Diaphragm Vacuum Pump Operating Instructions N920 AP.18

Operating Instructions
Read and observe these Operating Instructions!
Diaphragm Vacuum Pump
N920 AP.18
N920 AP.29.18
Contents
KNF Neuberger GmbH
Alter Weg 3
D-79112 Freiburg
Germany
Phone +49-(0)7664 / 5909-0
Fax +49-(0)7664 / 5909-99
E-Mail: [email protected]
www.knf.de
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
N920 KT.29.18G
Page
About this document..................................................................3
Use ............................................................................................4
Safety ........................................................................................5
Technical Data ..........................................................................7
Design and Function ...............................................................10
Installation and connection ......................................................12
Operation .................................................................................13
Servicing ..................................................................................16
Troubleshooting .......................................................................25
Spare parts and accessories ...................................................27
Returns ....................................................................................28
Health and safety clearance and decontamination form .........29
KNF 121416-121419 03/16
Translation of original Operating Instructions, english
Keep for future use!
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
1.
About this document
About this document
1.1. Using the Operating Instructions
The Operating Instructions are part of the pump.
 Carefully study the Operating Instructions before using a
pump.
 Always keep the Operating Instructions handy in the work
area.
 Pass on the Operating Instructions to the next owner.
Project pumps
Customer-specific project pumps (pump models which begin with
“PJ” or “PM”) may differ from the Operating Instructions.
 For project pumps, also observe the agreed upon specifications.
1.2. Symbols and Markings
Warning
A danger warning is located here.
Possible consequences of a failure to observe the
warning are specified here. The signal word, e.g.
WARNING Warning, indicates the danger level.
 Measures for avoiding the danger and its consequences are specified here.
Danger levels
Signal word Meaning
DANGER
warns of immediate danger
WARNING
CAUTION
Consequences if not observed
Death or serious injuries
and/or serious damage are the
consequence.
warns of possible
Death or serious injuries
danger
and/or serious damage are
possible.
warns of a possibly Minor injuries or damage are
dangerous situapossible.
tion
Tab. 1
Other information and symbols
 An activity to be carried out (a step) is specified here.
1. The first step of an activity to be carried out is specified here.
Additional, consecutively numbered steps follow.
This symbol refers to important information.
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
3
Use
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
2.
Use
2.1. Proper use
The pumps are exclusively intended for transferring gases and
vapors.
Owner's responsibility
Operating parameters and
conditions
Only install and operate the pumps under the operating parameters
and conditions described in chapter 4, Technical data.
Make sure that the installation location is dry and the pump is
protected against rain, splash, hose and drip water.
Requirements for
transferred medium
Before using a medium, check whether the medium can be transferred danger-free in the specific application case.
Before using a medium, check the compatibility of the materials of
the pump head, diaphragm and valves with the medium.
Only transfer gases which remain stable under the pressures and
temperatures occurring in the pump.
Accessories
Laboratory equipment or additional components connected to a
pump have to be suitable for use with the pneumatic capabilities of
the pump (see chapter 4).
2.2. Improper use
The pumps may not be operated in an explosive atmosphere.
The pumps are not suitable for transferring dusts.
The pumps are not suitable for transferring liquids.
The pumps must not be used to create vacuum and overpressure
simultaneously.
An overpressure must not be applied to the suction side of the
pump.
4
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
3.
Safety
Safety
Note the safety precautions in chapters 6. Installation and
connection, and 7. Operation.
The pumps are built according to the generally recognized rules of
technology and in accordance with the occupational safety and
accident prevention regulations. Nevertheless, dangers can result
during their use which lead to injuries to the user or others, or to
damage to the pump or other property.
Only use the pumps when they are in a good technical and proper
working order, in accordance with their intended use, observing the
safety advice within the operating instructions, at all times.
Personnel
Make sure that only trained and instructed personnel or specially
trained personnel work on the pumps. This especially applies to
assembly, connection and servicing work.
Make sure that the personnel has read and understood the operating instructions, and in particular the "Safety" chapter.
Working in a safetyconscious manner
Observe the accident prevention and safety regulations when
performing any work on the pump and during operation.
Do not expose any part of your body to the vacuum.
Open housing parts with notice sticker (see fig. 1) only after
separating mains plug from power source.
Fig. 1: Notice sticker
Handling dangerous media
When transferring dangerous media, observe the safety regulations when handling these media.
Handling flammable media
Be aware that the pumps are not designed to be explosion-proof.
Make sure the temperature of the medium is always sufficiently
below the ignition temperature of the medium, to avoid ignition or
explosion. This also applies for unusual operational situations.
Note that the temperature of the medium increases when the pump
compresses the medium.
Hence, make sure the temperature of the medium is sufficiently
below the ignition temperature of the medium, even when it is
compressed to the maximum permissible operating pressure of the
pump. The maximum permissible operating pressure of the pump
is stated in the technical specifications (see chapter 4).
If necessary, consider any external sources of energy, such as
radiation, that may add heat to the medium.
In case of doubt, consult the KNF customer service.
Environmental protection
Store all replacement parts in a protected manner and dispose of
them properly in accordance with the applicable environmental
protection regulations. Observe the respective national and international regulations. This especially applies to parts contaminated
with toxic substances.
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
5
Safety
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Standards
The pumps conform to the Directive 2011/65/EU (RoHS2).
The pumps conform to the safety regulations of the EC Directive
2014/30/EU concerning Electromagnetic Compatibility and the EC
Directive 2006/42/EC concerning Machinery.
The following harmonized standards have been used:

