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HYDRAULIC FREYSSI FLAT JACKS
Hydraulic Flat Jacks • Freyssi Flat Jacks • Complex Flat Jack Systems
HYDRAULIC FLAT JACK - RENTAL • SALES • SERVICE
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FLAT JACKS
Temporary Flat Jacks • Permanent Flat Jacks
• Complex Flat Jack Systems • Calibrated Flat Jacks for Weighing
Hydraulic Freyssi Flat Jacks
WB Equipment provides a diverse selection of low-profile Flat Jacks with capacities ranging from 8 to 1000 tons. These ultra-compact jacks, known for their impressive thrust capabilities, are essential tools in the civil and construction sectors.
Their versatility makes them ideal for a variety of applications, including lifting heavy structures, performing stressing operations, transferring loads to temporary or permanent supports, and pre-loading buildings, steelworks, or bridge bearings for long-term stability.
In the years since their invention by Eugene Freyssinet in 1934, many techniques have been evolved for many applications:
Hydraulic Flat Jacks
Advantages of Freyssi Flat Jacks
- Known Forces
- Precise Control
- Low Height For Limited Access
- Low Bearing Stresses
- Out Of Parallel Tolerance
- Between Jacking Surfaces
- Temporary, Removable Jacks
- Permanent, Sacrificial Jacks
- Structural Lifting
- Underpinning
- Control Of Thrust Forces
- Maintenance Of ConstantThrust
- Adjustment Of Support Reactions
- Pretressing
- Structural Pre-Loading
- Loading Of Seismic Isolators
- Arch De-Centering
- Control Of Settlement
- Measurement Of Forces
- Weighing Of Offshore Structures
- Permanent Shimming
WB Equipment offers a variety of jacking techniques tailored to address challenges in both new construction and existing structures. Our jacks can operate vertically to lift structures and horizontally to move them.
Applications include:
- Bridge lifting and sliding
- Bearing replacement
- High strength bar tensioning
- Load transfer
- Pre-stressing
- Settlement control
- Force measurement and weighting
Post-tensioning, a reinforcement method utilizing high-strength steel strands or bars, enables longer clear spans, thinner slabs, and structural systems that would otherwise be impossible due to site constraints or architectural requirements.
Jack Types
Conventional Hydraulic Jacks: Available up to 1000 tonnes capacity, equipped with swivel heads and locking collars. Our expertise as a bearing manufacturer allows us to add PTFE and elastomer sliding surfaces to the jack head, accommodating limited vertical and horizontal structural movement. The locking collar permits removal of the hydraulic system after pressurization.
Flat Jacks: Also available up to 1000 tonnes capacity, these jacks can operate in gaps of 50 mm or less. For temporary situations where jack removal is necessary, inflation is achieved using hydraulic oil. For permanent installations, such as bearing pre-loading or structural lifting, the jack can be inflated with cementitious grout or transfused under load with grout later.
Hydraulic Circuits
Jacking forces are managed using either powered or manually operated hydraulic pumps. Mechanical or electronic measurement of hydraulic pressures and structural movements ensures careful monitoring and control of the structure as it is jacked. Jacks can be connected in complex circuits, allowing for operation in unison, in groups, or individually.
Propping Solutions
Our in-house temporary works designers often engineer alternative jacking solutions for temporary works where conventional propping systems are specified. These solutions offer significant advantages in terms of speed, cost, and improved access, eliminating the need for temporary foundations or excavation.
Bearing Replacement
We provide a comprehensive “one-stop” bearing replacement service, both as a principal contractor and as a subcontractor. Combining our expertise as a bridge bearing manufacturer and designer with our proficiency in jacking systems and knowledge of specialty construction chemicals (such as grouts and epoxies), we deliver efficient and effective solutions.
Additionally, we incorporate processes like hydrodemolition and diamond drilling, supplied by our preferred partners in these specialist trades. Our in-house temporary works designers offer innovative alternatives to conventional propping, providing time and cost benefits to our clients.
Hydraulic Flat Jack Chart
Hydraulic Flat Jack Detailing Guidlines
Temporary flat jacks
Temporary flat jacks are crucial for bridge jacking applications, offering hydraulic jacking and monitoring equipment for lifting tasks. These flat jacks are specifically designed for temporary use and are meant to be removed afterward. They are usually inflated with water or hydraulic oil.
Key advantages of temporary flat jacks include:
- Functioning as load cells when connected to pressure gauges or transducers, equipped with digital read-outs.
- Pre-loading steelwork with temporary support systems.
- Facilitating continuous load monitoring and adjustment.
- Utilizing multiple flat jack circuits for uniform loading.
