Servomex SERVOPRO Plasma, Руководство оператора

Страница: 71 / 82

Plasma Gas Analyzer
69 02001001A_9
3 DUAL BACKGROUND ANALYZERS
3.1 NOTE TO THE READER
The SERVOPRO PLASMA trace Nitrogen in Argon or Helium analyzer version is shipped
configured for Argon. When changing background gases from Argon to Helium, or vice versa,
all the previously in use background gases must be purged before attempting any calibration.
Normally this will take up to 24 hours.
3.2 User Manual
This User Manual applies to both versions of SERVOPRO PLASMA analyzer, i.e. Argon or
Helium. Since the most popular version is Argon, the manual refers to Argon as background
gas. When Helium is the background gas, replace the word Argon by Helium as required.
You must read this addendum to know how to select Argon or Helium backgrounds.
3.3 Flow control system
The flow control valve used in the SERVOPRO PLASMA trace Nitrogen analyzer for Helium
background is the same as the one for the Argon version. This valve is not a tight shut off
valve. Its purpose is to maintain the flow at the default flow set point, i.e. 75 cc/min. It is
possible to have a little flow (usually not more than 10 cc/min for inlet pressure of 10 psig)
even if the flow set point value is 0 cc/min. This is acceptable for normal operation. Note that
the plasma will shut off when the real flow is below 20 cc/min for more than 30 seconds. The
analyzer should be operated and calibrated with a flow set point of 75 cc/min and stable inlet
pressure. The ideal inlet pressure range is between 5 to 15 psig.
3.4 Leaks
The most critical point in trace Nitrogen analysis is to avoid the pollution of the sample stream.
The leak integrity of the sampling and calibrating system is critical for the performance of the
analyzer, no doubt can subsist about this. Be aware that leaks are more critical with helium
than with argon.
Furthermore, the sample must be as dry as possible. You should use the supplied trap to
keep the sample dry. It is also recommended to have one trap for each calibration cylinder.