Graco 24M398, Instructions Manual

Page: 24 / 38

Volume Balancing the Mix Manifold
24 3A0590R
Volume Balancing the Mix Manifold
If the mix manifold is mounted on the machine, you do
not need to adjust the restrictor (F). Leave open two
turns minimum.
When the manifold is remote, two things must be done
to reduce momentary ratio errors that can occur due to
the compressible nature of paint hoses.
• Adjust Restriction
• Select correct sized hoses
Adjust Restriction at the Mix
Manifold
The B side restrictor (F) in the mix manifold is only used
when the mix manifold is positioned remote from the
machine with a short mix hose to the spray gun.
The restrictor (F) controls “lead/lag” ratio errors of the A
and B flow into the static mixer tubes. These errors
occur momentarily when the gun opens. The error is
caused by differences in viscosity, volume, and hose
expansion between the proportioner outlets and the mix
point.
Adjust the restrictor (F) stem clockwise while spraying
until you see a slight rise in the B side pressure gauge.
The point where the pressure starts to rise is a good
adjustment setting.
restrictor stem
Unless you are dispensing directly out of the mix
manifold and mixer, this an approximate adjustment.
For low viscosity fluids, an optional 40 mesh screen can
be installed in the mix manifold, in front of the restrictor.
This keeps the carbide tapered stem and seat from
plugging.
For high viscosity 1:1 applications, the entire restrictor
assembly and seat can be removed and replaced by a
high pressure 3/4 npt plug.
Hose Selection for Feeding A
Remote Mix Manifold
The mix manifold can be removed from the machine and
used closer to the spray gun to minimize the mixed
material in the hoses and reduce flush solvent with the
following restrictions.
• Only one mix manifold can be used on a
proportioner.
• Splitting flow to two or more guns can only be done
after the two fluids are mixed.
This applies to applications that are not 1:1 ratio, and
don’t have near balanced viscosities.
Balance the hoses inside area sizes in relation to the
mix ratio by volume. This is most important when the
mix manifold gets close to the spray gun.
The proportioner will put out the two materials in the
exact ratio by volume. If the hose sizes are not balanced
to the ratio, one hose will always come up to pressure
first. This ratio error at the mix point can occur anytime
that there is a change in pressure. Balance the hose
sizes by effective area, not by inside diameter.
Area = (3.1416 * radius
2
) or see Table 1.
Table 1: Volume Ratio of “A” to “B” Hose
For balancing purposes, it is always assumed that
the A side is the high volume side.
Example:
At a 4:1 mix ratio, a 1/2 in. ID resin hose and
a 1/4 in. ID hardener hose matches the 4:1 volume ratio.
Mix Ratio
Hose Selection
“A” x “B” Volume Ratio
1:1 1/2 x 1/2 1.0:1
3/8 x 3/8
1.5:1, 2:1 1/2 x 3/8 1.78:1
2:1 3/8 x 1/4 2.25:1
2.5:1 3/8 x 1/4 2.25:1
3:1
4:1
1/2 x 1/4 4.0:1