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Liuzhou Yuqiao Prestressed Engineering Technology Co., Ltd.

How a Through-Type Jack Works

Release date:

2019-03-27

A through-type jack is a dual-action jack that uses two hydraulic cylinders—one for tensioning the prestressing tendons and the other for pressing against the anchorage device. This type of jack is ideal for tensioning systems with a central core. Here’s how it works: When tensioning the prestressing tendon, oil flows into the tension cylinder’s port while the pressure cylinder’s port returns oil. As a result, the pressure cylinder, connecting sleeve, and support sleeve move together to the right, firmly pressing against the anchor ring. Meanwhile, the tension cylinder, along with the end cap nut, plug, and through-type sleeve, moves as a single unit to the left, pulling the tool anchor and thereby tensioning the prestressing tendon. During the anchoring phase, while maintaining consistent tension force, oil is introduced into the pressure cylinder’s port. The pressure piston, protective sleeve, and pressure head then move together to the right, forcefully driving the wedge-shaped clamping mechanism deep into the anchor ring. At this point, the tensioning process is securely locked in place.

The through-type jack is a dual-action jack that uses two hydraulic cylinders to tension prestressing tendons and simultaneously press against the anchorage. The through-type jack is suitable for tensioning with strips.

Its working principle is: when the prestressing tendon is tensioned, oil flows into the tension cylinder nozzle, pushing against the compression cylinder.

The oil nozzle returns the oil, causing the top-pressure cylinder, connecting sleeve, and support sleeve to move as a single unit to the right, firmly pressing against the anchor ring. Meanwhile, the tension cylinder, end-cap nut, plug, and through-center sleeve work together to drive the tool anchor leftward, tensioning the prestressed reinforcement. During the anchoring and pressure-fixing phase, while maintaining stable tension force, the top-pressure cylinder’s oil nozzle opens to allow oil flow, pushing the top-pressure piston, protective sleeve, and pressure head—now integrated as one—to move rightward with great force, firmly seating the wedge into the anchor ring. At this point, the tension cylinder’s oil nozzle retracts, while the top-pressure cylinder’s oil nozzle remains open, initiating the hydraulic return stroke of the tension cylinder. Finally, both the tension cylinder and top-pressure cylinder’s oil nozzles simultaneously retract, allowing the top-pressure piston to return to its original position under the action of spring force.

For structures with large spans, such as those requiring significant elongation like long steel cable bundles, a through-type jack is the ideal choice.

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