Groove for
sample-flow
unit
Groove for
O-ring
Label for
Dosing
Volume
Alignment Groove
for attaching to
Control Cylinder
using hex set
screws
Figure 4-7
Liquid Injection Valve Body
4.2.3
Troubleshooting
Faults, Causes, Remedies
Fault
Causes
Remedy
All peaks appear smaller
Sample flow unit (15) or injection
blocked. Buildup of material on in‐
jection stem.
Clean injection hole, stem (6), va‐
porizer (16) and sample flow unit
(15).
Replace gaskets (14) if necessary.
Peaks are becoming wide and shifted to longer
times. Baseline becomes negative before injec‐
tion of sample.
Vaporizer (16) is contaminated.
Baseline becomes positive before injection of
sample.
Gasket (14) between sample flow
and vaporizer is leaking.
Interruption in chromatogram: sample is not get‐
ting injected.
Leaky pneumatic actuator, grease
used up, O-rings (4) damaged, con‐
trol pressure too low.
Clean pneumatic actuator, replace
O-rings, and grease sliding surfa‐
ces and O-rings.
Peaks too small and too wide, especially those
with higher boiling points.
Heating plate is faulty. Vaporization
temperature too low.
Replace heating plate. Set higher
equalization temperature.
Injection quantity slowly rises until a double peak
results (with calibration medium). Poor peak
form, platform following peak. Increase in base‐
line. Visible discharge of sample.
Worn gaskets (14) and/or stem (6). Replace gaskets (14) or stem (6).
The section of the injection stem that is normally
in the sample flow stream (near the notch) is
rough. Material wear on this section of the stem
is visible using a magnifier. The effect is signifi‐
cantly less on the rest of the stem.
Corrosive sample
Possibly replace injection stem (6)
by version made of another material
more compatible with the sample
chemical, such as Hastelloy.
Thin scratches are visible (with a magnifying
glass) on the stem near the sample groove.
These scratches run along the stem for several
millimeters.
Sample is contaminated by particles
(most frequent case). The particles
get lodged in the gasket and scratch
the stem during injection.
Check filter from sample system
and replace if necessary. Replace
stem (6) and gasket (14).
Valves
4.2 Liquid Injection Valve
Maxum II Valves and Oven Components
Service Manual, 10/2018, A5E42019844001
39