DIN EN 61010-1

DIN EN 61326-1 class A

DIN EN 50581
The pumps correspond to IEC 664:
Customer service and
repairs

the overvoltage category II

the pollution degree 2.
Only have repairs to the pump carried out by the KNF Customer
Service responsible.
Only authorized personnel should open those parts of the housing
that contain live electrical parts.
Use only genuine parts from KNF for servicing work.
6
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Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
4.
Technical Data
Technical Data
The pump is supplied by a universal power supply with integrated overload protection. It is protected against overheating
by a temperature sensor on the motor board and equipped with
overcurrent protection.
If one of these safety functions is triggered, the pump will be
shut down and must be manually reset, as follows:
 Separate pump from electrical power supply.
 Remove the cause(s) of the fault before restarting.
Pump materials
N 920 AP.18
N 920 AP.29.18
Component
Pump material
Pump head
Diaphragm
Valve
Aluminum
EPDM
EPDM
Tab. 2
N 920 KT.29.18G
Component
Pump material
Pump head
Diaphragm
Valve
Gas ballast valve
PPS
PTFE-coated
EPDM
PVDF
Tab. 3
Refer to the type plate for the pump’s electrical configuration.
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
7
Technical Data
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
N 920 AP.18
N 920 AP.29.18
Pneumatic performance
Max. permissible operating
pressure [bar g]
Ultimate vacuum [mbar abs.]
Delivery rate at atm. pressure
[l/min]*
0.5
1.5
max. 21
Pneumatic connections
Hose connection [mm]
ID 9
Ambient and media temperature
Permissible ambient
temperature
Permissible media
temperature
+ 10 °C to + 40 °C
+ 5 °C to + 40 °C
Other parameters
Weight [kg]
Dimensions : L x H x W [mm]
Maximum permissible ambient
relative humidity
Max. altitude of site [m above
sea level]
10.5
324 x 226 x 158
80 % for temperatures up to
31 °C, decreasing linearly to
50 % at 40 °C
2000
Electrical Data
Automatic mains power adjustment
Max. operating current [A]
Power consumption pump [W]
Maximum permitted mains
voltage fluctuations
Protection class motor
Tab. 4
8
100-240 V
50/60 Hz
1.3
120
+/- 10 %
IP20
* Liters in standard state (1,013 mbar)
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Technical Data
N 920 KT.29.18G
Pneumatic performance
Max. permissible operating
pressure [bar g]
Ultimate vacuum [mbar abs.]
Delivery rate at atm. pressure
[l/min]*
0.5
2.0
≤ 5 with open gas ballast
max. 21
Pneumatic connections
Hose connection [mm]
ID 10
Ambient and media temperature
Permissible ambient
temperature
Permissible media
temperature
+ 10 °C to + 40 °C
+ 5 °C to + 40 °C
Other parameters
Weight [kg]
Dimensions : L x H x W [mm]
Maximum permissible ambient
relative humidity
Max. altitude of site [m above
sea level]
8.5
324 x 226 x 158
80 % for temperatures up to
31 °C, decreasing linearly to
50 % at 40 °C
2000
Electrical Data
Automatic mains power adjustment
Max. operating current [A]
Power consumption pump [W]
Maximum permitted mains
voltage fluctuations
Protection class motor
Tab. 5
100-240 V
50/60 Hz
1.4
135
+/- 10 %
IP20
* Liters in standard state (1,013 mbar)
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
9
Design and Function
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
5.
Design and Function
Design
1
2
3
4
5
6
Inlet (suction side)
Outlet (pressure side)
Potentiometer
(only N 920 AP.29.18 and
N 920 KT.29.18G)
Power switch
Gas ballast valve
(only N 920 KT.29.18G)
Interface to vacuum controller VC 900
Fig. 2: Design N 920 KT.29.18G
Function Diaphragm Pump
1
2
3
4
5
6
7
Outlet valve
Inlet valve
