VICI 450 Dynacalibrator - Manual (Page 17)

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so a source of pressurized gas must be connected to its carrier inlet and its dilution
inlet. On the remaining three input configurations, these inlets are part of the gas
stream bypass loops, discussed in a later paragraph. However, the bypass loops
may be left disconnected, and since they are downstream from the internal pump,
external pressurized gas sources may be connected to the dilution inlet and/or the
carrier inlet. The most commonly used gas is dry air; however, dry nitrogen or any
other comparably inert gas including ambient air may also be used.
CAUTION: Externally supplied pressurized gas sources MUST
be limited to a pressure range of 10 psig minimum to 15 psig
maximum at these inlets.
Bypass Loops
Only those Dynacalibrators with internal pumps are equipped with fittings for
bypass loops in either or both the carrier and dilution streams (input configura-
tions -3X, -4X and -5X). The fittings – labeled CARRIER OUTLET, CARRIER INLET,
DILUTION OUTLET, and DILUTION INLET – are downstream from the pump, so
the loops must be completed in order for the internal pump to be used . The
purpose of the loops is to expedite the installation of external filters, scrubbers,
dehydrators, etc., into the two internal streams before each is mixed with the
trace gas. All plumbing should be as short as possible, and the devices should
not restrict the flow in either stream below their normal operating rates. If a
separate gas supply is connected to either inlet, the input pressure should be
between 7 and 15 psig, and the companion outlet should be capped.
If external devices are not required, then the outlet ports must be directly
plumbed to their companion inlet ports.
Span and Zero Outlets
The primary outlet on the Model 450 is labeled SPAN OUTLET. A ZERO OUTLET
fitting is included only on those units equipped with the non-pressurized inter-
nal pump option. The span outlet may be either permanently plumbed to the
calibrate input port of an analyzer or temporarily connected to its sample input for
calibration, depending on the capabilities of the analyzer.
NOTE: The span outlet port should be directly connected
to the analyzer input with a minimum length of tubing.
Altering the output stream in any manner may affect the
concentration of calibration gas in the stream.
The zero outlet port provides a scrubbed supply of ambient air for a zero point
calibration. Since it is not pressurized, the zero outlet requires suction from the
analyzer being calibrated.
Overflow Vent
All Dynacalibrators include an overflow vent to dump excess calibration gas,
ensuring that analyzers sensitive to sample feed pressure receive zero and
span gas at near atmospheric pressure. The overflow vent is therefore usually
left open, or plumbed to an external exhaust point with large diameter tubing.
External devices (filters, etc.) or tubing with too small a diameter on the overflow
vent may cause an undesirable increase of pressure at the analyzer’s input.
Getting Started