Quality Control - Revision history

Tkokotas at 12:46, 19 November 2018

2018-11-19T12:46:41Z

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			''Developed by Silja Tea Nielsen''


	Defects and errors in construction projects have been subject to attention in the media and debates throughout the years. A general consensus of a lack of quality on the construction sites exists, thus an increasing effort have been made to improve the quality of construction projects by a number of political initiatives<ref name="art1Kir">Schultz, Casper S.; Jørgensen, Kirsten; Bonke, Sten and Rasmussen, Grane M. G.; Architectural Engineering and Design Management; Taylor and Francis Group; 2015, "Building defects in Danish construction: project characteristics influencing the occurrence of defects at handover"</ref>. When managing quality in a project an important aspect is Quality Control (QC), which is the focus of this article. First the definition of QC is elaborated and examples of process QC and product QC is given, in order to clarify the difference between the two types of QC. The standard DS/ISO 21500 outlines different aspects that have to be considered when performing QC, why these are mentioned in the article. Different QC policies and techniques exist and their objectives, advantage and disadvantages are elucidated. At last limiting conditions when performing QC are stated.		Defects and errors in construction projects have been subject to attention in the media and debates throughout the years. A general consensus of a lack of quality on the construction sites exists, thus an increasing effort have been made to improve the quality of construction projects by a number of political initiatives<ref name="art1Kir">Schultz, Casper S.; Jørgensen, Kirsten; Bonke, Sten and Rasmussen, Grane M. G.; Architectural Engineering and Design Management; Taylor and Francis Group; 2015, "Building defects in Danish construction: project characteristics influencing the occurrence of defects at handover"</ref>. When managing quality in a project an important aspect is Quality Control (QC), which is the focus of this article. First the definition of QC is elaborated and examples of process QC and product QC is given, in order to clarify the difference between the two types of QC. The standard DS/ISO 21500 outlines different aspects that have to be considered when performing QC, why these are mentioned in the article. Different QC policies and techniques exist and their objectives, advantage and disadvantages are elucidated. At last limiting conditions when performing QC are stated.

S133558: /* Definition of Quality Control */

2017-06-22T08:04:05Z

Definition of Quality Control

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	=Definition of Quality Control=		=Definition of Quality Control=

	The aim of QC in construction projects is to assure high quality of the construction being built and the individual processes within the project. In this content “high quality” denotes fulfilling standards and the established quality requirements of the specific project <ref name="winch">Winch, Graham M.; Wiley-Blackwell; 2010; "Managing Construction Projects; Second edition "</ref>. It is important to investigate the causes of the arising problems, as well as finding ways to eliminate unsatisfactory performance when performing QC, thus corrective, preventive and predictive QC policies are essential. QC is a part of managing conformance in construction projects, and QC can continuously be improved by ~~performing~~ [[Total Quality Management]].		The aim of QC in construction projects is to assure high quality of the construction being built and the individual processes within the project. In this content “high quality” denotes fulfilling standards and the established quality requirements of the specific project <ref name="winch">Winch, Graham M.; Wiley-Blackwell; 2010; "Managing Construction Projects; Second edition "</ref>. It is important to investigate the causes of the arising problems, as well as finding ways to eliminate unsatisfactory performance when performing QC, thus corrective, preventive and predictive QC policies are essential. QC is a part of managing conformance in construction projects, and QC can continuously be improved by [[Total Quality Management]].

	== Product Quality Control vs. Process Quality Control ==		== Product Quality Control vs. Process Quality Control ==

S133558: /* Quality control techniques */

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Quality control techniques

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 =Quality control techniques=
-Various techniques and tools to perform QC are developed through time. Frequently used tools are Ishikawa's seven tools <ref name="IshikawaBook">Ishikawa, Kauro, Tokyo 3A Corporation, 1990, "Introduction to Quality Control "</ref>:
+Various techniques and tools to perform QC are developed through time. Frequently used tools are Ishikawa's seven tools <ref name="IshikawaBook">Ishikawa, Kauro, Tokyo 3A Corporation, 1990, "Introduction to Quality Control "</ref>:  Cause-and-effect diagram, Check sheet, Control chart, Histogram, Pareto chart, Scatter diagram, Flow charts. In the following two of the tools (Cause-and-effect diagrams and Flow charts) will be described in relation to QC in construction projects.
 == Cause-and-effect diagrams ==

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Value stream mapping (Flow charts)

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	==Value stream mapping (Flow charts)==		==Value stream mapping (Flow charts)==

	[[File:Valuestreammapping.png\|thumb\|\|400px\|'''Figure 8'''~~, With value stream mapping you can identify elements in a current process that generates non-conformance, and thereby improve the process for future state~~<ref name="VSMpic">Lean homebuilding, "Value stream mapping ", access: 13-06-2017, https://leanhomebuilding.wordpress.com/2010/04/14/value-stream-maps-visualizing-waste/]</ref>.]]		[[File:Valuestreammapping.png\|thumb\|\|400px\|'''Figure 8'''<ref name="VSMpic">Lean homebuilding, "Value stream mapping ", access: 13-06-2017, https://leanhomebuilding.wordpress.com/2010/04/14/value-stream-maps-visualizing-waste/</ref>, With value stream mapping you can identify elements in a current process that generates non-conformance, and thereby improve the process for future state.]]

