When I lift a heavy bridge or steel structure at several points, even a small height difference can create serious damage, delay, and safety risk.

hydraulic synchronous lifting system lifting a bridge

I use this system when a heavy structure must move as one controlled unit. In the sections below, I will explain how the system works, what parts it needs, and how I keep every lifting operation safe and accurate.

If each hydraulic cylinder moves at a different speed, the structure can tilt, twist, or lose balance. I need a control method that finds these differences early and corrects them before they become dangerous.

I keep lifting points synchronized through a closed-loop control process. Displacement sensors measure the height of every lifting point, while pressure sensors measure the load and hydraulic pressure. The PLC compares the actual data with the target data and adjusts valve flow and pressure in real time.

displacement sensors and PLC control for hydraulic lifting

How does the closed-loop process work?

I divide the control process into four simple actions:

1. I set the target height. I enter the required lifting distance through the HMI.
2. The sensors collect data. Each lifting point sends displacement and pressure data to the PLC.
3. The PLC compares the data. It checks the difference between the target position and the actual position.
4. The valves adjust the flow. The system changes oil flow and pressure to slow down or speed up each cylinder.

This process continues during the whole operation. If one lifting point moves faster, I reduce its oil flow. If another point moves slower, I increase its flow within the safe working range. This helps me keep the structure level.

Why is millimeter control important?

I cannot judge the position of a large structure by looking at it from the ground. A small error at one lifting point can become a large error across a bridge or steel frame. This is why I use sensors instead of visual checks alone.

The system can support synchronous lifting, synchronous lowering, and proportional lifting. For example, I can set several cylinders to rise at the same speed. I can also set one group to rise twice as far as another group when the project requires a controlled slope.

In my work, I treat the PLC as the decision center and the hydraulic cylinders as the execution units. The sensors connect both sides. They show the PLC what is happening, and the PLC tells the hydraulic system what to do next. This repeated feedback is what allows me to control a large load with small, accurate movements.

I cannot achieve stable synchronous lifting with hydraulic cylinders alone. I need a complete system that combines power, measurement, control, and protection. Each part has a different job, but all parts must work together.

I normally divide the system into four main subsystems: the hydraulic power and execution system, the signal sensing and detection system, the control and decision system, and the safety protection system.

main components of a hydraulic synchronous lifting system

1. Hydraulic power and execution system

I use a high-pressure electric hydraulic pump station to provide the required oil flow and pressure. The pump station sends hydraulic oil through a multi-channel valve group. Each channel controls one cylinder or one lifting point.

Depending on the project, I may use single-acting or double-acting high-pressure hydraulic cylinders. A single-acting cylinder normally lifts with hydraulic pressure and returns through an external force or its own load. A double-acting cylinder uses hydraulic pressure for both lifting and lowering.

2. Signal sensing and detection system

I place a displacement sensor at each lifting point. The sensor may use a draw-wire design or laser measurement. I also install pressure sensors to monitor the force and pressure at each point.

These sensors give me two important views. Displacement data tells me where each point is. Pressure data tells me how the load is distributed. I need both types of data because height alone cannot show whether a point is carrying an unusual load.

3. Control and decision system

I use a PLC as the main control unit. The PLC receives sensor signals, calculates the difference between lifting points, and sends control signals to the valve group.

I use an HMI to enter lifting distances, speed limits, alarm values, and other settings. The HMI also allows me to view the current position, pressure, alarm status, and operating mode.

4. Safety protection system

I use hydraulic check valves, balance valves, and mechanical locking rings to protect the structure. The hydraulic lock can help hold the cylinder position when the system stops. The mechanical lock gives me a second layer of support.

At KIET Hydraulics, I see this four-part structure as the base of a reliable lifting solution. If one part is missing, I may lose control, feedback, or protection. When I design a system, I check the complete chain instead of selecting cylinders in isolation.

A lifting system may have enough power and still be unsafe if I do not control the load, the movement, and the stopping process. I need a clear operating plan before I start the pump.

I improve safety by combining automatic control with mechanical protection, careful testing, and continuous monitoring. I never depend on one safety device or one operator observation.

safe operation of a hydraulic synchronous lifting system

I begin with the load and lifting-point plan

Before operation, I identify the total weight of the structure and the expected load at every lifting point. I also check the support condition, cylinder capacity, lifting distance, and possible changes in the center of gravity.

A heavy structure may not share its weight evenly. Wind, friction, structural stiffness, and contact conditions can change the load during lifting. I use pressure data to watch these changes while the system is working.

I use limits and alarms

I set limits for displacement difference, pressure, lifting speed, and total stroke. If one value moves outside the safe range, the PLC can stop the system or issue an alarm.

I also use an emergency stop function. The operator must be able to stop the pump and hold the load quickly when an unexpected condition appears.

I use hydraulic and mechanical locks together

A hydraulic check valve can help prevent oil from flowing back when the pump stops. A balance valve can help control movement and reduce sudden descent. A mechanical locking ring can support the load without depending only on hydraulic pressure.

I prefer this double protection because hydraulic components can lose pressure over time. Mechanical locks give me a physical barrier. I use them during pauses, inspections, and long lifting operations.

I test the system before full lifting

I first check the hoses, fittings, electrical connections, sensor signals, valve actions, and alarm functions. I then perform a low-distance test. I compare the actual movement of each point with the PLC display.

I once saw how quickly a small difference could draw attention during a heavy lifting test. One point moved slightly faster than the others, so I stopped the operation and checked the flow setting. The problem was small, but the early stop protected the structure and gave me useful information. This is why I use gradual testing instead of moving directly to the full lifting distance.

For projects involving bridges, large steel structures, buildings, marine equipment, or oversized transport, I also keep communication clear between the operator, site engineer, and safety team. I explain the target movement and the stop conditions before the operation starts. A precise hydraulic system works best when the people around it follow the same plan.

I use hydraulic synchronous lifting systems to control heavy structures with accurate feedback, stable movement, and layered safety from the first lift to the final position.