Agilent Technologies 6850 GCs Instruction Manual

Installing an Auxiliary Pressure
Agilent 6850 GCs
Accessory G3349B
Control Module
This kit contains:
The module is factory-assembled. Do not disassemble it during installation.
Description Quantity
Cable tie .062-.625 diameter 2
Hex nut w/lockwasher 1
Disposable wrist strap 1
Minifold label 1
Restrictor kit 1
• FID air restrictor (brown) 3
• Blue dot restrictor 3
• O-rings (6 pk) 1
• Tube zero restrictor 3
• External H2flow limiter 2
• External Flow Restrictor Install Guide 1
Aux. press. control module assembly (with covers) 1
Back panel replacement for the GC 1
6850 GC user information CD 1
ChemStation software CD 1
Installation sheet (this document) 1

2
Installing an Auxiliary Pressure Control Module
Parts identification
Parts identification
Aux. pressure
assembly
Minifold label
Hex nut
w/lockwasher
control module

Installing an Auxiliary Pressure Control Module
Required tools
3
Required tools
•Torx®T-20 screwdriver
• Needle-nose pliers
Overview
Caution Before starting, review the safety information listed at the end of this
document.
1. Disconnect the GC.
2. Install the new module.
3. Restore the GC to operating condition.

4
Installing an Auxiliary Pressure Control Module
Disconnect the GC
Disconnect the GC
WARNING Hydrogen gas is flammable and potentially explosive. Before replacing the
module, turn off the hydrogen gas at the source.
1. Turn off the GC and unplug the power cord. Allow time for all heated
zones to cool.
2. Disconnect all cables from the GC.
3. Turn all gases off at their sources. Disconnect the carrier and detector
gas tubing from the back panel of the instrument.
Disconnect gas supply tubing
from these fittings

Installing an Auxiliary Pressure Control Module
Install the new module
5
4. Remove the seven T-20 screws on the back panel. Save the screws.
5. Tilt the top of the panel away from the GC.
If you have a Series II GC, save this panel. Otherwise, set this panel
aside because you will no longer use it. A new panel comes with the kit.
Install the new module
Caution Always hold the module by its support bracket to avoid damaging board
components.
1. Change one or more auxiliary channel frits, if needed. See “Changing
the flow restrictors (optional)” on page 8.
Remove

6
Installing an Auxiliary Pressure Control Module
Install the new module
2. If you will be using the back panel from the kit, use needle-nose pliers to
remove the knockouts for the ribbon cable and power cable slots.
3. Remove the tape from around the new control module and thread the
ribbon cable through the slot in the back panel.
4. Attach the ribbon cable to the pneumatics control board (at P9).
High voltage power
Low voltage power
Ribbon cable slot
Ribbon cable connector

Installing an Auxiliary Pressure Control Module
Install the new module
7
5. Gather the excess gas tubing from the gang fitting block in a loop and tie
it together with a cable tie.
6. Attach the control module to the back panel by hooking the tabs on the
module just inside the ribbon cable slot. Position it so you can insert the
threaded stud through the hole in the panel. On the inside, use the hex
nut with lockwasher to hold the stud in place.
7. Install the back panel.
Gas tubing
Cable tie
Control module
Nut holding stud in place

8
Installing an Auxiliary Pressure Control Module
Install the new module
Changing the flow restrictors (optional)
The auxiliary channels are controlled by a pressure setpoint. To work
properly, there must be adequate flow resistance downstream of the
pressure sensor. The auxiliary channel pneumatics manifold provides a frit-
type restrictor for each channel.
Four frits are available:
The red dot frit is in all three channels when the instrument is shipped.
Figure 1 and Figure 2 show approximate pressure/flow relationships for the
three dot frits, assuming there is no significant resistance downstream of the
frits.
If the Zero resistance frit is installed, the user must provide flow resistance
downstream and generate the pressure/flow relationships.
WARNING When hydrogen is used, dangerously high flows are possible if insufficient
flow resistance is provided downstream of the supply tube. Always use
either the High (blue dot) or Medium (red dot) frit with hydrogen. You may
also want to use the restrictor kit that comes with this accessory. Its
installation document describes using it for the 6890 GC, but still applies to
the 6850 GC.
Frit marking Flow resistance Agilent part number
Blue Dot High 19234-60660
Red Dot Medium 19231-60770
Brown Dot Low 19231-60610
None (brass tube) Zero G1570-20540

Installing an Auxiliary Pressure Control Module
Install the new module
9
Figure 1. Pressure requirements for AUX EPC flow restrictors
with air, nitrogen, or helium
19234-60660
(blue dot)
19231-60770
(red dot)
19231-60610
(brown dot)
10
0
80
20
30
40
50
60
70
Minimum
source
pressure
(psig)
0.1 100.0 1000.01.0 10.0
Gas Flow in mL/min
(Ambient conditions: 25°C, 14.7 psia)

10
Installing an Auxiliary Pressure Control Module
Install the new module
Figure 2. Pressure requirements for AUX EPC flow restrictors
with hydrogen
19234-60660
(blue dot)
19231-60770
(red dot)
19231-60610
(brown dot)
10
0
80
20
30
40
50
60
70
0.1 100.0 1000.01.0 10.0
(Ambient conditions: 25°C, 14.7 psia)
Gas Flow in mL/min
Minimum
source
pressure
(psig)