Severn Trent VAX4600 Series, Instruction Manual

115.6001.10

- 10 -

1.3.3

Operating Pressure

Vaporizer:

   Minimum: 45 psi

   Normal: 100 psi

   Maximum allowable working pressure: 666 psi @ 212°F (however, rupture disk will

rupture at

275 psi)

The vaporizer chamber is stamped with a U and W-L stamp which means it is arc or gas welded and
for lethal service.

1.3.4

EMC Testing

The vaporizer has been evaluated for RF interference over a frequency range of 80-1000 MHZ and
showed overall acceptable immunity. However, it may show a low level of susceptibility to radio
frequency emissions as listed below. Additionally, no interference will be seen unless the intensity of
field strength at these frequencies exceeds 2.3 volts/meter.

Frequencies (MHZ)

180-200

420-465

207-210

563-570

367-380

684-701

380-405

738-746

Interference of any duration will not effect the vaporizer’s performance unsafely at any frequency.
Intermittent operation under conditions of RF interference will not effect the instrument’s operation
irreversibly. Prolonged operation under conditions of RF interference, though not unsafe, may
damage some instrument components and is not recommended.

1.4

Principle of Operation

Liquid is transferred from its source (cylinder, ton container, rail car) to the vaporizer chamber by source
pressure. The chamber is immersed in a temperature controlled heated water bath, which increases the
temperature of the chemical causing it to vaporize. Liquid chemical enters the chamber and automatically
maintains the required level as necessary to meet the vaporization rate for the gas demand. A change in
demand will automatically cause the liquid level to adjust. As the gas vaporizes and rises, it is deflected
around internal baffles and is superheated as it leaves the chamber. Superheat is a function of the system
pressure and temperature, refer to Figure 2 to calculate actual superheat. After the gas leaves the
vaporization chamber, it proceeds to the pressure reducing valve, which decreases and regulates the
downstream pressure to approximately 40 psig (270 kPa/ 2.7 bar). The regulated gas then enters the
dispensing system and continues on to the point of application.