Stop-valve.
1. (
Hydraulics.) A valve which closes a pipe against the passage of fluid.
The large valve used in water-mains is known by this name.
It is usually a disk which occupies a chamber above the pipe when the passage-way through the latter is open, and is driven down by a screw to
stop the aperture, its face being pressed against the seat by the contact of the rear with wedging abutments.
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The smaller device, with a spigot, is called a stop-cock (which see). See also three-way valve.
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Stop-valve. |
In
Kearney's stop-valve for water-mains (
Fig. 5901), the casing
a has a circular opening for the ends of the supplypipe
b b. c is the valve, which is raised or lowered by means of the screw
d. When open, it slides into the chamber at the bottom of the casing, leaving the water-way clear; in order to open it the worm
e is thrown into gear with the worm-wheel
f, and when it is started the worm may be thrown out of gear and power applied directly to the screw.
This lessens the labor of opening and closing the valve under great pressure, and the opening being effected very gradually at first, avoids the danger of bursting the pipe by sudden pressure.
g is a cock for drawing off or forcing out any foreign matters which may collect at the bottom of the valvecasing.
Fig. 5902 is the
McClelland valve.
It is a hollow cone, the hollow being of a diameter greater than the bore of the pipes.
The body of the valve is cast upon and within bronze rings, which serve for bearings.
Fig. 5903,
A, B. The gate when raised is received in a box above the pipe-joint
b. In
A, the screw which operates the gate is turned by a hand-wheel, and an indicator
a shows its position in the pipe.
B has a double gate, shown at
C, with one of the faces removed; when the gate is shut down, wedges within the casing
b enter between the two wedges
c c′, forcing the two faces against their proper bearing surfaces, to prevent leakage.
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Stop-valve. |
Fig. 5904,
D, E. A perspective and section of a small stop-valve having a wedge-shaped valve, whose form renders it self-packing.
2. (
Steam-engineering.) Stop-valves, or
communi-
cation-valves, are fitted in the steam-pipes where they leave the several boilers, and in the connecting-pipes between the boilers, in such a manner that any boiler or boilers may be shut off from the others, and from the engines.
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Stop-valve for steam-enginery. |
In
Fig. 5905, it is designed that the bore of the pipe, chamber, and opening in the valve-seat shall be the same.
