Aalborg GFC - Manual (Page 17)

6.2 Flow Path Cleaning
Inspect visually the flow paths at the inlet and outlet ends of the meter for any
debris that may be clogging the flow through the meter. Remove debris carefully
using tweezers and blowing low pressure clean air or Nitrogen from the inlet side.
If the flow path is not unclogged, please return meter to Aalborg
7 for servicing.
Do not attempt to disassemble the sensor.
Disassembly will invalidate calibration.
6.2.1 Cleaning the Inlet Filter Screen in GFC17 Models
Unscrew the inlet compression fitting of meter. Note that the Restrictor Flow
Element (RFE) is connected to the inlet fitting.
The Restrictor Flow Element (RFE) is a precision flow divider inside the trans-
ducer, which splits the inlet gas flow by a fixed ratio to the sensor and main flow
paths. The particular RFE used in a given Mass Flow Controller depends on the
gas and flow range of the instrument.
Carefully disassemble the RFE from the inlet connection. The 50 micron filter
screen will now become visible. Push the screen out through the inlet fitting. Clean
or replace each of the removed parts as necessary. If alcohol is used for clean-
ing, allow time for drying before re-assembling.
Carefully re-install the RFE and inlet fitting, avoiding any twisting and deforming
the RFE. Be sure that no dust has collected on the O-ring seal.
Note: Over tightening will deform and render the RFE defective.
It is advisable that at least one calibration point be checked after re installing the
inlet fitting - see section (7).
IT IS NOT RECOMMENDED TO ATTEMPT TO DISASSEMBLE,
OR REPAIR GFC37, GFC47, GFC57, GFC67 AND GFC77 MODELS.
DISASSEMBLY NECESSITATES RE-CALIBRATION.
6.2.2 Valve Maintenance for GFC17/37/47 Models
The solenoid valve consists of 316 and 416 stainless steel, and VITON
7 (or
optional EPR or KALREZ
7) O-rings and seal materials. No regular maintenance
is required except for periodic cleaning.
It is advisable that at least one calibration point be checked after re-installing the
inlet fitting - see section (7).
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