BUSCH COBRA NF 0750 A User manual

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COBRA
Dry Screw Vacuum Pumps
NF 0750 A, NF 0950 A
Water-Cooled Version (WCV)
Instruction Manual
0870232965 | -0003_en-US | Original instructions 11/24/2022

Table of Contents
2 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
Table of Contents
1 Safety..................................................................................................................................................................... 4
2 Product Description............................................................................................................................................. 5
2.1 Operating Principle ............................................................................................................................................. 6
2.2 Intended Use ....................................................................................................................................................... 6
2.3 Start Controls....................................................................................................................................................... 7
2.4 Standard Features............................................................................................................................................... 8
2.4.1 Water Cooling........................................................................................................................................ 8
2.4.2 Temperature Switch ............................................................................................................................. 8
2.4.3 Sealing Systems..................................................................................................................................... 8
2.5 Optional Accessories........................................................................................................................................... 8
2.5.1 Gas Ballast Valve ................................................................................................................................... 8
2.5.2 Silencer................................................................................................................................................... 8
2.5.3 Barrier Gas System ............................................................................................................................... 8
2.5.4 Inlet Filter............................................................................................................................................... 9
3 Transport .............................................................................................................................................................. 10
4 Storage .................................................................................................................................................................. 11
5 Installation ........................................................................................................................................................... 12
5.1 Installation Conditions........................................................................................................................................ 12
5.2 Connecting Lines / Pipes .................................................................................................................................... 13
5.2.1 Suction Connection............................................................................................................................... 13
5.2.2 Discharge Connection .......................................................................................................................... 13
5.2.3 Cooling Water Connection................................................................................................................... 14
5.2.4 Barrier Gas System Connection (Optional) ........................................................................................ 15
5.3 Filling Oil............................................................................................................................................................... 16
6 Electrical Connection........................................................................................................................................... 18
6.1 Machine delivered without Variable Speed Drive ........................................................................................... 18
6.2 Wiring Diagram Three-Phase Motor (Pump Drive)......................................................................................... 19
6.3 Electrical Connection of the Monitoring Devices ............................................................................................ 21
6.3.1 Wiring Diagram Temperature Switch................................................................................................. 21
7 Commissioning..................................................................................................................................................... 22
7.1 Start Procedure.................................................................................................................................................... 24
7.2 Shutdown Procedure .......................................................................................................................................... 25
8 Maintenance......................................................................................................................................................... 26
8.1 Maintenance Schedule ....................................................................................................................................... 28
8.2 Oil Level Inspection............................................................................................................................................. 28
8.3 Cleaning the Inlet Screen ................................................................................................................................... 29
8.3.1 Cleaning the Inlet Screen with Vertical Flange G3 or DN100 .......................................................... 29
8.3.2 Cleaning the Inlet Screen with Horizontal Flange G3....................................................................... 30
8.3.3 Cleaning the Inlet Screen with Double Flange G2 ............................................................................ 31
8.4 Cleaning the Gas Ballast Filter (Optional)......................................................................................................... 32
8.5 Oil Change............................................................................................................................................................ 32
9 Overhaul................................................................................................................................................................ 35
10 Decommissioning................................................................................................................................................. 36
10.1 Dismantling and Disposal .................................................................................................................................. 36
11 Spare Parts............................................................................................................................................................ 37
12 Troubleshooting................................................................................................................................................... 38
13 Technical Data...................................................................................................................................................... 40

Table of Contents
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 3 | 44
14 Oil........................................................................................................................................................................... 41
15 EU Declaration of Conformity............................................................................................................................. 42
16 UK Declaration of Conformity ............................................................................................................................ 43

