Aalborg XFM Digital - Manual (Page 24)

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6.2 Flow Path Cleaning
Before attempting any disassembly of the unit for cleaning, try inspecting the flow
paths by looking into the inlet and outlet ends of the meter for any debris that may
be clogging the flow through the meter. Remove debris as necessary. If the flow
path is clogged, proceed with steps below.
Do not attempt to disassemble the sensor. If blockage of the sensor tube is not alle-
viated by flushing through with cleaning fluids, please return meter for servicing.
6.2.1 Restrictor Flow Element (RFE)
The Restrictor Flow Element (RFE) is a precision flow divider inside the trans-
ducer which splits the inlet gas flow by a preset amount to the sensor and main
flow paths. The particular RFE used in a given Mass Flow Meter depends on the
gas and flow range of the instrument.
6.2.2 XFM 17 Models
Unscrew the inlet compression fitting of meter. Note that the Restrictor Flow
Element (RFE) is connected to the inlet fitting. 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 cleaning, allow time for drying.
Inspect the flow path inside the transducer for any visible signs of contaminant. If
necessary, flush the flow path through with alcohol. Thoroughly dry the flow paths
by flowing clean dry gas through.
Carefully re-install the RFE and inlet fitting avoiding any twisting and deforming to
the RFE. Be sure that no dust has collected on the O-ring seal.
6.2.3 XFM 37/47 Models
Unscrew the four socket head cap screws (two 10-24 and two 6-32) at the inlet
side of the meter. This will release the short square block containing the inlet com-
pression fitting.
CAUTION: DISASSEMBLY MAY COMPROMISE CURRENT CALIBRATION.
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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 (7.2.3).
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