Transfer chamber
Diaphragm
Eccentric
Connecting rod
Pump drive
Fig. 3: Pump head
Diaphragm pumps transfer, compress (depending on pump version) and evacuate gases and vapors.
The elastic diaphragm (4) is moved up and down by the eccentric
(5) and the connecting rod (6). In the downward stroke it aspirates
the gas to be transferred via the inlet valve (2). In the upward
stroke, the diaphragm presses the medium out of the pump head
via the outlet valve (1). The transfer chamber (3) is hermetically
separated from the pump drive (7) by the diaphragm.
10
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Design and Function
Function diaphragm stabilization system
(only N 920 AP.18 and N 920 AP.29.18)
1
2
3
Balancing connection for
vacuum chamber
Vacuum chamber
Stabilization diaphragm
Fig. 4: Function diaphragm stabilization system
An additional diaphragm, the so-called stabilization diaphragm (3),
separates the underside of the working diaphragm from the “crank”
space of the pump (see fig. 4). The space between the two diaphragms, called a vacuum chamber (2), is connected with the
suction side of the pump via an balancing connection (1). This way,
the vacuum chamber has approximately the same pressure as the
working space of the diaphragm pump. The pressure difference
between the upper and underside of the diaphragm approaches
zero. The working diaphragm remains stable, independent of the
inlet pressure of the pump. This improves the suction speed of the
pump significantly, over its entire working range.
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
11
Installation and connection
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
6.
Installation and connection
Only install the pumps under the operating parameters and conditions described in chapter 4, Technical data.
Observe the safety precautions (see chapter 3).
6.1. Installation
 Before installation, store the pump at the installation location to
bring it up to room temperature.
Dimensions
Cooling air supply
Installation location
 See chapter 4, Technical data, for the dimensions of pump.
 Install the pump so that the motor fan can intake sufficient
cooling air.
 Make sure that the installation location is dry and the pump is
protected against rain, splash, hose and drip water.
 Choose a safe location (flat surface) for the pump.
 Protect the pump from dust.
 Protect the pump from vibration and jolt.
6.2. Connection
Connected components
Pump exhaust
Connection
 Only connect components to the pump which are designed for
the pneumatic data of the pump (see chapter 4).
 If the pump is used as a vacuum pump, safely discharge the
pump exhaust at the pump’s pneumatic outlet.
A marking on the pump head shows the direction of flow.
1. Remove the protective plugs from the pneumatic connectors of
the pump.
2. Connect the suction line and pressure line.
3. Lay the suction and pressure line at a downward angle to
prevent condensate from running into the pump.
4. If necessary, use the interface cable to connect the pump with
the vacuum controller VC 900 (Fig. 2/6, see Chapter 10.2
Accessories for interface cable). Further information on connecting see operating instructions VC 900.
5. Insert the power cable’s plug into a properly installed
shockproof socket.
12
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
7.
Operation
Operation
7.1. Preparing for Start-up
Before switching on the pump, observe the following points:
Pump
Operational requirements
 All hoses attached properly

Fan openings not blocked

Specifications of the power supply correspond with
the data on the pump’s type plate.

The pump outlet is not closed or constricted.

