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Box CleverJanuary 2006

A working airport is not the best place to create a construction site. So when it came to building new passenger corridors to meet the needs of security legislation, BAA did it all in the factory. Tony Matthews goes airside.

Delays and gate closures cost the airport business big money and cause inconvenience to travellers. With airports operating almost around the clock, any construction work becomes a complex process. If that construction work involves the movement of passengers, then it gets even more complicated.

Large numbers of construction workers milling around in secure areas can create a security risk. The storage of construction equipment, building materials and waste can also have a destabilising effect on airport logistics, particularly if it leads to aircraft stands being taken out of duty.

Nevertheless, these issues have to be addressed from time to time, particularly with new security legislation demanding that passengers are totally segregated on their way to and from the aircraft.

For BAA, this legislation has meant embarking on a two-year segregation programme at Gatwick (Piers 2 and 3) and Heathrow (Piers 5 and 6) for the building of new passenger corridors. One of BAA's primary objectives was to achieve a reduction in airside construction during peak travel hours (06:00 h to 22:00 h).

Rather than assemble on-site, BAA decided to pre-assemble the corridors off-site and deliver them to site for rapid erection. According to Nigel Fraser, Head of Products and Controls, BAA's aspiration was to have 65% of construction work done away from the main airport areas.

Hence the corridor modules were manufactured at a prefabrication facility in a timed, flow process. They were then transported to Gatwick or Heathrow for overnight installation. At the end of the project, over 1.3 km of corridors had been built and installed.

To achieve its goals, BAA created a virtual company called the Common Product Team (CPT). The team comprised MACE, Mansell and Crown House. Guided by BAA, the team designed, developed and manufactured the corridors from premises in Crawley.

Offsite manufacturing

Implementation of the BAA corridor programme went through three phases (with distinct evolutionary activities between each phase):

  • Series A: Gatwick Pier 2
  • Series B phase l: Gatwick Pier 3 and Heathrow Pier 5
  • Series B phase 2: Heathrow Pier 6.

The manufacturing process was based on flowline manufacture, a process also known as one-piece flow typically used in the automotive industry. One-piece flow involves moving one work piece at a time between operations.

The decision to employ one-piece flow manufacturing was to achieve predictable workflow under controlled quality conditions, with minimal work in progress. The process reduced scrap and waste and lead to higher productivity, which in turn lead to a greater return on investment.

Compared to traditional batch production, flowline manufacture produces modules as required, rather than by producing in volume and stockpiling. In this way, items are pulled from the manufacturing plant by the demands of the site rather than being pushed into a stockpile by the factory.

The characteristics of build-to-demand manufacturing include on-the-spot resolution of problems, while accommodating on-demand variations of the modules without loss of time. Achieving this required meticulous planning, assiduous monitoring and great attention to detail in work schedules.

Comprehensive training was provided for all trade operatives and managers, which was especially important in the early stages of the project where skilled operatives came from a variety of supply-chain partners and had to be trained in CPT's processes and procedures.

A matter of Takt

For the first manufacturing phase (the Gatwick Pier 2 corridors) the CPT took the existing design of airport corridor and adapted it for off-site manufacture. First, the CPT team divided the corridor into transportable four-metre lengths.

A fundamental element of the lean production process involved Takt, (the German word for rhythm). In the context of a lean production process Takt is the rate or time that a completed product can be produced to meet customer demand. In a Takt time of two minutes, the production line should produce a complete product or assembly. For the BAA project, the Takt time for the Series A corridor was eight hours, reducing to four hours for the Series B corridor.

In the CPT's case, its customers were the installation teams at Gatwick and Heathrow who had a restricted period overnight in which to install the corridor modules. Initially, the individual assembly sequences did not fit precisely into the eight-hour timeframes, but by optimising and developing the manufacturing processes, accurate and repeatable eight-hour steps were devised.

The process became very precise. "At any point in the day I could tell exactly where we were in the manufacturing cycle to within a few minutes," said factory manager David Moore.

The CPT also placed emphasis on the management and maintenance of a clean, efficient and effective workplace. A Japanese continuous improvement methodology was implemented, known as the 5S (see box: The 5S process). The 5S process was adopted to ensure the safety and welfare of employees, to improve productivity, and to promote a positive image of the activities to the CPT's customers.

"The first installed unit was the prototype", said Bob Older, project manager for Taylor Woodrow Construction at Gatwick. "Certain critical details, such as weatherproofing the connections between corridors and the adjoining towers, had to be resolved on-site by the installation team. Nevertheless, there was good communication and the various parties worked well together to resolve issues."

In the context of the Series A corridor project, a lot of time was lost initially through learning and optimising the manufacturing processes, but once this was overcome, 100% effectiveness was quickly achieved.

Despite delays, the manufacturing-to-installation interfaces and sequences worked well. On average, 20 m of corridor was installed per week.

Step-change evolution

From the baseline of experience and data gathered during the Gatwick Pier 2 programme, the CPT embarked on the development of a completely new concept for Gatwick Pier 3 and Heathrow Pier 5.

To achieve the manufacturing step-change it wanted, the CPT engaged an experienced industrial designer to create a module family known as Series B, which was completely designed for a manufacturing process.

The Series B module was far more comprehensive than the Series A, with twice its content, including a lightweight aluminium construction. The module included a floor, heaters, buggy rails and other elements not included in the earlier corridor modules.

The module was also a more elegant design which permitted manufacture without the need of scaffolding and allowed units to be connected more efficiently during installation.

Despite the apparent complexity of this design compared to the Series A module, the Takt time for this module was set at four hours to accommodate the demand of two concurrent construction projects - one at Gatwick (102 units) and the other at Heathrow (65 units).

Significantly, this designed for manufacture methodology allowed the CPT to use non-framework suppliers for the production of component parts of the module production line. This manifested itself in components such as the glazing mullions, which the glazing specialists were able to design as load-bearing members, thus removing the need for a structural frame.

As with the Series A modules, the production of the Series B modules involved a learning curve. However, whereas the turbulence lasted for 13 weeks for the Series A corridors, problems were sorted out much quicker with Series B modules - around six weeks. The new modules were also easier to install on site.

The second phase of the Series B manufacture and installation at Heathrow Pier 6 was a natural progression from the Gatwick Pier 3 and Heathrow Pier 5 activities. While the design team and suppliers remained the same, a number of skilled construction workers in the factory were replaced by agency-sourced multi-skilled labour. This led to further cost-savings.

Post construction analysis

The BAA corridor programme was designed for offsite manufacture from its inception. At each stage of its development, offsite manufacturing brought significant benefits to BAA.

Through a combination of design for manufacture, lean manufacturing, and increasing use of non-traditional skills and expertise, security was enhanced and quality was improved.

Installation speed improved from 20m per week with series A to 48m per week with series B.

And, says BAA, there is scope for even more improvement.

Construction compliance

Stress-free compliance with Building Regulations, including airtightness, sound insultation and ventilation