Electronic Vaporizer - GE Datex-Ohmeda Aisys Carestation Reference Manual

Aisys
2.11.2 Electronic
vaporizer
2-38
Agent is delivered from the subsystem in one of two configurations depending on
whether cassette pressure is below or above Mixer output pressure. If cassette
pressure is above Mixer output pressure, all fresh gas is routed through the
Backpressure Regulator and agent is metered out of the pressurized cassette. If
cassette pressure is below Mixer output pressure, some fresh gas is routed through the
cassette, where it picks up agent vapor. The remaining fresh gas passes through the
Backpressure Regulator. The mixed fresh gas and agent vapor from the subsystem is
sent to the CGO.
A Backpressure Regulator (16) builds a pressure at the input to the vaporizer to drive
gas through the cassette, if necessary. It is not needed to check flow in the reverse
direction. A pressure relief valve (17) limits the maximum outlet pressure.
The Inflow and Outflow Flowmeters (26, 27) measure flow by developing a pressure
drop across a flow restrictor. The Outflow Flowmeter is used for control, while the Inflow
Flowmeter is used for safety. Each Flowmeter includes a zeroing valve that temporarily
shorts a pressure transducer's ports together for an accurate zero measurement. The
zeroing valves may be energized during Standby to heat the Flowmeter Manifold to
prevent agent condensation.
An Inflow Check Valve (28) prevents unmetered agent vapor from flowing backwards
and entering the fresh gas stream.
Inflow and Outflow Valves (29, 30) direct flow in the subsystem, opening for agent
delivery and closing for other system states, including safety conditions. The Outflow
Valve must open for agent delivery, while the Inflow Valve opens if cassette pressure is
lower than Mixer output pressure.
The Scavenge Valve (31) opens periodically during system checkout and, when a
cassette is not installed, to automatically sample ambient pressure.
A liquid prevention valve (32) blocks liquid from entering the subsystem in the event
that an overfilled cassette is present. This valve can also become temporarily blocked if
cassette temperature exceeds Flowmeter Manifold temperature significantly, causing
agent condensation. Clearing the blockage depends on the rate of agent evaporation.
Variable control of flow from the cassette is accomplished with a Proportional Valve
(33) under software direction.
Connection Valves (34) open and close automatically when a cassette is installed into
or removed from the cassette bay.
04/08 M1046983