BUSCH COBRA NX 0950 A User manual

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COBRA
Dry Screw Vacuum Pumps
NX 0950 A Water-Cooled Version (WCV)
Instruction Manual
0870222540 | -0003_en-US | Original instructions 10/27/2022

Table of Contents
2 | 44 Instruction Manual COBRA NX 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............................................................................................................................................... 7
2.4.1 Water Cooling........................................................................................................................................ 7
2.4.2 Temperature Switch ............................................................................................................................. 7
2.4.3 Sealing Systems..................................................................................................................................... 7
2.5 Optional Accessories........................................................................................................................................... 7
2.5.1 Gas Ballast Valve ................................................................................................................................... 7
2.5.2 Silencer................................................................................................................................................... 7
2.5.3 Barrier Gas System ............................................................................................................................... 7
2.5.4 Inlet Filter............................................................................................................................................... 8
2.5.5 Inlet Check Valve................................................................................................................................... 8
3 Transport .............................................................................................................................................................. 9
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 .......................................................................................................................... 14
5.2.3 Cooling Water Connection................................................................................................................... 15
5.2.4 Barrier Gas System Connection (Optional) ........................................................................................ 16
5.3 Filling Oil............................................................................................................................................................... 17
6 Electrical Connection........................................................................................................................................... 19
6.1 Machine delivered with a Variable Speed Drive .............................................................................................. 20
6.2 Electrical Connection of the Variable Speed Drive.......................................................................................... 21
6.3 Wiring Diagram Variable Speed Drive (VSD).................................................................................................... 22
6.4 Start / Stop Connection ...................................................................................................................................... 23
6.5 Wiring Diagram Three-Phase Motor (Pump Drive)......................................................................................... 23
6.6 Electrical Connection of the Monitoring Devices ............................................................................................ 24
6.6.1 Wiring Diagram Temperature Switch................................................................................................. 24
7 Commissioning..................................................................................................................................................... 25
7.1 Conveying Condensable Vapors........................................................................................................................ 26
8 Maintenance......................................................................................................................................................... 27
8.1 Maintenance Schedule ....................................................................................................................................... 28
8.2 Oil Level Inspection............................................................................................................................................. 29
8.3 Cleaning the Inlet Screen ................................................................................................................................... 29
8.4 Cleaning the Gas Ballast Filter (Optional)......................................................................................................... 30
8.5 Oil Change............................................................................................................................................................ 30
9 Overhaul................................................................................................................................................................ 33
10 Decommissioning................................................................................................................................................. 34
10.1 Dismantling and Disposal .................................................................................................................................. 34
11 Spare Parts............................................................................................................................................................ 35
12 Troubleshooting................................................................................................................................................... 36

Table of Contents
Instruction Manual COBRA NX 0950 A WCV_EN_en 3 | 44
13 Technical Data...................................................................................................................................................... 38
14 Oil........................................................................................................................................................................... 39
15 EU Declaration of Conformity............................................................................................................................. 40
16 UK Declaration of Conformity ............................................................................................................................ 41

1 | Safety
4 | 44 Instruction Manual COBRA NX 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.

Product Description | 2
Instruction Manual COBRA NX 0950 A WCV_EN_en 5 | 44
2 Product Description
EB IN, IS
OUT
PMR MP
BGR VSDCWD
SI
OSG
GBOFPTSCWO
BGCBGMODP
BGFOFP
CWDODPOSG
CWI
NP MP
OUTCD
GBS
Description
IN Suction connection (Inlet) OUT Discharge connection (Outlet)
BGC Barrier gas connection BGF Barrier gas flow meter
BGM Barrier gas manometer BGR Barrier gas pressure regulator
CD Condensate drain 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 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
VSD Variable Speed Drive

2 | Product Description
6 | 44 Instruction Manual COBRA NX 0950 A WCV_EN_en
NOTE
Technical term.
In this instruction manual, we consider that the term ‘machine’ refers to the ‘vacuum pump’.
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 NX 0950 A WCV_EN_en 7 | 44
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
- Fluoroelastomer (FKM/FPM)
●In doubt, please contact your Busch representative.
2.3 Start Controls
The machine is equipped with a variable speed drive.
2.4 Standard Features
2.4.1 Water Cooling
The machine is cooled by a cooling water circuit in the cylinder cover and cylinder.
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 [➔24]).
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 [➔7].
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
The barrier gas system allows the supply of compressed air or nitrogen into the motor side shaft
seals in order to improve the sealing efficiency.

