Griffco Valve G-Series 4 - Manual (Page 2)

INTRODUCTION
GRIFFCO diaphragm back pressure valves
are used to enhance the performance of
chemical feed pumps and systems by
providing a constant discharge head
pressure. These valves also function as an
anti-siphon valve. The diaphragm is held
against the seat by the internal spring. Back
pressure is adjustable from 0 - 150 psi via the
adjustment screw. When the inlet pressure
exceeds the preset pressure the diaphragm
lifts off the seat and the chemical flows to the
injection point. After each discharge stroke of
the pump, as the pressure drops, the
diaphragm reseats itself.
GRIFFCO diaphragm pressure relief valves
are designed to protect chemical feed pumps
and systems from overpressure caused by
defective equipment or blockages in the
chemical line. The 3 port design allows
chemical to flow through the valve via an
internal chamber. When the pressure in the
chemical line exceeds the preset pressure of
the valve the diaphragm lifts off the seat and
the chemical then flows out the bottom port
back to the chemical tank. Relief pressure is
adjustable via the adjustment screw in the top
of the valve.
Back Pressure Valve:
Generally, the back pressure valve can be
installed anywhere in the discharge line,
provided there is some downstream pressure
at the dosage point. If there is no
downstream pressure the back pressure
valve should be installed at the dosage point
to prevent siphoning and drainage of the
chemical line. The valve can be installed
either vertically or horizontally. All GRIFFCO
valves are factory set at 50 psi, unless
otherwise specified. Field adjustment is
possible with the adjustment screw.
Back pressure valve performance will be
enhanced with the installation of a pulsation
dampener to smooth out the discharge /
suction cycles of the pump. Thus, the
diaphragm is free to float inside the valve
chamber, minimizing the wear on the stress
points of the diaphragm. Pulsation
dampeners will also reduce the pressure drop
across the valve by reducing peak flows.
Backpressure valves should be installed
downstream of the dampener. For most
applications diaphragm type dampeners are
required. Generally speaking 5 to 10%
dampening is sufficient. Consult with your
pump manufacturer to get his
recommendations.
Pressure Relief Valve:
Installation should be made as close to the
chemical pump discharge valve as possible,
without any equipment, especially shut-off
valves, between the valve and the pump.
Direction of flow must be across the valve,
however the side of entry is not important.
The valve can be installed either vertically or
horizontally. All GRIFFCO valves are factory
set at 50 psi, however field adjustment is
possible with the adjustment screw.
The optimum installation for the relief valve is
to vent the relief port back to the chemical
tank, or directly to a containment area.
However if this is not possible, the relief port
can be piped back into the suction side of the
pump. This will apply the suction head to the
relief port. To compensate, divide the NPSH
by 4 and add this pressure to the relief valve
setting. Do not put a shut off valve in the relief
line.