Buffered laydown

How does Buffered laydown work, step by step?

1. 1

   Step 1: Decide how much buffer the project actually needs

   The size of the buffer follows the variability it has to absorb, not a rule of thumb. The logistics manager assesses the reliability of the factory, the length and exposure of the route, the frequency of weather stoppages, the installation rate and the consequence of a stopped crane, and sets a target stock in terms of work - typically expressed as a number of days or shifts of installation held on the ground rather than as a number of units. Holding more than that ties up land and money and increases handling and damage; holding less leaves the project exposed. The target is reviewed as the project settles down, and on a well-behaved supply chain it is usually reduced.

2. 2

   Step 2: Find and design the laydown area

   The area is chosen for its access as much as its size - a laydown that a trailer cannot get into or that the crane cannot reach is not a laydown. It is then designed: formation and surfacing capable of carrying the delivery vehicles and the handling plant in wet weather, falls and drainage so it does not become a bog, a defined layout of stacking positions with circulation between them, and separate routes for vehicles and pedestrians. Where the ground is soft or made up, a working platform is designed and certified in the same way as for any other tracked plant. Lighting, security fencing and CCTV follow if components will be held overnight, because modules and their fit-out are attractive to thieves.

3. 3

   Step 3: Plan the stacking arrangement before anything arrives

   How components are stacked determines whether the buffer works. Positions are allocated by the sequence in which components will be called off, so nothing needed early is buried behind something needed late. Bearing points, packing, stacking heights and whether components may be stacked at all are matters for the designer and the manufacturer, and the arrangement they specify is followed rather than improvised on the day. Stacks are laid out so that the handling plant can reach any position without moving three other components first, which usually means more space and fewer tiers than the first sketch assumes.

4. 4

   Step 4: Receive, check and book components in

   Each component is checked against the delivery paperwork and inspected for transit damage on arrival, before it is set down, and then booked into a stock record against its allocated position. The record is the whole point of the buffer - a stock of components nobody can locate is not a buffer, it is an obstruction. Condition on arrival is photographed and recorded, so that damage arising later in the laydown is distinguishable from damage that arrived with the load.

5. 5

   Step 5: Protect what is stored

   Components are protected to the manufacturer's requirements once landed - factory protection left in place, coverings secured against wind, open ends and service penetrations sealed, and standing water kept out of floor cassettes and module bases. Components with fit-out, insulation or finishes already installed are the vulnerable ones, and on many projects they are the reason the buffer is under cover or wrapped rather than simply stacked in the open. Protection is inspected on a routine cycle, because a cover that has blown off in week one and is noticed in week four has already done the damage.

6. 6

   Step 6: Call components off in sequence

   Components are drawn from the buffer as the installation face is ready, lifted from their stacking position and either taken directly to the crane or trans-shipped to the delivery point. Each call-off is recorded against the stock so the level is always known, and the delivery schedule is adjusted to keep the stock near its target. In practice this is where a buffer earns its keep: the installation gang works to its own rhythm, and the deliveries are managed to keep the stock topped up rather than to keep the crane fed hour by hour.

7. 7

   Step 7: Re-inspect before installation

   A component that has been stored is inspected again before it is lifted into the building - for weather damage, for movement or distortion at the bearing points, for water where water should not be, and for the condition of lifting points and protection. Anything found is dealt with on the ground, where access is easy and cheap. This inspection is the main defence against the buffer's central risk, which is that stored components quietly deteriorate and the problem is only discovered once they are in the building.

8. 8

   Step 8: Run the area down and reinstate it

   As installation nears completion the buffer is deliberately run down rather than allowed to end with a scatter of leftovers, and the area is cleared, its packing and protection removed and disposed of, and the ground reinstated or handed back. On rented ground this is a contractual obligation with a date attached, and on site it usually frees an area that the following trades want for their own use.