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Last edited 24 Jan 2019
Change control: a quality perspective
 Executive summary
Change is a risky business. In particular, it is a significant risk on all construction projects. Therefore, the determination and implementation of changes on a project constitute risks that need to be recognised and addressed through appropriate processes. Any change brings potential instability to the works that can be related to the final product or to the management system that supports it. It can also be a recipe for additional cost or rework.
There are three vital stages:
- Knowing the initial status.
- Knowing the desired end status.
- Managing the change.
Strict controls during the time of change are essential to reduce the risks to quality, cost or schedule. These controls should cover both the mechanics of the change process and the communication of the changes to those who need to implement them. Communication during all stages of the change process is also key to minimising risk.
Knowledge of the initial status allows change to be defined and communicated under control, understanding the full financial and schedule impacts of the change, as well as recognising the effect that the change has on all aspects of the project. The revision status of civil works, hardware and software is known as its configuration and is defined as its configuration status. Knowing the configuration status at all times is the foundation for maintaining control over change
Changes to the configuration can arise for several reasons. These include:
- External changes brought about through a client’s request, revisions to legislation, standards or codes or new requirements from statutory undertakers or local councils.
- Changes during the design process to increase value or correct errors
- Changes in construction methodology (scheduling, materials, supply arrangements, construction/installation techniques, equipment, testing and commissioning arrangements, etc).
- Changes during construction due to unforeseen events or differences between the expectations of the designers and the reality on site.
There are, of course, many other reasons for change to occur. It is their timing and control that makes the differences.
Changes can arise for several reasons. Some of these are:
- Requests from the client or his representatives and/or regulatory bodies.
- Changes to legislation, standards or regulations.
- Unclear initial requirements.
- Human error during the design process.
- Unclear interfaces.
- Human error during the construction process.
- Lack of availability of materials or parts.
- Unexpected circumstances arising during construction/installation, such as. unforeseen ground conditions.
- They can arise during the design phase (design changes) and during the construction and commissioning phase (field changes).
Any change will cause a disturbance in the established routines the project is following, even when they are being introduced to establish a better controlled environment. It should not be forgotten that any change requires to be implemented by people, which means that not only is the physical design changed, but that the process by which it will be constructed may also change.
These changes often occur as the client develops a clearer idea of the end product they desire or through simple changes of mind, especially during the design phase. They may also occur due to changes in legislation or requirements imposed by statutory undertakers. Changes such as these are normally at the client’s risk, in that they will request the change.
The contractor has an opportunity to confirm the feasibility, cost and potential effect on schedule before presenting a proposal. The change may also require a change to the contract, especially if the scope has increased or decreased. The change should be reflected into the formal requirements for the works and then treated as a design change.
During design, opportunities often present themselves for creating additional value. Details may be discovered in specifications that mean that the original design is no longer practicable or that there is a more effective solution to the project. Close examinations of technical standards reveal the need to make change. Interchangeability and interfaces between different elements of the design cause issues.
For these reasons and many others, changes need to be controlled. Each change should first be considered against its place in the design: how will the change affect its surroundings; what other parts of the design will be affected, including handbooks. The design change note that is raised should clearly define the change, the drawings, specifications and other data involved and the person(s) responsible for implementing the change. Consideration should be given to the possibility of the change requiring a change to the contract.
At some point, the design process needs to be passed into the hands of the constructors. Clearly, designing has to stop to provide a stable configuration from which to undertake the works. This point is known a design freeze, following which no changes may occur without strong controls being applied by all functions. There are occasions where some change is permitted, particularly where the construction has not proceeded to the point where the design documentation is required.
Many project proceed with design and construction taking place in parallel. This requires additional care to ensure that the project’s status is considered fully during the change management process. This works both ways in that design can have an influence on construction and vice versa.
 Control of changes during construction
Field design changes are almost inevitable. They can occur for several reasons:
- In setting out the works, the interfaces between adjacent items may not have been recognised.
- Errors in the design may not have been corrected prior to approval to construct.
- Practical difficulties may arise during construction.
- Human error in construction.
- Failure to follow the approved management arrangements.
All changes must be approved prior to implementation. While this is important at all stages of the project, it is particularly important to assure all changes with the designer before they are implemented on site – with the possible exception of minor changes that can be reversed easily or cannot have any further effect on the successful outcome of the works. A typical example may be the moving of a clock in a control room by a few millimetres to allow a piece of trunking to be fitted more easily.
One particular concern occurs when the client discusses change directly with a sub-contractor or with a member of the craft team without discussing it first with the contractor. A discipline needs to be in place to record this and to approve the change and its consequences prior to implementation.
Those working in one discipline may not realise the effect that their change may have on others. The craft worker who installs his HVAC trunking differently to the design may not recognise the difficulty that the installer of cable trays may have in finding enough space for his work.
