Gambro AK 95, Service Manual

Page: 28 / 247

AK 95 / AK 95 S Service Manual
HCEN 9134 Rev. 10.2005
Technical Description
2:7
Treatment
Fluid part:
This technical description of the AK 95 S is
based on the flow diagram on page 2:5.
Water is taken in through a pressure regulator,
PR 1 , and a heat exchanger , before entering
the AK 95 S fluid-unit. The pressure regulator is
set to approximately 600 mmHg, measured after
the heat exchanger.
The inlet pressure switch, INPS , detects too
low pressure. If the inlet pressure is too low (less
than +99 mmHg), the inlet valve,
INVA , is
closed, the heater is switched off and the
AK 95 S enters the fluid bypass mode. An atten-
tion will be given when the pressure is too low.
The inlet pressure should be constant, but
normally there are small fluctuations. The
second pressure regulator,
PR 2 , is used to
ensure a constant pressure, approximately
+130 mmHg. Normaly during treatment INVA
is open.
The main function of the temperature transduc-
ers in the AK 95 S is to measure the dialysis
fluid temperature and control the heat regula-
tion. The regulating temperature transducer,
T
Reg
, is located after the heater.
The T
Reg
transducer is used in the fast tempera-
ture control loop. The set value for the loop is the
set value entered by the user adjusted for the
measured temperature drop to the conductivity
cell B.
The temperature drop is calculated when the
temperature measured at cond.cell B is stable.
The temperature considers to be stable when it
has been in a window of ± 0.25 °C for one minute
or more.
The function of the flow switch is to sense if
there is fluid flow or not through the heater.
If the flow switch does not detect flow, the
heater will be switched off in order to protect the
heater from overheating.
There is a temperature transducer in each
conductivity cell, used for compensating the
conductivity calculation.