Impact Sealing Performance

Sealing performance is a critical factor that affects the quality and reliability of various products in different industries. From automotive to aerospace, sealing technology plays a crucial role in ensuring that machines, equipment, and components function as intended.

In this article, we will explore the impact of sealing performance on product quality and reliability, and how it can affect the overall performance of a product.

1. Speed

When the speed is low (≤0.03/s), the stability of the machine operation and whether there is a chance of creeping phenomenon should be considered.
When the speed is high (≥0.8m/s), the lubricating ink may be damaged so that the seals generate heat due to the friction caused by the lack of lubrication, resulting in a significantly reduced service life. It is suggested that the rubber-to-plastic composite seal works at speeds of 0.3m/s to 1.2m/s.

2. Temperature

At a low temperature, the elasticity of rubber-to-plastic composite seal will be reduced, resulting in leakage and even a harder and more brittle oil seal. At a high temperature, it will expand and soften, causing a rapid increase in the frictional resistance of the oil seal during operation and a decrease in pressure resistance. It is recommended that the rubber-to-plastic composite seal works at a temperature of -10°C to +80 °C.

3. Operating pressure

The startup pressure is important to oil seals. The oil seals with low friction performance and small aerodynamic resistance should be chosen for the low pressure operation. Rubber-to-plastic composite seal is not suitable for the environment below 2.5Mpa. At high pressure, the seal pressure should be considered, and antiextrusion rings should be adopted. There are also special requirements for groove processing.

4. Operating medium

Apart from strictly adhering to the manufacturer’s recommended operating medium, it is crucial to keep it clean. Contaminated or aging oil not only leads to system component failure but also accelerates the aging and wear of the oil seal.Moreover, the dirt may scratch the seal or be embedded in the seal, causing seal failure. Regularly checking oil quality and cleanliness, replacing oil filters and oil as per maintenance specifications is crucial. Residual air in the cylinder’s oil when compressed by high pressure generates an instant high temperature that can burn or carbonize the oil seal. To avoid this happening, gas should be exhausted when the hydraulic system starts to operate.It’s important to operate the hydraulic cylinder at low speed and pressure for a few minutes to drain any residual air in the oil before it can function correctly.

5. Lateral load

Generally, the support ring must be installed on the piston to ensure that the cylinder can withstand heavier loads. The seal and support ring have different functions. A seal cannot replace the load-bearing function of a support ring. Therefore, hydraulic cylinders subject to lateral force must be equipped with a support ring with strong load-bearing capacity, or a metal ring for heavy loads, to prevent oil seal leakage and abnormal wear due to operation under eccentric conditions.

6. Hydraulic shock

There are many factors that would cause a hydraulic shock.For example, an excavator bucket striking a stone or a crane lifting or unloading a heavy object can cause it. Additionally, high-pressure and high-flow hydraulic systems may generate hydraulic shock during actuator reversal if the reversing valve’s performance is poor. The instantaneous high pressure generated by the hydraulic shock may be several times the working pressure of the system, which will tear the oil seal or the oil seal will be partially caught in the gap within seconds, causing serious damage. To address hydraulic shock, cylinders should have abuffer ring and a retaining ring installed on their piston rod. The buffer ring should be placed in front of the oil seal to absorb the majority of the impact pressure, while the retaining ring should prevent the oil seal from being crushed into the gap and breaking at the root under high pressure.

7. Processing accuracy of cylinder

If the moving surface’s roughness (Ra) exceeds 0.8μm, the oil seal’s leakage and wear value may rise. To avoid damage to the rubber-to-plastic composite seal during assembly, consider the following design and installation factors for hydraulic cylinders:

1)Cylinder

a: Material: carbon steel; aluminum alloy, bronze, stainless steel, etc. can be adopted for low-pressure system and good friction conditions.
b: Surface quality and roughness: The inner surface generally needs to be honed, polished or rolled. And it is required to achieve a surface roughness of 0.1 to 0.8 μm without vertical and horizontal patterns.

2) Piston rod

a: Material: carbon steel and chrome-plated steel; aluminum alloy, bronze, stainless steel, etc. can be adopted for low-pressure system and good friction conditions.
b: Surface quality and roughness: The roughness (Ra) is required to be 0.2 to 0.4 μm, and the surface is hard chrome plated after heat treatment. The piston rod of the hydraulic cylinder for construction machinery may be scratched by sand and gravel, so its surface hardness should be higher than HRC 60.
c: Installed groove of the oil seal
d: Partial structural design
e: Sliding fit clearance of wear ring f and extrusion gap of oil seal g

Conclusion:

In conclusion, sealing performance is a critical factor that affects the quality and reliability of products in various industries. Maintaining optimal sealing performance is essential to ensuring that a product meets the required quality standards and performs as intended. Regular sealing maintenance can prevent seal failure, minimize downtime, and extend product lifespan.By understanding the impact of sealing performance, manufacturers can improve the quality and reliability of their products, leading to increased customer satisfaction and loyalty.