Document Number: HAV-001-013 Issue: C

DSMS Gas Analysis System

Operator's Manual

Hiden Analytical Limited

420 Europa Boulevard

Warrington

WA5 7UN

England

Tel: +44 (0)1925 445225 E-mail: info@hiden.co.uk

Fax: +44 (0)1925 416518 Web site: http://www.HidenAnalytical.com

A N A LY T I C A L
DSMS Gas Analysis System Operator's Manual

Manual Number: HAV-001-013 Issue: C Date: March 2019

The Hiden Analytical Limited Website

Information on Hiden Analytical Limited and its wide range scientific instruments for

research, development and production applications can be obtained from the Hiden

Analytical Limited Website at http://www.HidenAnalytical.com.

Amendment history

Issue: C MV001-007 Date: March 2019. Re-written for VCU and CPU version.

DSMS Gas Analysis System Issue: C

HIDEN ANALYTICAL
Contents

Welcome to the DSMS Operator's Manual ·································· i

Copyright notice ··················································· i

Acknowledgements ················································· i

Warnings and Cautions··············································· i

Typographical conventions ············································ i

Terminology ······················································ i

Instructions······················································· i

Importance of this Manual ············································ ii

Technical assistance ················································ ii

Amendments ····················································· ii

1 Safety ·························································· 1

1.1 Relevance··················································· 1

1.2 Warnings and cautions ·········································· 1

1.3 System use ·················································· 1

1.4 Symbols···················································· 4

1.4.1 General·············································· 4

2 Introduction ······················································ 5

2.1 Documentation ··············································· 5

2.2 Contents sheet················································ 5

2.3 Introduction to the DSMS ········································ 5

3 System description ················································· 6

3.1 Introduction ················································· 6

3.2 The ultra-high vacuum pumping system ······························ 6

3.3 Bypass/inlet evacuation rotary pump································· 8

3.4 Pressure gauges··············································· 8

3.5 Pressure units ················································ 8

3.6 Inlet system ················································· 9

3.6.1 Safety ··············································· 9

3.6.2 General description······································ 9

3.7 The mass spectrometer ········································· 11

3.8 Heaters···················································· 11

3.9 Vacuum Control Unit ·········································· 11

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Contents
3.10 Identification················································ 13

4 Technical data···················································· 14

4.1 Electrical specification ········································· 14

4.2 Environmental data ··········································· 14

5 Installation ······················································ 15

5.1 Introduction ················································ 15

5.2 Preparation ················································· 15

5.3 System assembly ············································· 16

6 Operation ······················································· 20

6.1 System start-up from atmospheric pressure ··························· 20

6.2 Sampling using the inlet system ··································· 21

6.3 Cryo-shield operation ·········································· 22

6.4 System shut down ············································ 23

7 Troubleshooting ·················································· 24

7.1 Fault finding guide············································ 24

7.1.1 Vacuum Control Unit ··································· 24

7.1.2 Scroll pump ·········································· 25

7.1.3 Rotary pump ········································· 25

7.1.4 Turbo pump fails to reach full speed ························· 27

7.1.5 Total pressure gauge ···································· 27

7.1.6 Edwards AIGX-S ion gauge ······························· 28

7.1.7 Mass spectrometer ····································· 29

7.1.8 Emission Failure······································· 31

7.2 Leak checking ··············································· 32

8 Maintenance ····················································· 33

8.1 Maintaining System safety ······································ 33

8.2 Filament renewal ············································· 34

8.3 Inlet assembly ··············································· 35

8.3.1 Removal ············································ 35

8.3.2 Fitting the inlet········································ 37

8.3.3 Replacing the molecular leak ······························ 38

8.4 Bake-out··················································· 39

8.5 Rotary pumps ··············································· 40

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8.5.1 Testing the pump ······································ 40

8.6 Scroll pumps················································ 40

8.6.1 Testing a scroll pump ··································· 41

8.7 Diaphragm pumps ············································ 41

8.7.1 Testing a diaphragm pump ································ 41

8.8 Turbo pumps················································ 41

8.8.1 Testing the turbo pump ·································· 41

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Contents
This page is left blank to maintain the format of the manual.

