4-11
Brooks
®
Model 5850i
Section 4 Maintenance
Installation and Operation Manual
X-TMF-5850i-MFC-eng
Part Number: 541B108AAG
November, 2008
and the total travel of the valve. If the air gap is too small, the plunger travel
may be insufficient to fully open the valve. Also, the magnetic force may be
too high for a given valve coil voltage. If the air gap is too large, the
magnetic force will be insufficient to raise the plunger and the valve will not
open.
NOTE: Prior to starting the valve adjustment procedure, check to insure that
the orifice is properly seated and that the valve parts are not bent or
damaged.
D. Adjustment Procedure
(Refer to Section 5, Spare Parts for Spacer Kit)
a. Remove the electronics cover (23) from the controller. Insure that the
connector from the coil assembly (2) is properly reconnected to the
PC Board after the electronics cover is removed.
b. Perform the electrical and gas connections to the controller following
the instructions in Section 2 of this manual. Use a clean dry inert
gas, such as nitrogen, for this procedure. Do not apply gas pressure
to the controller at this time.
c.
Disassemble the control valve following the procedure given in
Section 4-4A above. Note the number, locations and thicknesses of
all spacers (9 and 10).
d. Decrease the preload of the valve by 0.005 inches by either remov-
ing a 0.005-inch small preload spacer or by adding a 0.005-inch
large preload spacer. Refer to Figure 4-2.
e. Reassemble the valve following the assembly procedure in Section 4-
4a.
f. Adjust setpoint for zero percent flow, apply normal operating pressure
and check for valve leak-through by observing the output signal.
g. If the valve leaks through, increase the preload by 0.005" and go to
Step h. If the valve does not leak through, repeat Steps d, e, f and g.
h. Apply normal operating gas pressure and adjust setpoint for 100%
flow.
Note: Due to possible heat capacity and density differences between the
test gas and actual process gas for which the MFC was sized, it may be
necessary to increase the inlet pressure to obtain proper control at 100%
flow.
i. Measure the valve voltage by connecting a voltmeter between test
point 3 (TP3) and test point 4 (TP4). Refer to Figure 4-3.
j1. If the flow controller output signal is 100% and the valve voltage is
less than 11.5 V, the valve adjustment is complete.
j2. If the flow controller output signal is 100% and the valve voltage is
greater than 11.5 V, decrease the air gap with a small 0.005 inch air
gap spacer. Refer to Figure 4-2. Repeat Steps h and i.
j3. If the flow controller output signal is less than 100% and the valve
voltage is greater than 11.5 V, this condition indicates that the inlet
pressure is too low and/or the orifice size is too small. First check
Section 4-6 to insure that the orifice size is correct.
k. Proceed to Section 3 and perform “3-4 Calibration Procedure,” if
required.