1 | Safety
4 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
1 Safety
Prior to handling the machine, this instruction manual should be read and understood. If anything
needs to be clarified, please contact your Busch representative.
Read this manual carefully before use and keep for future reference.
This instruction manual remains valid as long as the customer does not change anything on the
product.
The machine is intended for industrial use. It must be handled only by technically trained personnel.
Always wear appropriate personal protective equipment in accordance with the local regulations.
The machine has been designed and manufactured according to state-of-the-art methods. Never-
theless, residual risks may remain, as described in the following chapters and in accordance with the
chapter Intended Use [➔6]. This instruction manual highlights potential hazards where appropri-
ate. Safety notes and warning messages are tagged with one of the keywords DANGER, WARNING,
CAUTION, NOTICE and NOTE as follows:
DANGER
... indicates an imminent dangerous situation that will result in death or serious injuries if not
prevented.
WARNING
... indicates a potentially dangerous situation that could result in death or serious injuries.
CAUTION
... indicates a potentially dangerous situation that could result in minor injuries.
NOTICE
... indicates a potentially dangerous situation that could result in damage to property.
NOTE
... indicates helpful tips and recommendations, as well as information for efficient and trou-
ble-free operation.
WARNING
... indicates a potentially dangerous situation related to the presence of an oxygen level of
more than 21%.

Product Description | 2
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 5 | 44
2 Product Description
EB IN, IS
MTB
PMR MP
CWDOSG
TS CWO
ODP
OFP
CWDODPOSG
CWI NP
MP
OFP
SI OUT
GBGBS
Description
IN Suction connection (Inlet) OUT Discharge connection (Outlet)
CWD Cooling water drain plug CWI Cooling water inlet
CWO Cooling water outlet EB Eye bolt
GB Gas ballast valve GBS Gas ballast silencer
IS Inlet screen MP Magnetic plug
MTB Motor terminal box NP Nameplate
ODP Oil drain plug OFP Oil fill plug
OSG Oil sight glass PMR Plug for manual rotation of rotors
SI Silencer TS Temperature switch
NOTE
Technical term.
In this instruction manual, we consider that the term ‘machine’ refers to the ‘vacuum pump’.

2 | Product Description
6 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
NOTE
Illustrations
In this instruction manual, the illustrations may differ from the machine appearance.
2.1 Operating Principle
The machine works on the one-stage, twin-screw pump principle.
Two screw rotors rotate inside the cylinder. The pumped medium is trapped between the cylinder
and screw chambers, compressed, and transported to the gas outlet. During the compression pro-
cess, the two screw rotors do not come into contact with each other or with the cylinder. There is no
need for a lubrication or an operating fluid in the compression chamber.
2.2 Intended Use
WARNING
In case of foreseeable misuse outside the intended use of the machine.
Risk of injuries!
Risk of damages to the machine!
Risk of damages to the environment!
●Make sure to follow all instructions described in this manual.
The machine is intended for the suction of air and other dry, non-aggressive, non-toxic and non-ex-
plosive gases.
Conveying of other media leads to an increased thermal and/or mechanical load on the machine
and is permissible only after a consultation with Busch.
The machine is intended for the placement in a non-potentially explosive environment.
The machine is capable of maintaining ultimate pressure, see Technical Data.
The machine is suitable for continuous operation.
Permitted environmental conditions, see Technical Data.

Product Description | 2
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 7 | 44
WARNING
A specific Oxygen version (see nameplate) can convey process gas with > 21% vol. oxygen.
The following warning and precautions additionally apply for the Oxygen version if process
gas with > 21% vol. is drawn:
●The barrier gas system is mandatory, see Sealing Systems [➔8] and Barrier Gas System [➔8].
●Installation conditions: the installation area must be ventilated in such a way to prevent unaccept-
able levels of oxygen, see Installation Conditions [➔12].
●Use only a type of oil approved and recommended by Busch for oxygen applications, see Filling
Oil [➔16] and Oil [➔41].
●Follow the additional commissioning instructions, see Commissioning [➔22].
●Follow the additional maintenance instructions, see Maintenance [➔26] and Oil Change [➔32].
●Use only Busch genuine spare parts, see Spare Parts [➔37].
Nameplate of the oxygen version of the machine
NOTICE
Chemical compatibility of the process gases with the machine component materials.
Risk of corrosion inside the compression chamber which can reduce performance and its life-
time!
●Check if the process gases are compatible with those following materials:
- Cast iron
- Steel
- Stainless Steel
- Aluminum
- Fluor elastomer (FKM/FPM)
●In doubt, please contact your Busch representative.
2.3 Start Controls
The machine comes without start controls. The control of the machine is to be provided in the
course of installation.
The NF 0950 A must be equipped with a variable speed drive* for 72Hz operation.
The NF 0750 A must be operated at 60Hz with a variable speed drive* or on a grid with 60Hz supply
frequency.
* not included in the scope of supply