DSMS Gas Analysis System Document Number: HAV-001-013

HIDEN ANALYTICAL
Welcome to the DSMS Operator's Manual

The purpose of this manual is to provide information on the DSMS Gas Analysis system.

Copyright notice

© 2019 by Hiden Analytical Limited. All rights reserved.

Information in this document is subject to change without notice and does not represent a

commitment on the part of Hiden Analytical Limited.

Acknowledgements

®Microsoft, Windows and MS-DOS are registered trademarks of Microsoft Corporation.

All brand names and product names are trademarks, registered trademarks, or trade

names of their respective holders.

Warnings and Cautions

In this Manual, a Warning is an instruction that draws the operator’s attention to the risk 

of injury or death; a Caution is an instruction that draws attention to the risk of damage

to the product or process.

Warnings and Cautions are placed immediately before the text to which they refer; they

are headed by WARNING or CAUTION respectively. The associated explanatory text

is in bold. If several Warnings or Cautions apply at one point in the text, they are

numbered with the most important appearing first.

Typographical conventions

For ease of identification the names of menu commands, keys, dialog items and screen

text are typographically distinct from the ordinary text of this Manual. These distinctions 

are as follows:

Menu commands, dialog items, such as buttons and check boxes, and text that appears on 

the display screen are presented in bold typeface; thus File menu, Enter button.

Keys are presented in bold, italic text; thus Esc, Return, Space bar.

Terminology

Terminology that accords with basic Windows principles is included in this Manual.

Instructions

For clarity, the instructions given in this Manual are presented in two columns. The

left-hand column provides imperative instructions that are numbered sequentially to

provide a step-by-step guide through the functions. The right-hand column describes the

system’s response (where appropriate) and gives any additional information that may be

of relevance.

Issue: C i DSMS Gas Analysis System

Preliminary Pages
Importance of this Manual

This Manual should be regarded as part of the product described herein.

Technical assistance

Hiden Analytical Limited try to ensure the information presented in this manual is

comprehensive, relevant and accurate. If the reader thinks there is a mistake, requires

some clarification or needs further information please do not hesitate to contact Hiden.

Technical assistance can be obtained from the Hiden Analytical Limited Service

Department which can be contacted on:

Email: service@hiden.co.uk

Tel: +44 (0)1925 445225

Fax: +44 (0)1925 416518

In the U.S.A. and Canada, technical assistance can be obtained from Hiden Analytical

Inc.:

Email: service@hideninc.com

Tel: 603 924 5008

Fax: 603 924 5009

Toll-free phone: 1-888-96 HIDEN

Option 1 U.S.Sales Office

Option 2 U.S.A. & Canada Corporate Office & Service Department

Option 3 U.K. Manufacturing Facility

Details of worldwide local support can be found on the Hiden Analytical website:

www.HidenAnalytical.com.

Amendments

This Manual will be updated, as necessary, to cover modifications to the product. Minor

amendments may take the form of Addenda, which will normally be located at the back

of the Manual.

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1 Safety

1.1 Relevance

This manual relates to the Hiden Analytical Limited DSMS quadrupole mass

spectrometer gas analysis system.

This manual describes the hardware, installation procedure, operation and maintenance.

DSMS component modules have their own manuals which will be supplied with this

manual.

Hiden Analytical's MASsoft operating software used in conjunction with the DSMS is

described in the MASsoft manual. The DSMS may be supplied with other Hiden software

applications which will have their own manuals.

1.2 Warnings and cautions

In this manual WARNINGS and CAUTIONS have the following meanings and are

denoted as shown.

WARNING

WARNINGS draw attention to procedures, practices, conditions or

the like, which if not performed correctly or adhered to could result 

in injury to personnel.

