My Linkedin Profile

FLAT JACKING

Stroke and Closed Height

The stroke of the flat jack is equivalent to the internal recess of the flat jacks where the thrust plates are placed. This is always a maximum of 25mm stroke, where larger strokes are required flat jacks can in some instances be stacked, although it may be that using a hydraulic cylinder may be a more appropriate solution. The closed height of the jack is always 32mm and an installation gap of 35mm should be allowed for.

Thrust Plates

The circular steel plates that sit within the recess of the flat jack are referred to as thrust plates and are typically 12mm thick to ensure that the load is dispersed evenly over the flat jack and not on the edges. The edges of the plates in contact with the flat jack rim are profiled (rounded off) to fit within the recess without causing damage.

 

[heading subtitle=”” size=”5″ heading_class=”content_heading” heading_style=”style-1″]FLAT JACKING APPLICATIONS[/heading]

Flat jacks are used for hydraulically loading and lifting temporary and permanent works such as pre-loading steel beams or capping beam props. The low profile of the flat jack makes it perfect for fitting into tight gaps where a typical hydraulic cylinder couldn’t fit.

The relatively low cost of the flat jack allows the jacks to be left in-situ permanently when inflated with grout or resin. The flat jack deforms under an internal hydraulic pressure to load or lift the adjacent structure.

Temporary Loading

Temporary loading of the flat jack will require the use of either hydraulic oil or water to inflate the jack, where the flat jack is to be left in-situ under load for an extended period, hydraulic oil should be used.

The flat jack will be installed with a gauge or pressure transducer to allow any required changes in loading to be monitored visually or digitally.

Permanent Loading

Permanent loading of the flat jack will require the use of either an epoxy resin or non-shrink cementitious grout to inflate the jack, once hardened the flat jack loading cannot be adjusted.

Transfusion

Transfusion of the flat jack allows the jack loading to become locked-in as part of the permanent structure after any live loading changes have been made. The process replaces the hydraulic fluid or water with a resin or cementitious grout that will harden over a set period. Transfusion can also be carefully carried out when the flat jack is under load in special circumstances.

Documents

Please click here for Praeter Engineering’s flat jack datasheet

Please click here for Praeter Engineering’s flat jack capabilites

[heading subtitle=”” size=”5″ heading_class=”content_heading” heading_style=”style-1″]FLAT JACKING[/heading]

What are Flat Jacks?

A flat jack is a circular mild steel capsule, formed from 2 separate steel plates that have been spun along the edges. The steel plates are then welded together to create a torus profile around the circumference and a recess in the centre of the flat jack.

An inlet and outlet pipe are then welded to the flat jack and are fitted with either a needle or ball valve depending on the fluid to be used. The outlet pipe is normally fitted with a plug. They are supplied complete with two machined thrust plates.

Design, Supply and Install

Praeter Engineering Ltd are equipped to carry out the full design, supply and installation of a fully bespoke flat jack system along with any live monitoring required. Our installation will be carried out by our trained specialist operatives. We can supply flat jacks with capacities from 50kN up to 10,000kN.

 

[heading subtitle=”” size=”5″ heading_class=”heading” heading_style=”style-1″]FLAT JACK PROFILE[/heading]
[heading subtitle=”” size=”5″ heading_class=”heading” heading_style=”style-1″]PRAETER ENGINEERING’S FLAT JACK SIZES[/heading]

If you have an application that requires a bespoke flat jack size and solution not listed above do not hesistate to get in contact.