Edwards ELD500 Series User manual

edwardsvacuum.com
ELD500 LEAK DETECTOR
INSTRUCTION MANUAL
Publication number: D135-10-880
Issue: C
Original Instructions

Copyright notice
© Edwards Limited 2018. All rights reserved.
Trademark credits
Edwards and the Edwards logo are trademarks of Edwards Limited.
D135-10-880C - Copyright notice

Declaration of Conformity
This product has been manufactured under a quality management system certified to ISO9001:2015
This declaration is based on the requirements of ENISO17050-1 and the relevant Directives
P200-10-169-C
Edwards Ltd,
Innovation Drive,
Burgess Hill,
West Sussex,
RH15 9TW, UK
The following product
Leak detection system – ELD500:
ELD500 WET, 200 - 240 V AC, 50/60 Hz D13510903
ELD500 WET, 100 V AC, 50/60 Hz D13510904
ELD500 WET, 100 - 120 V AC, 60 Hz D13510906
ELD500 DRY, 200 - 240 V AC, 50/60 Hz D13520903
ELD500 DRY, 100 V AC, 50/60 Hz D13520904
ELD500 DRY, 100 - 120 V AC, 60 Hz D13520906
ELD500 FLEX D13530000
Is in conformity with the relevant requirements of European CE legislation:
2006/42/EC
Machinery Directive
2014/35/EU
Low Voltage Directive
2014/30/EU
Electromagnetic Compatibility (EMC) Directive
2011/65/EU
Restriction of Certain Hazardous Substances (RoHS) Directive
Based on the relevant requirements of harmonised standards:
EN61010-1:2010
Safety requirements for electrical equipment for measurement, control and laboratory use.
General requirements
EN61326-1:2013
Electrical equipment for measurement, control and laboratory use. EMC requirements.
General requirements
Class A, Industrial Immunity
The product also complies with the following:
2012/19/EU
Waste from Electrical and Electronic Equipment (WEEE) Directive
This covers all product serial numbers from the date of this Declaration onwards.
03.08.2018, Burgess Hill
Peter Lamb
Senior Manager, Scientific Pump Technology
Date and Place

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D135-10-880C - Contents
Page i
Contents
Safety 1
Key to the symbols ............................................................................................................ 1
Symbols of vacuum technology ................................................................................... 3
Definition of terms ...................................................................................................... 3
Description 5
Design and function .......................................................................................................... 5
Vacuum diagram ELD500 WET .................................................................................... 6
Vacuum diagram ELD500 DRY ..................................................................................... 8
Vacuum diagram ELD500 FLEX .................................................................................... 9
Vacuum method ........................................................................................................ 10
Partial flow method ................................................................................................... 11
Sniffer mode .............................................................................................................. 11
Supplied equipment .................................................................................................. 11
Technical data ................................................................................................................. 12
Technical data ELD500 WET ...................................................................................... 12
Physical data ......................................................................................................... 12
Electrical data ....................................................................................................... 13
Other data ............................................................................................................ 13
Environmental conditions .................................................................................... 13
Technical data ELD500 DRY ....................................................................................... 13
Physical data ......................................................................................................... 13
Electrical data ....................................................................................................... 14
Other data ............................................................................................................ 14
Ambient conditions .............................................................................................. 15
Technical data ELD500 FLEX ...................................................................................... 15
Physical data ......................................................................................................... 15
Electrical data ....................................................................................................... 16
Other data ............................................................................................................ 16
Environmental conditions .................................................................................... 17
Dimensional drawings ............................................................................................... 17
Ordering information ...................................................................................................... 19
Accessories ..................................................................................................................... 20
Sniffer line (ELD500 SL) .............................................................................................. 20
Remote control RC wired and RC wireless ................................................................ 21
Partial flow adaptor (ELD500) .................................................................................... 21
ELD500 auto-start cable ............................................................................................ 21
Default settings ............................................................................................................... 22
Installation 25
Placement ....................................................................................................................... 25
Conforming utilisation .................................................................................................... 25
Ambient conditions ........................................................................................................ 25
Electrical connections ..................................................................................................... 26
Mains power .............................................................................................................. 26
Connection for the controller signal and accessories ................................................ 27
dcs/8664/06/2018

