Metrohm 875 KF Gas Analyzer - Manual (Page 39)

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4 Operation
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4.2.7 Automatic addition of methanol, automatic reagent replacement
(optional accessories)
The anolyte in the coulometer cell consists mainly of methanol, which is
removed to a considerable extent by the sample gas and the rinsing gas.
The fill level of the measuring solution therefore decreases by approx.
8 mL per hour under normal operating conditions. In order to avoid mal-
functions and faulty measurements, the missing methanol must be added
regularly. This can be done manually with a syringe. Alternatively, the KF
Gas Analyzer can be equipped with a dosing device to add methanol cycli-
cally that is part of the optional scope of delivery. The rate at which the fill
level decreases depends on the composition and temperature of the ano-
lyte. The fill level can be increased if necessary using the
Addition of methanol method. The Reagent replacement method is
used for a complete exchange of anolyte.
4.2.8 Rinsing with solvent (optional accessories)
If liquefied gases contain nonvolatile components, these components pre-
cipitate in the piping of the KF Gas Analyzer. This is particularly the case
for used refrigerants, which are usually contaminated with compressor
oils. To prevent the sensitivity of the mass flow controller's sensors being
compromised by such substances, an oil filter made of sintered stainless
steel is located beneath the vaporizer. However, an infeed of larger
amounts of oil results in a measurable retardation of the water in the pip-
ing and additionally increases the flow resistance of the oil filter, as its
pores are covered by the oil. If samples contaminated with oil are to be
measured, the system has to be rinsed with a suitable solvent from time to
time.