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Cooling water outlet
Cooling water inlet
Flushing gas
Cooling gas
3.4 Cooling system
TWISTER pumps are water cooled. They are distinguished in:
3.4.1 Fresh water cooling
The fresh water cooling system is characterised by a continu-
ous flow of the cooling water through a hollow space between
the inner and outer wall of the chamber. For safety reasons the
cooling system is equipped with a temperature switch and a
flow switch.
3.4.3 Cooling gas
This purge is intended to cool the rotors and internals which
are heated by gas compression.. Since this compression heat
can reach above 200° C in the discharge side, a cooling purge
is needed to cool the gases. In most cases, an atmospheric air
cooling purge is used, this is the standard purge.
An air filter is provided near the discharge side of the casing
for this purge.
Cooling gas capacity see table page 4.
Remark: The TWISTER VSB 120 does not require any cooling
gas!
(1) Purge gas flow
This purge gas flow can vary according to operating
vacuum level
(2) Type of Cooling Purge
1. Standard: Atmosphere purge through air filter
2. Using Heat Exchanger, Recycle process gases after
cooling through the heat exchanger.
3. As an alternative other gases may be used.
3.5 Gases
3.5.1 Sealing gas (see picture
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)
The sealing gas is located on the pressure side between the
mechanical spring plate and the single lipped shaft seal. It pre-
vents process gases and liquids from entering the gear box
and the bearings.
The maximum gas pressure allowed is 1,5 bar (abs). The me-
chanical seals guarantee a sealing up to 4 bar (abs.).
3.5.2 Cleaning gas
This purge is used to clean the inside the pump before stop-
ping. Before stopping the pump, purge with N
2
gas, steam or
cleaning agent for 20 to 30 minutes after closing the main suc-
tion valve to clean sticky process materials or process gases.
This purge is especially important when pumping corrosive/
toxic or sticky materials like resin etc.
3.6 Bleeding valve
The suction side of the pump is equipped with a bleeding valve
which implies two functions
On start run:
In an hazardous environment the pump in neutralized with an
inert gas.
While bringing the pump to operating temperature it is flooded
with inert gas.
Shutting the pump down:
After the process the pump is neutralized with an inert gas.
3.4.2 Circulation Cooling
The circulation cooling system is equipped with a radiator. Two
different types of radiators can be used: Air-water radiator: A
bypass piping and a 3-way valve with integrated temperature
controller bypass the cooling water around the air-water. Dur-
ing operation of the pump a temperature switch monitors the
water temperature and a flow switch supervises the water flow
rate. The radiator is equipped with an integrated fan. The cool-
ing circuit is furthermore equipped with a tap through which it is
filled, an expansion tank, a relief valve and a manometer.
Cooling gas
Flushing
gas
Cooling gas
Flushing gas
Water-water radiator: The external cooling circuit is connected
to the factory’s main water supply. It is equipped with a dust
trap and a temperature controlled valve. This valve remains
closed during the start run of the pump.
The internal cooling circuit is equipped with a temperature
switch that monitors the cooling water temperature and a flow
switch that regulates the water flow rate. The circuit includes
furthermore a tap through which it is filled, an expansion tank,
a relief valve and a manometer.