D135-10-880C - Contents
Page ii
Option (accessories) ............................................................................................. 27
Digital out (CONTROL) .......................................................................................... 27
Digital in (Control 2) ............................................................................................. 28
Recorder/RECORD ................................................................................................ 28
SERIAL/RS232 ....................................................................................................... 29
Remote control (REMOTE1) ................................................................................. 29
Remote control (REMOTE2) ................................................................................. 29
CHARGE ................................................................................................................ 30
Vacuum connections ................................................................................................. 30
Inlet port ............................................................................................................... 30
Exhaust ................................................................................................................. 30
Vent ...................................................................................................................... 30
Gas ballast connection ......................................................................................... 31
Connection of an external pump (only ELD500 FLEX) .......................................... 31
Operation 33
Media compatibility/purge gas ....................................................................................... 33
Start-up ........................................................................................................................... 33
Display ....................................................................................................................... 33
The Display in run-up mode ...................................................................................... 34
The display in standby mode ..................................................................................... 34
Gas ballast/purge ...................................................................................................... 34
The display in measurement mode ........................................................................... 34
Call for calibration ..................................................................................................... 35
Speaker volume ......................................................................................................... 35
Status line in the display ............................................................................................ 35
Measurement mode with bar graph ......................................................................... 36
Measurement mode with trend information ............................................................ 36
First operation check ...................................................................................................... 36
Needed equipment .................................................................................................... 36
Start-up and measure ................................................................................................ 37
Internal calibration ............................................................................................... 37
Verification with an external test leak ................................................................. 37
Measure with a test object ................................................................................... 38
Switch off .............................................................................................................. 38
Control panel .................................................................................................................. 39
Softkeys ................................................................................................................ 41
Special functions ................................................................................................... 41
Numerical entries ................................................................................................. 41
Interfaces ........................................................................................................................ 43
Location of control ..................................................................................................... 43
Define recorder output ........................................................................................ 44
RS232 .................................................................................................................... 46
Define PLC outputs ............................................................................................... 46
Define PLC inputs .................................................................................................. 47
Scaling recorder output ........................................................................................ 49
PLC sample rate .................................................................................................... 49
Operation ........................................................................................................................ 49
Main menu ................................................................................................................ 50
View ........................................................................................................................... 52

D135-10-880C - Contents
Page iii
Scale linear/logarithmic ............................................................................................. 52
Display-range auto/manual ....................................................................................... 53
Time axis .................................................................................................................... 54
Contrast ..................................................................................................................... 54
Background in standby .............................................................................................. 55
Lower display limit ..................................................................................................... 55
Mode .............................................................................................................................. 56
Trigger and alarms .......................................................................................................... 56
Trigger level 1 ............................................................................................................ 57
Trigger level 2 ............................................................................................................ 57
Trigger level 3 ............................................................................................................ 57
Units .......................................................................................................................... 58
Volume ...................................................................................................................... 58
Alarm delay ................................................................................................................ 59
Audio alarm type ....................................................................................................... 59
Pinpoint ................................................................................................................ 60
Leak rate prop. ..................................................................................................... 60
Setpoint ................................................................................................................ 60
Trigger alarm ........................................................................................................ 60
Calibration ...................................................................................................................... 61
Settings ........................................................................................................................... 61
Vacuum settings ........................................................................................................ 62
ELD500 WET ......................................................................................................... 62
ELD500 DRY .......................................................................................................... 62
ELD500 FLEX ......................................................................................................... 63
Automatic purge ................................................................................................... 63
Vent delay ............................................................................................................. 64
Vacuum ranges ELD500 DRY/ELD500 FLEX ........................................................... 64
Vacuum ranges ELD500 DRY ................................................................................. 65
Partial flow setup/pump setup ............................................................................. 66
Enable partial flow mode ..................................................................................... 66
Partial flow setup for the ELD500 WET/DRY ........................................................ 66
Partial flow setup ELD500 FLEX ............................................................................ 67
Vacuum settings ELD500 FLEX .............................................................................. 67
Partial flow setup for the ELD500 FLEX ................................................................ 68
Sniffer factor ......................................................................................................... 69
SL extender interface setting ................................................................................ 69
Machine factor ..................................................................................................... 69
Leak rate internal test leak ................................................................................... 70
Purge in measurement ......................................................................................... 70
Filter and background ................................................................................................ 70
Calculate inlet area background ........................................................................... 71
Background suppression ...................................................................................... 71
Leak rate filter ...................................................................................................... 72
Mass ........................................................................................................................... 72
Miscellaneous (language, calibration request, service interval...) ............................ 72
Time and date ....................................................................................................... 73
Language .............................................................................................................. 73
Calibration request ............................................................................................... 73
Service interval fore-pump ................................................................................... 74
Service interval exhaust oil filter .......................................................................... 74

