General Questions

Our payment policy is as follows:

A 30% advance payment is required at the time of order placement. This advance payment should be made via wire transfer (T/T).
The remaining 70% of the order amount is to be paid before the shipment of the goods, also via wire transfer (T/T). Please ensure that accurate banking information is provided to facilitate the smooth completion of the transaction.

Delivery Time and Ports

The delivery time is between 15 to 25 days. Shipments can be made from either Qingdao or Tianjin ports, and we also accommodate any other ports specified by the customer. Please provide the desired port information when confirming the order to ensure we can arrange the shipping according to your requirements. We are committed to timely delivery and meeting your specific needs.

Mold Costs

For the majority of our products, we have established and fully operational production lines. So there are no additional costs beyond the product itself. In special cases where unique molds or additional production requirements are necessary. We will waive this mold fee after the order reaches the specified quantity and upon receipt of the payment. This approach ensures that customers only incur charges directly associated with their product needs and not with extraneous costs.

Preparation

Before starting the disassembly, make sure to gather all necessary tools and materials. You’ll need a cylinder seal removal tool, a cleaner, and some clean cloths. Additionally, have new cylinder seals and an appropriate amount of lubricant ready.

Disassembly Steps

Shut down the hydraulic system: Position the piston rod so it’s not under pressure to avoid any deformation.

Remove the old seal: Use the seal removal tool to carefully extract the old seal from the cylinder, being cautious not to scratch the inner walls.

Clean the components: Thoroughly clean the inner walls of the cylinder and the piston rod using cleaner and a cloth to remove any residue.

Install the new seal: Apply lubricant to the piston rod, then fit the new seal onto it.

Reassemble the piston rod: Slowly push the piston rod back into the cylinder, ensuring the new seal is correctly positioned and secure.

Inspection and Testing

Check the piston rod: Ensure that the piston rod moves freely without any sticking.

Conduct a pressure test: Pressurize the cylinder to check for any leaks and confirm that it operates correctly.

Observe the piston rod movement: During the pressure test, ensure the piston rod moves smoothly without any unusual noises.

Final inspection: Release the pressure and double-check that the piston rod and cylinder interior are clean and free from any debris.

There are many types of hydraulic cylinders. The working principles of different hydraulic cylinders are different. We have prepared a more detailed explanation of the working principles of hydraulic cylinders for you.

  • Use calipers to measure the inner and outer diameter of the cylinder tube.
  • Measure the diameter of the piston rod.
  • Measure the diameter of the two pin holes.
  • Measure the thickness of the two lugs (ears).
  • Measure the size of the oil port.
  • Finally, use a tape measure to determine the center distance between the two pin holes.

We have prepared for you a more detailed explanation of measuring hydraulic cylinders.

Internal Leakage in Hydraulic Cylinders

Internal leakage in a hydraulic cylinder refers to the situation where fluid leaks from the high-pressure chamber to the low-pressure chamber through various gaps inside the cylinder. This type of leakage is often difficult to detect and is usually identified through system performance indicators such as insufficient thrust, reduced speed, unstable operation, or an increase in oil temperature. Ideally, such leaks should be diagnosed through proper measurement procedures.

Internal leakage in hydraulic cylinders typically occurs in two areas:

1. Static Seal Between the Piston Rod and the Piston

In agricultural machinery, the piston and piston rod are often connected using a locking nut, with an O-ring installed on the sealing surface between the two. If installed correctly and securely, this can effectively prevent leakage at this location.

2.Dynamic Seal Between the Cylinder Liner and the Piston

This is the primary pathway for internal leakage. The causes of leakage here include:
Cylinder liner and piston wear, which increases the gap beyond acceptable limits, allowing the high and low-pressure chambers to communicate.
Worn, scratched, or aged piston seals (typically Y-ring seals), leading to poor sealing.
Improper loading on the piston rod or excessive clearance between the guide bushing and piston rod, causing the piston to tilt towards one side of the cylinder wall. This misalignment or uneven wear of the piston leads to internal leakage.
If internal leakage is suspected, all mating parts should be carefully inspected. To repair a cylinder liner, boring the inner hole and fitting it with a larger diameter piston is a common method. Experience suggests that if a newly replaced Y-ring seal on the piston lasts about three months, the outer diameter of the newly machined piston should be increased by 0.4mm compared to the original size. If the Y-ring lasts only about one month, the piston diameter should be increased by 0.6mm. Increasing the piston’s diameter effectively enhances the pre-compression of the seal, ensuring its lip firmly adheres to both the cylinder wall and piston, achieving an initial seal. When manufacturing pistons, wear-resistant cast iron or 45# steel are recommended materials.

 Proper Use and Maintenance

The leakage in hydraulic cylinders is related to various factors, including design, manufacturing, assembly, usage, and maintenance. In addition to the leakage issues and solutions mentioned above, the following points should be noted during use and maintenance:

1. Proper Assembly and Installation

After disassembly, all parts should be thoroughly cleaned, and new seals should be installed. Care should be taken not to damage the sealing surfaces when installing the seals. The tightening force for fasteners and threaded joints should conform to the specified values and be applied evenly.

2. Prevent Contaminants from Entering the Hydraulic System

If the hydraulic fluid is contaminated, debris can accumulate in the seal grooves, leading to poor sealing. In dynamic seals, solid particles in contaminated oil can cause abrasive wear between the seal and the contact surface, leading to premature seal failure.

3. Proper Use and Maintenance

Ensure the system is not operated above its pressure rating, regularly check the hydraulic fluid, keep the oil temperature below 65°C, and periodically clean or replace filters. Address any system leaks promptly.
A hydraulic cylinder is a common hydraulic component used to perform lifting, tilting, and other actions in machinery. During its use, it may be necessary to disassemble and repair the hydraulic cylinder. Below is an example of how to disassemble and reassemble a single-acting lifting cylinder.