2 | Product Description
8 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
2.4 Standard Features
2.4.1 Water Cooling
The machine is cooled by a cooling water circuit in the cylinder cover, cylinder and in the motor.
2.4.2 Temperature Switch
The temperature switch monitors the cooling water temperature of the machine.
The temperature switch has one switch point:
Switch point T = 70°C Trip, the machine must be stopped, pin 1+2 (see Electrical Connection
of the Monitoring Devices [➔21]).
2.4.3 Sealing Systems
The machine is equipped with labyrinth seals on the motor side and suction side.
Sealing systems prevent the process gas going to the bearings chambers.
Depending on the application, the sealing systems efficiency can be improved with a barrier gas sys-
tem, see Barrier Gas System [➔8].
WARNING
The barrier gas system is mandatory for the suction of process gas with a volume of oxygen
higher than 21% (>21%).
2.5 Optional Accessories
2.5.1 Gas Ballast Valve
The gas ballast valve mixes the process gas with a limited quantity of ambient air to counteract the
condensation of vapor inside the machine.
The gas ballast valve has an influence on the ultimate pressure of the machine, see Technical Data.
2.5.2 Silencer
A silencer at the discharge connection (OUT) can be provided to reduce the exhaust gas noise.
2.5.3 Barrier Gas System
WARNING
The barrier gas system is mandatory for the suction of process gas with a volume of oxygen
higher than 21% (>21%).
The barrier gas system allows the supply of compressed air or nitrogen into the motor side shaft
seals to improve the sealing efficiency.

Product Description | 2
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 9 | 44
2.5.4 Inlet Filter
The inlet filter protects the machine against dust and other solids in the process gas. The inlet filter
is available with a paper or polyester cartridge.
1
Description
1 Connection size: G3'

3 | Transport
10 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
3 Transport
WARNING
Suspended load.
Risk of severe injury!
●Do not walk, stand or work under suspended loads.
WARNING
Lifting the machine using the motor eye bolt.
Risk of severe injury!
●Do not lift the machine using the eye bolt fitted to the motor. Only lift the machine as shown.
NOTICE
In case the machine is already filled with oil.
Tilting a machine that is already filled with oil can cause large quantities of oil to ingress into
the cylinder.
●Drain the oil prior to every transport or always horizontally transport the machine.
●To find out the weight of the machine, refer to the chapter Technical Data or the nameplate (NP).
●Make sure that the eye bolt(s) (EB) is/are in faultless condition, fully screwed in and tightened by
hand.
●Check the machine for transport damage.
If the machine is secured to a base plate:
●Remove the machine from the base plate.

Storage | 4
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 11 | 44
4 Storage
NOTICE
Long storage time.
Risk of damage to the machine!
●Seal all apertures with adhesive tape or reuse provided caps.
If the machine is to be stored for more than 3 months:
●Wrap the machine in a corrosion inhibiting film.
●Store the machine indoors, dry, dust free and if possible in original packaging preferably at
temperatures between 5 ... 55 °C.

5 | Installation
12 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
5 Installation
WARNING
Lack of oxygen regulation knowledge.
Risk of fire!
●Installation, commissioning, and maintenance must only be carried out by qualified personnel
who are informed about the applicable safety regulations and trained in the handling of oxygen.
●Accident prevention regulations or methods must imperatively be complied with.
Seek further information:
- European Industrial Gases Association “EIGA” www.eiga.eu (EIGA SAG NL 79/04).
- Berufsgenossenschaft Rohstoffe und chemische Industrie "BG RCI” www.bgrci.de (Merkblatt M
034 Sauerstoff).
5.1 Installation Conditions
WARNING
The machine is not absolutely gas tight!
Risk of fire!
●The installation area must be aired in such a way to prevent unacceptable levels of oxygen.
NOTICE
Use of the machine outside of the permitted installation conditions.
Risk of premature failure!
Loss of efficiency!
●Take care that the installation conditions are fully complied with.
●Make sure that the environment of the machine is not potentially explosive.
●Make sure that the ambient conditions comply with the Technical Data.
●Make sure that the environmental conditions comply with the protection class of the motor and
the electrical elements.
●Make sure that the oil sight glass (OSG) remains easily visible.
●Make sure that enough space remains for maintenance work.
●Make sure that the machine is placed or mounted horizontally, a maximum deviation of 1° in any
direction is acceptable.
●Check the oil level, see Oil Level Inspection [➔28].
●Make sure that the cooling water complies with the requirements, see Cooling Water Connection
[➔14].

