Project development

The reader will appreciate that the design of, for example, a large construction project from its conception, will involve technical input from architects and engineering designers in a wide variety of associated disciplines. It is vital that all contributors to the overall scheme talk the same language and that only compatible computer software packages are in use for the separate areas of work. In addition, the management contractor must have access to the designs as work is in progress. Before the age of CAD it was the practice to have countless meetings in order to co-ordinate progress.

Design obviously continues in steps and in planning and construction work problems arise, and designers need to be in a position to make modifications to overcome them, before progressing to the next phase.

A typical case study illustrating the activity associated with this type of work is the construction of the new Civil Aviation Authority 'en-route' centre, built at Southampton. This prestige building and installation controls all the air traffic passing through Britain's airspace and houses controllers operating banks of electronic and computer equipment where only an efficiency of 100% is acceptable. The building services engineer must ensure that the environment to keep both controllers and equipment comfortable is maintained 24 hours a day, seven days a week.

Due to the extensive use of computers at the centre, a huge amount of electrical, heating, ventilating and air conditioning plant needed to be installed. Different specialist contractors were responsible for these services under the stewardship of the management contractor.

The fast track nature of the design and construction, required an extensive application of CAD, where individual contractors responsible for electrical, mechanical and ducting work, were 'net-worked' on site, and could refer to CAD data from each other.

At this development, it was accepted by contractors that for some drawings it was practical to work in three dimensions to make it easier, for example, to ensure clearances between piping and ductwork in the more cramped areas. Layout drawings in 3D permitted engineers to demonstrate clearly to other parties where, for example, electrical cables and conduits were likely to plough straight through heating and ventilation ducts. Potential problems were solved on screen rather than emerging during construction. In addition, adequate access for maintenance purposes and replacement of equipment could be confirmed. The draughtsman can check designs by altering the angles from which arrangements are viewed on screen.

In the design of many heavy engineering plant layouts it is often the practice to build a scale model of the plant as design work progresses. The function of the model is to keep a running check on the feasibility of the installation. Obvious improvements can then be incorporated.

Constructions of chemical plants and oil refineries are typical examples. After completion of the project, models may be used for publicity purposes and to assist in the education of technicians who operate and service the equipment. Three dimensional modelling has many other applications in the film and entertainment industry and drawings in 3D can materially assist in comprehension.

When many workstations have to be installed for a design team, it is vital to agree on working methods. Recommendations for useful Standards in Construction Drawing Practice are detailed in Chapter 27.

Agreement is necessary on the organization of many aspects of work and in CAD, these include the use of layers, the groupings of the various sections of construction designs, use of colours so that similar ductwork appears on the screen in the same shade, procedures for the transfer of data between several drawing offices, methods of structuring data for archiving and to help future retrieval. The quality of all drawing work needs to be uniform and conform to BS 8888 for a complete understanding and to avoid ambiguity. It is essential that all contributors work as a team and in harmony if planning deadlines are to be kept, as obviously, delays in one area of construction can hold up another contractors work, and may result in financial loss.

The designs for services and installations originate from specifications and schematic layouts, supplied by Consulting Engineers, acting on behalf of the Clients or Agents.

For layout work a typical draughting package which covers all aspects of services, such as electrical, lighting, communication, alarms, ductwork, sanitary and mechanical plant, is desirable and time saving. Standard symbols can be inserted on their apropriate drawing layer, rotated automatically to align with a wall or ceiling grid and automatically scaled so that they are plotted at the correct scale. These settings can also be customized to enable you to predefine commonly used layers and sizes.

The Building Services Library supplied by

HEVACOMP,

109 Regents Park Road,

London

NW1 8UR

is a typical package which covers these requirements and permits you to store up to 600 of your own symbols using tablet or pull down menus. The package will assist in the creation of working drawings and in the detailing of, for example, sections of ductwork, the program will prompt for the dimensions, elevation and layer; subsequent sections of ductwork are then able to attach automatically, matching the layer and size.

Parametric routines are also used to efficiently design a wide variety of bends, tees, branches and transition pieces for all types of square, rectangular, circular and oval ductwork.

Schedules of fittings need to be created with essential information and if necessary interfaced with other database or spreadsheet programs, in order to prepare bills of materials.

Electrical wiring systems for lighting and services must be designed in accordance with I.E.E. Wiring Regulations and programs are available to provide the essential requirements of both the electrical designer and contractor.

The ELEC program from HEVACOMP can be used to calculate all cable, cpc and fuse sizes, as well as voltage drops, earth fault loop impedances, and short circuit currents. Schematic diagrams are easily prepared up to AO in size, showing load descriptions, protective device and cable sizes as well as sub-main details.

Reporting facilities include:

Board and way data,

Cable sizes and voltage drops,

Short circuit currents and disconnection times,

Discrimination charts,

Input data,

Calculation file data,

Load current summary,

Voltage drop summary,

Equipment schedules.

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