When the gas ballast valve is open, no reactive,
explosive, or otherwise hazardous mixtures can
form (otherwise, contact KNF Service).
Tab. 6
7.2. Starting
 Only operate the pump under the operating parameters and
conditions described in chapter 4, Technical data.
 Make sure the pump is used properly (see chapter 2.1).
 Make sure the pump is not used improperly (see chapter 2.2).
 Observe the safety precautions (see chapter 3).
Hazard of the pump head bursting due to excessive
pressure increase
WARNING
 Do not exceed max. permissible operating
pressure (see chapter 4).
 Monitor pressure during operation.
 If the pressure exceeds the maximum permissible operating pressure, immediately shut down
pump and eliminate fault (see chapter 9. Troubleshooting).
 Only throttle or regulate the air or gas quantity in
the suction line to prevent the maximum permissible operating pressure from being exceeded.
 If the air or gas quantity in the pressure line is
throttled or regulated, make sure that the maximum permissible operating pressure of the
pump is not exceeded.
Excessive pressure (with all of the related hazards) can be
prevented by placing a bypass line with a pressure-relief valve
between the pressure and suction side of the pump. For further
information, contact your KNF technical adviser.
Pump standstill
 With the pump at a standstill, open pressure and suction lines
to normal atmospheric pressure.
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
13
Operation
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Automatic starting can cause personal injury and
pump damage
When the operation of the pump is interrupted by the
WARNING thermal switch, the pump will restart automatically
after cooling down.
 After triggering of the thermal protection or in the
event of power failure, remove the pump’s mains
plug from the socket so that the pump cannot
start uncontrollably.
 Attempt work on the pump only if the pump is
separated from mains power.
7.3. Switching pump on and off
Switching pump on
The pump may not start up against pressure during switch-on.
This also applies in operation following a brief power failure. If
a pump starts against pressure, it may block. This activates the
thermal switch, and the pump switches off.
 Make sure that no pressure is present in the lines during
switch-on.
 Switch on pump with mains switch (see fig. 2).
Depending on the level of the applied electrical voltage, initialization of the electronics can take up to one second, before the
pump starts.
Switching off the pump/removing from operation
 When transferring aggressive media, flush the pump prior to
switch-off to increase the service life of the diaphragm (see
chapter 8.2.1).
 Switch off pump with mains switch (see fig. 2).
 Open pressure and suction lines to normal atmospheric pressure.
 Disconnect the power source.
7.4. Adjusting the flow rate
N 920 AP.18
The flow rate cannot be varied.
N 920 AP.29.18 und N 920 KT.29.18G
The pump's speed can be varied via the potentiometer (fig. 2/3).
The flow rate can be adjusted this way.
14
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Operation
7.5. Operating the pump via VC 900
(only N 920 KT.29.18G)
If the interface cable (accessories) is connected, the pump can be
operated via the vacuum controller VC 900. For further information on
operating see operating instructions VC 900.
7.6. Gas ballast
Personal injury caused by poisoning or explosion
and damage to the pump
 Make sure that no reactive or explosive mixtures
will be produced when the gas ballast valve is
WARNING
open.
Fig. 5: Gas ballast switch
When transferring vaporous media, opening the gas ballast
valve can minimize the formation of condensation in the pump
heads.
Opening the gas ballast valve deteriorates ultimate vacuum
performance.
The gas ballast valve is opened and closed via the gas ballast
switch (see Fig. 5).
Please contact KNF Service if you require an inert connection for
the gas ballast.
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
15
Servicing
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
8.
Servicing
8.1. Servicing Schedule
Component
Pump
Diaphragm and
valve plates
Servicing interval
Regular inspection for external damage or
leaks
Replace at the latest, when pump output
decreases
Tab. 7
8.2. Cleaning
When cleaning, make sure that no liquids enter the inside of
the housing.
8.2.1. Flushing Pump
Personal injury caused by poisoning or explosion
and damage to the pump
 When flushing the pump with inert gas, make
sure that the gas ballast valve is closed so no
WARNING
reactive or explosive mixtures can form.
 Before switching off the pump, flush it with air (if neccesary for
safety reasons: with an inert gas) for about five minutes under
atmospheric conditions (ambient pressure).
If inert gas is used:
Connect the inert gas feed to the gas inlet of the pump and
close the gas ballast valve. The safety precautions in Chapter
3 must be observed at all times.
8.2.2. Cleaning Pump
 Only use solvents for cleaning if the head materials cannot be
attacked (check the resistance of the material!).
 If compressed air is available, blow out the components.
16
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Servicing
8.3. Changing Diaphragm and Valve Plates
8.3.1. N 920 AP.18 and N 920 AP.29.18
Conditions
Spare parts/tools