Installation | 5
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 13 | 44
5.2 Connecting Lines / Pipes
●Remove all protective covers before installation.
●Make sure that the connection lines cause no stress on the connection of the machine; if neces-
sary use flexible joints.
●Make sure that the line size of the connection lines over the entire length is at least as large as
the connections of the machine.
In case of long connection lines, it is advisable to use larger line sizes in order to avoid a loss of effi-
ciency. Seek advice from your Busch representative.
5.2.1 Suction Connection
WARNING
Unprotected suction connection.
Risk of severe injury!
●Do not put hand or fingers in the suction connection.
NOTICE
Ingress of foreign objects or liquids.
Risk of damage to the machine!
If the inlet gas contains dust or other foreign solid particles:
●Install a suitable filter (5micron or less) upstream from the machine.
Several executions are available and typically include a mesh screen.
Connection size(s):
– G3, vertical or horizontal
– 2 x G2, horizontal
– ISO DN100, DIN 28404, vertical
5.2.2 Discharge Connection
NOTICE
Discharge gas flow obstructed.
Risk of damage to the machine!
●Make sure that the discharged gas will flow without obstruction. Do not shut off or throttle the
discharge line or use it as a pressurized air source.
Connection size(s):
At the silencer (SI) discharge connection
– G3, horizontal
●Make sure that the counter pressure (also termed back pressure) at the discharge connection
(OUT) does not exceed the maximum allowable discharge pressure, see Technical Data.

5 | Installation
14 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
5.2.3 Cooling Water Connection
CWI
CWO
Description
CWI Cooling water inlet CWO Cooling water outlet
●Connect the cooling water connections (CWI / CWO) to the water supply.
Connection size:
– G1/2, ISO 228-1 (CWI / CWO)
●Make sure that the cooling water complies with the following requirements:
Supply capacity l/min 8 ... 16
Water pressure bar 1 ... 6
Supply temperature °C +5 ... +30
Required pressure differential across supply
and return
bar ≥ 1
●To reduce the maintenance effort and ensure a long product lifetime we recommend the follow-
ing cooling water quality:
Hardness mg/l (ppm) < 90
Properties Clean & clear
PH value 7 ... 8
Particle size µm < 200
Chloride mg/l < 100
Electrical conductivity µS/cm ≤ 100
Free chloride mg/l < 0.3
Materials in contact with the cooling water Stainless steel and cast iron

Installation | 5
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 15 | 44
NOTE
Water hardness unit conversion.
1 mg/l (ppm) = 0.056 °dh (german degree) = 0.07 °e (english degree) = 0.1 °fH (french degree)
5.2.4 Barrier Gas System Connection (Optional)
WARNING
The barrier gas system is mandatory for the suction of process gas with a volume of oxygen
higher than 21% (>21%).
PRV FMEBGCMAN
Description
BGC Barrier gas connection FME Flow meter
MAN Manometer PRV Pressure regulating valve
●Connect the barrier gas connection (BGC) to the gas supply.
Connection size:
– G1/4, ISO 228-1
●Make sure that the gas complies with the following requirements:
Gas type Dry nitrogen or air
Gas temperature °C 0 ... 60
Maximum gas pressure bar 13
Recommended pressure setting at the pres-
sure regulating valve (PRV)
bar(a) 3
Filtration µm 5
Recommended flow rate SLM (standard li-
ter per minute)
15 ... 20

5 | Installation
16 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
5.3 Filling Oil
WARNING
Process gas with > 21% vol. oxygen and use of an inappropriate oil.
Risk of fire!
●Use only a type of oil approved and recommended by Busch for oxygen applications.
NOTICE
Use of an inappropriate oil.
Risk of premature failure!
Loss of efficiency!
●Only use an oil type which has previously been approved and recommended by Busch.
For oil type and oil capacity see Technical Data and Oil [➔41].