D135-10-880C - Contents
Page iv
Service message exhaust oil filter ........................................................................ 74
Parameter save/load ................................................................................................. 75
Load parameter set .............................................................................................. 75
Save parameter set ............................................................................................... 75
Monitoring functions ................................................................................................. 75
Maximum evacuation time ................................................................................... 76
Contamination protection .................................................................................... 77
Pressure limits for vacuum mode. ........................................................................ 77
Pressure limits for sniff mode ............................................................................... 78
Information ..................................................................................................................... 79
Service ....................................................................................................................... 80
Access control ................................................................................................................. 80
Zero ............................................................................................................................ 80
Access to CAL function ............................................................................................... 81
Change menu-PIN ...................................................................................................... 81
Calibration ...................................................................................................................... 81
Introduction ............................................................................................................... 81
The calibration routines ............................................................................................. 82
Internal calibration .................................................................................................... 82
External calibration .................................................................................................... 82
Factor of calibration - range of values .................................................................. 84
Switching off/shutting down .......................................................................................... 85
Maintenance 87
Safety information .......................................................................................................... 87
Maintenance intervals .................................................................................................... 87
Service ............................................................................................................................ 87
Maintenance work .......................................................................................................... 88
Opening of the ELD500 .............................................................................................. 88
Exchanging the filter mats ......................................................................................... 89
Exchanging the oil ...................................................................................................... 89
Oil change .................................................................................................................. 90
Cleaning ..................................................................................................................... 91
Exchanging the fuses ................................................................................................. 91
Exhaust oil filter ......................................................................................................... 93
Turbomolecular pump ............................................................................................... 93
Calibrated leak TL7 ......................................................................................................... 93
Technical data ............................................................................................................ 93
Factory inspection ..................................................................................................... 93
Maintenance kit ordering numbers ........................................................................... 94
Troubleshooting 95
Hints for troubleshooting ............................................................................................... 95
List of errors and warnings ............................................................................................. 95
Waste disposal 105

D135-10-880C - Contents
Page v
List of Figures
View of the ELD500 ................................................................................................... 5
Vacuum diagram ELD500 ........................................................................................... 6
Vacuum diagram ELD500 DRY ................................................................................... 8
Vacuum diagram ELD500 FLEX .................................................................................. 9
Dimensions ELD500 ................................................................................................. 17
Dimensions ELD500 side view ................................................................................. 18
Dimensions ELD500 FLEX ......................................................................................... 19
Remote control RC wireless .................................................................................... 21
Side views of the ELD500 ......................................................................................... 26
Display: measurement mode with bar graph .......................................................... 35
Display: measurement mode with bar graph .......................................................... 36
Control panel ........................................................................................................... 39
Zero activation ......................................................................................................... 40
Undo zero ................................................................................................................ 40
Numerical entry of the trigger level, sample of the digit ........................................ 42
Trigger level, change of the first digit ...................................................................... 42
Recorder output: Pirani ELD500, P1 and P2 ............................................................ 44
Recorder output: P1 and P2 Legacy ........................................................................ 45
Recorder output: Leak rate exponent ..................................................................... 45
Recorder output: Leak rate mantissa ...................................................................... 45
Recorder output: Leak rate logarithmic, default setting ......................................... 45
Display: main menu ................................................................................................. 50
Overview menu structure ........................................................................................ 51
Display: view menu ................................................................................................. 52
Display: mode menu ................................................................................................ 56
Display: trigger and alarms menu ............................................................................ 56
Pinpoint: change of the frequency in the leak rate window (TR1=Triggerlevel 1) .. 60
Setpoint: change of the frequency above the trigger level 1 (TR1= Trigger level 1) 60
Display: calibration menu ........................................................................................ 61
Display: settings menu ............................................................................................ 61
Display: information menu ...................................................................................... 79
Display: access control menu .................................................................................. 80
Display: external calibration, Step 1 ........................................................................ 82
Display: external calibration, Step 2 ........................................................................ 83
Display: external calibration, Step 3 ........................................................................ 83
Display: external calibration, Step 4 ........................................................................ 83
Display: external calibration, Step 5 ........................................................................ 84
Display: external calibration, Step 6 ........................................................................ 84
Display: external calibration, Step 7 ........................................................................ 84
Back view of the ELD500 ......................................................................................... 88
Opening of the mechanical hood ............................................................................ 88
Assembly fuses ........................................................................................................ 92

