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Tandem Seal, outside sealing
The Hunger TDA tandem seal for outside sealing is used to seal pistons, plungers and accumulators. It can be applied with mineral oils and in modified form also with water base fluids, fire rsistant fluids, and compressed air. The TDA seal consists of 2 parts, an elastic ring of PUR with a sealing lip and a slide ring of abrasion resistant PTFE-Bronze-compound with a sealing edge. Prior to fitting, the sealing lip protrudes beyond the nominal diameter of the seal and is pressed against the cylinder wall after fitting. Thus effective sealing is provided even at zero pressure. The slide ring is surrounded by the elastomer sealing ring and moves axially in direct contact with the inside of the tube. With increasing pressure and compression of the sealing ring, it is the slide ring which is predominantly pressed against the inside of the cylinder. The slide ring sealing edge produces an annular cavity where any seepage oil that has passed the elastomer lip is collected.
The seepage oil is held back by the sealing edge, such that the emerging piston rod remains dry. During the return stroke, the collected oil is forced back into the cylinder. The outer sealing surface of the TDA mainly comprises the external slide ring which has excellent sliding properties. When combined with a surface finish of Ra 0.3- 0.5 µm on the cylinder tube, minimum friction levels are achieved with highly efficient sealing and long service life. There is no stiction, no unacceptable heat generation, and above all no stick-slip effect.
