Lean Construction Ireland Annual Book of Cases 2021 25 on effect on quality required a crew to grind the slab to achieve the finish at a cost of €1,680.Again, the overall cost could have amounted to €31,920. • The total exposure on this issue equated to more than €100,000. We created a Cause and Effect diagram to help with the determination of the elements of the problem.This helped us to focus on the critical few causes of the problem we were trying to solve. Figure 2. Cause and Effect Diagram Figure 3 shows the concrete pump and the area of the swap-over where the root cause of the problem lay. Figure 3. The Concrete Pump Analyse Having completed the first pour, it became evident that some streamlining of the process would be required to improve efficiency. We therefore held a Kaizen event with the team to review the current process and the issues it raised, and to develop solutions for subsequent pours.To get the pour completed within 10 hours, the swap-over between placing boom 1 and placing boom 2,whilst washing out the line back to the pump, was highlighted as being critical. It became clear that it was more beneficial to pour the slab in two separate large pours rather than split it up into the four smaller pours as originally planned. In addition, we determined that the swap-over needed to be achieved in 45 minutes and not the existing 150 minutes. From our analysis, it became evident that the main issue we faced was the swap-over between the placing booms. A secondary issue was the spider pump locations. Although we had picked these beforehand, we still had to lift them with the tower crane three times instead of the planned two because they didn’t reach exactly where we wanted to.The solution we proposed to adopt included the following elements: • Ensure that the slab pours were completed between 17:00 and 18:00 to allow time for the quality of finish required on the last 30% section of the slab. • Work with the Local Authority to determine if they would agree to start the pour 1 hour earlier and allow us to take advantage of this time before peak morning traffic. • Determine the optimum number of pours for the slab in conjunction with the reinforced concrete formwork contractor and the concrete supplier. • Review and standardise the procedure around cleaning out the lines from the first placing boom to the static concrete pump, and then swapping over the pipework connections to the second placing boom to complete the second half of the pour. • Determine the optimum positions for the spider pumps so as to maximise their use and minimise the number of moves required, thus releasing the tower crane for other critical tasks. • Take an as-built record of the ideal locations of the spider pump on the deck by our engineers and set these out again for each pour. Figure 4 is an isometric view of a typical floor.Our original plan was to divide the pour into 4 sections. Having discussed this with the team involved,we decided to go with 2 pours as depicted in Figure 4. Figure 4. IsometricView of aTypical Floor Another key item was ensuring that we efficiently ramped up the flow rate from the commencement of the pour to the point in time at approx. 11:00 when we needed to clean out the first placing boom line and swap-over the pipework connections to place boom 2. We communicated this process to the concrete supplier so they were aware of the need to slow down the pour rate for approx. 45 minutes while the changeover happened.They then needed to ramp back up to the original rate to start pouring again at full pace, either through the placing boom on its own or through the placing boom connected to the spider pump. Case 6
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