D135-10-880C - Contents
Page vi
List of Tables
ELD500 WET physical data ...................................................................................... 12
ELD500 WET electrical data ..................................................................................... 13
ELD500 WET other data ........................................................................................... 13
ELD500 WET environmental conditions .................................................................. 13
ELD500 DRY physical data ....................................................................................... 13
ELD500 DRY electrical data ...................................................................................... 14
ELD500 DRY other data ........................................................................................... 14
ELD500 DRY ambient conditions ............................................................................. 15
ELD500 FLEX physical data ...................................................................................... 15
ELD500 FLEX electrical data ..................................................................................... 16
ELD500 FLEX other data .......................................................................................... 16
ELD500 FLEX environmental conditions .................................................................. 17
Option (accessories) connector pin-outs ................................................................. 27
Digital out (CONTROL) connector pin-outs .............................................................. 27
Digital in (Control 2) connector pin-outs ................................................................. 28
Recorder/RECORD connector pin-outs .................................................................... 28
SERIAL/RS232 connector pin-outs ........................................................................... 29
Remote control (REMOTE1) connector pin-outs ..................................................... 29
Remote control (REMOTE2) connector pin-outs ..................................................... 30
Status line symbol meanings ................................................................................... 35
PLC outputs ............................................................................................................. 46
PLC inputs ................................................................................................................ 48
Spare parts for ELD .................................................................................................. 94
Fault finding ............................................................................................................. 96

D135-10-880C - Safety
Page 1
Safety
Key to the symbols
Important instructions relating to technical safety and safe operation are emphasised by
symbols.
The Edwards ELD500 leak detector has been designed for safe and efficient operation when
used properly and in accordance with these operating instructions. It is the responsibility of
the user to carefully read and strictly observe all safety precautions described in this section
and throughout the Operating Instructions. The ELD500 must only be operated in the proper
condition and under the conditions described in the Operating Instructions. It must be
operated and maintained by trained personnel only. Consult local, state, and national
agencies regarding specific requirements and regulations. Address any further safety,
operation and/or maintenance questions to our nearest office.
Failure to observe the following precautions could result in serious personal injury.
WARNING:
Warnings are given where failure to observe the instruction could result in injury or death
to people.
CAUTION:
Cautions are given where failure to observe the instruction could result in damage to the
equipment, associated equipment and process.
Note:
Emphasizes additional application information and other useful information provided within
these operating instructions.
During all maintenance and connection work, ensure the mains cable has been
disconnected and does not carry a mains voltage. The leak detector must only be used with
the hoods closed. The electrical connections must only be provided by a trained electrician
as specified, for example, by the regulations EN 50110-1.
Avoid exposing any part of the human body to the vacuum. Only handle the leak detector
when the pump is vented.
After a mains power failure the leak detector can run up automatically once more.
Before changing oil or fuses, make sure that the mains cable have been disconnected.
The leak detector is not suited for operation in explosion hazard areas.
During operation the pump can become so hot that there is a danger of burns
(> 70 °C (158 °F)). Provide protection against contact with the hot components.
Contaminated parts can be detrimental to health and environment. Before beginning to
work, find out whether any parts are contaminated. Adhere to the relevant regulations and
take the necessary precautions when handling contaminated parts.

