8. Ultrafiltration
removed from the rinse block only during Prime and Dialysis
Modes. Otherwise an alarm is triggered.
The dialyzer is the source of the ultrafiltrate by allowing the flow
of fluid from the patient into the Instrument through the dialyzer
membrane.
8.3.9 Particle Filter ("Pre" Dialysate Pressure Pump)
This filter traps particulate matter larger than 150 microns
upstream of the dialysate pressure pump. Particulate matter in the
flow equalizer and UF flow meter can cause ultrafiltration errors.
The service life of the particle filters depends on the rate at which
material collects on the filter screens, increasing the filter pressure
drop. Ultimately the performance of the Instrument may be
affected.
If filter clogging is due to precipitation of dialysate in the fluid
path, the filters must be replaced as part of the fluid path cleaning
process.
Refer to Section 16, Preventive Maintenance, for a recommended
routine maintenance schedule.
8.3.10 Dialysate Pressure Pump Recirculation Loop
The dialysate pressure pump recirculation loop is located
downstream from the dialyzer. It pumps spent dialysate from the
dialyzer to the flow equalizer. It also helps equalize the pressure
differences in the compartments of the flow equalizer. A third
function is to generate the pressure necessary to fill the UF flow
meter. This recirculation loop includes:
• dialysate pressure pump (DP pump)
• UF removal regulator
• UF flow meter
• UF drain line connector (sample port)
• input pressure equalizer (refer to Section 8.3.4).
8.3.10.1 Dialysate Pressure Pump
The dialysate pressure pump is located in the dialysate flow path.
It operates in a loop that allows it to circulate fluid at a different
but constant speed depending on each of the dialysate flow rates.
It runs at about 1500 mL/min, when the dialysate flow is set to 500
mL/min. This does not affect the rate of fluid flow past the
dialyzer. The DP pump circulates fluid through the dialysate
157-1278-915 Rev A 8-15
January 2004
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