Pump is switched off and mains plug is removed from the
socket

Pump is clean and free of hazardous materials

Tubes removed from pump’s pneumatic inlet and outlet
Spare part/tool
Service Set (according to chapter 10)
Allen key 4 mm
Felt-tip pen
Stabilization diaphragm (if required)
Tab. 8
Information on procedure
 Always replace diaphragm and valve plates together to maintain the pump performance.
Health hazard due to dangerous substances
in the pump!
Depending on the substance transferred, caustic
WARNING burns or poisoning are possible.
 Wear protective clothing if necessary, e.g.
protective gloves.
 Flush pump before replacing the diaphragm and
valve plates (see chapter 8.2.1).
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
17
Servicing
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Head cover
Screw
Intermediate plate, head 1
Valve plate
O-ring (ø 24 x 2)
O-ring (ø 5.5 x 2)
Intermediate plate, head 2
Intermediate plate, head 3
Diaphragm, head 1
Diaphragm, head 2
Diaphragm, head 3
Connecting rod, head 2
Connecting rod, head 3
Adapter
Pump housing
Fan
Stabilization diaphragm
O-ring (ø 5.5 x 2)
Screw
Fig. 6: Exploded drawing N 920 AP.18 / N 920 AP.29.18
18
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Servicing
Remove pump head
1. Undo the nine screws (2) in the head cover (1) and lift the
head cover off the pump housing (15) (see fig. 6).
2. Mark the position of intermediate plate (3) and adapter (14)
relative to each other by a drawing line with a felt-tip pen. This
helps avoid incorrect assembly later.
3. Mark the position of intermediate plate (7) and adapter (14)
relative to each other by two drawing lines with a pencil.
4. Mark the position of intermediate plate (8) and adapter (14)
relative to each other by three drawing lines with a pencil.
5. Lift the intermediate plates (3), (7)and (8) off the adapter.
Change diaphragms
1. Turn the three diaphragms (9), (10) and (11) outwards with
your hands, counter-clockwise. For this, turn the fan (16) such
that you can easily grip each diaphragm with your hands.
For diaphragms (10) and (11):
Make sure the diaphragm spacers being between diaphragm
and connecting rod do not fall into the pump housing.
If diaphragm spacers should adhere to the diaphragms, take
them off and put them on the thread of the corresponding
connecting rod.
The same number of diaphragm spacers must be mounted
as were used for the previous assembly. This is necessary, in
order to ensure the pump's pneumatic performance.
2. Remove the valve plates (4) and O-rings (5) from the intermediate plates (3), (7) and (8).
3. Remove O-ring (6) from the intermediate plate (3).
4. Remove O-ring (18) from adapter (14).
Carry out steps 5 to 11 only if the stabilization diaphragm also
shall be changed.
5. Loosen the two screws (19) and remove the adapter (14) from
the pump housing (15).
The stabilization diaphragm (17) is now visible.
6. Remove the existing diaphragm spacers from the stabilization
diaphragm (17).
It is important to later re-install the same quantity of diaphragm
spacers in order to ensure the pump's pneumatic performance.
7. Use the assembly key to loosen the stabilization diaphragm
(17) and then manually screw it out (in the counterclockwise direction).
8. Screw in the new stabilization diaphragm (17) and tighten it
hand-tight with the assembly key.
9. Put spacer(s) onto the thread of the new stabilization diaphragm (17) (same number).
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
19
Servicing
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
10. Place the adapter (14) onto the pump housing (15).
The adapter must be aligned flush with the pump housing (15).
This is important for later installation of the diaphragm (9).
11. Tighten the two screws (19) to hand-tightness.
Begin with the outermost screw and make sure that the adapter (14) does not move while you are tightening the screws.
12. Screw the new diaphragm (9) into the thread of the stabilization diaphragm (17) and tighten it by hand.
To ensure proper pump performance, it is important to maintain a uniform distance everywhere between the outer edge of
the diaphragm (9) and the adapter (14). If the distance is not
uniform, you must re-loosen the screws (19) and re-align the
adapter so the distance is the same everywhere.
Before you finally tighten the diaphragms, you are recommended to move the diaphragm to the upper dead center by
rotating the fan (16).
13. Screw the new diaphragm (10) and (11) onto the connecting
rods (12) and (13) and tighten it by hand.
Mount valve plates, intermediate plates and head cover
1. Lay the new O-ring (18) on the adapter (14).
2. Lay the new valve plates (fig. 7/4) and the new O-rings (5) on
the intermediate plates (3), (7)and (8).
Upper and lower sides of the valve plates are identical. For
correct position see fig. 6.
3. Lay the new O-ring (6) on the intermediate plate (3).
4. Place the intermediate plates (3), (7)and (8) on the adapter
(14) in the position indicated by the drawing lines.
5. Place the head cover (1) on the pump housing (15); tighten the
screws (2) hand tight, evenly and diagonally.
Fig. 7: Position of valve plates
6. Dispose of the old diaphragms, valve plates and O-rings
properly.
Final steps
1. Reconnect suction and pressure line to the pump.
2. Reconnect the pump to the electricity supply.
If you have any questions about servicing, call your KNF technical
adviser (see last page for contact telephone number).
20
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Servicing
8.3.2. N 920 KT.29.18G
Conditions
Spare parts/tools

