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The SNI39 is an asymmetrical U-ring specifically designed to seal piston rods. The seal is installed around the moving piston rod and is used as a single seal in hydraulic applications.
The profile is single acting and intended for one-sided pressure load. Its installation direction must therefore correspond to the side from which the hydraulic pressure is applied. Pressure build-up increases the sealing effect of the profile.
The SNI39 has an asymmetrical profile with a shortened inner lip and a recessed sealing lip. The profile also features an additional support and sealing edge and a tight fit on the outer diameter.
The entire seal is made of TPU. This profile design combines the sealing function around the piston rod with protection against the ingress of dirt.
The shortened inner lip and recessed sealing lip are characteristic components of the asymmetrical SNI39 profile. The sealing lip provides contact with the piston rod and supports the static and dynamic sealing effect.
The SNI39 has a low recirculation capacity. During selection, this functional characteristic should be assessed in combination with the application, piston rod movement and other operating conditions.
The additional support and sealing edge protects the sealing area against the ingress of dirt. This edge is an integrated part of the profile and provides protection where the piston rod moves into and out of the cylinder.
For correct operation, the seal must be combined with a carefully cleaned installation space and a piston rod with the specified surface quality.
The SNI39 is a single-acting rod seal for one-sided pressure load. As hydraulic pressure builds up, the sealing effect of the profile increases.
The seal must therefore be installed in the correct direction. The pressure side, position of the sealing lip and available installation space must be checked before installation.
The SNI39 has a tight fit on the outer diameter. This characteristic supports the positioning of the profile in the installation groove.
The groove dimensions and installation-space design must match the selected size. Depending on the dimensional range, the seal can be installed in different installation-space configurations.
The SNI39 rod seal is intended for mobile hydraulics and construction machinery. The profile has a broad application spectrum and is described as a reliable design for moderately demanding applications in general industry.
The stated product advantages include good static and dynamic sealing performance, high wear resistance and simple snap-on assembly. The SNI39 also offers a good price-performance ratio and is manufactured by certified external suppliers.
The SNI39 is made of TPU. The material supports the high wear resistance and good static and dynamic sealing performance of the profile.
When assessing the material, temperature, pressure, sliding speed and the applied medium must be considered together. Any approvals and certificates depend on the specific compound.
The SNI39 is suitable for hydraulic oils in accordance with DIN 51524 parts 1-3 and for lubricating oils. The seal can also be used with mineral oil-based lubricating greases.
The flame-retardant hydraulic fluids HFA, HFB and HFC according to VCMA 24317 are also specified. During selection, verify that the applied medium falls within the stated compatibility of the compound.
The SNI39 has an operating temperature range from -40 to +100 °C. The maximum sliding speed is 0.5 m/s and the maximum permissible pressure is 40 MPa.
These operating limits are maximum values and may not all be reached simultaneously. The suitability of the seal should therefore be assessed using the complete combination of temperature, pressure, sliding speed, medium and installation conditions.
Consult the valid material data sheet for current information about approvals and certificates. This information depends on the specific compound and therefore cannot be listed exhaustively for every version.
The cylinder housing and piston rod must be provided with chamfers to prevent damage to the rod seal. The length and angle of these installation chamfers must correspond to the installation-space drawing.
The groove flanks require a surface roughness of Ra ≤ 3 µm. The groove base must have a surface roughness of Ra ≤ 1.8 µm. The mating surface of the piston rod requires a surface roughness of Ra ≤ 0.4 µm.
According to the data sheet, the SNI39 can be installed in an axially open or closed, cut groove. Semi-open or closed installation spaces are also possible for a limited dimensional range. The selected configuration must correspond to the dimensions and associated installation drawing.
Deburr sharp edges and provide smooth chamfers and radii. Clean the installation space carefully before installation and remove dust, dirt, metal chips and other contaminants.
Do not pull the seal over sharp edges, threaded ends or recesses such as feather key grooves. Use a mounting sleeve where necessary to protect the profile. Oil or grease the piston rod before installation.
Store the SNI39 at a temperature below 25 °C. Avoid direct sources of heat, direct sunlight and condensation in the storage area.
The seal must not be exposed to ozone or ionising radiation. The storage recommendations are based on the revision of ISO 2230 dated 16 September 1992.
First check the required piston rod and groove dimensions. Then align the installation direction with the one-sided pressure load and determine which installation-space configuration is suitable for the relevant size.
Also assess the temperature range from -40 to +100 °C, the maximum sliding speed of 0.5 m/s and the maximum pressure of 40 MPa. These maximum values may not all be reached simultaneously. Check the medium, surface requirements, installation conditions, low recirculation capacity and any compound-dependent approvals.
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