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The KNA28 is a single-acting seal for sealing pistons in mobile hydraulic applications. The profile is designed for applications in which hydraulic pressure is applied to the seal from one side.
The asymmetrical piston seal is made from TPU and has a tight fit on the inside diameter. The profile shape supports static sealing at standstill and dynamic sealing while the piston is moving.
The KNA28 is made entirely from TPU. The asymmetrical profile has an external main sealing lip and a recessed sealing lip.
The seal has a tight fit on the inside diameter. According to the data sheet, preloading of the profile provides static tightness before hydraulic pressure builds up.
The KNA28 is a single-acting piston seal and is therefore designed for a one-sided pressure load. Its asymmetrical construction makes the correct installation direction important.
The external main sealing lip must be positioned correctly in relation to the pressure side. During selection and installation, the side from which hydraulic pressure builds up must therefore be established.
The preload of the KNA28 provides static tightness. The profile therefore supports sealing even before full hydraulic pressure is present.
According to the data sheet, the sealing effect increases as pressure builds up. The combination of preload and pressure support therefore determines the operation of the piston seal.
The KNA28 is intended for mobile hydraulics and, according to the data sheet, has high wear resistance. The profile has also been proven under extreme conditions.
Its reliable design has a broad application spectrum and is suitable for moderately demanding applications in general industry. Suitability remains dependent on the complete combination of pressure, temperature, speed, medium and installation conditions.
The KNA28 hydraulic piston seal is designed for mobile hydraulic applications. Its asymmetrical construction, static preload and pressure-supported sealing effect are the main functional characteristics of the profile.
The stated product advantages include proven performance under extreme conditions, high wear resistance and a good price-performance ratio. The KNA28 is manufactured by certified external suppliers.
The KNA28 is made entirely from TPU. When selecting the seal, the suitability of this material must be assessed in combination with the medium, temperature, pressure, sliding speed and conditions within the installation space.
For current information about material properties, approvals and certificates, consult the valid material data sheet for the respective compound.
The KNA28 is suitable for hydraulic oils according to DIN 51524 part 1-3 and for lubricating oils. The piston seal can also be used with lubricating greases based on mineral oils.
The specified media also include the flame-retardant hydraulic fluids HFA, HFB and HFC according to VCMA 24317. When selecting the seal, verify that the medium falls within the stated resistance of the TPU compound.
The KNA28 hydraulic piston seal has a temperature range of -40 to +100 °C. Its maximum sliding speed is 0,5 m/s and the maximum permitted pressure is 40 MPa.
These application limits are maximum values and may not all be reached at the same time. The suitability of the seal must therefore be assessed using the complete combination of temperature, pressure, sliding speed, medium and installation conditions.
For current information about approvals and certificates, consult the material data sheet valid for the respective material. This information depends on the specific compound and cannot be listed exhaustively in the product data sheet.
The cylinder housing and piston must be chamfered to prevent damage to the seal. The length and angle of these installation chamfers must correspond to the installation-space drawing.
The surface roughness of the groove flanks must be Ra ≤ 3 µm. The groove base must have a surface roughness of Ra ≤ 1,8 µm. A surface roughness of Ra ≤ 0,4 µm applies to the mating surface.
An axially accessible installation space is required for small diameters. For inside diameters larger than 25 mm, the KNA28 can be installed in a cut groove.
Carefully clean the installation space before assembly and remove dust, dirt, metal chips and other contaminants. Do not pull the seal over sharp edges, threaded ends or cavities such as feather key grooves. Use a mounting sleeve if necessary.
Heating the seal in oil to 80 °C makes the TPU more elastic and simplifies installation. Grease the piston seal before fitting the cylinder.
The KNA28 must be stored at a temperature below 25 °C. Avoid direct heat sources, direct sunlight and condensation in the storage room. Do not expose the seal to ozone or ionizing radiation.
The storage recommendations are based on the revision of ISO 2230 dated 16.09.1992. Observe all specified environmental conditions during storage.
When selecting a KNA28 hydraulic piston seal, first check the required dimensions, available installation space and direction of the one-sided pressure load. Match the installation direction of the asymmetrical profile to the pressure side.
Then assess the temperature range of -40 to +100 °C, maximum sliding speed of 0,5 m/s and maximum pressure of 40 MPa. These values may not all be reached at the same time. Check the medium, surface requirements, installation conditions and any compound-dependent approvals as well.
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