FLAT JACKS

If existing structures have to be held up by means of piles or beams, it is sometimes necessary to preload the supporting section. This preloading can be effected with a flat jack, which is generally left behind in the structure.

The flat jack consists of a steel casing, the dimensions of which are enlarged by injecting it with mortar. The flat jack has a very small overall height. It can exert very large forces.

The flat jack is built up of two steel dishes welded together. The jack has two connections: a supply tube and breather tube opposite each other. These connections are 50 mm long and have a 3/8" G screw thread. Flat jacks are available with connecting tubes in other positions. The standard shape is round, but a square or an oval shape is also available.

Depending on the application water, oil, cement mortar or synthetic resin are injected to put the jacks under pressure. The maximum operating pressure is 150 bars. As the stroke of the jack increases, the effective surface area of the jack decreases, so that the force becomes less. If the stroke of one jack is insufficient, two or more jacks can be put on top of each other.

The jack is placed between two steel plates or is set in concrete. The height of the smallest jack, including the steel plates is 30 mm.

APPLICATIONS OF FLAT JACKS:

• jacking structures;
• holding up structures on new foundations;
• preloading foundation piles, columns or beams;
• measuring forces.

TECHNICAL INFORMATION ON FLAT JACKS:

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