DAU-20 Instruction Manual
2
1-3. Protector (thermal protector)
1) This pump is fitted with an automatic reset thermal protection relay for overload protection. This
device shuts off the motor power supply circuit automatically to prevent burn-out if the motor
temperature rises due to a pump fault which prevents rotation, or if load becomes excessive.
2) It is recommended that additional protective devices (eg. earth leakage breaker, motor breaker)
be fitted.
1-4. Gas Ballast Valve (important)
Standard equipment of this pump includes a gas ballast valve. This valve is effective when absorbing
condensable gas. There are cases that ultimate pressure of the pump becomes high after the
condensable gas was absorbed as the condensable gas is changed to liquid state and remains in the
pump chamber.
(This pump is not corrosion resistant.)
When air is inhaling from the gas ballast valve just before of the compression process of the pump, the
condensable gas shall be exhausted with air via an exhaust valve without changing to the liquid state.
However, the condensable gas remains in the pump chamber if large quantity of condensable gas is
exhausted or after having exhausted condensable gas without opening a gas ballast valve because of
a limit in throughput capacity of condensable gas by the gas ballast valve
Confirm whether hazardous, explosive compound is generated or not before using the gas ballast
valve.
See "Warning" (8)(9) on P. 06.
WARNING
See "Caution" (6) on P. 07.
CAUTION
In case the gas ballast valve is left open when condensable gas
is not exhausting, power loss or rise of ultimate pressure shall
be resulted.
Close the gas ballast valve when condensable gas is not
exhausting.
Note
