Brooks Instrument 5866M - Manual (Page 31)

Brooks Instrument Model 5866 Pressure Controller
5-8
CAUTION
The procedure described below requires the disassembly of the
control valve. Be certain to remove gas pressure prior to disassembly
to prevent injury.
A. Adjustment procedure, Normally Closed (N.C.) control valve
Refer to Figure 5-3 for spacer locations and nomenclature for the Normally
Closed (N.C.) control valve. Refer to Section 7, spare parts for the spacer
part numbers and the spacer kit part number. The preload determines the
initial force required to raise the valve seat off the orifice and start gas flow.
If the preload is insufficient the valve will not fully close and gas will leak
through when the valve is closed. If preload is excessive the magnetic
force generated between the plunger and stem will be insufficient to raise
the plunger and the valve will not open.
1. Make the bench testing set up as shown in Figure 5-2. Disconnect the
valve connector from the side of the Model 5866 and connect it to the
variable power supply and voltmeter as shown. Polarity is not important.
2. Remove gas pressure. Disassemble the control valve following the
procedure given in Section 5-3, above. Note the orifice size, which is
marked on the orifice face. Referring to Figure 5-3, note the number,
location and thickness of all spacers (9 and 10).
3. Decrease the preload of the valve by .005" by either removing a .005"
small (9) preload spacer or by adding a .005" large (10) preload spacer.
4. Reassemble the control valve following the assembly procedure in
Section 5-4, above.
5. Apply 5 psig to the inlet of the Model 5866 if equipped with 0-1 bar
transducer. Apply 10 psig for instruments equipped with other
transducers.
6. Apply zero Volts to the control valve and observe the flow.
7. If the valve leaks through, remove the gas pressure and increase the
preload by .005" and go to Step 8. If the valve does not leak through
repeat Steps 2 through 6.
8. Apply 5 psig to the inlet of the Model 5866 if equipped with 0-1 bar
transducer. Apply 10 psig for instruments equipped with other
transducers.
9. Apply 14.5 Volts to the valve using the variable power supply and
observe the flow.
10.Compare the flow with the minimum flow listed in Table 5-3. The
minimum flows have been listed with reference to both 0°C and 70°F for
convenience. Be sure to use the column that is correct for the flow
meter used in the set up. The outlet pressure at the controller must be
less than 0.4 psig (10 inches of water).
11.If the observed flow is greater than the flow listed in Table 5-3 go to
Step 13.
12.If the observed flow does not achieve the minimum flow, then increase
the air gap by adding a large .005" air gap spacer (10) to increase the
valve travel. Repeat Steps 8, 9, 10 and 11.
13.Apply 11.5 Volts to the valve using the variable power supply. Observe
the flow and compare it to the minimum flow values listed in Table 5-3.
14.If the observed flow is greater than the flow listed in Table 5-3 the valve
adjustment is complete.
15.If the observed flow is less than the flow listed in Table 5-3 decrease the
air gap by adding a small 0.005" air gap spacer (9). Repeat Steps 13 and 14.