Brooks Instrument 5861E - Manual (Page 24)

4-4
Model 5861E
Section 4 Maintenance Installation and Operation Manual
X-TMF-5861E-MFM-eng
Part Number: 541B107AAG
November, 2008
sensor assembly is defective and must be replaced. Refer to Section 4-4
for the disassembly and assembly procedures to use when replacing the
sensor.
Note: Do not attempt to disassemble the sensor.
Cleaning Procedures
Should the Model 5861E Mass Flowmeter require cleaning due to
deposition, use the following procedures:
1. Remove the unit from the system.
2. Refer to Section 4-4 to disassemble the meter.
3. Use a hemostat or tweezers to push a 0.007" dia. piano wire through the
flow sensor tube to remove any contamination. For best results push the
wire into the downstream opening of the sensor tube (end closest to the
control valve). The sensor tube can be flushed with a non-residuous
solvent (Freon TF® recommended). A hypodermic needle filled with
solvent is a convenient means to accomplish this.
4. Deposits of silicon dioxide may be removed by soaking the internal parts
in solution of 5% of hydrofluoric acid (5 parts hydrofluoric acid (HF), 95
parts water (H
2
O)) followed by Freon TF.
5. Sintered type restrictor elements should be replaced as it is not always
possible to adequately remove deposits from them. Wire mesh and
A.C.L.F.E. type restrictor elements can be cleaned in an ultrasonic bath.
Refer to Section 4-7 for the correct restrictor to use.
6. Blow all parts dry with dry nitrogen and reassemble. Refer to Section 4-
4b (assembly).
7. Purge the assembled controller with dry nitrogen.
8. Perform the calibration procedure in Section 3-4.
9. When the flowmeter is reinstalled in the system, the connections should
be leak tested and the system should be purged with dry nitrogen for 30
minutes prior to start-up to prevent the formation of deposits.
4-3 Sensor Tube
The sensor tube is part of a calibrated flow divider that is designed to
operate within a preset gas flow range. The sensor assembly may be
removed or replaced by referring to Section 4-4, Disassembly and
Assembly. If the sensor assembly is cleaned and reinstalled, a calibration
check should be performed. Refer to Section 3-4.