CAUTION

CAUTIONS draw attention to procedures, practices, conditions 

which if not performed correctly or adhered to could result in

damage to the equipment described in this manual and/or to

peripheral equipment connected to the equipment described herein.

1.3 System use

WARNING

This equipment, when installed and connected as described in this

Manual, is suitable for use as a Mass Spectrometer; any attempt to

use it for any other purpose may expose the operator to injury, is

liable to damage the instrument and will invalidate its Warranty.

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If in doubt as to its suitability for an application, please contact Hiden Analytical Limited

for advice.

WARNING

1. The equipment must be fully installed and configured for

normal operation before it is powered-up; failure to do this may

cause injury to the operator and damage to the equipment.

2. The equipment must be earthed; failure to do this may cause

injury to the operator and damage to the equipment.

CAUTION

1. Any connections to other equipment should be undertaken by

suitably qualified personnel and must not compromise

equipment safety.

2. Any equipment connected to any input/output port must operate

at Safe Extra Low Voltage (SELV) levels (normally in the range

-50 V to +50 V) in accordance with EN 61010:1993 to meet the

requirements of the Low Voltage Directive (LVD) 73/23/EEC.

CAUTION

The mains power plug and socket is the primary disconnect device

for the DSMS; it must be easily identifiable and accessible by the

operator.

WARNING

HAZARDOUS GASES

Users must be fully aware of all safety requirements related to gases 

being sampled by the instrument.

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HIDEN ANALYTICAL
DSMS users must make themselves aware and adhere to all of the necessary safety

precautions related to any hazardous gases, toxic gases or potentially explosive gas

mixtures sampled by the instrument.

If in any doubt the user's on-site safety officer or department should be contacted for

advice.

Information regarding potential gas hazards can be obtained by, but not limited to,

reading the applicable COSHH (Control of Substances Hazardous to Health) data sheet

and taking advice from the gas supplier.

WARNING

This instrument is not suitable for use in life or safety critical

applications.

CAUTION

The system must not be moved while the turbo pump is at

operational speed. Inertial shock loading of the turbo pump rotor

at operational speed may cause severe pump damage.

CAUTION

Do not use silicone grease on any seals connected to the mass

spectrometer vacuum chamber as there is a risk of ion

source/quadrupole contamination leading to significant loss in

system sensitivity.

WARNING

Protective gloves and face mask must be worn when removing the

inlet unit's cover.

The Heated Molecular Leak Assembly incorporates ceramic paper insulation which may

pose a long term health risk due to sub six micron filament size fibres in the material.

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1.4 Symbols

1.4.1 General

The following symbols may be found on the equipment:

Alternating current.

Earth terminal.

On (suuply).

Off (supply).

Caution, risk of electric shock.

Background colour: yellow.

Symbol and outline: black.

The above symbol is displayed adjacent to connectors carrying

voltages greater than 1000 V.

Caution, refer to associated documents.

Background colour: yellow.

Symbol and outline: black

Hot surface.

Background colour: yellow. Symbol and outline: black.

The above symbol is displayed on surfaces that reach high

temperatures or on covers which, when removed, reveal hot surfaces.

The WEEE directive symbol on the rear panel of the RC Interface

unit.

The disposal of the equipment described in this manual MUST be in

accordance with local regulations.

For EU member countries please contact Hiden Analytical Limited for

advice.

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HIDEN ANALYTICAL
2 Introduction

2.1 Documentation

This manual describes the DSMS quadrupole mass spectrometer gas analysis system. The 

system hardware, installation, operation and maintenance procedures are described in this 

manual. Additional options and features may be described in addenda which accompany

this manual. 

DSMS systems are used with Hiden's MASsoft Windows based software which is

described in the MASsoft manual. 

In addition to this manual each of the modules used in the DSMS has its own manual

which is supplied with the system. 

Manuals for the vacuum pumps and gauges will also be supplied with the system.