D135-10-880C - Safety
Page 2
Failure to observe the following precautions could result in damage to the pump.
 Unauthorized opening or modifications of the mechanical or electrical components of
the leak detector void the warranty.
 The leak detector must only be opened by such persons who have been authorised by
Edwards.
 The leak detector can be damaged when using the wrong voltage. The voltage must be
in the range 230 V (+/- 5%) or 115 V (+/- 5%) depending on the leak detector version.
Make sure that the mains voltage rating on the ELD500 coincides with the locally
available mains voltage.
 When the ELD500 is running in closed rooms the exhaust has to be put out of doors so
that the oil vapour can not be breathed in.
 Ensure a sufficient air cooling. The air inlet as well the air discharge openings must
never be obstructed.
 The ELD500 is designed for indoor use only.
 Operate the ELD500 only in the permitted temperature range between +10 °C and
+40 °C.
 Only synthetic oil (L31001) must be used in the wet pump.
Pumping condensible gases and steams: When pumping test sample water vapour that is
inside the test object can attain to the fore-pump. With the water vapour that is in the air -
especially in humid areas or when using humid or wet test samples - the acceptable
compatibility of water vapour or capacity of water vapour respectively can be exceeded.
The steam in the oil of the pump condenses when the water vapour rises over the acceptable
value. So the attribute of the oil changes and danger of corrosion occurs for the pump.
While using the leak detector with condensible gases and steams the oil of the fore-pump has
to be controlled regularly. So condensation of water vapour in the pump can be recognized.
Usually the oil is light and lucent. When water vapour is inside it gets blear and milky at
operating state temperature.
When turning the pump off water vapour condensates and raises the part of water in the oil.
The leak detector must not directly be switched off after the process, in which condensible
gases or steams are pumped, is finished. It must be running (at least 20 minutes) with opened
gas ballast valve until the oil of the pump is freed from detached steam.
When not taking care of this instruction there can be a corrosion within the pump, which will
not be covered by our warranty.
The height of the oil of the pump has to be controlled regularly.
The normal intervals of changing the oil from the producer have to be taken care of. See
instructions of the rotary vane pump.

D135-10-880C - Safety
Page 3
Symbols of vacuum technology
Given in the following are some important symbols which are used in this instruction manual.
Definition of terms
Vacuum pump in general
Turbo molecular pump
Measuring instrument
Valve
Term Description
Auto ranging
The range of the pre-amplifier and the vacuum ranges
are selected automatically.
The auto ranging feature of the ELD500 covers the
entire range or leak rates depending on the selected
operating mode. Not only the leak rate signal, but also
the pressure in the test sample (inlet pressure P1) and
the fore vacuum pressure (P2) are used for control
purposes. Range switching between the main ranges
is performed via valves. Fine range switching within
the main ranges is implemented by switching over the
gain factor of the pre-amplifier.
Mass alignment
This function automatically aligns the mass
spectrometer so that a maximum leak rate is
displayed. The control processor changes the voltage
which accelerates the ions in the selected mass range
until a maximum ion current is detected by the ion
detector. During each calibration the mass alignment
is run automatically.
Auto zero
Determination and automatic adaptation of the
internal background.
Through this function, the internal zero level of the
instrument is determined which is then subtracted
from the current leak rate signal. This function is run
during the calibration process or when operating the
start push button, provided the ELD500 has been
running previously for at least 20 seconds in the
standby or vent mode.
GROSS
GROSS is a measurement mode which allows high
inlet pressure (15 to 0.2 mbar). The smallest
detectable leak rate is 1 x 10-7 mbar l/s.

