VICI NP2 - Manual (Page 3)

2
Introduction
Theory of Operation
The purification substrate in the Valco purifiers is a non-evaporable
gettering alloy, with a nominal composition of zirconium, vanadium, and
iron. This alloy must be heated so that the oxide layers on the particle
surface are eliminated. This process must be performed under a vacuum or
in at atmosphere of helium (for the HP2) or nitrogen (for the NP2).
Although the gettering alloy will purify even at ambient temperatures, raising
the temperature vastly improves the life span and efficiency of the alloy.
However, the elevated temperature causes hydrogen generation, which is
trapped only at temperatures below 250°C. Therefore the Valco purifiers
have been designed to operate at a fixed temperature gradient which yields
a long life span and high efficiency and insures that any hydrogen gener-
ated will be trapped.
Accurate temperatures at the inlet (380-400°C) and at the outlet (170-
190°C) are maintained with the use of a precision 24 VDC power supply.
Power Supply Requirements
As stated on the purifier, the power supply must conform to EN 61010-1:
Section F.2.1 Limited circuit. This section mandates that the power source
must be limited to 42.4 VDC or less (open circuit). In addition, the energy
must be limited by one of the following means:
• the current under any condition of load, including short circuit, is not
more than 8A measured after 1 minute of operation
• the source is rated or set to limit its power to 150 VA under any
condition of load
• an overload protector or circuit component opens to interrupt the
power output at a lower value than 150 VA under any condition
including short circuit
The power supply is critical for safe and proper opera-
tion of this unit. It is therefore recommended that the
purifer be used only with the power supply received
with it.