Project Information
- Project Name: Hydraulic Jack for a Large Crane
- Applied Equipment: 90-Ton Port Crane
- Application: Cargo lifting at a port
- Cylinder Model: HSG250 × 180 × 1000
- Working Pressure: 25 MPa
- Cylinder Bore: 250 mm
- Cylinder Outside Diameter: 299 mm
- Stroke: 1,000 mm
- Required Lifting Force: Approximately 90–100 tons
Project Background
The customer operated a large crane for lifting cargo at a port. The crane’s original hydraulic cylinder had an 80 mm piston rod, a 220 × 220 mm mounting flange, and a stroke of only 400 mm.
Although the existing cylinder could be installed on the crane, its limited stroke could no longer satisfy the customer’s lifting requirements. The customer therefore wanted to replace it with a new hydraulic jack offering a 1,000 mm stroke and an approximate lifting capacity of 90–100 tons.
During the initial discussion, the customer proposed a pressure requirement of up to 600 bar. However, selecting a hydraulic cylinder based only on the requested pressure could result in unnecessary system pressure, excessive stress on the seals and cylinder components, and higher requirements for the associated hydraulic equipment.
AISOAR therefore evaluated the crane application, required lifting force, available installation dimensions, original mounting arrangement, and proposed cylinder dimensions before determining the final cylinder configuration.
Customer’s Special Requirements
The cylinder had to provide a much longer stroke while remaining compatible with the existing crane structure. Several technical requirements needed particular attention.
1. Stroke Increased from 400 mm to 1,000 mm
Increasing the stroke by 600 mm changed the structural conditions of the cylinder. The longer piston rod required sufficient rigidity and surface hardness to withstand the load without excessive deformation or an increased risk of damage during operation.
2. Large Hollow Piston Rod
The new cylinder used a 180 mm piston rod with an 80 mm hollow section. This configuration reduced unnecessary weight, but the rod still had to maintain sufficient strength under the specified lifting load.
The rod structure, wall thickness, material properties, and processing method therefore had to be considered together rather than treating the hollow rod as a standard solid piston rod.
3. Lifting Force of Approximately 90–100 Tons
The hydraulic jack needed to generate sufficient pushing force to lift the required load reliably. The cylinder bore and actual working pressure therefore had to be matched through force calculations instead of directly adopting the initially proposed 600 bar pressure.
4. Compatibility with the Original Installation
The replacement cylinder needed to fit the crane’s existing installation position. Its flange dimensions, connection arrangement, overall structure, and interface locations had to be confirmed using the customer’s original cylinder drawing, crane photographs, and dimensional sketch.
5. Reliable Sealing Under High Load
The seals needed to withstand the selected working pressure and repeated heavy-load operation. An unsuitable sealing arrangement could lead to seal extrusion, internal leakage, external leakage, or premature failure.
6. Application-Specific Factory Testing
Before delivery, the cylinder needed to be tested with particular attention to operating pressure, pressure holding, movement, sealing performance, and load-bearing capability.
AISOAR’s Customized Hydraulic Cylinder Solution
This is equivalent to a theoretical pushing force of approximately 125 tons. After considering hydraulic efficiency, friction, and an appropriate operating margin, the configuration can provide the required working force of approximately 90–100 tons.
Cylinder Bore and Working Pressure Calculation
For a cylinder with a 250 mm bore, the theoretical pushing force at 25 MPa is calculated as:
This is equivalent to a theoretical pushing force of approximately 125 tons. After considering hydraulic efficiency, friction, and an appropriate operating margin, the configuration can provide the required working force of approximately 90–100 tons.
Therefore, a working pressure of 25 MPa was selected for the final design. This eliminated the need to operate the cylinder at the initially proposed 600 bar while still meeting the required lifting force.
Reducing unnecessary system pressure also helps lower the stress applied to the cylinder barrel, seals, ports, hoses, and related hydraulic components.
Strengthened Hollow Piston Rod
The piston rod diameter was increased to 180 mm, with an internal hollow diameter of 80 mm. The rod dimensions were selected according to the longer stroke and heavy-load application.
The piston rod received heat treatment and chrome plating to improve:
- Surface hardness
- Wear resistance
- Corrosion resistance
- Resistance to surface damage
- Service reliability during repeated extension and retraction
Special attention was given to the relationship between the hollow rod structure, 1,000 mm stroke, and required lifting force.
Installation-Compatible Structure
The new cylinder was designed according to the mounting arrangement of the original unit. The flange and connection dimensions were reviewed so that the customer could replace the previous 400 mm stroke cylinder without carrying out major modifications to the crane structure.
This design approach reduced the installation risk normally associated with replacing an existing cylinder with a substantially longer model.
High-Pressure Sealing Arrangement
The sealing system was selected according to the final 25 MPa working pressure and the heavy-load lifting conditions. The objective was to prevent seal extrusion and maintain stable sealing performance during pressurization, pressure holding, and repeated operation.
The sealing and guiding components also help maintain alignment between the piston rod and cylinder barrel, particularly important for a large-diameter, long-stroke cylinder.
Project Result
The completed hydraulic jack provided a 1,000 mm stroke and a calculated pushing force of approximately 96.2 metric tons at 25 MPa, meeting the customer’s required lifting force of 90–100 tons.
Compared with the original 400 mm stroke cylinder, the customized solution provided a substantially longer lifting range while maintaining compatibility with the crane’s existing mounting arrangement. The strengthened hollow piston rod, suitable sealing system, and application-specific pressure selection also improved the cylinder’s reliability under heavy-load operation.
The completed design provided:
- A longer lifting stroke
- Approximately 90–100 tons of required working force
- Improved piston rod strength and surface durability
- Reliable sealing under high-load conditions
- Compatibility with the original installation
- More appropriate operating pressure for the application
Custom Hydraulic Cylinders for Crane Applications
AISOAR designs and manufactures customized hydraulic cylinders and hydraulic jacks for port cranes, mobile cranes, lifting equipment, construction machinery, and other heavy-duty applications.
Customers can provide an existing drawing, damaged cylinder, equipment photograph, dimensional sketch, or required operating parameters. Our engineering team can evaluate the bore, rod diameter, stroke, pressure, mounting arrangement, and required output force to develop a suitable replacement solution.
Send us your cylinder drawing and crane operating requirements to discuss a customized hydraulic cylinder solution.
