Making off-site production work

While the factory end of off-site production (prefabrication) is a smooth processes, there are many on-site issues to be considered. MARCUS DICKS explains.When off-site-production (OSP) techniques are used, a high-quality, engineered product is built in a factory and brought to site. It is from this point that problems can start. The product (e.g. a distribution module, a skid-mounted plant item or even a packaged plant room) often simply does not fit. Problems with interface detailing, tolerances, and poor construction process management are preventing the full benefits of OSP being realised on site. The benefits of off-site production are well documented and include the following. • Cost savings at every level of the supply chain (typically in excess of 10%). • Faster return on investment for the client. • Reduced programme times. • Improved site activities and site management (less labour and materials handling). • Savings in space allocated to building services. • Improved quality control. • Fostering of team working and a manufacturing ethos. So why are the benefits not being realised? There are three main causes. Culture. The UK construction industry is very traditional and resistant to change. Fitters make things fit! They can work round problems and poor information to make systems work. So why should the industry change? Misconceptions. Whilst visiting a hospital extension project for an OSP case study, the M&E site manager revealed how much he liked OSP as he did not have to manage anything on site, it had all been done for him! He was missing the point. He needed to manage different aspects of the process in order to let the specialists perform to their full ability. Lack of experience. Managers are unaware of the issues that need to be addressed to make OSP work on site. There is a need for information and training, as well as good communication with experienced specialist manufacturers. BSRIA has been identifying and listing the problematical management processes associated with the site activities in deploying OSP elements and reviewing published data for their solutions. It became obvious during the early stages of the review, that there is a vast amount of published information covering OSP in construction — including pre-fabrication, pre-assembly, standardisation and modularisation, most of which is extolling the virtues with little content of any substance. In particular, there was hardly any information about problematical site management processes or their solutions. The industry is still reluctant to talk about problems in public, and the case studies were anecdotal ‘good news stories’ without detail. Previous work examining the manufacture and installation of pre-assembled plant at Kings College Hospital [1] led the author to attendinga seminar by Rethinking Construction entitled: ‘Manufacturing the future’ [2] on 15 November 2001. Presentations outlined views by clients, contractors, consultants, manufacturers and academics. The examples cited successful projects and applications, but without giving any detail or evidence of what had really happened. The occasion provided an opportunity for the presenters to sell their products and services, but left the audience with lots of unanswered questions about the detail. Review of the 1998-99 BSRIA investigation into the pre-fabrication and pre-assembly of engineering services [3] revealed a list of six critical success factors that need to be considered for the successful application of OSP. • Motivation • Design • Procurement • Logistics • Site installation and assembly • Testing and commissioning To identify problematical management processes associated with site activities of deploying OSP elements, a series of site visits and interviews was completed that concentrated on the issues of logistics and site installation and assembly. The following describes a series of real issues and suggested solutions that were revealed during the study: Logistics problems and solutions Transportation of OSP items to site. Issues: Police called away from escorted loads, can lead to stranded loads, delays, increased crane hire costs. Road closures and out-of-hours delivery ‘windows’ create restrictions, and can lead to large delays if missed. Solutions: Better reconnaissance and planning, use of specialist handling contractors, better liaison with the Police (Police escorts are no longer mandatory), avoidance of road closures, good organisation and selection of lifting equipment. Delivery of manufactured items out of sequence Issues: Early delivery requires temporary storage, double or triple handling, and may lead to damage. Late delivery leads to delays, and time wasted. Solutions: Improved planning of the delivery and installation sequence. Better liaison between the manufacturer and the site. Poor access for unloading modules on site Allowances are often not made for access of large modules, delivery vehicles, mobile cranes, and lay-down areas. The planning, organisation and control of logistics can be complicated, especially on large, busy or congested sites. Problems with the OSP logistics can have a knock-on effect on the logistics of the whole project. Poor access for moving modules on site Issues: Large modules delivered to site often do not fit. Iron bars used instead of large-diameter wheels are used to roll modules across uneven floors due to a lack of clearance. Openings are often not large enough to get modules into the building. This basic problem is widespread. Solutions: Early integration of specialists. Better planning and surveys. Installation & assembly problems and solutions OSP components installed incorrectly Issues: Untrained labour used for ‘simple’ OSP installations has led to some components being installed the wrong way round. This causes extra work to rectify problems with modifications, which can lead to delays. Solutions: Improved training of installers; different skills are often required than those used for traditional installation. Better technical site supervision. Improved labelling of components. Poor co-ordination with the site services and structure Issues: Modules cannot be installed as planned because other services are in the way or the structure is not as it should be. This can lead to extra work, re-routing of services, additional structure penetrations, modification of modules and delays. Solutions: Better design co-ordination, OSP producer inputting to the design process, full site survey prior to installation. Poor co-ordination between different installing trades on site Issues: Other trades in the way, materials in the way, incomplete preceding activities, congested work areas, other trades working out of sequence. All the above can conspire to delay or even prevent the installation of OSP modules. Solutions: Better planning, sequencing, co-ordination, de-confliction, work area control, and, buy-in from all trades. Tolerance issues Issues: tolerances in the factory are generally much tighter than those on site. Manufactured components often don’t match up with what has been produced on site. Discrepancies will require remedial work, modifications, and produce delays. Solutions: Input from OSP specialists early in the design process, identification of critical tolerances on site, buy-in from the site based trades. Summary / future actions To fully achieve the benefits of OSP, the following issues should be addressed: • Early integration of expertise • Co-operation and buy-in by all parties • Co-ordination and planning for OSP • Logistics integration • Attention to structural detail (tolerances) and site installed M&E services • Sharing lessons learned • Training and education BSRIA will publish a full Technical Note covering the detailed findings of this research with practical guidance on how to make OSP work, on site. Marcus Dicks is with BSRIA, Old Bracknell Lane West, Bracknell, Berks RG12 7AH. References [1] BSRIA Report 16556/1 Edition 3, ‘Pre-assembled plant at Kings College Hospital’ March 2002. [2] Rethinking Construction, ‘Manufacturing the future’, compilation of presentations from the seminar, November 2001. [3] Wilson D. G., Smith M. H. and Deal J, Prefabrication and preassembly – applying the techniques to building engineering services, BSRIA ACT 1/99.
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The efficient production of building-services equipment in a factory can often be followed by problems on site. (Top left) Limited headroom can require plant to be rolled into position using metal bars instead of wheels — often over an uneven floor. (Above right) Previously installed services can obstruct later installation work. (Left) Manufactured components may not line up on site.
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