4.1 A system leakage test shall be performed.
The probe shall be disconnected from the exhaust system and the end
plugged. The analyser pump shall be switched on. After an initial
stabilization period all flow meters shall read zero. If not, the
sampling lines shall be checked and the fault corrected.
4.2 The maximum allowable leakage rate on the
vacuum side shall be 0.5% of the in-use flow rate for the portion
of the system being checked. The analyser flows and bypass flows may
be used to estimate the in-use flow rates.
4.3 Another method is the introduction of a concentration
step change at the beginning of the sampling line by switching from
zero to span gas. If after an adequate period of time the reading
shows a lower concentration compared to the introduced concentration,
this points to calibration or leakage problems.
4.4 Other arrangements may be acceptable subject
to approval of the Administration.