D135-10-880C - Safety
Page 4
FINE
FINE is a measurement mode with inlet pressure
< 0.2 mbar. The minimum detectable leak rate is
≤ 5 x 10-12 mbar l/s.
PRECISION
Precision is a measurement mode for the ELD500 DRY
only from an inlet pressure < 0.01 mbar. In this mode
the ELD500 DRY has the highest sensitivity, the
minimum detectable leak rate is
≤ 3 x 10-11 mbar l/s.
Fore-vacuum pressure Pressure in the fore vacuum between turbo pump and
rotary vane pump.
Internal helium background
The existing helium partial pressure in the
measurement system. The level of the internal helium
background is measured in the standby mode and
subtracted from the measured signal.
Minimum detectable leak rate The smallest leak rate the ELD500 is able to detect
(≤ 5 x 10-12 mbar l/s) in vacuum mode.
Menu
The menu allows the user to program the ELD500
according to his requirements. The menu has a tree
architecture.
Measurement mode The ELD500 measures the leak rate of the test sample.
Default Status of the ELD500 when supplied by the factory.
Term Description

D135-10-880C - Description
Page 5
Description
The ELD500 is a leak detector for helium or hydrogen. This instrument may be used to detect
the location and the size of leaks on objects under test in two different ways:
When the test sample has been evacuated first and is sprayed with helium on the outside. It
is required that a vacuum connection is provided between the ELD500 and the test sample
(vacuum mode).
or
when a helium overpressure is provided in the test sample and the test sample is searched
from the outside with a sniffer probe which is attached to the inlet port (sniffer mode).
Figure 1 View of the ELD500
Design and function
The ELD500 basically is a helium leak detector for vacuum applications, that is, the part under
test is evacuated while the test is performed. The vacuum is achieved with a pumping system
that is part of the ELD500. In addition the vacuum can be generated by pumps which are set
up in parallel to the ELD500.
The ELD500 FLEX needs a fore vacuum pump, dry or wet version, to be connected because
this unit has no internal roughing pump. The connection (DN25 KF) is on the side or under the
bottom of the ELD500 FLEX (Figure 7).
Another operating mode of the ELD500 is the Sniffer mode which can only be used when a
sniffer line (see Sniffer mode) is hooked up.
1. Inlet flange 2. Control panel

D135-10-880C - Description
Page 6
Vacuum diagram ELD500 WET
The vacuum diagram below shows the major components inside the ELD500 WET.
Figure 2 Vacuum diagram ELD500
The mass spectrometer (MS) is mainly composed of the ion source with cathode, the
magnetic separator and the ion collector.
Gas molecules getting into the mass spectrometer are ionized by the ion source. These
positively charged particles are accelerated into the magnetic field following a circular path,
the radius of which depends on the mass-to-charge ratio of the ions. When mass 4 is selected
(Default setting) only helium ions can pass this filter and reach the ion collector where the
stream of the ions is measured as an electrical current. When selected another mass than 4,
only the corresponding ions can pass the filter.
For operation the mass spectrometer requires a vacuum level in the range of 1 x 10-4 mbar
and lower. This pressure is provided by the turbo molecular pump which in turn is backed up
by a fore vacuum pump.
1. MS: Mass Spectrometer, Helium sensor (180° magnetic field mass
spectrometer)
2. Turbo molecular pump (TMP, provides high vacuum conditions in the MS)
3. Pirani gauge P2 (fore vacuum pressure)
4. Fore pressure pump (provides the fore vacuum pressure for the TMP and
pumps down the parts under test)
5. Inlet Port
6. Pirani gauge P1 (inlet pressure)
V1 to V7: Electromagnetic Valves to control the gas flows

D135-10-880C - Description
Page 7
Besides maintaining the pressure in the mass spectrometer the pump system is used to
evacuate the test parts. It is made sure that the pressure in the mass spectrometer is low
enough under all circumstances. The valves V1, V2a, V2b, V4a control the gas flows when
measuring. Valves V3 and V5 are used to vent the system and the Turbo pump, valve V6
controls the gas ballast function of the fore vacuum pump. Valve V7 opens and closes the
internal test leak during calibration.
With the pressure in the test part being lower than ambient pressure sprayed helium (or
Hydrogen as forming gas) can penetrate into the part in case of a leakage. As soon as the
pressure conditions allow it one of the valves to the TMP opens. Now Helium can penetrate
into the mass spectrometer contrary to the pumping direction of the TMP.

