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Pump perfomance
5.1
Ultimate pressure
The term “ultimate pressure” as employed in the catalogue and in this manual is defined
as “the minimum pressure obtained by the pump without the introduction of gas from
the pump inlet (i.e. the non-load condition).” For this pump, measurement is performed
using the specified pump oil with only a Pirani vacuum gauge installed at the pump inlet
port.
Also, the actual ultimate pressure of the vacuum device becomes higher than that noted
in t he catalogue for the following reasons.
The vacuum gauge is installed at a distance from the pump, and the steam and a variety
of gases are generated by water droplets and rust on the inside walls of the pump and
piping.
The volatilization ingredient which melted into pump oil does gasification again and
raises arrival pressure. （Deterioration of the pump oil）
When there is a source of supply of the gas such as omissions of vacuum (leak) in a
vacuum course, arrival pressure becomes loud.