2 | Product Description
8 | 44 Instruction Manual COBRA NX 0950 A WCV_EN_en
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'
2.5.5 Inlet Check Valve
In order to avoid reverse rotation after switching off, the machine can be equipped with an inlet
check valve.
The inlet check valve also prevents fast venting of the connected vacuum system.
The inlet check valve can also be equipped with a pressure sensor (please contact your local Busch
representative for further information).
1
2
Description
1 Connection size: G3' 2 Connection size: G1/2

Transport | 3
Instruction Manual COBRA NX 0950 A WCV_EN_en 9 | 44
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.
●Make sure that each of the slings used to lift the machine has a minimum length of 400 mm.
●Make sure that the length of each sling is exactly the same.

3 | Transport
10 | 44 Instruction Manual COBRA NX 0950 A WCV_EN_en
21
Description
1 Minimum length: 400 mm 2 Minimum length: 400 mm
●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 NX 0950 A WCV_EN_en 11 | 44
4 Storage
●Seal all apertures with adhesive tape or reuse provided caps.
NOTICE
Long storage time.
Risk of damage to the machine!
●Due to a long storage time the capacitors of the variable speed drive can lose efficiency because
of electrochemical processes. In the worst case, it can lead to a short-circuit and therefore to a
damage to the variable speed drive of the machine.
●Connect the machine every 18 months for 60 minutes to the mains.
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 NX 0950 A WCV_EN_en
5 Installation
5.1 Installation Conditions
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.
~20 cm
~50 cm
~20 cm
~50 cm
●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 installation space or location is vented such that sufficient cooling of the ma-
chine is provided.
●Make sure that cooling air inlets and outlets of the motor and VFD fans are not covered or ob-
structed and that the cooling air flow is not affected adversely in any other way.
●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 of 1° in any direction
is acceptable.
●Check the oil level, see Oil Level Inspection [➔29].
●Make sure that the cooling water complies with the requirements, see Cooling Water Connection
[➔15].
If the machine is installed at an altitude greater than 1000 meters above sea level:
●Contact your Busch representative, the motor should be derated or the ambient temperature
limited.

Installation | 5
Instruction Manual COBRA NX 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 machine‘s connection; if necessary 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.
Connection size(s):
– G3
– ISO DN100, DIN 28404
If the machine is used as part of a vacuum system:
●Busch recommends the installation of an isolation valve in order to prevent the machine from
turning backwards.

5 | Installation
14 | 44 Instruction Manual COBRA NX 0950 A WCV_EN_en
5.2.2 Discharge Connection
1
Description
1 Discharge variants (without silencer)
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 machine discharge connection:
– G3, horizontal (orientable 180°)
– ISO DN100, DIN 28404, vertical (without discharge elbow)
At the silencer (SI) discharge connection (Optional):
– ISO DN100, DIN 28404, 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.

Installation | 5
Instruction Manual COBRA NX 0950 A WCV_EN_en 15 | 44
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 +10 ... +30
Required pressure differential across supply
and return
bar ≥ 1
Cooling water supply temperature in Fahrenheit degrees:
– +50 … +86 °F
●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

5 | Installation
16 | 44 Instruction Manual COBRA NX 0950 A WCV_EN_en
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)
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
Air quality (only for air) Acc. to ISO
8573-1
Class 5.4.4.

Installation | 5
Instruction Manual COBRA NX 0950 A WCV_EN_en 17 | 44
5.3 Filling Oil
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 [➔39].

5 | Installation
18 | 44 Instruction Manual COBRA NX 0950 A WCV_EN_en
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.

Electrical Connection | 6
Instruction Manual COBRA NX 0950 A WCV_EN_en 19 | 44
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 electro- magnetic 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 [➔40] or UK Declaration of Conformity [➔41]).

6 | Electrical Connection
20 | 44 Instruction Manual COBRA NX 0950 A WCV_EN_en
6.1 Machine delivered with a Variable Speed Drive
DANGER
Live wires. Carry out any work on the variable speed drive and motor.
Risk of electrical shock!
●Electrical installation work must only be executed by qualified personnel.
DANGER
Maintenance work without disconnecting the variable speed drive.
Risk of electrical shock.
●Disconnect and isolate the variable speed drive before attempting any work on it.
High voltages are present at the terminals and within the variable speed drive for up to 10 min-
utes after disconnection of the electrical supply.
●Always ensure by using a suitable multimeter that no voltage is present on any drive power termi-
nals prior to commencing any work.
NOTICE
The admissible motor speed exceeds the recommendation.
Risk of damage to the machine!
●Check the admissible motor speed range, see Technical Data.
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
Incorrect connection.
Risk of damage to the variable speed drive!
●The wiring diagrams given below are typical. Check the connection instructions/diagrams.
●Make sure that the power supply for the drive is compatible with the data on the nameplate of
the variable speed drive.
●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.
●If the variable speed drive is not equipped with a lockable disconnect switch, provide it on the
power line so that the machine is completely secured during maintenance tasks.