D135-10-880C - Description
Page 8
Vacuum diagram ELD500 DRY
The ELD500 DRY has a diaphragm pump as fore vacuum pump, making it suitable for
applications where oil sealed systems can not be used. Furthermore the ELD500 DRY contains
one more valve, the valve 4b. This valve opens step by step to regulate the inlet pressure into
the turbo pump.
Figure 3 Vacuum diagram ELD500 DRY
1. MS: Mass Spectrometer, Helium sensor (180° magnetic field mass spectrometer)
2. Turbo molecular pump (TMP, provides high vacuum conditions in the MS)
3. Pirani gauge P2 (fore vacuum pressure)
4. Diaphragm pump (provides the fore vacuum pressure for the TMP and pumps
down the parts under test)
5. Inlet Port
6. Pirani gauge P1 (inlet pressure)
V1 to V7: Electromagnetic Valves to control the gas flows

D135-10-880C - Description
Page 9
Vacuum diagram ELD500 FLEX
The ELD500 FLEX has no roughing pump integrated as the other models. Therefore it can be
used with an external pump only. This pump can be oil sealed or a dry version with a roughing
capacity between 2.5 and 65 m3/h. This pump has to be connected to the DN25 KF at the side
or under the bottom of the ELD500 FLEX.
Figure 4 Vacuum diagram ELD500 FLEX
1 MS: Mass Spectrometer, Helium sensor (180° magnetic field mass
spectrometer)
2 Turbo molecular pump (TMP, provides high vacuum conditions in
the MS)
3 Pirani gauge P2 (fore vacuum pressure)
4 Fore pressure pump (provides the fore vacuum pressure for the
TMP and pumps down the parts under test)
5 Inlet Port
6 Pirani gauge P1 (inlet pressure)
V1 to V7: Electromagnetic valves to control the gas flows

D135-10-880C - Description
Page 10
Vacuum method
For the purpose of leak detection on a test sample (vacuum method), the sample has to be
evacuated so that Helium or Hydrogen which is sprayed on to the outside, can enter through
any leaks due to the pressure differential for detection by the ELD500.
The test sample is evacuated - START button (Figure 16 item 10) - by the backing pump or the
external pump. In the case of larger test samples an additional external partial flow pump
with a corresponding linking valve may be connected in parallel as required.
Inlet valve V1 is opened so that the evacuation can take place. At the same time all other
valves are closed in order to prevent an unacceptable pressure increase in the mass
spectrometer.
In this context (valve V2a closed) the turbo molecular pump is operated without being
supported by the rotary vane pump. Since generally no gas is pumped out of the mass
spectrometer, p2 remains constant or increases only slowly.
The condition for the evacuation process described here is maintained until the inlet pressure
p1 has dropped <15 mbar. Now the valves V2a and V2b are opened additionally. Possibly
present Helium or Hydrogen may now flow upstream against the pumping direction of the
turbo molecular pump into the mass spectrometer where it is detected. This measurement
mode is called GROSS. In this mode, leak rates down to 10-8 mbar l/s can be detected.
Since the rotary vane vacuum pump continues to evacuate the test sample via valves V2a,
V2b and V1 the inlet pressure p1 will continue to drop. When the pressure drops below p1 <
0.2 mbar, the ELD500 will switch to the FINE mode, that is, valve V1and V2b closes and valve
V4a opens so that the gas flow enters the turbo molecular pump at the side. This offer two
advantages:
1. A part of the high pumping speed of the turbo molecular pump remains available for
further evacuation of the test sample. The response time is inversely proportional to
pumping speed.).
2. The advantages offered by the counter flow principle can still be utilized
In the FINE mode the full sensitivity of the ELD500 is reached.
Because of the higher base pressure of the diaphragm pump the switching from GROSS to
FINE mode of the ELD500 DRY is done by the valve V4b. When the pressure drops below
3.5 mbar the valves V1 and V2b will be close and V4b opens step by step. When valve V4b is
open completely, pressure < 0.1 mbar, V4a will open also to get the maximum pumping
speed. In PRECISION mode the ELD500 DRY opens the valve V4b only, with the disadvantage
of low pumping speed but with the highest sensitivity.
When the leak detection process is stopped – STOP-button – all valves except valve V2a are
closed.
Valve V3 is opened during venting of the inlet or test sample.