Brooks Instrument 5851E - Manual (Page 37)

Brooks ® Model 5851E
4-5
Section 4 Maintenance
Installation and Operation Manual
X-TMF-5851E-MFC-eng
Part Number: 541B104AAG
November, 2008
4. Inspect the orifice for clogging by holding it in front of a light source and
looking for light through the bore. Clean by soaking in a suitable non-
residuous solvent and directing a stream of compressed clean, dry
Nitrogen through the bore.
5. Deposits of silicon dioxide may be removed by soaking the internal
parts in solution of 5% hydrofluoric acid (5 parts hydrofluoric acid and
95 parts water (H
2
O)) followed by Freon TF.
6. Sintered type restrictor elements should be replaced as it is not pos-
sible 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.
7. Blow all parts dry with clean, dry Nitrogen and reassemble Refer to
Section 4-4b, (assembly).
8. Purge the assembled controller with clean, dry Nitrogen.
9. Perform the calibration procedure in Section 3-4.
10.When the controller is reinstalled in the system, the connections should
be leak-tested and the system purged with clean, 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.
4-4 Disassembly and Assembly
Note: The Model 5851E Mass Flow Controller should be disassembled and
assembled in a clean environment to prevent particulate contamination.
A. DISASSEMBLY
The numbers in ( ) refer to the spare parts exploded view in Figure 5-1.
WARNING
If it becomes necessary to remove the controller from the system
after exposure to toxic, pyrophoric, flammable, or corrosive gas,
purge the controller thoroughly with a dry inert gas such as nitrogen,
before disconnecting the gas connections. Failure to correctly purge
the controller could result in fire, explosion, or death. Corrosion or
contamination of the mass flow controller upon exposure to air may
also occur.
1. Remove the jam nut (1) on top of the valve assembly.
2. Unplug the valve connector from the electronics cover and remove the
coil assembly (2).
3. Remove the hex socket screws (3) securing the valve retaining plate
(4) attaching the valve stem assembly (6).