Specifications

77
Operation
Operation of gas ballast
Regeneration of
pump oil
Pumping condensable
vapours
Choice of pump and system
Choice of oil
Assembly
In a pump stored with the same oil for a long time, condensed vapours may
contaminate the oil bath and affect performance. This is also the case after
pumping vapours and when the oil appears cloudy or discolored through the
sight glass.
- Run the pump, shutting it off from the system at the inlet by a valve or a
plug.
- Open the gas ballast and allow the pump to operate for 1/2 hour to
1 hour, or longer if the oil remains cloudy. This operation accelerates the
temperature rise of the pump while eliminating residual vapours present in
the oil bath.
To pump with condensable products, it is necessary to operate with a hot
pump. For this, isolate the pump from the system and allow it to operate for
1/2 hour with the gas ballast open, or 1 hour (if possible) with the gas
ballast closed. When the oil bath is hot, the condensation of vapours in
the pump is reduced or prevented.
The pump’s capacity to eliminate condensable vapours is related to their type,
the pump temperature and the quantity of air introduced by the gas ballast.
Thus, for high vapour levels in a system, the single-stage pump is more
suitable. However, when not pumping vapours, its ultimate pressure is higher.
Care should be taken to limit the inlet pressure of the pump to its maximum
admissible water vapor pressure with the pumped product. This is obtained
by reading the pump characteristic table for water vapour.
The use of cold traps or condensers are recommended when large quantities
of vapours are to be extracted. Excessively intense or prolonged pumping may
cause the products condensed in the trap to be evaporated a second time.
Choose an oil which facilitates the separation of pumped products which may
be condensed in the oil bath (anti-emulsion oil for water-based compounds,
etc.) (see page 67).
The condensation of vapours at the pump exhaust is reduced if:
- the pump and oil temperature are high;
- the pressure at the exhaust is as low
as possible (removal of the oil mist
eliminator...);
- the condensates are collected
separately from the oil bath and do not
block the exhaust duct.
For this:
- avoid using any vertical ducting which
promotes the condensation of products
and the return of these products to the
pump.
- use a condensate collector;
In. Exh.