Hydraulic cylinder operating conditions generally refer to the external loads driven by the cylinder, the working medium, the environment, and other conditions. There's no globally standardized, precise numerical standard for categorizing hydraulic cylinder operating conditions. They are generally classified as light-duty, medium-duty, and heavy-duty. This classification is more of an industry convention or empirical concept, integrating pressure, structure, application scenario, and design philosophy.
When selecting appropriate seals and guides, the cylinder type and its application are two primary selection criteria. Applications are generally classified as light-duty, medium-duty, or heavy-duty. These classifications are somewhat subjective, and pressure load values vary slightly across different industries, regions, and operating conditions. However, load levels generally adhere to the following guidelines.
Light-duty hydraulic cylinders
Light-duty hydraulic cylinders, used in indoor stationary equipment, can have the following characteristics:
System pressures up to 160 bar (2300 psi), with peak pressures ≤ 250 bar. Temperatures up to 70°C (160°F)
Rare or no pressure peaks occur when system pressure is too high
Excessive side loads on the guides, and side forces (side loads) are very low.
Working fluid: Well-filtered, no internal or external contamination.
Application environment with moderate to limited temperature fluctuations.
Duty cycle: Short strokes at working pressure, regular movement at minimum working pressure.
Industry applications: Machine tools; lifting equipment; mechanical handling equipment; injection molding machines; automatic control equipment; agricultural machinery; packaging equipment; aviation equipment; light-duty dump trucks
Medium-duty hydraulic cylinders
Medium-duty hydraulic cylinders may have the following characteristics:
System pressures up to 250 bar (3625 psi), peak pressure ≤ 350 bar
Temperatures up to 90°C (195°F)
Moderate pressure peaks occur when system pressure is too high, resulting in indirect high pressure.
Working fluid: Well-filtered, no internal contamination. Moderate sideways loads and moderate lateral forces are present on the guide.
The application environment is subject to significant temperature fluctuations and typical external contaminants such as dust and moisture.
Duty: Indoor or outdoor operation, with regular full-stroke motion under operating pressure.
Industry Applications: Heavy lifting equipment; agricultural machinery; light-duty road vehicles; cranes; heavy-duty machine tools; injection molding machines; coal mining machinery; aviation equipment; hydraulic presses; heavy-duty dump trucks; heavy machinery handling equipment.
Heavy-Duty Hydraulic Cylinders
Heavy-duty hydraulic cylinders, such as those used in off-road earthmoving or forestry equipment, can have the following characteristics:
System pressures up to 400 bar (5800 psi)
Temperatures exceeding 90°C (195°F), with peaks exceeding 110°C (230°F)
Frequent pressure peaks occur when the system pressure is too high, and the system typically operates under high pressure.
Working Medium: The working medium is subject to internal and external contamination.
Large sideways loads (lateral forces) are present on the guide, typically caused by heavy components or high accelerations. Harsh environments with wide temperature ranges and typically severe external contaminants.
Duty: Full stroke at maximum operating pressure.
Industry Applications: Casting equipment; Forging equipment; Coal mining equipment; Heavy construction machinery; Heavy off-highway vehicles; Heavy hydraulic presses.
The terms "light, medium, and heavy duty" are more of a general description of hydraulic cylinder design levels, manufacturing standards, and applicable scenarios.
When selecting the appropriate seal, it's important to choose a product that meets the corresponding pressure rating and service life based on actual operating parameters, achieving redundant sealing performance. This is especially true in the medium and heavy-duty applications. Given the overall cost of repairing and replacing inferior seals, reliability is far more important than initial cost. Due to the inherent dimensional accuracy and consistency of machined seals, cross-sections can be freely optimized based on operating conditions and performance requirements without having to consider mold release. They are completely flash-free, with a smooth and uniform surface, eliminating premature failure caused by wear and leaks.
Crocker's oversized seals are the most recommended choice for oversized, heavy-duty hydraulic cylinders used in tunnel boring machines, large presses, metallurgical rolling mills, giant excavators, etc.
