Pressure Balancing Using The Orifice Valve Assemblies - Graco HFRL Setup And Operation Manual

Operation
Pressure Balancing Using the
Orifice Valve Assemblies
The MD2 valve for HFRL and HFRS systems is pro-
vided with orifice valve blocks on both of the inlet ports.
The orifice blocks are assembled at the factory with no
orifices installed. An orifice kit is provided with a range
of orifice sizes to balance pressures. The orifice size is
etched on the side of the orifice body and there are two
orifices provided in each size. One of the orifices in
each size will be stamped on the hex end with an "A".
Use the orifices stamped with the "A" in the RED side
orifice block. The orifices with no letter etched on the
hex end are to be used on the BLUE side.
A ORIFICE
LOCATION
ADJUSTMENT
Orifices can be installed in one or both orifice blocks as
a tool to increase the outlet pressure in the correspond-
ing material hose. The orifice valves are equipped with
a needle valve that can be adjusted with the provided
allen wrench.
42
B ORIFICE
SIZE
1. Before installing, insert the allen wrench into the
hex end of the orifice valve to adjust the needle
position.
2. Verify the needle valve is in the fully open position
by turning counter-clockwise until rotation stops.
After installation, the needle valve can be turned
clockwise to further increase pressure.
NOTE: Always run the material first at the desired flow
rate with no orifice valves installed to evaluate the dis-
pense pressures generated for each material.
NOTE: Appropriate orifice valve selection is essentially
done by trial. The following can help determine if it is
necessary to increase the outlet pressure and help
select an orifice.
a. The outlet pressure for heavy-paste viscosity
materials should be at least 2 times higher than
the z-pump feed pressure (as determined by
the material pressure regulator). Max outlet
pressure is equal to 3000 psi (21 MPa, 207 bar)
and the feed pressure should be below 1500
psi (10 MPa, 103 bar).
b. The outlet pressure for lower viscosity-flowable
materials should be 3-4 times higher than the
z-pump feed pressure. Dispense pressures for
this viscosity range should be in the 750 psi
(5 MPa, 52 bar) to 1000 psi (7 MPa, 69 bar)
range.
c. The outlet pressures of both material hoses
should be as close as possible to each other
and within a suggested range of 10%. See
System Screen 3, page 66.
3. Install orifice valves only if the outlet pressure
needs to be increased. See Maintenance starting
on page 44 for details.
4. If rule a and b above are met by both materials,
install an orifice valve in the lower pressure side,
only if required to balance the outlet pressures.
5. If neither rule a or rule above are met by either
material, install an orifice valve in both orifice
blocks to raise the pressure and allow pressure bal-
ancing.
3A2175Z