2.2 Contents sheet

Each DSMS system is supplied with a configuration information document placed at the

front of the white Hiden manuals ring binder. This is a custom document describing the

features and options fitted to the particular system. This document has a reference

number beginning HA-111-. The first page of this document is the Contents Sheet which

lists all the manuals relevant to the particular instrument.

2.3 Introduction to the DSMS

Hiden Analytical Limited quadrupole mass spectrometers may be directly connected to

user’s systems where the monitored pressures are from the Ultra High Vacuum (UHV)

region up to approximately 1x10-4 mbar; analyses at higher pressures require additional

vacuum pumps and the mass spectrometer gauge head mounted in a suitable housing. 

The DSMS Gas Analysis System provides these features.

The DSMS Gas Analysis System is designed for applications requiring optimum

sensitivity and stability. The system is typically configured with cross-beam sample

ionisation to minimise contamination and memory effects.

The basic system is configured for use with a UHV turbomolecular pumping system and

combined cold cathode/ion gauge pressure measurement. A variety of inlet systems, for

sampling from the user’s vacuum system or process, are available; these are selected to

suit the application.

Each DSMS System is integrated with one of the Hiden Analytical Limited high

sensitivity quadrupole mass spectrometers, with mass ranges up to 510 amu.

An optional liquid nitrogen cryo-panel may be fitted which, when combined with the

UHV turbomolecular pumping system, will enhance detection levels to the

part-per-billion (ppb) regime for many species.

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3 System description

3.1 Introduction

Figure 1 shows a typical DSMS Gas Analysis System.

The system is mounted on a supporting frame assembly. This assembly may be

trolley-mounted for increased mobility. The trolley mounting option provides additional

storage space and rack mounting facilities (front panel mounting) for electronic

equipment.

3.2 The ultra-high vacuum pumping system

The mass spectrometer gauge head, total pressure gauge and optional cryo-shield are

mounted in the mass spectrometer vacuum chamber. Ports are provided for the turbo

pump and inlet system.

Two inlet connection ports may be incorporated in the UHV housing:

1. 70 mm diameter Conflat flange, type DN-35-CF, for connection of the main inlet

system.

2. 34 mm diameter Conflat flange, type DN-16-CF, for connection of additional sample

lines generally sampling from medium vacuum levels through an isolation valve and

incorporating replaceable orifices for pressure reduction.

The UHV turbo pump is attached to the mass spectrometer vacuum chamber. The UHV

turbomolecular pumping set comprises:

• Turbo pump.

• Turbo pump backing pump; this is a scroll pump. Optional a two-stage rotary

pump or membrane (diaphragm) pump may be used. The turbo pump and scroll

pump provide an oil-free vacuum in the UHV housing.

• Drive electronics.

• Vacuum Control Unit (VCU).

• Venting device.

A turbo isolation valve may be fitted between the UHV housing and the turbo pump to

allow isolation of the housing under vacuum before venting; this reduces the pump-down

time on restarting the turbo pump.

The VCU interfaces the turbo pump controller, backing pump and venting operations; it

also gives a single switch start-up of the pumping set. The VCU also provides

interlocking for protecting the mass spectrometer filaments. Automatic venting protects

the mass spectrometer and mass spectrometer vacuum chamber from pump oil

contamination when the turbo pump is not running.

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A N A LY T I C A L

ON OFF

CPU

Heating

Capillary Power Unit

A N A LY T I C A L

Heated BypassInlet

Bypass Line

Capillary PowerUnitVacuum ControlUnit

RC InterfaceUnit

Scroll Pump

Pump IsolatingPlate

64

RFHead

Total PressureGauge

Backing Line

InletConnection

TurbomolecularPump

Mass Spectrometer VacuumChamber

541

640

8911

Figure 1 Typical DSMS System
3.3 Bypass/inlet evacuation rotary pump

Bypass pumping provides pressure reduction when sampling using the atmospheric

capillary, and evacuation of the inlet system volume. Pressure in the bypass inlet will,

typically, be in the millibar region.

