7. Dialysate Preparation
On the suction stroke, the piston is pulled toward the stepper motor
drawing in concentrate. The piston is also rotating as it draws in
the concentrate. When it reaches a null point (the end-of-stroke),
the flow into the pump is stopped.
The piston continues to rotate until it opens to an outlet into the
Instrument. It then pumps concentrate out during the discharge
stroke as the piston is pushed away from the stepper motor. The
pump continues to rotate and again reaches a null point (end-of-
stroke). Then the rotation starts over again.
Two upper ports in the pump are used for water to lubricate the
piston. See Figure 7-5.
Both concentrate pumps are protected from particles by a 74-
micron filter.
During rinse, the concentrate motor operates at the same ratio as
the concentrate formulation to flush concentrate or disinfectant
from the concentrate pump chamber. The “A” concentrate line
must be attached to the “A” rinse fitting to receive rinse water
from this port.
For disinfecting, the “A” concentrate line is attached to the
disinfectant rinse fitting and the disinfect line is connected to the
disinfect bottle, therefore the “A” concentrate pump delivers
disinfectant to the fluid path.
157-1278-914 Rev A 7-9
January 2004
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