Field changes can be initiated in the field and by site design staff. Prior to implementation, they should be offered for review to a competent designer and the design only changed following approval. It is, of course, vital that craft on site are informed about the change. While this should require a reissue of the design information, it may be more practical to issue the approved change form to the field for construction.
This is particularly useful where small changes are made and update of drawings has a heavy cost implication. One warning, however: there is a risk that one drawing has so many approved change requests that it becomes unwieldy and difficult to read. This is because even small changes can have unexpected consequences. Several small changes can result in a significant impact when taken together.
- Interchangeability (electrical and mechanical)
- Maintenance and user manuals
- Spares and spares ranging
- Training for users and maintainers
- Installation/Construction instructions,
- Inspection and test plans, schedules and records, including parameters to be measured.
Approved design changes should be marked up on the design documentation – signed and dated, of course. This has two advantages. Firstly, there is a clear definition of the design that is to be constructed, which makes interpretation easier for the people constructing and secondly, the ‘red line’ design is created as construction progresses, rather than hoping to pick up all the changes at the end. It also helps to confirm that no unapproved changes have occurred.
The use of ‘red line’ drawings is a practical and established mechanism for recording changes during construction. Care is needed to ensure that all changes are recorded (eg changes in construction methodology may have a fundamental impact on the method of adjustment/amendment/ renovation/demolition at a later date). This is particularly important when the people who know what happened have already left the site and, in many cases, cannot be contacted!
Note that a ‘red line’ drawing is an accurate mark-up of the constructed product. It is used, once approved, to create the as-built design that is offered for use by the client as a definition of the product as delivered. There will be an on-going responsibility for the works under warranty arrangements that will be stated in the contract so the information needs to be accurate, especially as clients may make changes after handover.
 Configuration management
The basis of all change is knowing the status of the project at all times. This status has to be properly defined to the level that is relevant to the various elements of the project. It is a fundamental principle that change cannot be made without knowing the initial state. Here are three examples:
Example 1: For civil construction, this is generally the revision status of the drawings, technical specifications, codes or other design data that clearly define the build, together with the testing/commissioning/handover status during the latter stages of the works. The level to which the configuration status account is taken should be sufficient that no further information is needed to provide a clear definition of all component parts. This should include the requirements definition, preliminary design and the detailed/shop drawings and are termed ‘configuration items’ that are listed in the configuration status account.
Example 2: For mechanical and electrical works, this should include all the configuration items required for the civil work, together with the serial numbers and, where appropriate, the revision status of any individual items. The level here should be at the point ‘line replaceable unit’. A line replaceable unit is the largest item that is replaced during maintenance and returned to the supplier or scrapped and is, again a configuration item.
Example 3: Complex electronic systems can have a complex configuration status, as this needs to cover both the list of all line replaceable units, together with the definition of the build of the software, probably at module level.
As can be seen, the knowledge that is required can be very detailed and very extensive. The overall knowledge is known as the configuration status of the project and is listed in a configuration status account. It is important not to underestimate the amount of time and energy that is required to develop and maintain the configuration status account. On a large project, such as a railway upgrade or power station build, it is almost impossible to control the configuration if this is not started at the very beginning of the design process. For example, it took over six hours to create the configuration status account for a single cabinet with three rows of printed circuit boards, recording the board numbers, serial numbers and software status.
 Configuration control
Configuration control is simple in concept – always know the revision status of the constructed product. The complexity arises from the vast amount of information that must be collected and maintained up to date. The challenge is to start collecting the information at the very start, rather than trying to catch up at the end.
As stated above, knowing the configuration status at all times is of vital importance to the control over the project. Any proposed change should be reviewed for its effect on the entire configuration. This should include adjacent items, technical specifications, operator’s manuals, interchangeability, spares quantities and ranging, competence of constructors and operators and maintenance regimes to mention but a few. With the exception of the simplest and most obvious of changes, review of change to the configuration should be undertaken by a multi-disciplined team and by not a single person.
Generally, all constructed product is created from a hierarchy of parts. For an electrical or mechanical system, the smallest element that would be returned to the manufacturer in case of a defect occurring can be known as a ‘Line Replaceable Unit’. The vital point is that a failed item has to be replaced with a part that is electrically and mechanically interchangeable. For this reason, the revision status of these parts needs to be sufficiently well defined so that a suitable replacement may be provided. For civil works, this is simpler in a way, as the configuration status is the revision status of the (as-built) drawings, technical specifications and other design data that were used to construct.
Identification includes the revision status, obviously, which means that strict control must be maintained over change.
Original article written by Keith Hamlyn, reviewed by Andrew Baker on behalf of the Chartered Quality Institute, Construction Special Interest Group, and accepted for publication by the Competency Working Group.
--ConSIG CWG 13:31, 05 Jan 2019 (BST)
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- Design freeze: a quality perspective.
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- Quality manuals and quality plans.
- Scope creep.
- Value engineering.
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