74 AK 98™ Dialysis Machine - Technical description
HCEN12630 Revision 07.2015
Program version 1.xx
differs more than set value (default 15%) between the two pumps. Refer to the
operator's manual for the AK 98 dialysis machine for more information.
The value that triggers the alarm or attention can be logged as FI_PumpSpeedRatio.
The value may vary between 850 and 1150 (default). The limits can be preset as a %
(default 15%) pump speed deviation.
The variable is calculated as:
(Pump speed pump A* Dose A) / (Pump speed pump B * Dose B)
The ideal value is 1. Dose = The dilution of the concentrate depending on the
concentrate preset.
3.3.3.5 Degassing/flow pump system
3.3.3.5.1 Degassing circuit
A natural process, when mixing A- and B-concentrate is the generation of free gas,
carbon dioxide. This must be removed since it will disturb both conductivity- and flow
measurements. The bypass tube from the top of the second mixing chamber diverts
the gas away from the cell but doesn’t remove it.
This takes place in a degassing circuit, consisting of a restrictor, a pump, and a
degassing chamber. By pulling the fluid through the restrictor a negative pressure of
approx. -600 mmHg is created (default -610). The gas expands to larger bubbles and
enters the chamber:
Figure 3-15. See chapter 11: "Fluid unit - flow path".
As the gas and air builds up in the chamber, the fluid level will drop until the point
where the floater drops. The gas then escapes the top of chamber since there is
suction here from the Suction pump. As a result, the floater jumps up again and seals
the outlet, until more gas forces the fluid level down.
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