Before Disassembling:

Ensure the hydraulic oil inside the cylinder is drained to prevent leakage, contamination, and hazards.

Disassembly:

Secure the cylinder on a workbench, then use a wrench or socket wrench to remove the connection nuts at both ends of the cylinder.

Handling Internal Components:

Pay attention to the piston and seals inside the cylinder to avoid damage or loss during disassembly.

Inspection and Replacement:

After disassembly, inspect and replace the seals inside the cylinder to ensure its sealing integrity and longevity.

Reassembly:

When reinstalling, ensure the connection nuts at both ends of the cylinder are tightened properly to avoid leaks or looseness.

Filling and Bleeding:

Fill the cylinder with hydraulic oil and remove any air bubbles to ensure proper operation.
In summary, disassembling and reassembling a single-acting lifting cylinder requires attention to safety and detail to ensure the cylinder’s proper function and durability.
Common Issues and Recommendations for Hydraulic Cylinders

1. Cylinder Does Not Operate

  • Oil Line Blockage: If the pressure oil cannot enter the cylinder due to a blocked oil line, clear the blockage.
  • Improper Installation: Poor connection or installation may cause the cylinder to be affected by external forces. Reinstall the cylinder correctly.

2. Cylinder Operates, but Movement is Too Slow

  • Insufficient Oil Supply: If the hydraulic pump is not supplying enough oil, causing low pressure, troubleshoot the pump.
  • Excessive System Leakage: Check the sealing performance of various components and pipelines.
  • Leakage Between Rod Chamber and Non-Rod Chamber: If high-pressure oil leaks from the piston seal to the low-pressure chamber, replace the piston seal assembly.
  • Excessive Wear: If the cylinder tube or piston is excessively worn, consider repairing or replacing it.

3. Cylinder Crawling

  • Air in the Cylinder: Bleed the air from the cylinder.
  • Foreign Matter and Moisture: If foreign particles and moisture cause local damage or sintering, grind the cylinder wall and investigate the cause of contamination.
  • Improper Installation: Misalignment of the centerline with the guide sleeve’s track requires reinstallation.
  • Tight Seals: Adjust the seals if they are too tight.
  • Misalignment of Piston and Rod: Correct the alignment.
  • Misalignment of Guide Sleeve and Cylinder: Align as necessary.
  • Bent Piston Rod: Straighten the piston rod.
  • Poor Cylindrical Accuracy: Bore and grind the cylinder tube, and fit a new piston if needed.

4. Jitter or Noise

  • Air in the Cylinder: Bleed the air.
  • Tight or Rough Sliding Surfaces: Polish the sliding surfaces.
  • Damaged Piston Seals: If high-pressure oil leaks quickly into the low-pressure chamber causing noise, replace the piston seal.
5. End-of-Cylinder Impact
  • Excessive Cushioning Clearance: Reduce the cushioning clearance to improve buffering.
  • Faulty One-Way Valve in the Cushioning Device: Replace the one-way valve.

6. Cylinder Leakage

  • Damaged Seals: Replace the seals.
  • Deformed or Damaged Parts: Realign or replace the parts as necessary.

Methods for Securing Hydraulic Cylinders

  1. Bolt Fixing: Pre-drill holes in the base of the hydraulic cylinder and the workbench or machinery, then secure the hydraulic cylinder to the base using bolts. This method is simple and reliable, suitable for smaller hydraulic cylinders.
  2. Welding Fixing: Weld the base of the hydraulic cylinder to the workbench or machinery to ensure a strong and permanent attachment. This method is suitable for larger hydraulic cylinders as it provides greater holding strength.
  3. Clamping Fixing: Use clamping devices, such as nuts or clamping blocks, to clamp the hydraulic cylinder to the workbench or machinery. Adjust the clamping force to secure the hydraulic cylinder. This method is ideal for situations where frequent replacement of the hydraulic cylinder is required.
  4. Spring Fixing: Insert springs between the base of the hydraulic cylinder and the workbench or machinery to use elastic force to hold the hydraulic cylinder in place. This method is suitable for applications where cushioning and vibration reduction are needed.
  5. Support Fixing: Use support frames, support feet, or support chains to support the hydraulic cylinder.
  6. Important Considerations: When choosing a support method for a hydraulic cylinder, consider the size, weight, and working environment of the hydraulic cylinder to ensure the safety and stability of the support method. Additionally, regularly check the support components during installation and use to ensure they are functioning properly.
Before our products are shipped, they undergo thorough quality testing to ensure reliability and performance.
For example, while the standard operational pressure is 16 MPa (megapascals), we test our products at pressures ranging from 20 to 22 MPa.
This rigorous testing ensures that the products can withstand pressures beyond their normal operating conditions, confirming their durability and effectiveness under stress.
This process helps us guarantee that each product meets high-quality standards and performs reliably in its intended application.
We utilize advanced powder coating and spray painting techniques that are well-established and proven. We can accommodate any color requirements you have, whether they are standard or custom. Our skilled team ensures precise color mixing and application to meet your exact specifications and quality standards for each product.
Our cylinder tubes are made from Q355B steel, which is tempered to enhance strength and durability.
The material undergoes cold drawing and tempering processes to ensure stable performance and longevity. The piston rods are crafted from either 45# steel or 40Cr steel, both of which are carefully selected and processed to provide exceptional strength and reliability, ensuring excellent performance under various operating conditions.

If you have any other questions, please feel free to contact us. We will reply to you as soon as we receive your question.