| 摘要 |
<p>A vent valve having a pilot-valve, for oil-tanker storage tanks, comprises a flared casing offering maximum flow section when the associated obturator member is in the open position, within the casing and beneath a seat terminating the same, the seat having a diameter at least equal to that of the inlet conduit of the casing and being surmounted by a flame-guard and a discharge nozzle both of which are external to the casing. The vent valve may comprise a main expandable valve with a rigid inner end-surface which is profiled by an outwardly directed border the end section of which is fixedly restrained level with the widest part of the casing and is joined by a deformable, flexible and annular wall to a movable upper or outer end-surface having a central profiled extension, which end-surface is provided with a lining which forms a seal upon contacting the sealing seat.</p> |
