| 摘要 |
<p>A control valve includes a valve body 112, a valve stem, and a control element. The valve body receives the stem and includes a packing 128 box housing a packing set 130. A packing follower 132 includes a bore 133 sized to receive the stem and includes an upper portion 136, a lower portion 138, and a bearing surface 140, the lower portion sized to extend into the valve bonnet to engage the packing set to apply a first compressive force to the packing set, the upper portion including threads 144 and having an upper counterbore 146 housing a secondary seal ring 166. A nut 148 operatively engages the threads of the upper portion of the packing follower, the nut positioned to apply a second compressive force to the secondary seal ring, and a spring 170 is positioned between the packing flange 160 and the bearing surface 140 of the packing follower, wherein the first compressive force is independent of the second compressive force.</p> |
