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Statistical Process Control in the Construction Industry Dr Mohamed AICHOUNI Monday, November, 21 st,

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Presentation on theme: "Statistical Process Control in the Construction Industry Dr Mohamed AICHOUNI Monday, November, 21 st,"— Presentation transcript:

1 Statistical Process Control in the Construction Industry Dr Mohamed AICHOUNI Monday, November, 21 st, 2011 © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

2 Quality Definition and Characteristics Quality is defined by the totality of features and characteristics that satisfy customers needs” () Quality is defined by the totality of features and characteristics that satisfy customers needs” (ASQ) Quality Characteristics Variables Can be measured or expressed with some unit, such as height, length (m), mass (kg), cycle time (s), concrete strength (MPA) etc.. Attributes Can be counted such as number of defects, errors, accidents etc.. Process Variations

3 Process Variations and Quality Quality is inversely proportional to variability Quality is inversely proportional to variability (Variability & Quality are enemies). delivery timeswork practices: morewaste higher costspoor qualitydelivered to our customers The more variation in product characteristics, in delivery times, in work practices: the more waste, higher costs and poor quality, is delivered to our customers. (Out of the Crisis, 1982) © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

4 Process Variations Causes 1.Common causes 1.Common causes are ever-present in the process; ========= Natural Variations 2.Special causes 2.Special causes are intermittent effects that must be investigated immediately. Assignable Causes Variations ========= Assignable Causes Variations Management should help people identify and remove special causes and reduce the occurrence of common causes Management should help people identify and remove special causes and reduce the occurrence of common causes in the process. © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

5 Process Improvement Process Improvement is basically about the reduction of variability in processes, products and services. Business ExcellenceIt results in waste reduction, quality improvement, Customer Satisfaction and more importantly to Business Excellence. © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

6 How to Improve Processes and Quality ? Study and Understand Process Variation. Use Appropriate Quality Tools (The 7 Basic tools (Statistical Process Control), the 7 New Tools for Management and Planning etc.. Set Process improvement teams Use Employee suggestions © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

7 Kaoru Ishikawa (1972) Seven Basic Quality Tools Kaoru Ishikawa (1972) Called the Magnificent Seven Called the Magnificent Seven They are simple visual tools based on the use of data to study and understand the things we do (Process) so that we can improve the quality of products and services. They are simple visual tools based on the use of data to study and understand the things we do (Process) so that we can improve the quality of products and services. © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

8 Flow Chart Flow Chart Check Sheet Check Sheet Pareto Analysis Pareto Analysis Histogram – Process Capability Histogram – Process Capability Cause-and-Effect Diagram Cause-and-Effect Diagram Scatter Diagram Scatter Diagram Control Charts (SPC) – Process Stability Control Charts (SPC) – Process Stability Seven Basic Quality Control Tools Magnificent Seven 1234 Dirt Old Temp Fault x x x x x x x x x x x x x x x x UCL LCL Process © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

9 Control Chart (SPC Chart) What is it? Quality Management tool, showing whether a process is working predictably and smoothly. What is its use? To monitor, control and improve process performance overtime by studying variation and its source. Variable Y X (Time) Upper limit Lower limit Average/Spec Common Causes Variation Special Cause Variation Out of Statistical Control Situation © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

10 What Does a Control Chart Do ? Focuses attention on detecting and monitoring process variation over time; guide to local or management action Distinguishes special from common causes of variation, as a guide to local or management action; Serves as a tool for ongoing control of a process; Helps improve a process to perform consistently and predictably Helps improve a process to perform consistently and predictably for higher quality, lower cost, and higher effective capacity; Provides a common language for discussing process performance. Variable Y X (Time) Upper limit Lower limit Average/Spec Common Causes Variation Special Cause Variation Out of Statistical Control Situation © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

11 Control Charts Interpretation © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA Stable processStable process: one which performs with a high degree of consistency at an essentially constant level for an extended period of time In-control –“In-control” out-of- control state.A process that is not stable is referred to as being in an out-of- control state. This is due to the existence of Special causes in the process, It requires immediate cause-effect analysis to eliminate the special cause of variation.

12 Histograms What is it? A Histogram is a bar graph used to present frequency data. What is its use? Histogram provides an easy way to evaluate the distribution of the process and to have a precise look at process variations. How the process distribution with respect to Customer Specifications (USL, LSL) How the process distribution with respect to Customer Specifications (USL, LSL) Is the Process Capable to meet our customer requirements ? Is the Process Capable to meet our customer requirements ? LSL USL © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA frequency Category

13 Applications of SPC tools in the Construction Industry World Class Research © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