Pump is switched off and mains plug is removed from the
socket

Pump is clean and free of hazardous materials

Tubes removed from pump’s pneumatic inlet and outlet
Spare part/tool
Service Set (according to chapter 10)
Allen key 4 mm
Phillips-head screwdriver No. 2
Felt-tip pen
Tab. 9
Information on procedure
 Always replace diaphragm and valve plates together to maintain the pump performance.
Health hazard due to dangerous substances
in the pump!
Depending on the substance transferred, caustic
WARNING burns or poisoning are possible.
 Wear protective clothing if necessary, e.g.
protective gloves.
 Flush pump before replacing the diaphragm and
valve plates (see chapter 8.2.1).
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
21
Servicing
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Screws of pump handhold
Pump handhold
Screws of head cover
Head cover
Cover
Screws of cover
Screws of head plate
Disk spring at screw (7)*
Washer at screw (7)*
Head plate
Intermediate plate
O-ring (ø 24 x 2)
Valve plate
Intermediate plate
Intermediate plate
Diaphragm
Adapter
Housing
Screws
Fan
Connecting rod
Diaphragm
Gas ballast valve
* see fig. 10
Fig. 8: Exploded drawing N 920 KT.29.18G
Remove pump head
1. Undo both screws (1) of pump handhold (2); remove pump
handhold (see fig. 8).
2. Undo the nine screws (3) of the head cover (4).
3. Undo two screws (6) each, and remove both covers (5) at head
cover (4).
4. Lift the head cover (4) off the pump housing (18).
5. Lift off head plate (10) with intermediate plates (11), (14) and
(15).
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Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Servicing
Change diaphragms
1. Turn the diaphragms (16) (2 pieces) and (22) (1 piece) outwards with your hands, counterclockwise. For this, turn the fan
(20) such that you can easily grip each diaphragm with your
hands.
Make sure the diaphragm spacers being between diaphragm
and connecting rod (21) do not fall into the pump housing.
If diaphragm spacers should adhere to the diaphragms, take
them off and put them on the thread of the corresponding
connecting rod.
The same number of diaphragm spacers must be mounted
as were used for the previous assembly. This is necessary, in
order to ensure the pump's pneumatic performance.
2. Screw the new diaphragms (16) (2 pieces) and (22) (1 piece)
onto the connecting rods (21) and tighten it by hand.
Before you finally tighten the diaphragm, you are recommended to move the diaphragm to the upper dead center by
rotating the fan (20).
3. Put head plate (10) with intermediate plates (11), (14) and (15)
on adapter (17).
Change valve plates
1. Mark the position of head plate (10) and intermediate plate
(11) relative to each other by a drawing line with a felt-tip pen.
This helps avoid incorrect assembly later.
2. Mark the position of head plate (10) and intermediate plate
(14) relative to each other by two drawing lines with a pencil.
3. Mark the position of head plate (10) and intermediate plate
(15) relative to each other by three drawing lines with a pencil.
4. Undo the three screws (7) in head plate (10) and remove head
plate from intermediate plates (11), (14) and (15).
5. Remove valve plates (13) and O-rings (12) from intermediate
plates (11), (14) and (15).
Instead of lying on intermediate plate, O-rings could stick to
head plate (10).
6. Lay the new valve plates (13) and the new O-rings (12) on the
intermediate plates (11), (14) and (15).
Upper and lower sides of the valve plates are identical. For
correct position see fig. 9.
Fig. 9: Position of valve plates
7. Dispose of the old diaphragms, valve plates and O-rings
properly.
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
23
Servicing
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Mount pump head
1. Place head plate (10) on intermediate plates (11), (14) and
(15) in the position indicated by the drawing lines.
At the front edge the three intermediate plates must lie in a
line on which head plate is placed flushly.
2. Tighten the three screws (7) of head plate (10) carefully slightly
hand-tight.
Fig. 10: Position and orientation of
disk (8) and washer (9) at
screw (7)
For position and orientation of disk spring (8) and washer (9)
of screw (7) see fig. 10.
3. Place head cover (4) on pump housing (18).
4. Tighten the nine screws (3) of head cover (4) slightly in the first
instance. Start with the screws of medium pump stage, then
tighten the screws on the right, at least these on the left.
5. Now, tighten the screws (3) firmly; tighten the center screws
first, then continue outward.
If the screws are stiff to turn, the intermediate plates do not
lie in a line at front edge, or intermediate plates and head
plate are not placed flushly (see step 1).
6. Remount the covers (5).
7. Remount pump handhold (2).
Final steps
1. Reconnect suction and pressure line to the pump.
2. Reconnect the pump to the electricity supply.
If you have any questions about servicing, call your KNF technical
adviser (see last page for contact telephone number).
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Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
9.
Troubleshooting
Troubleshooting
Extreme danger from electrical shock!
 Disconnect the pump power supply before working
on the pump.
DANGER  Make sure the pump is de-energized and secure.
 Check the pump (see Tab. 10 to 13).
Pump does not transfer
Cause
No voltage in the power source
Fault remedy
 Check room fuse and switch on if necessary.
Thermal switch has operated
following to over-heating.