	Value stream mapping (VSM) is a preventive QC technique, that focus on understanding the details of all the discrete elements in a process <ref name="winch">Winch, Graham M.; Wiley-Blackwell; 2010; "Managing Construction Projects; Second edition "</ref>. The current value stream of the process can be visualized and in this way sources that produces non-conformance are discovered and eliminated. This method helps individuals to understand the process instead of focusing on the result of the process alone. This can increase the overall efficiency the process. Value-stream mapping makes it possible to identify effective testing equipment, testing strategies and quality control loops <ref name="QVSM">Haefnera, Benjamin; Kraemera, Alexandra; Staussa, Torsten; Lanzaa, Gisela, Variety Management in Manufacturing. Proceedings of the 47th CIRP Conference on Manufacturing Systems, 2014, "Quality Value Stream Mapping "</ref>. Figure 8 is an illustration of the overall structure of a VSM. It is shown that the VSM takes form as a flow chart, which identifies the flow of materials and information.		Value stream mapping (VSM) is a preventive QC technique, that focus on understanding the details of all the discrete elements in a process <ref name="winch">Winch, Graham M.; Wiley-Blackwell; 2010; "Managing Construction Projects; Second edition "</ref>. The current value stream of the process can be visualized and in this way sources that produces non-conformance are discovered and eliminated. This method helps individuals to understand the process instead of focusing on the result of the process alone. This can increase the overall efficiency the process. Value-stream mapping makes it possible to identify effective testing equipment, testing strategies and quality control loops <ref name="QVSM">Haefnera, Benjamin; Kraemera, Alexandra; Staussa, Torsten; Lanzaa, Gisela, Variety Management in Manufacturing. Proceedings of the 47th CIRP Conference on Manufacturing Systems, 2014, "Quality Value Stream Mapping "</ref>. Figure 8 is an illustration of the overall structure of a VSM. It is shown that the VSM takes form as a flow chart, which identifies the flow of materials and information.

S133558: /* Cause-and-effect diagrams */

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Cause-and-effect diagrams

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	== Cause-and-effect diagrams ==		== Cause-and-effect diagrams ==
	[[File:CauseEffectDiagram.png\|thumb\|\|400px\|'''Figure 6''': Structure of a cause effect diagram with six chosen categories of causes, which all have an influence on the overall problem. The secondary cause are attached to the primary causes by small arrows <ref name="CED">Wikipedia, "Ishikawa diagram ", access: 11-06-2017, https://en.wikipedia.org/wiki/Ishikawa_diagram]</ref>.]]		[[File:CauseEffectDiagram.png\|thumb\|\|400px\|'''Figure 6''': Structure of a cause effect diagram with six chosen categories of causes, which all have an influence on the overall problem. The secondary cause are attached to the primary causes by small arrows <ref name="CED">Wikipedia, "Ishikawa diagram ", access: 11-06-2017, https://en.wikipedia.org/wiki/Ishikawa_diagram</ref>.]]

	Cause-and-effect diagrams also go under the names “fishbone diagram” (due to the shape) and “Ishikawa diagram” (after the inventor of the technique). The diagram separates the problem (the effect of the causes) from the causes. The basic idea of the technique is to work back from the problem by asking: “why did it occur”, thus finding the different roots to the problem <ref name="winch">Winch, Graham M.; Wiley-Blackwell; 2010; "Managing Construction Projects; Second edition "</ref>. Each cause is thereby found by using a form of brainstorm technique, and they are grouped under different categories. A cause can either be a primary cause or a secondary cause. The structure of the diagram is shown on Figure 6.		Cause-and-effect diagrams also go under the names “fishbone diagram” (due to the shape) and “Ishikawa diagram” (after the inventor of the technique). The diagram separates the problem (the effect of the causes) from the causes. The basic idea of the technique is to work back from the problem by asking: “why did it occur”, thus finding the different roots to the problem <ref name="winch">Winch, Graham M.; Wiley-Blackwell; 2010; "Managing Construction Projects; Second edition "</ref>. Each cause is thereby found by using a form of brainstorm technique, and they are grouped under different categories. A cause can either be a primary cause or a secondary cause. The structure of the diagram is shown on Figure 6.


