Teledyne 9110E - Nitrogen Oxides Analyzer - Manual (Page 222)

Troubleshooting & Repair Model 9110E Instruction Manual
208 M9110E Rev B
to be replaced. This filter cartridge (Figure 3-2) filters chemicals that can cause
chemiluminescence and, if saturated, these chemicals can break through to the
reaction cell, causing an erroneously high AutoZero value (background noise).
• A dirty reaction cell can cause high AutoZero values. Clean the reaction cell
according to Section 9.3.9.
• Finally, a high HVPS voltage value may cause excess background noise and a high
AZero value. The HVPS value changes from analyzer to analyzer and could show
nominal values between 450 and 800 V. Check the low-level hardware calibration of
the preamplifier board and, if necessary, recalibrate exactly as described in Section
11.6.5 in order to minimize the HVPS.
11.5. Subsystem Checkout
The preceding sections of this manual discussed a variety of methods for identifying
possible sources of failures or performance problems within the analyzer. In most cases this
included a list of possible causes and, in some cases, quick solutions or at least a pointer to
the appropriate sections describing them. This section describes how to determine if a
certain component or subsystem is actually the cause of the problem being investigated.
11.5.1. Simple Vacuum Leak and Pump Check
Leaks are the most common cause of analyzer malfunction; This section presents a simple
leak check, whereas Section 11.5.2 details a more thorough procedure. The method
described here is easy, fast and detects, but does not locate, most leaks. It also verifies the
sample pump condition.
• Turn the analyzer ON, and allow at least 30 minutes for flows to stabilize.
• Cap the sample inlet port (cap must be wrench-tight).
• After several minutes, when the pressures have stabilized, note the SAMP (sample
pressure) and the RCEL (vacuum pressure) readings.
• If both readings are equal to within 10% and less than 10 in-Hg-A, the instrument is
free of large leaks. It is still possible that the instrument has minor leaks.
• If both readings are < 10 in-Hg-A, the pump is in good condition. A new pump will
create a pressure reading of about 4 in-Hg-A (at sea level).
11.5.2. Detailed Pressure Leak Check
If a leak cannot be located by the above procedure, obtain a leak checker similar to TAI
part number 01960, which contains a small pump, shut-off valve, and pressure gauge to
create both over-pressure and vacuum. Alternatively, a tank of pressurized gas, with the
two stage regulator adjusted to ≤ 15 psi, a shutoff valve and pressure gauge may be used.
CAUTION
Once tube fittings have been wetted with soap solution under a pressurized
system, do not apply or re-apply vacuum as this will cause soap solution to be
sucked into the instrument, contaminating inside surfaces.
Do not exceed 15 psi when pressurizing the system.
• Turn OFF power to the instrument and remove the instrument cover.