Where a scroll pump is used to back the turbo pump bypass pumping is provided by

connection to the backing line. Where a rotary backing pump is used a bypass/inlet

evacuation rotary pump is used. Typically, a 2.5 m3/h two-stage rotary vane pump is

connected to the inlet system via a flexible hose. An integral isolation valve isolates the

vacuum line when the pump is switched off.

A foreline trap may be fitted to ensure that there is no pump oil contamination.

3.4 Pressure gauges

CAUTION

In systems where a pressure gauge is not fitted, wait 15 to

30 minutes after switching on the turbo pump before running the

mass spectrometer; failure to do this may damage the instrument. 

Use mass 18 and mass 28, or the mass spectrometer total pressure

reading, as an indication of the manifold total pressure.

A cold cathode or active ion gauge is usually fitted to monitor the mass spectrometer

vacuum chamber total pressure. An interlock prevents mass spectrometer operation at too 

high a pressure.

A Pirani gauge may be used for measuring the bypass line vacuum.

3.5 Pressure units

The International System of Units (SI) derived unit for pressure is the Pascal (Pa).

Since the Pa is such a small unit the common multiple unit used for vacuum pressure

measurement is the hectopascal (hPa) where 1hPa = 100Pa.

Standard atmospheric pressure is 101,325 Pa or 1013hPa. 

In Europe the common unit for vacuum pressure measurement is the millibar (mbar).

Atmospheric pressure is approximately 1bar or 1000mbar and 1bar = 100,000Pa

So very conveniently 1hPa = 1mbar.

In the USA the common unit for vacuum pressure measurement is Torr.

Atmospheric pressure is 760Torr.

Therefore 760Torr = 101325Pa

and 1Torr 133Pa or 1.3hPa and 1.3mbar

1hPa = 1mbar ≈ 0.76Torr

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3.6 Inlet system

The inlet system and connection lines for the DSMS will depend on the application.

The inlet will comprise:

• A heated molecular leak inlet assembly, described in this section

either

• A heated capillary inlet, described in it's own manual

or

• A high pressure capillary inlet, described in it's own manual.

Note

Information in this section is taken from the Hiden Analytical document reference

HAV-002-003C.

3.6.1 Safety

WARNING

Protective gloves and face mask must be worn when removing the

unit's cover.

During normal operation it is not necessary to remove the unit's cover.

The cover must be removed to carry out maintenance operations such as replacing the

molecular leak as described in Section 8.3 of this manual. When removing the cover and

carrying out work on internal parts of the unit a face mask and protective gloves must be

worn.

The Heated Molecular Leak Assembly incorporates ceramic paper insulation which may

pose a long term health risk due to sub six micron filament size fibres in the material.

For further information and Safety Data Sheets please contact Hiden Analytical Limited.

3.6.2 General description

Figure 2 shows the Heated Molecular Inlet Assembly.

The unit is configured for use in conjunction with the HPR20 and DSMS range of mass

spectrometer sampling systems.

The inlet enclosure consists of a steel box with ceramic paper insulating lining.

The inlet incorporates a molecular leak assembly, an all-metal bypass isolation/control

valve and an all-metal sample isolation valve.

Two heaters are fitted, one inside the enclosure and one around the direct inlet

assembly/mounting flange; these may be operated to reduce condensates in the inlet

system.

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WARNING

The outside of the Heated Molecular Inlet Assembly will become

hot when the internal heater is switched on; touching this may

cause burns.

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Mounting flange type DN-35-CF

with integral molecular leak

Outer cover

Bypass pumping connection

port DN-10-KF

Sampling capillary connection

point [1⁄4“ (6.35 mm) o.d.]

Sample isolation valve Bypass isolation/control valve

Figure 2 Heated molecular inlet assembly
The normal operating temperature inside the enclosure is 120 °C.

All fittings are stainless steel and the ferrules are Vespel or stainless steel rated to

temperatures in excess of 250 °C.

