Graco 25R128, Setup - Operation - Repair

Page: 45 / 92

Operation
3A7526B 45
Ratio Check Procedure
Perform the Ratio Check Procedure at startup and after
rebuild.
1. Weigh six small cups and label as indicated. Record
weights.
2. Remove Static Mixer Package (AH) from MD2
Dispense Valve (AE).
3. Install the ratio check nozzle onto the MD2
Dispense Valve (AE).
4. Dispense into a waste container to prime the ratio
check nozzle.
5. Place cups as indicated under ratio check nozzle
and cycle the machine one time.
6. Repeat until all three sets of cups have been used.
7. Re-weigh all six cups and record weights.
8. Subtract weight of empty cups from weight of filled
cups to get material weights.
9. Complete ratio calculations.
The following formula can be used when the density or
specific gravity of both the “A” and “B” components are
known and only one of the ratios:
Example:
A material has a weight ratio of 10:1, the “A” material
has a specific gravity of 1.20 and the “B” material has a
specific gravity of 1.00. To calculate volume ratio:
Shutdown
1. Remove Static Mixer Package (AH) from MD2 Dis-
pense Valve (AE).
2. Place a waste container below the MD2 Dispense
Valve (AE) and activate a small shot to flush mixed
material out of the valve.
3. Perform the Pressure Relief Procedure on page
46.
4. Turn off the system power.
5. Wipe the Nose Piece (AJ) with a clean rag, being
careful to avoid contact between dispense
materials.
6. Install the PTFE night cap (1:1 valves - 15K652)
and retaining nut (15K688) on the MD2 Dispense
Valve (AE).
Weight Ratio
=
Specific Gravity
Volume Ratio Specific Gravity
10:1
=
1.20
Volume Ratio 1.00
Volume Ratio =
10
1.20
Volume Ratio = 8.33:1