Graco ProMix 2KS Operation page 46

System Operation
Balancing A/B Pressure
If component B pressure is too high, it will push the com-
ponent A stream aside during B injection. The valve will
not open long enough, causing a High Ratio alarm.
If component B pressure is too low, it will not be injected
in sufficient volume. The valve will stay open too long,
causing a Low Ratio alarm.
Selecting the correct component B restrictor size and
balancing the A/B pressures will keep the system in the
proper pressure range, resulting in a consistent mix
ratio.
F . 57 shows the A to B pressure balance, read at the
IG
proportioner inlet. It is recommended that the compo-
nent B pressure be 5-15% higher than the component A
pressure to keep the system in the control range, hold
the proper mix ratio, and obtain properly mixed material.
If pressures are not balanced ("B Pressure Too High" or
"B Pressure Too Low"), it may not be possible to hold the
desired mix ratio. The system will generate an off ratio
alarm and stop operation.
NOTE: In multi-flow rate systems, it is recommended
that you set up the system to run properly at the highest
flow rate, to ensure adequate fluid supply across the
flow rate range.
In dynamic dosing, component A dose valve is con-
stantly on. Component B dose valve will cycle on and
off; one cycle every 0.5 – 1.0 seconds indicates proper
balance.
Monitor system performance by watching the EasyKey
display for warning messages which provide information
on system performance, and adjust pressures accord-
ingly. See Table 6 on page 47.
F . 56. B Pressure Too Low, displayed on EasyKey
IG
46
B Pressure
Too High
A Pressure
F . 57. A/B Control Range with Properly Sized
IG
Restrictor
B Pressure
Too High
A Pressure
NOTE: If the restrictor is too small, it may be
necessary to supply more differential pressure
than is available in your system.
F . 58. A/B Control Range with Too Large a
IG
Restrictor
B Pressure
Too Low
B Pressure
B Pressure
Too Low
B Pressure
312776B