- Ability to transition seamlessly from temporary to permanent applications.
Freyssi Hydraulic Flat Jacks
- The flat jack is composed of a mild steel capsule, circular in shape, with an initially dumbbell-shaped cross section. Ground steel thrust plates are fitted to the dished portions before the jack is positioned between the surfaces to be separated. When inflated with a liquid, the hydrostatic pressure is transmitted by the flat portions of the capsule through the thrust plates, while the toroidal rim deforms to allow the flat faces to move apart. The maximum operating pressure is 150 bar (2,200 psi), which ensures that the flat jack exerts low bearing pressures on the jacked surfaces.
- The maximum recommended opening stroke of a flat jack is approximately 1 inch, equal to the depth of the toroidal rim.
- Two pipe connections, typically welded into the jack rim at 90 degrees to each other, provide the inlet for inflation and serve as a vent during filling, with the latter being capped off afterward.
Calibrated Flat Jacks & Weighing
A pre-opened flat jack, equipped with a pressure gauge or transducer, sealed, and calibrated in a press, can serve as a robust and accurate load cell. This load cell can be used in tandem with a standard flat jack of the same size.
The twin jacks are then installed beneath a structure at designated weighing positions. When the standard flat jack is inflated to support the structure, the pressure registered in the calibrated flat jack can be referenced against its calibration graph to provide an accurate weight measurement.
This method allows for the precise weighing of offshore structures, from modules weighing several hundred tonnes to complete integrated decks exceeding 30,000 tonnes, with an accuracy of +/- 1%. For lighter structures, an arrangement offering greater accuracy is available if necessary.
Temporary Flat Jacks
Oil Inflation – When flat jacks are to be used for a limited period and subsequently removed inflation is usually done with hydraulic fluid. For small numbers of jacks, requiring relatively small volumes of oil, simple hand pumps may be used for inflation. Larger jacks or large numbers of jacks may require electric or diesel powered pumps.
Hydraulic Circuits – Single or multiple flat jacks can be inflated individually or on inter-connected circuits. Each jack has a needle valve for locking off and may be fitted with a pressure gauge if required.
Permanent Flat Jacks
Where a force is required to be permanently applied to a structure, flat jacks are inflated under pressure with an epoxy resin by means of a special resin injection cylinder. The epoxy resin hardens over a period of time to leave the force permanently applied. This type of application is suitable for pre-loading new or additional steelwork in structures, underpinning works and structural bearing installation.
This method is often used where sufficient room is not available for wedging or grouting the jacking gap.
In certain circumstances, it may be necessary to carry out the initial inflation on hydraulic oil with resin inflation being carried out at a later date. An oil to resin transfusion system is then required.
Complex Flat Jack Systems
In applications using multiple flat jacks the hydraulic pumping circuitry can be arranged appropriately using pipe and compression fitting or flexible hoses and quick release couplings.
Individual jacks are usually fitted with manual needle valves. Pressure gauges may be fitted to individual jacks, downstream of their needle valves, instead of or in addition to a common ring main gauge. Differing loads in neighboring jacks may thus be locked in and monitored as necessary.
For especially complex operations solenoid valves, electronic pressure transducers and computer control, monitoring and data logging systems may be used.
Calibrated Flat Jacks & Weighing
A flat jack which has been pre-opened, fitted with a pressure gauge or transducer, sealed and then calibrated in a press can be used as a robust, accurate load cell. This load cell can be placed in tandem with a standard flat jack of the same size.
The twin jacks are then installed beneath a structure at weighing positions. The weight of the structure taken by inflation of the standard flat jack registers a pressure in the calibrated flat jack which, by reference to its calibration graph, provides an accurate weight.
Using this principle, offshore structures ranging from modules of several hundred tonnes to complete integrated decks of over 30,000 tonnes to an accuracy of +/- 1%. Where necessary for lighter structures, an arrangement is available with greater accuracy.
We are your exclusive source for Freyssi patented flat jacks, a must for permanent load transfers underpinning, minimum clearance and seismic applications. If you have applications requiring electronic or hydraulic load cells for precise monitoring of loads, we have them for rental or sale up to 1500 Tons.
Our major lines include: Enerpac, OTC/Power Team, Coffing/Yale, Harrington, Multiton, Norwolf, TK/Simplex, Parker hose/fittings and quick couplers, Lincoln, Blackhawk, Rodgers, commercial pumps, cylinders & valves, Sunstrand, Vickers, Eaton, Rexroth and more.
Ask for literature including a complete product list detailing the lines we represent. Our “shop set-up” ability to provide complete equipment packages for new shops with items such as jacks, presses, material handling equipment, hand and power tools,compressors and air distribution systems.
