General Construction; General; Construction; Technical Specifications - Rietschle TWISTER VSB 120 Manual De Instrucciones

3. General Construction

3.1 General

The Rietschle TWISTER pumps gases
and vapours by use of two screw ro-
tors, having a profile comprising a plu-
rality of curves, i.e. Archimedean curve,
Quimby curve and arc, which rotate
smoothly with a certain clearance
maintained between each other and
inside wall of the casing.
The gases and vapours being pumped
are smoothly pressurised up to the
pressure on the discharge side. The
pump is so constructed as to prevent
oil from entering the pumping cham-
ber. The power of the motor is trans-
mitted to the gear by a coupling.

3.2 Construction

• Rotor shaft: The rotor shaft is
made of high grade spheroidal
graphite cast steel, and precision machined through numerical control by a special machine. It is perfectly dynamically
balanced after the rotor is machined.
• Timing Gear: The timing gears are the most important part of the screw vacuum pump, and they are required to maintain
the precision clearance between the rotors. The tooth surface is heat cured, and then polished with a special high precision
tooth polishing machine for noise reduction.
• Bearing: The bearings on the fixed end are angular contact ball bearings and on the floating end are roller bearings of
heavy load capacity. These bearings have been selected for high speed and heavy load service and to assure the accurate
maintenance of clearances between gears and between rotors.
• Shaft sealing suction side: The shaft sealing consists of two double lipped shaft seals.
Shaft sealing pressure side: A mechanical spring plate assures sealing between the chamber and the gear box. An
additional single lipped shaft seal in combination with sealing gas prevents foreign particles from entering the sealing
system.
Shaft sealing gear box: A single lipped shaft seal seperates the gear box from the atmospheric pressure.
• Oil Level Gauge: The Oil Level Gauge is located in the Front End Cover. Oil should be supplied to the top level of Red
mark. If the oil level is too low, Gear, Bearing and Mechanical Seal will be damaged as a result of improper lubrication. The
timing gears, bearings and mechanical seals are splash lubricated. Check oil level and look for contamination when the
pump is stopped.

3.3 Technical specifications

VSB
Nominal (theoretical) Displacement
Ultimate vacuum
Discharge pressure
Motor rating
Speed
Port size (Suction / Discharge)
Gear oil
Max. internal pressure
Cooling water
Cooling water pressure
Cooling gas
Sealing gas
Seal type
Weight
Note:
(1) The quantity of oil listed is only for reference, and surplus should be available. It should be noted that fluorine and mineral
based oils can be used. For shipping, we supply pure gear oil.
(2) The Cooling Water flow quoted is based on water temperature of 20° C. The amount of water will vary when using an After
Cooler. Please check with Vendor's approved drawing.
50 Hz
m³/h
60 Hz
mbar (abs.)
bar (abs.)
50 Hz
kW
60 Hz
50 Hz
-1
min
60 Hz
DN
bar (abs.)
l/h
bar (abs.)
3
Nm
cm³/min
Front end plate
Rear end plate
Front end cover (drive shaft
kg
120 (30) 200 (30)
80 120
100 150
0,3 0,3
3,0 4,0
3,6 4,8
40 50 / 40
l 0,45 1,0
120 240
/h - -
Bellows type mechanical seal
120 240
- 4 -
320 (30) 430 (30) 800 (30)
220 330 560
260 400 700
0,3 0,3 0,05
ma. 1,3
5,5 7,5 15
6,5 9,0 18
2850
3450
50 / 40 80 / 50 100 / 80 150 / 100
1,6 1,8 2,0
10
480 660 1200
ma. 6
- 25 30
ma. 3
Lip seals
Oil seal
480 660 1200
2700 (20)
1700
2100
0,05
55
65
1450
1740
9,0
2160
30
2160