| 摘要 |
For the purpose of detecting cracks, cavities or pores in a lead covering moulded onto a copper conductor, the lead-covered conductor is lowered into a wet-type isostatic press in which the pressure medium consists of a penetration liquid, wherein the press is placed under pressure so as to force the penetration liquid into the defects. Surface liquid is removed from the pressure-treated conductor and the defects are indicated by the penetration liquid which seeps or "sweats" from the conductor. This indication of defects may be amplified, by applying a development liquid to the dry outer surfaces of the conductor. The pressure of the penetration liquid is preferably higher than the yield point of the protective covering, and is at least about 2000 bars in the case of lead protective coverings. |
