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As we mentioned in earlier articles：
- How complicated is the sealing of hydraulic cylinders? Six sealing methods explained
- Function and selection of common seals for hydraulic cylinders
- 12 types of hydraulic O-ring failure modes and prevention measures. Control and avoid oil leaks
- PTFE Step Seals and Glyd Rings for Hydraulic Cylinders
- How to correctly select seals during the design phase of a hydraulic cylinder?
Today we’ll discuss how to conduct incoming inspection of seals, which is very important in hydraulic cylinder manufacturing.
The hydraulic cylinder seals are very important. While O-rings have corresponding international/national standards for acceptance testing, we will focus on providing a preliminary description of the acceptance testing for the numerous other types of seals, given the complex market of seal suppliers and the thousands of different seal types available.
I. The Importance of Hydraulic Cylinder Seals
Seals can be considered the “lifeline” of a hydraulic cylinder, and are one of the most critical materials/components of a hydraulic cylinder. They function to prevent leakage, maintain pressure and efficiency, prevent contamination, and determine the service life and reliability of the hydraulic cylinder.
While the cylinder barrel tube and piston rod are the “rigid core” of the hydraulic cylinder, providing physical structure and strength, the seals are the “flexible core,” giving the rigid structure the essential function of “sealing.”
A hydraulic cylinder can completely fail due to minor defects in the seals, while an excellent sealing system can enable an ordinary cylinder body to perform stably and reliably.
II. How to Implement Testing During Incoming Inspection
The goal of incoming inspection is to quickly intercept defective products; therefore, the testing methods must be non-destructive, fast, and capable of detecting major defects.
1. Dimensional and Appearance Inspection
2. Performance check
Check performance characteristics such as hardness, tensile strength, elongation, compression set, resistance to media aging, and temperature rating to ensure they meet the requirements.
III. Incoming Inspection Operating Procedures
1. Receiving: Verify the model, quantity, and batch number.
2. Document Review: Immediately check the material certificate and factory inspection report accompanying the goods to confirm they are valid documents for the batch.
3. Dimensional and Visual Sampling Inspection: Perform inspection of critical dimensions and appearance using gauges and instruments according to the sampling plan.
4. Basic Performance Sampling Verification: Conduct hardness retesting or short-term oil immersion tests according to the plan (e.g., first inspection of a new batch, quarterly random inspection).
5. Judgment and Handling:
All qualified: Accept for warehousing, file documents.
Dimensions/Appearance unqualified: Issue a non-conformance report, return the goods or request the supplier to sort them.
Performance report missing/invalid, or significant discrepancies in basic verification: Suspend acceptance, hold the batch, escalate the issue, and request the supplier to provide a reasonable explanation or third-party retesting.
Generally, by adopting a combined approach based on the principle of “primarily focusing on self-inspection of critical dimensions, supplemented by reviewing supplier performance reports, and incorporating basic performance verification through sampling,” it is possible to ensure the reliability of seals to the greatest extent at a reasonable cost during the incoming inspection stage, laying a solid foundation for subsequent assembly and hydraulic cylinder performance.
At the same time, it is crucial to conduct thorough inspections and tests of all aspects of the hydraulic cylinder during reassembly, especially during the factory acceptance testing phase, to further identify potential problems and address them proactively.
Furthermore, it is essential to emphasize the importance of seal selection during the hydraulic cylinder design phase, as this is the most direct way to ensure reliability.
★★★Review of selected articles in our hydraulic cylinder engineering newsletters:
- How to choose between tie rod cylinder and welding cylinder?
- Common materials for hydraulic cylinders (III) – Common materials for cylinder heads, pistons, guide sleeves, and connecting parts
- Common materials for hydraulic cylinders (II) – Common materials and selection of piston rods
- Common materials for hydraulic cylinders (I) – Common materials and selection of cylinder barrel tubes
- Types and uses of single-acting hydraulic cylinders!
- Hydraulic cylinder classification, composition structure, main parameters and calculation!
- Hydraulic cylinder: How is synchronous control of multiple hydraulic cylinders achieved?
- How to adjust the speed of the hydraulic cylinder?
- Types and uses of double-acting hydraulic cylinders!
- How complicated is the sealing of hydraulic cylinders? Six sealing methods explained