| 摘要 |
PURPOSE:To enhance the sealing performance for a main steam isolator valve to be used in a nuclear power plant etc. by choosing the diameter of the poppet seat to a value larger than the height of the poppet guide and thereby increasing stability of the poppet. CONSTITUTION:Air bleeding at the under side of a cylinder actuates drop of a stem 1 and a poppet 3 will begin to sink along a circular guide 10 and a guide surface 11 at the inside of the divergent part 9 of the body 2. The poppet 3 slides on the internal surface to make contact with the point A in the valve seat 8. Even when sliding from this condition does not provide self alignment, the poppet 3 shall fall down being pushed by the stem 1 which will drop by its own weight with the point A as fulcrum, as shown by the arrow, and thereby the pilot hole 15 is blocked. Because the outer diameter of the poppet seat, D, is larger than the height of the poppet guide, L, the point C in the valve seat 8 will at this time make close contact earlier than the point B in the upper part. |
