Vaporizer Valve And Sump Assembly - Datex-Ohmeda Tec 5 Operation And Maintenance Manual

6.3

Vaporizer Valve And Sump Assembly

The vaporizer incorporates a vaporizing chamber and cover assembled between a cover base and an
interlock block, and is enclosed by an outer wrap.
A duct system lies within the cover and a rotary valve is located above the cover. The lower face of the
rotary valve incorporates ducts and a curved vapour control channel.
The internal baffle system is designed to limit any liquid anaesthetic agent from reaching the valve
mechanism if the vaporizer is tilted or even inverted. This system minimises the risk of drug
contaminating the valve mechanism and entering the patient circuit.
The spindle of the rotary valve passes through the interlock block and is connected to the control dial.
In the 0% position the rotary valve closes all gas passages except a link between the inlet and outlet
within the vaporizer. When the dial is turned past 0% to ON, the carrier gas is split into two streams
respectively designated by-pass flow and vaporizing chamber flow.
The vaporizing chamber consists of a woven helical wick which transmits gas flow. Surrounding this
helical wick is a woven outer wick which extends below the helical wick into the liquid agent.
The amount of agent picked up in the vaporizing stream can vary, due either to variation in room
temperature or to the cooling which takes place when the agent is vaporized. Variation of either
temperature or cooling rate can cause changes in the vapour pressures of the anaesthetic agents and
unless some form of compensating device is used the output of the vaporizer for a given flow and dial
setting can vary with time and temperature.
The vaporizer incorporates a temperature compensating device (thermostat), which utilises a bimetallic
strip that deflects according to its temperature to control the resistance offered to the flow of gas
through it. This deflection varies the relative proportions of the vaporizing chamber flow and the by-
pass flow.
If the temperature of the vaporizer decreases, the thermostat closes, the by-pass flow through the
thermostat decreases and therefore the vaporizing chamber flow increases.
Conversely, if the temperature of the vaporizer increases, the thermostat opens, the by-pass flow
through the thermostat increases and therefore the vaporizing chamber flow decreases.
Thus the output of the vaporizer remains relatively constant under conditions of changing temperature.
Page 18
August 1999
Tec 5 Vaporizer
O & M Manual Part No. 1105-0100-000