Installation | 5
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 17 | 44
When the oil filling is achieved:
●Write down the oil change date on the sticker.
Last oil change
__ / __ / ____
Oil type see nameplate
Change interval see
instruction manual
If there is no sticker (part no. 0565 568 959) on the machine:
●Order it from your Busch representative.

6 | Electrical Connection
18 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
6 Electrical Connection
DANGER
Live wires.
Risk of electrical shock.
●Electrical installation work must only be executed by qualified personnel.
CURRENT PROTECTION OF THE CUSTOMER INSTALLATION:
DANGER
Missing current protection.
Risk of electrical shock.
●Current protection according to EN 60204-1 must be insured by the customer on its installation.
●The electrical installation must comply with the applicable national and international standards.
NOTICE
Electromagnetic compatibility.
●Make sure that the motor of the machine will not be affected by electric or electromagnetic dis-
turbance from the mains, if necessary seek advice from Busch.
●Make sure that the EMC of the machine is compliant with the requirements of your supply net-
work system, if necessary provide further interference suppression (EMC of the machine, see EU
Declaration of Conformity [➔42] or UK Declaration of Conformity [➔43]).
6.1 Machine delivered without Variable Speed Drive
DANGER
Live wires.
Risk of electrical shock.
●Electrical installation work must only be executed by qualified personnel.
●Make sure that the power supply for the motor is compatible with the data on the nameplate of
the motor.
●If the machine is equipped with a power connector, install a residual current protective device to
protect persons in case of isolation default.
●Busch recommends installing a type B residual protective device suitable for the electrical in-
stallation.
●Provide a lockable disconnect switch or an emergency stop switch on the power line so that the
machine is completely secured in case of an emergency situation.
●Provide a lockable disconnect switch on the power line so that the machine is completely secured
during maintenance tasks.
●Provide an overload protection according to EN 60204-1 for the motor.

Electrical Connection | 6
Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en 19 | 44
●Connect the protective earth conductor.
●Electrically connect the motor.
NOTICE
The motor frequency is below 20 Hz.
Risk of damage to the machine!
●The motor nominal speed must always be higher than 1200 min-1 (20 Hz).
NOTICE
The admissible motor nominal speed exceeds the recommendation.
Risk of damage to the machine!
●Check the admissible motor nominal speed (nmax) on the nameplate of the machine (NP).
●Make sure to comply with it.
●Consult the Technical Data to get more information.
NOTICE
Incorrect connection.
Risk of damage to the motor!
●The wiring diagrams given below are typical. Check the inside of the terminal box for motor con-
nection instructions/diagrams.
6.2 Wiring Diagram Three-Phase Motor (Pump Drive)
●Make sure that you select the proper speed drive according to the motor specifications.
●Connect the motor to your external speed drive according to the operating instructions of your
external speed drive.
●Connect the motor cables as shown in the below wiring diagram.
NF 0950 A
Delta connection (low voltage): Star connection (high voltage):

6 | Electrical Connection
20 | 44 Instruction Manual COBRA NF 0750 A - NF 0950 A WCV_EN_en
NF 0750 A
Double star connection (low voltage):
T1
T6T3
T5T8
T4
T2
T7
T9
Star connection (high voltage):
T1
T6T3
T5T8
T4
T2
T7
T9
Connection of motor thermistors (3xPTC) (rec-
ommended):
P1 P2
NOTICE
Incorrect direction of rotation.
Risk of damage to the machine!
●Operation in the wrong direction of rotation can destroy the machine in a short time! Prior to
start-up, ensure that the machine is operated in the right direction.
The intended rotation direction of the motor is defined by the illustration below:
●Jog the motor briefly.
●With a phase rotation tester, check if the wiring corresponds to the correct direction of rotation.
If the rotation of the motor must be changed:
●Switch any two of the motor phase wires.
●Connect the motor temperature protection (Thermistors PTC. 3 x 155°C).
●Motor terminal box cable entries:
●2 x M25 x 1.5
●1 x M16 x 1.5