Brooks Instrument 5850E - Manual (Page 41)

4-9
Section 4 Maintenance &
Troubleshooting
Installation and Operation Manual
X-TMF-5850E-MFC-eng
Part Number: 541B102AAG
September, 2009
Brooks ® Model 5850E
the screws securing the valve retaining plate in diagonal pattern
(Refer to Figure 4-1) to 17 in/lbs.
9. Install the coil assembly (2) over the valve stem assembly (6)(NC
Valve) or (34)(NO Valve) install extension spacer nut (3)(NO Valve) and
secure with jam nut (1).
10.Install the printed circuit (PC) Board (15), secure with the bracket (24)
and two screws. Plug the connector from the sensor assembly onto the
PC Board. The flow arrow on the connector should be pointing toward
the valve assembly.
11.Install the electronics cover (23) on the controller, secure with three
screws (20). Plug the connector from the valve coil into the PC Board
through the hole in the electronics cover.
12.Prior to installation leak and pressure test to any applicable pressure
vessel codes.
C. Control Valve Adjustment
The Model 5850E control valve has been factory adjusted to insure proper
operation. Readjustment is only required if any of the following parts have
been replaced:
orifice (12)
valve stem (6)
plunger (7)
lower guide spring (8)
valve seat (11)
The valve is adjusted in Brooks' mass flow controllers by adding spacers (9
and 10) to the control valve assembly to vary the air gap and initial preload.
Spacers are used to affect the proper adjustment because they provide a
reliable and repeatable means for adjustment. Screw type adjustment
mechanisms can change with pressure or vibration and introduce an
additional dynamic seal that is a potential leak site and source for
contamination. Refer to Fig. 4-2 for spacer locations.
In April 1989 a new valve stem and plunger combination was incorporated
into the Model 5850E to improve the performance of the valve. These parts
can be used as replacements in any Model 5850E, but the stem and
plunger must be replaced at the same time.
The new style parts can be identified by a slightly curved surface on the
bottom surface of the valve stem and two small groves in the plunger. The
old style parts have a flat surface on the bottom of the stem and one or no
groove in the plunger. Please refer to Figure 4-2 for an illustration of the
difference.
Valves incorporating the old style parts may or may not have a small
diameter air gap spacer, and always use two lower guide springs. The new
style parts always include a .010" thick small diameter air gap spacer. For
devices with an orifice diameter of 0.020" and less the 0.025" thick lower
guide spring is used. For devices with an orifice diameter of 0.032" and
larger the 0.020" lower guide spring is used. Although the newer valve
parts are assembled slightly differently than the old parts, the adjustment
procedure that follows is the same for both types of parts.