Lifting an entire wind mill from 1699 with all its fittings by two metres is quite something. Funderings- en Vijzeltechnieken Bresser / van 't Wout Waddinxveen B.V. completed this 700 ton 'chore' in three days with Enerpac hydraulic lifting equipment.
The opportunity was also taken to correct the position of the slightly squint mill.
Since then the well-known Oranje mill has been waiting on steel supports for the time that it can once more turn on the reinforced dike.
Heightening the Oranje dike in Vlissingen is one of the final phases on the Delta project.
This dike remains still a weak link in the struggle against extremely high water and has to be heightened by two metres in order to protect the Zeeland countryside behind it from flooding.
In itself a water management project that presents no special challenges for our Dutch dike builders.
That is were there not a typical windmill from 1699 on the dike, a windmill that everybody wants to retain on the dike: the Oranje mill.
The Municipality of Vlissingen had as owner two options: take the mill apart and reconstruct it from scratch after heightening the dike, or lift the mill in situ to the required height.
Practical considerations and the desire to keep the mill that still operates on a daily basis resulted in adopting the latter option.
New foundation - after the necessary preparations the project was started at the beginning of February 2001.
The mill was given first a new concrete foundation about 75 cm thick that would also serve to support it during lifting.
While this foundation was being cast 28 groups of four, making in total 112 threaded rods with a length of about 3 metre were injected around and within the mill.
The entire foundation with mill is suspended from these threaded rods.
Recesses are also included in the foundation, in all cases between four threaded rods, for steel support pipes for the hydraulic lifting cylinders.
These support pipes rest in turn on the fixed base under the mill.
The lifting system was completed by 28 dual-operating hydraulic cylinders from Enerpac, each with a maximum capacity of 50 ton and divided into three separate groups.
When distributing the lifting jacks over the foundation the centre of gravity of the mill was taken into account, more power being required on the side of the vanes.
The total available lifting capacity is therefore 1400 ton.
A steel sleeve with transverse profile supports the bottoms of the cylinders.
Two 'separate' beams of reinforced I-profile are clamped to this sleeve and retained in place with nuts on the threaded rods.
On top of the cylinder a steel plate with a similar I-profile has been placed that rests on the piston and is secured with nuts to the four surrounding threaded rods.
Step by step - once assembled, the operation of the lifting system was relatively straightforward.
Pressure was applied to each cylinder with a heavy-duty Enerpac pump with three separate oil supplies, the total hydraulic installation being supplied by Tools B.V.
Amsterdam (Enerpac distributor).
The generator was on this occasion fitted with a separate control unit designed to supply the oil separately to three lifting groups.
When pressure was applied to the cylinders the plunger rods emerged, pressing the steel plate above them and hence the threaded rods, including the bottom four nuts upward.
After the cylinder had reached its maximum stroke, the bottom four nuts were screwed downward and the two bottom I-profiles clamped back onto the sleeve, securing the threaded rods in that position.
The plunger rod was then withdrawn, after which the nuts were screwed downwards in order to clamp the upper plate again to the plunger rod.
The lifting cycle could then be resumed.
Progress was checked at three points along the mill using three simple measuring rods.
In this way the mill was lifted step by step two metre and then secured to the steel support tubes with a rigid connector.
Now it is simply a question of waiting for the dike heightening to be completed and for the soil to set.