Chapter:
Topic:
INJECTORS AND GAS VALYES
Electric Valve Actuator Maintenance
If
the gas chromatograph
in
use is equipped
with
an electrically actuated multiport gas sampling
valve and, after discussing the trouble experienced •
~
with
the technical support staff at SRI Instruments,
a valve actuator replacement is deemed necessary.
then a replacement valve actuator may
be
purchased
(or ordered under warranty) and the replacement
may be performed
in
the field
by
the user.
By
following the steps outlined below, the
user may effect the replacement of the actuator
in
a relatively short period of time without much difficulty.
•••
SRI
gas chromatogram
equipped
with
electrically actuated gas sampling valve
•
•
e
•
VIEWOF
VALVE OVENAND
ACI1JATORASSEMBLIES AS
SEEN FROM FRONTOF UNIT
Thennostatted
valve oven
assembly
Electric valve
actuator
assembly
(=<I
---jf.-–
with
multiport
sampling valves)
Stand-offs and
-~JI:::.Iil'l":I~
valve stem collar -
STEP 1:
Remove power from the
unit
and allow
it
to
cool to ambient temperature. Disconnect
the power cord from the AC supply
(wall
outlet). Unplug the 5-wire modular plug on the cable that
exits the base of the actuator housing.
STEP 2:
Remove the two brass thumbscrews securing the valve oven cover. Then remove the
valve oven cover. Remove the top insulating blanket directly beneath the valve oven cover.
STEP 3:
Note that there are four holes in the insulating blanket
at the base of the valve stem. These holes permit access to four
Phillips-head screws that secure the valve oven to the stand-offs
mounted on the valve actuator through the bracket. Remove the
four screws (a magnetic device may
be
needed to retrieve the
screws through the insulation).
STEP 4:
Using a
9/64
n
Allen wrench, loosen the set
screw on the side of the collar securing the valve stem shaft.
This
will
release the valve assembly. Then
lift
the valve
oven slightly away from the actuator assembly
in
order to
insert the Allen wrench into the two set screws present in
the top surface of the collar ring. These screws go through
the bracket must
be
removed.
STEP 5:
Remove the four hexagonal stand-off posts
mounted through the bracket into the valve actuator assembly.
This
will
free the valve actuator assembly from the bracket
and permit replacement. Remove defective actuator assembly
and substitute with replacement valve actuator. Reassemble
in
the reverse order, from step 5 to step 1.
STEP 6:
Verify proper valve operation after reinstallation.
Verify that the valve position matches the position indicated on
the remote control wand. Listen
to
the valve when rotating to hear
for actuator jamming or other unusual noises.
If any difficulties are encountered during or after the valve
actuator replacement process, contact SRI Instruments technical
support for assistance at (310) 214-5092. If an actuator is suspected to be defective, consult with SRI
before attempting removal. The problem may
be
located elsewhere
in
the system and diagnosis may
be
possible over the telephone.
