when valve hydrostatic testing ,valve's sealing property that offen said is refers to:
          In the valve hydrostatic testing process, impediment medium divulging ability of valve each seal parts which is the most important technical  performance target when the valve examine  pressure .
         during valve experiment, most pays attention  to the valve seal service spot has following three:
        in on the 1- valve opens shuts (valve core) to meet in everywhere, the valve experiment with the valve seat two packing surfaces between to be called seals the organization test, here divulging named internal leakage, is also the usually called pass is lax, it will affect the valve interruption medium ability, regarding the block valve class, the internal leakage permits. the 2 valve measures on the test sample the padding and the valve lever and packing box's coordination place; The valve chest and valve cover's attachment point, these two occupy in the valve experiment to be called the outside seal organization test, outside these two divulging named leaks, namely the flowing medium divulges from the valve to the valve outside. Outside will leak will cause the material to lose, the pollution of the environment, will be serious when also will create the accident, therefore the valve examination process Chinese and foreign seal organization's examination and the repair will also be not allow to neglect, regarding flammable explosive, virulent or will have the emission medium, outside will leak cannot permit, thus the valve examination's final standard must have the reliable valve's leak-proof quality.