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Technical Requirements for Hydraulic Cylinders Based on Hydraulic System Components
① Anti-instability: To prevent bending or instability of the hydraulic cylinder’s piston rod at any position, the cylinder’s stroke length, load, and mounting configuration should be considered.
② Structural Design: The hydraulic cylinder design should take into account the anticipated maximum load and peak pressure.
③ Installation Rating: When determining all load ratings of a hydraulic cylinder, its mounting configuration should be considered.
Author’s Note: The rated pressure of a hydraulic cylinder only reflects the pressure-bearing capacity of the cylinder body and does not reflect the force transmission capacity of the mounting structure.
④ Loads Generated by Limits: When a hydraulic cylinder is used as a limiter, the cylinder size and mounting type should be determined based on the maximum load caused by the restrained component.
⑤ Shock and Vibration Resistance: Any components and accessories mounted on or connected to the hydraulic cylinder must be mounted or connected to prevent loosening caused by shock and vibration during use.
⑥ Accidental Pressure Increase: Measures should be taken in the hydraulic system to prevent accidental pressure increases exceeding the rated pressure due to differences in effective piston area.
⑦ Installation and Adjustment: The optimal installation method for hydraulic cylinders is to ensure that the load reaction acts along the cylinder’s centerline. Installation of hydraulic cylinders should minimize the following:
- a. Excessive deformation of the cylinder structure due to load thrust or tension;
- b. Inducing lateral or bending loads;
- c. Rotational speed of articulated mounting (which may necessitate continuous external lubrication).
⑧ Mounting Location: The mounting surface should not deform the hydraulic cylinder and should allow for thermal expansion. The hydraulic cylinder mounting location should be easily accessible for maintenance, adjustment of the buffer device, and replacement of complete components.
⑨ Mounting Fasteners: The selection and installation of fasteners used to mount the hydraulic cylinder and its accessories should be capable of withstanding all foreseeable forces. Foot-mounted hydraulic cylinders may exert shear forces on their mounting bolts. If shear loads are involved, consideration should be given to using a hydraulic cylinder with a mechanism for withstanding shear loads. Mounting fasteners should be sufficient to withstand overturning moments.
⑩ Buffers and Retarder: When internal buffers are used, the hydraulic cylinder design should take into account the effects of pressure increases caused by load deceleration.
⑪ Adjustable End-of-Stroke Stops: Measures should be taken to prevent loosening of external or internal adjustable end-of-stroke stops.
⑫ Piston Stroke: If the stroke length (including tolerance) is not specified in the relevant standards, it should be determined based on the application of the hydraulic system.
Author’s Note: For stroke length tolerances, refer to JB/T10205-2010. Alternatively, “maximum stroke” or “limit stroke” may be added to the basic parameters of hydraulic cylinders to accommodate cylinders with variable stroke lengths, such as “adjustable-stroke hydraulic cylinders.”
⑬ Piston Rod
- a. Materials, Surface Treatment, and Protection: Appropriate piston rod materials and surface treatments should be selected to minimize wear, corrosion, and foreseeable impact damage. The piston rod should be protected from foreseeable damage such as dents, scratches, and corrosion; a protective cover may be used.
- b. Assembly: For assembly, piston rods with threaded ends should have a structure that allows for the application of opposing forces with a wrench, see ISO 4395. The piston should be securely secured to the piston rod.
⑭ Maintenance of Seals and Wear Parts: Seals and other wear parts requiring scheduled maintenance should be easily replaceable.
⑮ Gas Exhaust
- a. Vent Location: Hydraulic cylinders installed on stationary industrial machinery should be designed with automatic venting or have an easily accessible external vent. During installation, the vent should be positioned at the highest position. If these requirements cannot be met, relevant maintenance and operating information should be provided.
- b. Exhaust Port: Hydraulic cylinders with an air chamber should be designed or equipped with an exhaust port to avoid hazards. The exhaust port should allow the cylinder to safely discharge air.