6
2) The pump operates automatically when temperature drops. Shut-off the power supply, and
determine the cause of operation of the thermal protection relay.
3) Once the cause of the fault has been removed, wait until the motor cools and restart
operation.
See Caution (6), P05
4.3 Precautions when starting
1) Starting in cold weather
Cold weather will increase the viscosity of bearing grease and harden diaphragms, resulting in
the pump being difficult to start. Follow the procedure below in such conditions.
a) Turn the switch ON/OFF 2~3 times with the inlet open to atmosphere until the pump starts. If
the pump still does not start, raise the ambient temperature to beyond 0°C.
b) With the inlet open to atmosphere, run the pump for a few minutes to warm it.
Commence normal operation once the pump has warmed.
2) Precautions regarding the intake-side pressure
Set the intake-side pressure to atmospheric pressure when starting the pump.
If the pressure is lower than atmospheric pressure, it will apply a load on the motor and may
prevent the pump from starting.
If it is necessary to maintain a vacuum, attach a shut-off valve or three-way valve between
the pump and vessel. Refer to fig.3.1 for a piping example using a shut-off valve.
5. Pump Performance
5.1 Pressure Achieved
The term “pressure achieved” as employed in the catalogue and in this manual is defined as “the
minimum pressure obtained by the pump without introduction of gas from the pump
inlet (ie the
no-load condition)”.
Note that the indicator values for pressure may differ between types of vacuum gauges.
The pressure achieved in practice is higher than that noted in the catalogue for the following
reasons.
(1) The fact that the vacuum gauge is mounted a distance from the pump, the steam generated
by water droplets and rust etc on the inside walls of the pump and piping, and a variety of
gases present in the system result in increased pressure.
(2) Leaks into the vacuum system introduce other gases, resulting in increased pressure.
5.2 Evacuation Rate
The maximum rate of evacuation is reached when air is introduced, and decreases slightly as
pressure is reduced.
The resistance of the piping system increases with small bore piping which extends over long
distances, and this reduces the rate of evacuation.
The declared rate of evacuation for this pump is the maximum value achieved with dry air.
5.3 Power Requirements
The power required to drive the pump is the total of the work required to overcome the rotational
resistance of the pump (mechanical work), and the work required to compress the air
(compression work), and is at a maximum at an inlet pressure of 2.7 x 10
4
~4 x 10
4
Pa. At
pressures below this range the compression work is considerably reduced and power is
expended in mechanical work.
!
Caution
