Graco TI12553a Balancing A/B Pressure, Pressure Too High, Pressure Too Low, Pressure B Pressure

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.

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BPressure Too High

System Operation

BPressure Too Low

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.

A Pressure B Pressure

FIG. 97. A/B Control Range with Properly Sized Restrictor

FIG. 97 shows the A to B pressure balance, read at the 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.

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B Pressure

Too High

BPressure Too Low

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 12 on page 88.

FIG. 96. B Pressure Too Low, displayed on EasyKey

A Pressure B Pressure

NOTE: If the restrictor is too small, it may be necessary to supply more differential pressure than is available in your system.

FIG. 98. A/B Control Range with Too Large a Restrictor

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