	A cause-and-effect diagram shows that there often are several roots to problem, and that several corrective/preventive actions have to be performed. This allegation becomes clear by grouping the causes under different categories, because it illustrates the difficulties of complex processes. The categories often include people, process/methods, equipment/machines, material, environment and management, as these are some of the essential elements in construction projects <ref name="CED">Wikipedia, "Ishikawa diagram ", access: 11-06-2017, https://en.wikipedia.org/wiki/Ishikawa_diagram]</ref>.		A cause-and-effect diagram shows that there often are several roots to problem, and that several corrective/preventive actions have to be performed. This allegation becomes clear by grouping the causes under different categories, because it illustrates the difficulties of complex processes. The categories often include people, process/methods, equipment/machines, material, environment and management, as these are some of the essential elements in construction projects <ref name="CED">Wikipedia, "Ishikawa diagram ", access: 11-06-2017, https://en.wikipedia.org/wiki/Ishikawa_diagram</ref>.

	==Value stream mapping (Flow charts)==		==Value stream mapping (Flow charts)==

S133558: /* Predictive Quality Control */

2017-06-22T07:51:07Z

Predictive Quality Control

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	This means predictions should be based upon analysis of data and well-founded arguments thus unnecessary actions are not initiated. Using the predictive QC policy it is important that the problem leave digital footprints before it occurs, otherwise predictions can not be made<ref name="maintance">Cyient, 2016, "Engineering solutions for predictive maintenance in rail"]</ref>. Valuable predictions can be made by modern technology, that makes it possible to collect and analyze large amounts of data from different systems. Monitoring processes makes it possible to perform real-time control and predict failures before they occur <ref name="sensors2">Navon, Ronie; Elsevier, Automation in Construction 14, 2005, "Automated project performance control of construction projects" </ref>. Various advanced sensor systems is developed and can be integrated as a part of the inspection procedures on the construction site. These systems create the opportunity of frequently gathering "as-built" data. The collected data have to be carefully analyzed and compared frequently with specifications and "as-designed" models. If divisions are found it has to be evaluated, if it will induce defects later on.		This means predictions should be based upon analysis of data and well-founded arguments thus unnecessary actions are not initiated. Using the predictive QC policy it is important that the problem leave digital footprints before it occurs, otherwise predictions can not be made<ref name="maintance">Cyient, 2016, "Engineering solutions for predictive maintenance in rail"</ref>. Valuable predictions can be made by modern technology, that makes it possible to collect and analyze large amounts of data from different systems. Monitoring processes makes it possible to perform real-time control and predict failures before they occur <ref name="sensors2">Navon, Ronie; Elsevier, Automation in Construction 14, 2005, "Automated project performance control of construction projects" </ref>. Various advanced sensor systems is developed and can be integrated as a part of the inspection procedures on the construction site. These systems create the opportunity of frequently gathering "as-built" data. The collected data have to be carefully analyzed and compared frequently with specifications and "as-designed" models. If divisions are found it has to be evaluated, if it will induce defects later on.

	=== Monitoring ===		=== Monitoring ===

S133558: /* Continuous, delivery and start-up control */

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Continuous, delivery and start-up control

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	Start-up QC at the shift between contractors can prevent errors from occurring. This way the quality of the previous work is assured and the following work is not going to hide defects. The hidden defects can potentially result in critical errors, which will be very expensive and time consuming to correct. This concept is also called "stop the line" in lean construction, where the following work are set on hold until all errors from previous work are corrected <ref name="LEAN">Simonsen, Rolf, Værdiskabende Byggeproces, 2017, "Lean Construction &		Start-up QC at the shift between contractors can prevent errors from occurring. This way the quality of the previous work is assured and the following work is not going to hide defects. The hidden defects can potentially result in critical errors, which will be very expensive and time consuming to correct. This concept is also called "stop the line" in lean construction, where the following work are set on hold until all errors from previous work are corrected <ref name="LEAN">Simonsen, Rolf, Værdiskabende Byggeproces, 2017, "Lean Construction &
	Last Planner System</ref>.		Last Planner System"</ref>.

	==Predictive Quality Control==		==Predictive Quality Control==

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Predictive Quality Control

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	==Predictive Quality Control==		==Predictive Quality Control==
	[[File:Predict.png\|thumb\|\|200px\|'''Figure 5<ref name="predicts">Skipprichard Leadership insights, "The Surprising Predictive Power of Analytics", access: 12-06-2017, https://www.skipprichard.com/the-surprising-predictive-power-of-analytics/]</ref>:''' Predictive QC alerts at trends of possible failure.]]		[[File:Predict.png\|thumb\|\|200px\|'''Figure 5<ref name="predicts">Skipprichard Leadership insights, "The Surprising Predictive Power of Analytics", access: 12-06-2017, https://www.skipprichard.com/the-surprising-predictive-power-of-analytics/</ref>:''' Predictive QC alerts at trends of possible failure.]]

