GE AKTApure, User Manual, Page: 501 / 522

9.15 Pressure control
Introduction
By using the function Pressure control to regulate the run, the method can be run with the set flow
rate without the risk of method stop due to pressure alarm. If the pressure approaches the pressure
limit, for example if the sample has higher viscosity than the buffer, the flow rate is automatically
lowered. Pressure control is enabled in the manual instructions Pumps:System flow or Pumps:Sample
flow. The default setting for Pressure Control is Off. To enable the function, set what pressure signal
to use. It is recommended to use the pre-column pressure. The instruction Advanced:Pressure control
parameters provides the P and I factors used in the regulator and can be adjusted for different columns,
see information further down.
In the Method editor, pressure control is enabled by selecting Control the flow to avoid overpressure
in the predefined phase Method settings.
Pressure control parameters
The table below describes the factors used for pressure regulation.
Description Parameter
Proportional component in PI pressure regulation. Reduces the error between
actual and requested target pressure, but may leave a permanent error. P factor
Integrating component in PI pressure regulation. Eliminates the stationary
error from the P factor, but introduces a slight instability that may lead to os-
cillation in the pressure and the actual flow rate. Set I = 0 to disable the I factor.
As a general guide use a small I factor for high pressure columns and a large
I factor for low pressure columns, see p. 502 for more recommendations. I factor
Sets the target value for the PI pressure regulation as a percentage of the
pressure limit. If the target pressure is too close to the pressure limit there is
a risk that a short pressure spike will trigger the pressure alarm. The pressure
limit is set in the Alarm pressure instruction. The Alarm pressure used for
pressure control depends on the settings in the System flow instruction. Target value for
pressure control
If the flow rate is reduced below the value set in Pressure control min flow
rate, the method is paused and the system is set to state ALARMS AND ER-
RORS. Pressure control
min flow rate
Pressure control min flow rate can be set either as volumetric or as linear
flow. A column type must be selected before using linear flow.
ÄKTA pure User Manual 29119969 AB 501
9 Reference information
9.15 Pressure control