Sample enters the inlet via the sampling capillary and passes over the molecular leak into

the bypass pump. The pressure in the inlet during sampling will typically be in the

1 mbar region. The sample enters the mass spectrometer ion source via the molecular

leak to give a typical mass spectrometer ion source pressure in the 1x10-6 mbar region.

3.7 The mass spectrometer

CAUTION

Ensure the pressure indicated by the total pressure gauge (if fitted)

is less than 1x10-4 mbar before operating the mass spectrometer;

failure to do this may damage the instrument.

Please refer to the appropriate mass spectrometer Operator’s Manual; this is supplied

with the system.

3.8 Heaters

WARNING

Beware of hot surfaces; touching these may cause burns.

CAUTION

1. Ensure that the system is under vacuum prior to operating the

heaters.

2. Switch off the heaters and allow the system to cool for

30 minutes before venting.

3.9 Vacuum Control Unit

DSMS vacuum system control is accomplished by the Vacuum Control Unit (VCU). The 

VCU provides:

• One button vacuum system start up and shut down

• A display of mass spectrometer vacuum chamber pressure

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• A setpoint output to protect the mass spectrometer filament

• Two addition vacuum gauge inputs

• Two additional setpoints for vacuum system interlocking

• 24V DC power for additional control units and ancillary components.

a Pressure reading from the gauge connected to the rear panel G1 connection.

This is the total pressure gauge (either a cold cathode or active ion gauge) fitted 

the mass spectrometer vacuum chamber.

b Pressure reading from the gauge connected to the rear panel G2 connection.

Not used in standard DSMS systems and will be blank because no gauge is

connected.

c Pressure reading from the gauge connected to the rear panel G3 connection.

Not used in standard DSMS systems and will be blank because no gauge is

connected.

d The gauge type for each of the three possible gauges. The options are AIM

(cold cathode gauge) and AIGX (active ion gauge).

e Pressure units for the gauge. The options are torr, mbar.

f Status for the three Setpoints. The options are OK or blank.

Setpoint 1 provides the over-pressure trip signal for the mass spectrometer and

is connected to the RC Interface TRIPS MSC11 connector. Setpoints 2 and 3

are not usually used in DSMS systems.

g Pump status. The options are ON and OFF.

h Turbo pump speed. Once the pumps are started the turbomolecular pump will

start to accelerate, when it has reached full speed 100% will be displayed.

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G1 1.2X10 -08

AIM

torr

G2 3.4X10 -07

AIM

torr

G3 5.6X10 -06

AIM

torr

SP 1-OK 2-OK 3-OK

PUMP ON TURBO = 100%

a

d

e

b

c

f

g h

Figure 3 VCU display
The DSMS total pressure gauge is connected as gauge 1 (VCU rear panel G1 connection) 

and provides the Set Point 1 signal. Typically the trip pressure is set to 9x10-5 mbar.

When the pressure is greater than 9x10-5 mbar the Set Point is enabled. The mass

spectrometer inhibit circuit is connected to this optically isolated transistor output.

For systems using a mass spectrometer with a pulse counting detector the trip pressure is

set to a lower value, typically, 5x10-6 mbar.

The total pressure gauge may be a cold cathode gauge or an active ion gauge. The gauge

type makes no difference to the system's operation.

3.10 Identification

The Works Reference (WR) No. uniquely identifies the instrument and is used by

MASsoft.

The number is displayed on the serial number label attached to left side of the system's

top cover. The WR number is the five digit number displayed in the WORKS REF

(WR) box, WR 16543 in Figure 4. It is worth making a note of this number if the left

side of the system will be inaccessible. 

The unit's WR number can be obtained by using the MSIU Test program and typing the

command:

pget ID

the WR number will be returned.

