Emerson Net Safety Millennium II SC310, Руководство пользователя

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6 Maintaining
6.1 Calibration procedure
There are specific steps to be followed when calibrating with the Millennium II Basic and
the Millennium II Transmitters. These steps should be followed if accurate results are to be
obtained. The calibration of Catalytic Bead sensors requires the presence of oxygen.
An air
balanced calibration gas should be used for calibration
, otherwise these sensors will not
calibrate properly. It is recommended that these sensors be calibrated every 3 months (90
days) to ensure proper functioning.
6.1.1 Calibrating with the Millennium II Basic Transmitter
When a catalytic bead sensor is fitted to a Millennium II Basic Transmitter, the default
setting of the transmitter’s DIP Switch 2 Positions is as follows:
Position 1 ON and
Positions 2, 3 and 4 all OFF. These DIP Switch positions should not be altered
. When
calibrating, follow the normal calibration procedure below using 50 percent span of the
specific LEL gas to be detected (target gas) for calibrations. If calibration is not
successful perform a manual reset. See Millennium II Basic Transmitter manual for manual
reset.
Methane as calibration gas:
If only Methane gas is available as calibration gas, then a specific correction factor (“K
Factor”) relating to the target gas (non-Methane) has to be manually entered using the
HART
®
Communicator. This feature is only available on Analog/HART Transmitter models.
The appropriate correction factor is dependent on the Lower Explosive Limit (LEL) of the
desired target gas as specified by the performance standard(s) applicable at the
installation site.
Table 6-1 and Table 6-2 provide correction factors for common gases and
their respective LEL values. Use 50 percent span Methane gas with the appropriate %
by volume as indicated below .
The tables below outline the primary detectable gases of the sensor. Multiple other gases
are however, detectable. Contact your representative regarding any gases not included in
tables below.
Table 6-1: K-Factors for ISA (N. American) LEL Values (Calibrate with 2.5% by Volume
Methane)
Gas LEL Correction factor
Propane 2.1% Volume 1.8
n-Butane 1.8% Volume 2.0
Isobutylene 1.8% Volume 2.1
Hydrogen 4.0% Volume 1.2
Ethane 3.0% Volume 1.4
Pentane 1.4% Volume 2.2
Safety Manual Maintaining
00809-0100-4310 May 2021
Net Safety SC310 21