HCEN12630 Revision 07.2015
Program version 1.xx
AK 98™ Dialysis Machine - Technical description 77
3.3.3.5.4 Adjustable dialysis fluid flow
The fluid flow in the AK 98 dialysis machine can be adjusted between 300 mL/min to
700 mL/min in 20 mL/min steps.
The control is done with an adjustable valve (DRVA) driven by a stepper motor with an
aspheric axis connected in parallel with a 200mL/min restrictor.
To make sure that the flow is stable, the machine will postpone an adjustment of the
flow 120 seconds before and 30 seconds after taration.
If a flow deviation of 30 mL/min or more (compared to the set flow) is detected
continuously for 3 minutes, an automatic adjustment of the flow will be triggered. The
automatic adjustment can be activated once after each self calibration of the UF cell
also called taration. The time needed to activate the automatic adjustment is only
counted when the dialysis fluid is considered to be stable.
3.3.3.5.5 Conductivity guard
The third conductivity cell, conductivity cell P, right after degassing, is used by the
protective system as a guard. Like the two cells used by the control system, it has its
own temperature transducer for temperature compensation of the conductivity
measurement.
The dialysis fluid is bypassed if the conductivity value differs more than ±5% from the
calculated set value and/or the temperature exceeds the limits. The low limit is 33°C
±0.5°C and the high limit is 40°C ±0.5°C.
Figure 3-17. See chapter 11: "Fluid unit - flow path".
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