Issue: C 13 DSMS Gas Analysis System

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INST. TYPE

BRAND

MANUFACTURER

PLACE OF ORIGIN

MODEL

DATE PRODUCED

VOLTAGE

CURRENT

WORKS REF (WR)

MASS SPECTROMETER

HIDEN

HIDEN ANALYTICAL

UNITED KINGDOM

A N A LY T I C A L www.HidenAnalytical.com

DSMS

25-12-18

230 V ac

10 A max.

WR 16543

Figure 4 Serial number label
4 Technical data

4.1 Electrical specification

Voltage: 100, 110 or 230 V a.c. (~).

Frequency: 50 to 60 Hz.

Power: 1000 VA typical.

Mains fuse: 20 mm HRC, 6.3 A T, 250 V (standard).

Installation category (overvoltage category): II.

Pollution degree: 2.

4.2 Environmental data

Operating temperature range: 5 to 40 °C.

Storage temperature range: 0 to 50 °C.

Note:

The equipment can be stored temporarily at temperatures down to -10 °C.

Relative humidity range: 20 to 80 % non-condensing.

DSMS Gas Analysis System 14 Document Number: HAV-001-013

HIDEN ANALYTICAL
5 Installation

5.1 Introduction

WARNING

1. This equipment must be fully installed and configured for

normal operation before it is powered-up; failure to do this may

cause injury to the operator and damage to the equipment.

2. This equipment must be earthed; failure to do this may cause

injury to the operator and damage to the equipment.

The system may be supplied in kit form or fully assembled; this will depend on the

system configuration and transit requirements.

For the typical system shown in Figure 1:

• the RF Head would be removed to reduced the chance of damage to the mass

spectrometer feedthrough

• the capillary would be removed from the inlet

• the pump isolating plate would be secured with two transit bolts.

5.2 Preparation

Before unpacking the DSMS system, check for signs of shipping damage. If the

packaging is damaged, notify the carrier immediately.

Check all the box contents against the packing list. If any parts are missing, notify the

carrier and Hiden Analytical Limited immediately.

Having inspected all the parts, place the main support frame close to the area in which it

is to operate but with room to work around the frame.

Issue: C 15 DSMS Gas Analysis System

HIDEN ANALYTICAL
5.3 System assembly

Refer to Figure 1.

A basic tool kit is required, including 10 mm and 13 mm spanners, metric hex keys,

screwdrivers, etc. 

Refer to the appropriate manufacturer’s manuals for the operating instructions for the

various items not of Hiden Analytical Limited manufacture.

For benchtop DSMS systems a suitable work bench capable of supporting the weight of

the DSMS must be used. Ensure there is sufficient space to work around the system

during installation. The DSMS must not be moved once it is started.

CAUTION

The system must not be moved while the turbo pump is at

operational speed. Inertial shock loading of the turbo pump rotor

at operational speed may cause severe pump damage.

For cart mounted DSMS systems ensure there is sufficient space to work around the

DSMS during installation. The DSMS must not be moved while the pumps are running.

The scroll pump is mounted onto a sub-plate secured to the lower trolley shelf by two M8 

transit screws. As part of the installation procedure:

1. Move the trolley in to its operational

location.

Ensure it is not powered up and the

pumps are therefore not running.

2. Lock the wheels. Press the tab downwards until it locks

into position.

3. Remove the two M8x25 cap head

screws that secure the scroll pump

sub-plate to the trolley lower shelf.

There is one mid-way on each side of

the plate.

Use the 6mm hex key supplied with

the system.

Retain the screws for future use.

4. Lower the four jacking legs by turning

the rose knobs in a clockwise

direction.

Once the jacking legs are in contact

with the floor the sub-plate will rise

above the trolley shelf.

Lower the legs as far as they will go.

If the system is moved reverse the above procedure to lock the scroll pump in place.

DSMS Gas Analysis System 16 Document Number: HAV-001-013

HIDEN ANALYTICAL
To install the DSMS system:

1. Remove any protective caps, cable

ties, etc. that have been fitted for

shipping purposes.

Protective plastic caps are fitted to the

backing line port, scroll pump and

stainless steel bellows.

