SCREW-DOWN STOP VALVES
A valve in which the disk is lifted from and lowered on to the body seat by a stem whose axis is perpen-icular to the face of the body seat. Screw-down stop valves may be:’—
a. Inside screw Where the actuating thread of the stem is engaged within the bonnet.
b. Outside screw Where the actuating thread of the stem is exterior to the bonnet.
TYPES OF SCREW-DOWN STOP VALVE
Globe valve A valve having a body in which the ends are in line with each other and in which the axis of the stem is at right angles to that of the body ends.
Oblique valve A valve having generally a spherical body in which the body ends are in line with each other and in which the axis of the stem is oblique to that of the body ends.
Angle valve A valve having generally a spherical body in which the body ends are at right angles to each other and in which the axis of the stem is in line with that of one body end.
Needle valve A form of screw-down stop valve, generally restricted to small sizes, which may have the body ends in line or at right angles with each other or may be of the oblique type. The disk is in the form of a needle point.
Other types These are usual ly described by reference to the disposition of the body ends in relation to each other, such as elbow valves, three-way or Tee valves. The component parts of these types of valves are identical with those for the types referred to above.