The COBRA BC 2000 F pumps are a combination of a screw vacuum
pump NW 0180 A (DP) and a Roots vacuum pump WY 1251 B (MB).
The Combi pumps are streamlined.
The COBRA BC 1000, 2000 F vacuum pumps are COBRA NW screw
vacuum pumps with cooling water and nitrogen circuits.
The COBRA NS screw vacuum pumps are driven by water-cooled
motors.
Principle of DP vacuum pumps
The COBRA NS screw vacuum pumps work by the principle of spiral
pumps. Two parallel screws (8) rotate in opposite directions in the
pump body. Entering gases are trapped between the flights of the
screws and the pump body. The gases are conveyed by the rotation of
the screws to the exhaust, where they are discharged.
Principle of MB vacuum pumps
The Roots vacuum pumps operate according to the approved principle
of the Roots type machine. Operation is both simple and effective.
Two lobes (9) with identical profiles rotate in opposition directions
within a casing. As they rotate, gas is drawn into the space between
each lobe and the casing where it is trapped and by the rotation
pushed out into the discharge. This action is repeated twice for each
revolution of each lobe and therefore four times for each revolution of
the drive shaft. There is no mechanical contact between lobes and
cylinder. So no oil lubrication is required.
The drive motor of roots pump is a water cooled canned motor.
Gas flow checks
A pressure sensor PSA at the discharge monitors the discharge
pressure. If the pressure reaches more than the limit value (alarm,
preset at the factory: 0.2 bar), the purge cycle starts.
Oil circuit
Since the complete operating principle works without contact, no oil
circuit is needed in the work area.
Cooling
The vacuum pump is cooled by
–
a direct cooling water circuit in the motors and the DP and MB
transmission casing. The flow regulating valve CWR of cooling
water is preset on 3-4 l/min at the factory. The water cools in the
DP and MB pumps motors, the two frequency inverters (VFD 1,
VFD 2) and the drive/ pump transmission DP system.
–
a direct cooling water circuit in the rear bearing (for exceptionally
cool running in option).
NOTE
: The COBRA BC 1000, 2000 F vacuum pumps are principally
dispatched without oil already in the vacuum pump but, without
cooling water. Before vacuum pump first startup, control the oil level
and the cooling liquid level. In the event of absence of one or the other
of these lubricants, please carry out the filling (please refer to the
various chapters of filling). Do not forget to connect the cooling water
supply before the first startup. Operation without these coolants can
result in damage to the vacuum pump.
Nitrogen system
The nitrogen system can be used in a number of different ways :
–
nitrogen
is
used
as
dilution
gas.
It
is
injected
inside
the
cylinder
on
two
different
places.
Nitrogen
flow
injected
in
the
middle
hole
is
preset
at
2
l/
min
and
can
be
adjusted
with
valve
DGR
2,
depending
on
the
application.
Nitrogen
flow
injected
in
the
hole
on
cylinder
endplate
side
is
preset
at
10
l/
min
and
can
be
adjusted
with
valve
DGR
1,
depending
on
the
application.
When
flow
is
too
low
a
warning
then
an
alarm
signal
is
generated
by
flowmeter
DGF
to
the
PLC.
Status
of
the
pump
depends
on
the
alarm
function
set
by
user
(factory
setting
:
None,
pump
continues
running
with
an
alarm).
Dilution
improves
the
screws
functioning,
especially
when
sucking
corrosive
gases.
–
nitrogen is used as sealing gas. The nitrogen is injected between
the transmission and the process gas to achieve good closeness.
The Nitrogen flow used for the sealing is set by two
orifice plate
s
(
f
). With
a pressure of 1,5 bar, the flow is around 8-10 l/min.
–
nitrogen is used as purge gas. The purge eliminates traces of
gases
remaining in the vacuum pump. The vacuum pump purge
cycle is
programmed in the control and starts, either after a STOP
operation or after an alarm function.
For a correct purge execution, the shut-off valve at the inlet
flange
must be closed. The purge cycle lasts about 30 min.
(Programmable time in the basic parameters).
Optional functions/ Use of available
accessories
A pressure sensor (PSA) mounted at the exhaust , controls the
overpressure at the exhaust. If overpressure is above 0,3 bar, pressure
sensor gives a warning then an alarm signal. Status of the pump
depends on the alarm function set by user (factory setting : None,
pump continues running with an alarm).
A temperature sensor PT100 (TS 4) mounted on the cylinder, measures
the temperature inside the cylinder (DP).
A silencer or sound absorber (accessory) at the exhaust reduces the
noise of the pump and collects any condensate.
A leak-protection non-return valve (optional) at the exhaust traps the
condensate in the pump when the pump is switched off.
The LCD controller processes the data of the sensors as follows:
–
PSA: exhaust pressure
–
TS 4: temperature inside the cylinder DP
–
MOT 1 and MOT 2: DP and MB current and speed
–
DGF: nitrogen flow rate, dilution
–
CWM: cooling water flow rate in motors/ transmission/ frequency
inverters
See "Installation and Maintenance Instructions, Busch PLC and Busch
LCD (No. 0870758077)".
On/ Off switch
The vacuum pump is delivered with a circuit breaker. The function
start/ stop can be done in Local by using the LCD controller or in
Remote by the production machine.
Versions
Further vacuum pump descriptions state the nominal displacement and
the design level.
Example: BC 2000 F
BC = standard version
2000 = 2000 m
3
/h
F = Design
Product description
BC 1000, 2000 F
Page 6
0870760874 (En)
Summary of Contents for COBRA BC 1000
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