User's Manual

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Determining the Ratio
Determine your system conditions
If these are your conditions – one primary pump, one
secondary pump, fluids are ready-to-spray viscosity –
set the ratio as explained under Setting the
Secondary Pump(s) on page 14.
If these are your conditions – one primary pump and
one secondary pump, fluids are NOT ready-to-spray
viscosity – the ratio must be determined after the
reducer is added to the base, as instructed in
Procedure 1.
NOTE: The addition of the reducer in the base causes
changes to the ratio. To prevent reducer evaporation,
store the base in closed containers.
NOTE: Some reducers have very little ability to lubri-
cate and may cause seals to dry out. To prolong seal
life, be sure your pump seals are compatible with the
base’s reducer. Contact your Graco distributor for the
correct seals to use.
Procedure 1: Base Is Pre-reduced
When adding reducer to the base before proportioning
with the VRHC System, determine the ratio of the
base/reducer mixture to the catalyst in order to set the
secondary pump at the correct position.
In this example, the instructions on the can say, “Mix 5
parts base to 1 part catalyst. Then reduce 3 parts of
this mixture to 1 part reducer.”
1. Add the parts of the base and catalyst to find the
parts mixture.
5 parts base
+ 1 parts catalyst
6 parts mixture
2. The next statement on the can says, “Reduce 3
parts of the mixture.” So divide the parts of the
mixture by 3 to find the parts reducer.
6 parts mixture
÷ 3 part catalyst
2 parts reducer
3. To determine the ratio of the secondary pump, add
the appropriate parts of base and reducer to find
the parts combined base/reducer.
5 parts base
+ 2 parts reducer
7 parts combined base/reducer to
1 part catalyst:
Result: The ratio of the secondary pump is 7:1.