How to determine the merits of the rubber oil seal

Rubber oil seals qualified products should meet the following conditions:
1, the oil seal surface is smooth, no defect, no distortion.
2 oil seal end face of the code identifies the need to match;
3, the outer edge of the oil seal skeleton should be upright, flat end face, deformed hand it can be restored to its original shape, let go.
4, with the skeleton of the shape of the rubber oil seals upright, circular end faces, placed on a glass plate should fit with the glass surface, no flexing phenomenon.
5, the entire circumference of the oil seal on the edge shape, thickness should be consistent with matching pieces of the test equipment, the cutting edge in supporting neck should be closely fit.
6, with a spring rubber oil seals, springs should be no rust, no distortion, and more firmly stuck in the spring slot. 50 * 72 * 12 rubber oil seals, for example. Oil seal from 1m height free fall, down 5 times each spring fell off more than once, then you can think with a good spring and oil seal.
Distributor bulk buy rubber oil seals can first take samples for immersion test, measuring the rate of change of the quality. For example, the oil seal with the transformer oil at a temperature of (70 ± 5) degrees in the 25th after 24h immersion, its rate of mass change should be in the range of 3% -5%.