SAFETY SHUT-OFF VALVE

摘要

Pressurized fluid is controlled by a reverse valve gate on a valve stem that extends through annular packing in a bore of a bonnet to a piston in an outer control chamber. Control fluid pressure moves the piston inward to open the valve against line pressure on the valve and/or spring pressure on the valve. In the absence of both line pressure and control pressure, the valve is closed by spring pressure. The control chamber construction permits quick replacement of control chamber seals. In the event of a fire, the control chamber seals disintegrate to release the control pressure and thus cause line pressure and/or spring pressure to close the valve. The valve stem packing may be conveniently expelled hydraulically for replacement. Various different control assemblies may be mounted interchangeably on the valve bonnet without disturbing the structure of the valve. An auxiliary control may be quickly mounted on the outer end of the control chamber to convert the shut-off valve to manual operation.