Connections or lines blocked.
External valve is closed or filter
is clogged.
Condensate has collected in
pump head.
Diaphragm or valve plates are
worn.
Disconnect pump from mains.
Allow pump to cool.
Trace cause of over-heating and eliminate it.
Check connections and lines.
Remove blockage.
Check external valves and filters.
 Detach the condensate source from the pump.
 Flush pump (see chapter 8.2.1).
 Replace diaphragm and valve plates (see chapter 8.3).
Tab. 10
Flow rate, pressure or vacuum too low
The pump does not achieve the output specified in the Technical data or the data sheet.
Cause
Fault remedy
Condensate has collected in
 Detach the condensate source from the pump.
pump head.
 Flush pump (see chapter 8.2.1).
There is gauge pressure on
 Change the pressure conditions.
pressure side and at the same
time vacuum or a pressure
above atmospheric pressure on
suction side.
Pneumatic lines or connection
 Disconnect pump from system to determine output values.
parts have an insufficient cross  Eliminate throttling (e.g. valve) if necessary.
section.
 Use lines or connection parts with larger cross section if
necessary.
Leaks occur on connections,
 Check that tubes sit correctly on hose nozzles.
lines or pump head.
 Replace leaky tubes.
 Eliminate leaks.
Connections or lines completely  Check connections and lines.
or partially clogged.
 Remove the clogging parts and particles.
Head parts are soiled.
 Clean head components.
Diaphragm or valve plates are
worn.
 Replace diaphragm and valve plates (see chapter 8.3).
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
25
Troubleshooting
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Flow rate, pressure or vacuum too low
The pump does not achieve the output specified in the Technical data or the data sheet.
Cause
Fault remedy
Replaced diaphragms and valve  Check that the spacers have been replaced onto the diaplates
phragm screw thread.
 Check head connection and hose connections for leaks.
 Possibly carefully tighten the screws of the head cover
crosswise.
Gas ballast still open.
 Close gas ballast.
Tab. 11
Pump is switched on, but does not run, the on/off-switch on the pump is not lit
Cause
Pump is not connected with the
power source.
No voltage in the power source
The pump’s overcurrent protection circuit has responded.
Fault remedy
 Connect pump to mains power.
 Check room fuse and switch on if necessary.
 Remove the pump from the source of electrical power.
 Determine and eliminate the cause of the overcurrent (e.g.
inproper pressure, liquid in the pump heads).
The pump must be unplugged for some seconds before the
electronics will allow to restart.
Tab. 12
Pump is switched on, but does not run, the on/off-switch on the pump is lit
Cause
The thermal switch has opened
due to overheating
Cause
 Remove pump´s mains plug from the socket.
 Allow pump to cool.
 Trace cause of over-heating and elimate it.
Tab. 13
Fault cannot be rectified
If you are unable to determine any of the specified causes, send
the pump to KNF Customer Service (see last page for the address).
1. Flush the pump to free the pump head of dangerous or aggressive gases (see chapter 8.2.1).
2. Clean the pump (see chapter 8.2.2).
3. Send the pump, together with completed Health and Safety
Clearance and Decontamination Form (Chapter 12), to KNF
stating the nature of the transferred medium.
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Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Spare parts and accessories
10. Spare parts and accessories
10.1. Spare parts
Service Set contains all replacement parts needed for one complete service:

