Selecting the right hydraulic hose is crucial for ensuring the safety, performance, and durability of the entire hydraulic system. To make the right choice, a number of technical criteria must be taken into account.
Basic parameters for selecting a hydraulic hose
When selecting a hydraulic hose, the following technical factors are crucial, as they determine its proper functioning within a given system:
- Working pressure: This is the maximum pressure that a hose can safely withstand during normal operation. The working pressure rating of a hydraulic hose must not be lower than the actual pressure in the system, taking into account any sudden pressure surges and short-term pressure spikes. Hoses are classified as low-pressure, medium-pressure, and high-pressure. High-pressure hoses may have single-, double-, or quadruple-braided steel reinforcement, and hoses designed for ultra-high-pressure applications are also available, such as thermoplastic hoses for pumps generating pressures of 700 bar and higher.
- Inner diameter: This parameter is directly related to the required flow rate of the hydraulic fluid in the system. Selecting the appropriate inner diameter ensures optimal system performance and prevents excessive hydraulic resistance. Maintaining the correct flow velocity of the hydraulic fluid also depends on the inner diameter of the hose.
- Type of medium: The type of medium to be transported through the hose must be precisely identified (e.g., hydraulic oil, water, fuel, chemicals). The hose material must be chemically resistant to that medium.
- Fluid temperature: The operating temperature of the fluid has a significant impact on the service life and physicochemical properties of the hose material. Both the minimum and maximum temperatures at which the hose will be used must be taken into account.
- Construction and reinforcement: The mechanical strength of a hose depends on the number and type of steel braids used. Hoses are classified as having one braid (e.g., 1SN), two braids (e.g., 2SN), four braids (e.g., 4SP, 4SH), or six braids (e.g., 6SH). A greater number of steel braids results in higher pressure resistance of the hose.
- Manufacturing standards: Hydraulic hoses are manufactured in accordance with specific industry standards, such as EN 853, EN 856, SAE J517, and ISO 18752. The ISO 18752 standard defines hose strength levels based on working pressure, classifying them, for example, from R500 (500 psi) to R4000 (4000 psi). The SAE J517 standard specifies requirements for construction, physical properties, and performance parameters, including working pressure, temperature range, flexibility, and minimum bend radius. Modern specifications are increasingly based on application conditions (working pressure, temperature, expected service life) rather than solely on hose construction.
- Hose length: The hose length must be precisely tailored to the specific geometric requirements of the hydraulic system in question.
- Mechanical properties: Considerations must be given to requirements regarding flexibility, minimum bending radius, tensile strength, and potential mechanical impact.
Markings on the hydraulic hose
Much of the important technical information about the hose is usually permanently marked on its outer layer. These markings provide key data, including:
- Inner diameter (given in millimeters or inches).
- Number of steel cords (e.g., 1SN, 2SN, 4SP, 4SH).
- The standard according to which the hose was manufactured (e.g., EN 853, EN 856).
- Operating pressure (expressed in MPa, bar, or PSI).
- Burst pressure (typically four times higher than the working pressure).
- Date of manufacture (often in the format of quarter and year).
If you have any questions regarding the proper selection of a hydraulic hose, it is always recommended that you consult a qualified specialist in the field of hydraulic systems.
