LEYBOLD 111065, Operating Instructions Manual

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Figure 6. Arrow - direction of rotation
5.6 Optional VFD Use
If desired the VARODRY pumps can be operated via an external variable frequency drive
(VFD). However it is not allowed to run the VARODRY with more than the nominal speed.
A range of suitable VFDs is available as accessories. Please consult Leybold if other types
of VFDs shall be used. The permissible motor speed defined in the technical data must
be obeyed.
Please note that the pump performance and power consumption is not a linear function
of motor speed.
5.7 Purge Gas/Gas Ballast Connection (optional)
The VARODRY has a gas ballast system and an optional seal-purge system. It consists of
three components.
1. Gas ballast
The VARODRY is equipped with a gas ballast which feeds ambient air into the pump
to dilute condensable vapors and keep the partial pressure below the condensation
level. The VARODRY offers two levels of water vapor tolerance, 20 mbar and 60
mbar. The tolerance level can be selected depending on the application
requirements. A high vapor tolerance will reduce the vacuum performance of the
pump. If the presence of condensable vapors in the pumped gases can be ruled out
the gas ballast can be closed. Using the gas ballast will improve the vapor handling
but reduce the vacuum performance of the pump.
2. Seal purge exhaust side (optional)
The VARODRY range has no hermetically sealed shaft feedthroughs at the exhaust
side. Therefore small amounts of gases inside the pump will escape into the ambient
air if no seal purge is used. In order to avoid this the shaft seals at the exhaust side
can be loaded with purge gas. The purge gas will create a gas barrier that will
prevent gas from inside the pump to escape. Note that a fraction of the purge gas
will also escape to the ambient. Make sure that the pump is operated in a room with
good ventilation if other gases than air are used as purge gas.
3. Seal purge inlet side
Inlet seal purge can be used if there is a risk that harmful amounts of dust or
condensable vapors are present at the inlet of the pump. Such substances could
migrate to the inlet side bearings of the pump and reduce the service interval
significantly. The inlet side purge is typically only used whenever the inlet pressure
increases and is active until a pressure equalization is reached.
Based on the pump type, the VARODRY has either a manual gas ballast or 3
solenoid valves for inlet & outlet seal purge and gas ballast mounted underneath the
pump enclosure.
300766038_002 - © Leybold
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Installation