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Keckley Float Valves
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Keckley
Float
Valves
 Application/Service: The No. 7 and 77
pilot controlled float valves are recommended when tight
closing is essential. They are commonly used to maintain
a water level in an open tank. They are best suited for
clean liquids not injurious to neoprene, leather or brass
parts. Standard design temperature is 125' F. For higher
temperatures up to 3500 F, the neoprene disc in the No. 7
or neoprene disc and leather cup in the No. 77 are
replaced by teflon parts.
Construction: Referring to the sectional views
on page 8, the inner valve consists of a hollow bronze
piston, somewhat larger in diameter than the seat bore,
and carrying the disc holder. The composition disc may be
replaced when worn. The soft disc will accommodate itself
to grit and wear and still close tight where a metal to
metal construction would leak.
The piston slides in a stationary bronze cylinder
attached to the cover or body. The pilot port is opened
and closed by the end of the stem which is moved by the
lever. A pin through the stem at its lower end permits
the inner valve to be lifted by the stem.
The guide yoke, with the lever and
float, can be turned and secured at any angle. The angle
and length of float rod can be adjusted at the rosette.
Operation: In the No. 7
valve, made in sizes 2 inches and smaller, water from the
inlet enters the space above the piston through a small
hole in the piston head. While the pilot port is open,
this water escape freely through the hollow valve post to
the outlet. The excess pressure under the piston, in
relation to the pressure above it, and the weight of the
float hold the valve open.
On closing the pilot port, the water pressure above
the piston quickly rises to equal and balance the inlet
pressure under the piston. Thereupon the inlet pressure
above the disc holder closes the valve. No leather cup is
required.
The disc closes in the direction of the flow through
the No. 7 valve. In the larger valves and for the higher
pressures, the "pull" of the water in passing
through the valve seat may cause the valve to close
suddenly from a nearly closed position. For this reason,
this valve is not made in sizes above 2 inches.
In the No. 77 valve, made in sizes 2
inches and larger, the inlet pressure is under the disc.
Water enters the chamber above the piston through the
strainer and the central and diagonal passages. If the
pilot port is open, this water escapes freely to the
valve outlet, so that the inlet pressure under the disc
opens the valve. When the pilot port is closed, the water
pressure above the piston quickly rises to equal the
inlet pressure under the disc and, due to the larger
piston area, the inner valve is moved toward the seat.
The disc closes against the inlet pressure and sudden
closing cannot occur in the No. 77. However, this valve
requires the piston to be fitted with a leather cup, the
friction of which may cause sluggishness on low inlet
pressures.
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