Newly Developed Lightweight Ultra-high Back Pressure Multi-strand Jack

The center hole jack is mainly used for the overall tensioning of multiplane anchorages. The jack is easy to operate, reliable in performance, and saves steel strands to the greatest extent. The jack is mainly used in the construction of bridges and other projects in conjunction with prestressed anchorages and tensioning equipment.

The working principle of the center hole multi-strand jack

The multi-strand jack is a double-acting jack that uses double hydraulic cylinders to stretch the prestressed tendons and press the anchorages. When the jack is tensioned, it is pressed against the working anchor. Install the working anchor on the front end of the piston, and install the working and tool wedges. The oil is fed through the electric oil pump. Under the pushing action of high-pressure oil, the piston moves forward, and the steel strand is driven to move forward under the action of the tool anchorage to realize the tension.

When using this jack, in addition to complying with the relevant regulations of the general prestressing operation process, the following items should also be paid attention to:

1. In order to ensure the accuracy of the tension force, the jack should be matched with an oil pump, a pressure gauge and an external high-pressure hose to calibrate the “oil pressure value – output force”. When calibrating, the active working state of the jack shall prevail, the graded record shall be taken, the average value of three measurements shall be taken, and the chart shall be drawn as the basis for tensioning.
2. In the following cases, the jack should be re-calibrated:
   (1) After the jack is disassembled and repaired;
   (2) The pressure gauge has been collided or malfunctioned;
   (3) When updating the pressure gauge;
   (4) Reuse the jack after it has been placed for a long time.
3. The jack should use No. 46 high-quality hydraulic oil, which does not contain water, acid, and other mixtures. The oil should be kept strictly clean, filtered frequently, and replaced regularly.
4. When installing the oil pipe, the interface part should be cleaned and wiped clean. Strictly prevent sand and dust from entering the jack, and minimize the number of disassembly and assembly. When the new oil pipe is used for the first time, do not directly connect it with the oil nozzle of the jack. It should be cleaned in advance or cleaned in the oil output by the oil pump before use. After removing the oil pipe, the jack and oil pump should be equipped with dust caps to prevent dirt from being mixed in.
5. The jack should be run more than three times without load before use to discharge the air in the cylinder.
6. The jack should be regularly repaired and cleaned according to the actual use situation. If faults, oil leakage, or scratches on the surface of the piston are found during the work, it should be stopped for maintenance.
7. During the working process of the jack, the operator should stand on both sides, and it is strictly forbidden to stand in the direction of the end face to avoid accidents.
8. The exposed working surface of the jack should be wiped frequently to keep it clean. After the work, the piston should be returned to the end. When not in use, it should be covered with a dustproof cover and placed indoors.