can make (using the times and activities given above). Please draw at least 3 cycles. Note any assumptions. If you use more slings, label the slings 1, 2, etc. (b) Determine the new cycle time, and utilisation of the crane and each of the gangs, after the cycle has continued long enough to overcome start-up effects. (c) How long will it now take to move the 30,000 blocks using the new operation? (d) Comment on the efficiency of the new operation. Part 3 20 marks Assume the following costs are involved. Crane 1 crew of workers 1 set of slings $875/day $1741/day $323/day (note: costs are accrued per hour, i.e. if work takes 5.2 hrs then charge for 6 hrs. Assume an 8 hr working day. If it runs over a day you cannot leave a pallet suspended) (a) What is the cost to move 30,000 blocks using the old method and what is the cost per lift. (b) What is the cost to move 30,000 blocks using the new methods and what is the cost per lift. (c) How much money overall has the contractor saved? (d) Overall, have you any advice to give to the contractor to improve efficiency on site? A crane is being used to lift pallets of concrete blocks onto the upper floor of a multi storey building under construction. Each pallet holds 500 blocks. The ground crew load the crane at ground level and another crew (upper crew) help unload on an upper floor. There is currently only one sling on site. The whole operation has been measured in a work study exercise and the information is shown in the table below. The pallets are moved to the same loading bay at the upper level. Elements of the process Standard time (minutes) 1.5 A. Ground crew secures sling around pallet. B. Ground crew attach sling to the crane hook. C. Crane raises hook, rotates jib and lands pallet. D. Upper crew unhooks sling. E. Upper crew removes sling from pallet. 0.5 2.5 0.5 1.0 0.5 1.0 H. Upper crew supervise the removal of the blocks from the loading bay ensuring the area is clear for the next delivery. 1.0 F. Upper crew connects empty sling to crane hook. G. Crane hook and sling is lowered to ground level. (you must include this as an "upper gang" activity in your chart, however you should ignore others at the upper level who may be part of this activity i.e. fork lift driver to lift and transport pallet to another part of the upper floor) I. Ground crew unhooks sling. Part 1 16 marks 0.5 (a) Construct a multiple activity chart to represent the total operation. Please draw at least 3 cycles. Note any assumptions made. (b) Determine the cycle time, and utilisation of the crane and each of the gangs, after the cycle has continued long enough to overcome start-up effects. (c) A total of 30,000 blocks need to be delivered. How long will this take using the described operation? Assume no break. (d) Comment on the efficiency of the operation and make suggestions for improving the utilisations. Part 2 20 marks (a) Draw a new multiple activity chart representing the best improvement you can make (using the times and activities given above). Please draw at least 3 cycles. Note any assumptions. If you use more slings, label the slings 1, 2, etc. (b) Determine the new cycle time, and utilisation of the crane and each of the gangs, after the cycle has continued long enough to overcome start-up effects. (c) How long will it now take to move the 30,000 blocks using the new operation? (d) Comment on the efficiency of the new operation. Part 3 20 marks Assume the following costs are involved. Crane 1 crew of workers 1 set of slings $875/day $1741/day $323/day (note: costs are accrued per hour, i.e. if work takes 5.2 hrs then charge for 6 hrs. Assume an 8 hr working day. If it runs over a day you cannot leave a pallet suspended) (a) What is the cost to move 30,000 blocks using the old method and what is the cost per lift. (b) What is the cost to move 30,000 blocks using the new methods and what is the cost per lift. (c) How much money overall has the contractor saved? (d) Overall, have you any advice to give to the contractor to improve efficiency on site?