How to determine the pros and cons of the rubber seal

The rubber seal qualified products shall meet the following conditions:
1, the oil seal surface is smooth, no defect, no distortion.
Oil seal side surface of the Code identifies the need to match;
3, skeleton oil seal to the outer edge should be correct, end formation, using the hand so that deformation can be restored to its original shape, let go.
4, the shape of the rubber seal with a skeleton correct side appear before a circle, put on a glass plate should fit the glass surface, flexing phenomenon.
5, the entire circumference of the oil seal on the edge shape, the thickness should be consistent with the trial installation of the component parts, the cutting edge in supporting the neck should be tightly fitting.
6, the rubber seal with a spring, the spring should be no rust, no deformation, and more firmly stuck in the spring slot. 50 * 72 * 12 rubber seals, for example. So that the oil seal landing from 1m high degree of freedom, 5 springs per drop off down to not more than 1, so that with good springs and seal.
7, the distribution of quantities of rubber oil seal, you can take samples to do the oil immersion test, to measure the quality of the rate of change. Such as oil seal on the 25th transformer oil after 24h immersion temperature (70 ± 5) degrees, the mass change rate should be between 3% -5%.