14 Applications in Concrete Production Processes © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

15 Applications in Concrete Production Processes Concrete is the most widely used material in construction industries. Therefore, it is necessary to understand and improve the efficiency of a concrete production process. Producers of concrete can use control charts to determine if the concrete production process is out-of-control and subsequently attempt to identify the root causes for the out-of-control situation. By identifying assignable causes of the out-of- control process, the producer can then improve the process by reducing product variation, unnecessary waste, or over-designed concrete mixtures. © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

16 Applications in Concrete Production Processes Hybrid Control Charts for Active Control and Monitoring of Concrete Strength, B. Laungrungrong; B. Mobasher; D. Montgomery; and C. Borror, Arizona State University JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JANUARY 2010 / 77 Historical Data of Concrete (Arizona Department of Transportation) were analyzed using SPC techniques. For the majority of concrete delivered to customers, the strength far exceeded that required for a particular project. Over-designed concrete mixtures : The amount of cement that could be saved by reducing the total cement content in the mixture is significant. Savings can be huge. Savings can be huge.

17 Applications in Concrete Production Processes Hybrid Control Charts for Active Control and Monitoring of Concrete Strength, B. Laungrungrong; B. Mobasher; D. Montgomery; and C. Borror, Arizona State University JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JANUARY 2010 / 77 Project (1) EWMA and CUSUM Control Charts were used to analyze concrete data This case represents an in-control stable and capable process. The process is stable under the acceptable level of concrete strength (greater than the fc`). No action is required on the process

18 Applications in Concrete Production Processes Hybrid Control Charts for Active Control and Monitoring of Concrete Strength, B. Laungrungrong; B. Mobasher; D. Montgomery; and C. Borror, Arizona State University JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JANUARY 2010 / 77 Project (2) Out of Control Process (points outside Control Limits) Unstable Process Poor Process capability : unacceptable level of concrete strength lower than the fc It is important to investigate the process and reduce variation with the goal being to bring the process back into statistical control and make it capable.

19 Applications in Concrete Process Hail University Projects Customer : UoH, Engineering College Building Producer : XXX Ready-Mix Concrete Co (Hail) Concrete Types : RMC 21 and RMC 35 Quality Characteristic: Concrete Compressive Strength (MPa) at 28 Days; Tests Data were taken from Third party laboratory (Period : March – October 2011) Data Analysis using Minitab Quality Software © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

20 Applications in Concrete Process Hail University Projects RMC 35 Fully Satisfied Customer (Delivered Strength varies : 102 – 181 % of Required ) Overdesigned Concrete BUT Overdesigned Concrete Producer Perspective: Production Process Variability Required Strength = 35 Mpa Delivered Mean = 46 Mpa Std Dev = 5.8 MPa Min = M Max = MPa © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

21 Applications in Concrete Process Hail University Projects RMC 35 1.Out of Control Situation and big variability in the concrete. 2.Management Decision to set up Quality Control Department led to improved process; 3.However, still some opportunity for Improvement exist.

22 Applications in Concrete Process Hail University Projects RMC 21 Fully Satisfied Customer (Delivered Strength varies from 137 to 207 % of Required ) Production Process Variability Required Strength = 21 Mpa Delivered Mean = 36.2 Mpa Std Dev = 4.2 Mpa Min = 28.7 Mpa Max = 43.8 Mpa Out of Control Process © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

23 Applications in Asphalt Production © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

24 Applications in Asphalt Production (a) Process with Problem / Without Problem Production Plant 24 I R -R charts indicate clearly process out of control = Lower Quality level of Asphalt. ????? For Process Improvement, reasons need to be investigated using appropriate quality tools 7 basic toolbox © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA LSL Target USL Product not meeting specificatio ns UC L LCL UC L LCL Target Histogram = Product (18.75 %) lower than specifications limit (LSL) required by customer. Process Capability ?

25 Applications in Asphalt Production (b) Process with Problem / Without Problem Production Plant 22 I R -R control charts indicate clearly in control process = Quality level high © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA UCL LCL UCL LCL LSL Target USL

26 © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA Applications in Asphalt Production Comparison of # Processes CP ≥ 1 Process Capability is acceptable ; CP ≥ 1.3 Process Capability excellent. Expected level of quality : high CP < 1 : Big problem with the process and the product quality. Process Not Capable to meet Customer Specifications

27 Conclusions Statistical Process Control (SPC) help construction industry to understand the process and to improve its efficiency and capability to meet customer specifications and requirements. When historical data are available on projects, better insight into operational procedures can be obtained through the use of control charts. Construction Companies can use SPC to reduce their cycle times and defect rates as well as their operational and administrative costs and, simultaneously, increase their products quality and their returns on investment. SPC allow construction companies to work leaner and faster, with greater quality and customer satisfaction levels, and lower costs and accident rates. © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA

28 A Final Word Quality Control begins with education and ends with education, Dr Kaoru Ishikawa © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA BinLaden QICRC team will be happy to provide the training according to the construction industry needs.

29 Thank you Dr Mohamed AICHOUNI © Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA


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