Double acting Piston Seal Type D
Type D is Metseals oldest seal with the highest sales. It is intended for sealing cylinders with double acting linear movements. It has the highest maximum contact pressure of all Metseals seal types, but never the less insignificant wear characteristics. It is most suited for applications where it can work as a double acting and not primarily as a single seal. After the wearing in period as a double acting sealing, the Type D will demonstrate a sealing surface corresponding to half the width of the seal. Therefore, it has a friction level that is higher than for example type SBF. Type D has, in the same direction of pressure, the ability to form hydrokinetic film in only in one direction of movement only. That means that above a certain speed, the friction will be lower in one of the direction of movement.
Type D is available for all diameters suited to cylinder diameters with H8 tolerance. For Ø80 and over, it is also variable for H10-tolerance.
Single-acting piston seal type SBF
Type SBF is a single acting pressure balanced piston seal that is fatigue free. In the first hand it is intended as a piston seal in high torque motors for industrial applications where a life span of 30,000 to 50,000 hours in continuous use at 35 MPa is required. In addition, the SBF type also possesses the ability that, even with abnormal wearing, it will not suffer fatigue and break. Such high wears can only take place if for some reason abrasive particles of silicon carbide and aluminum oxide get into the system. From the beginning the Type SBF was developed for one of Metseals most demanding customers. As the result was very good can we recommend it to all slowly operating hydraulic motors for example wheel motors for mobile applications. Type SBF is suited for H6 tolerance. It is not pre-stressed as Metseals other seal types but has an initial clearance between zero and the maximum deviation of for tolerance H6. At a certain relatively low pressure above zero, the seal will close. The Type SBF has an extreme low contact pressure and an extremely long life span. In case of abnormal high wear of the seal, it will gradually change to be of non-contact type, but with a very low sealing gap governed by the pressure. This allows very low leakage with negligible influence on the volumetric efficiency of the motor. Type SBF does not use an O-ring and can be with the same sealing groove as type D, but can also have shallower groove.