3 diaphragms

6 O-rings (ø 24 x 2)

6 valve plates

Only for N 920 AP.18 and N 920 AP.29.18:
2 O- rings (ø 5.5 x 2)
Spare parts
Service set for N 920 AP.18
Service set for N 920 AP.29.18
Service set for N 920 KT.29.18G
Service set for N 920 KT.29.18
Stabilization diaphragm
(only for N 920 AP.18 and N 920 AP.29.18)
Gas ballast valve
Order No.
057456
057456
305355
111905
056523
136104
Tab. 14
10.2. Accessories
Accessories
Silencer/ Filter G 1/8
Sealing for hose connector
Adjustable delivery through analog signal
input; for external control
Assembly key for stabilization diaphragm
(only for N 920 AP.18 and N 920 AP.29.18)
Interface cable
Vacuum controller – KNF pump (2m)
Interface cable
Vacuum controller – KNF pump (5m)
Order No.
007006
026906
on request
116885
307757
307758
Tab. 15
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
27
Returns
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
11. Returns
Pumps and systems used in laboratories and process-based
industries are exposed to a wide variety of conditions. This means
that the components contacting pumped media could become
contaminated by toxic, radioactive, or otherwise hazardous substances.
For this reason, customers who send any pumps or systems back
to KNF must submit a Health and safety clearance and decontamination form in order to avoid a hazardous situation for KNF employees. This Health and safety clearance and decontamination
form provides the following information, among other things:

physiological safety

whether medium-contacting parts have been cleaned

whether the equipment has been decontaminated

media that have been pumped or used
To ensure worker safety, work may not be started on pumps or
systems without a signed Health and safety clearance and decontamination form.
For optimal processing of a return, a copy of this declaration
should be sent in advance via e-mail, regular mail, or fax to KNF
Customer Service (refer to final page for address). In order to avoid
endangering employees who open the shipment's packaging,
despite any residual hazards, the original version of the Health and
safety clearance and decontamination form must accompany the
delivery receipt on the outside of the packing.
The template for the Health and safety clearance and decontamination form is included with these Operating Instructions and may
also be downloaded from the KNF website.
The customer must specify the device type(s) and serial number(s)
in the Health and safety clearance and decontamination form in
order to provide for the unambiguous assignment of the Declaration to the device that is sent to KNF.
In addition to the customer's declaration of physiological safety,
information about operating conditions and the customer's application are also of importance to ensure that the return shipment is
handled appropriately. Therefore, the Health and safety clearance
and decontamination form requests this information as well.
28
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
Diaphragm Vacuum Pumps N 920__.18 and N 920 KT.29.18G
Health and safety clearance and decont. form
12. Health and safety clearance and decontamination form
Translation of original Operating Instructions, English, KNF 121416-121419 03/16
29
KNF worldwide
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