	Predictions of possible failures is necessary, in order to determine preventive actions. Graham M. Winch states<ref name="winch">Winch, Graham M.; Wiley-Blackwell; 2010; "Managing Construction Projects; Second edition "</ref>:		Predictions of possible failures is necessary, in order to determine preventive actions. Graham M. Winch states<ref name="winch">Winch, Graham M.; Wiley-Blackwell; 2010; "Managing Construction Projects; Second edition "</ref>:

S133558: /* Preventive Quality Control */

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Preventive Quality Control

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	==Preventive Quality Control==		==Preventive Quality Control==
	[[File:Preventmistakes.png\|thumb\|\|200px\|'''Figure 4 <ref name="prevent">T&W Church solutions, "The Top 7 Mistakes Made by Church Building Committees and How to Prevent Them!!!", access: 12-06-2017, http://www.tw-church.com/The-Top-7-Mistakes-Made-by-Chur.html]</ref>:''' Preventive QC alerts before errors occur.]]		[[File:Preventmistakes.png\|thumb\|\|200px\|'''Figure 4 <ref name="prevent">T&W Church solutions, "The Top 7 Mistakes Made by Church Building Committees and How to Prevent Them!!!", access: 12-06-2017, http://www.tw-church.com/The-Top-7-Mistakes-Made-by-Chur.html</ref>:''' Preventive QC alerts before errors occur.]]

	By changing the strategy of QC from corrective to preventive the questions are changed to "can we do the job correctly" and "are we doing the job correctly" <ref name="TQMOakland">Oakland, John S., Quality and Reliability Engineering International, volume 9, issue 6, 1993, "Total quality management"</ref>. A certain amount of knowledge and experience is required in order to answer the questions, and thereby prevent failures and non-conformance from happening. It is a common problem that the people trying to control procedures do not have the necessary competencies to do so. For this reason [https://en.wikipedia.org/wiki/W._Edwards_Deming W. Edwards Deming], a guru of quality management, came with the advice <ref name="STC">Oakland, John S.; Rutledge Taylor and Francis Group, 2008, "Statistical Process Control", Sixth edition</ref>:		By changing the strategy of QC from corrective to preventive the questions are changed to "can we do the job correctly" and "are we doing the job correctly" <ref name="TQMOakland">Oakland, John S., Quality and Reliability Engineering International, volume 9, issue 6, 1993, "Total quality management"</ref>. A certain amount of knowledge and experience is required in order to answer the questions, and thereby prevent failures and non-conformance from happening. It is a common problem that the people trying to control procedures do not have the necessary competencies to do so. For this reason [https://en.wikipedia.org/wiki/W._Edwards_Deming W. Edwards Deming], a guru of quality management, came with the advice <ref name="STC">Oakland, John S.; Rutledge Taylor and Francis Group, 2008, "Statistical Process Control", Sixth edition</ref>:

S133558: /* Corrective Quality Control */

2017-06-22T07:49:21Z

Corrective Quality Control

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	==Corrective Quality Control==		==Corrective Quality Control==
	[[File:Failureillustration.png\|thumb\|\|200px\|'''Figure 3<ref name="Failure">The church of Jesus Christ of latter-day saints, "Helaman 1–6", access: 12-06-2017,https://www.lds.org/manual/book-of-mormon-teacher-resource-manual/helaman-1-6?lang=eng]</ref>:''' Corrective QC alerts after defects occur .]]		[[File:Failureillustration.png\|thumb\|\|200px\|'''Figure 3<ref name="Failure">The church of Jesus Christ of latter-day saints, "Helaman 1–6", access: 12-06-2017,https://www.lds.org/manual/book-of-mormon-teacher-resource-manual/helaman-1-6?lang=eng</ref>:''' Corrective QC alerts after defects occur .]]

	Corrective QC is necessary when non-conformance or a fatal event has occurred, thus corrective QC is defined as a reactive approach. This approach of QC is necessary because unexpected events and defect always will occur in construction projects. The ideal project where all problems are prevented is hard to establish, since many people, partners and processes are involved in the project. Questions like “have we met the requirements?” and “what went wrong?” are frequently asked, when using corrective QC.		Corrective QC is necessary when non-conformance or a fatal event has occurred, thus corrective QC is defined as a reactive approach. This approach of QC is necessary because unexpected events and defect always will occur in construction projects. The ideal project where all problems are prevented is hard to establish, since many people, partners and processes are involved in the project. Questions like “have we met the requirements?” and “what went wrong?” are frequently asked, when using corrective QC.