| 摘要 |
<p>A two-stage, non-flowing pilot valve operates a main relief valve of substantially greater capacity. The first stage of the pilot comprises a valve having a closure member 14 which cooperates with a seat assembly 28, 29 to define a restricted flow passage 38, 39 over at least a portion of the stroke of the closure member. In a preferred embodiment the main valve is mounted directly onto a pressure vessel which is to be vented at a predetermined pressure. The pilot is preferably mounted closely adjacent to the main valve for operating communication therewith. A ball selector provides means for conveniently connecting to a field testing either the pilot or the entire valve. <IMAGE></p> |