2. Connect the RF Cable HEAD

connector to the RF Head.

The 37 way D-type to 37 way D-type

cable, reference HA-077-041, connects 

the RF Head to the RC Interface RF

HEAD EL02 connector.

This cable is secured with plastic ties

for shipping. Cut the ties.

3. Connect the SEM detector supply

cable (reference HA-072-031) to the

bayonet connector on the probe

mounting flange.

This cable is secured with plastic ties

for shipping. Cut the ties.

4. Connect the RF Head to the mass

spectrometer probe.

The RF Head mates directly with the

vacuum feedthrough via the 12-way

feedthrough connector.

The centre pin on this connector is

spring loaded and engages with the

centre pin on the vacuum feedthrough.

Ensure this is making a good

connection.

The 12-way feedthrough connector

locates using a key-way machined in

the connector surround. Fit the RF

Head to the vacuum feedthrough so

that the key-way engages.

5. Tighten the clamping screws that lock

the RF Head in place on the Probe.

The screws may be M4 grub screws

(requiring a 2mm Allen key) or

thumbscrews.

6. Connect the DN-25-KF stainless steel

bellows to the DN-25-KF Tee

connected to the turbo pump outlet

port.

Use the supplied seals.

For cart systems; the scroll pump is

fitted in the cart and connected to the

turbo pump by the stainless steel

bellows. Therefore, steps 6. to 9. are

not required.

7. Connect the other end of the stainless

steel bellows to the scroll pump inlet

port.

Use the supplied seals.

Issue: C 17 DSMS Gas Analysis System

HIDEN ANALYTICAL
8. Connect the scroll pump control cable. D-type to D-type cable, reference

HA-057-592, connects the VCU E1

connector to the scroll pump logic

interface connector.

This cable is secured with plastic ties

for shipping. Cut the ties.

9. Connect the scroll pump mains inlet to

the DSMS mains distribution block.

Use the IEC to IEC connector lead

supplied.

10. Using one of the communications

cables provided, link the RC Interface

to the PC comms. port (or network

hub).

Communications may be via RS232,

USB or 10/100Base-T, but only one

type can be used at one time.

All three types of communications

cable are supplied with the system.

Refer to the Hiden Software Suite

Installation Guide.

11. If the USB port is being used to

communicate with the PC install the

USB drivers from the Hiden Software

disc.

Install the drivers before switching on

the RC Interface unit.

12. If the system is to be vented by gas

other than ambient air, connect the gas

supply to the vent valve.

A supply of dry gas connected to the

vent valve at system shutdown will

reduce the water vapour level and

hence reduce the pump-down time for

the next operation. The gas pressure

should be in accordance with the vent

valve manufacturer’s instructions,

typically 0.3barg.

13. If the system is fitted with the gas

purge option connect the purge gas

supply to the gas sealing valve fitted to 

the turbo pump.

The fitting will typically be a 1/4 inch

compression fitting. 

Connect a regulated supply of dry inert

gas such as nitrogen. Set the regulator

pressure to 0.3barg (5psig).

The valve is factory set to allow a flow 

of approximately 50ml/min.

14. If the scroll pump is fitted with the gas

ballast option connect a source of

regulated dry inert gas such a nitrogen.

The fitting will typically be a 1/4 inch

compression fitting. 

Set the regulator pressure to 0.3barg

(5psig).

The flow meter valve is typically set to 

0.5 to 1 l/min.

DSMS Gas Analysis System 18 Document Number: HAV-001-013

HIDEN ANALYTICAL
15. If the system incorporates rotary

pumps, add oil to the pumps.

Refer to the appropriate manufacturer's 

manuals.

Suitable oil is supplied with the

system. A funnel is supplied with the

system.

CAUTION

The mains power plug and socket is the primary disconnect device

for the DSMS; it must be easily identifiable and accessible by the

operator.

15. When the rest of the mechanical and

electrical installation is complete,

connect the IEC320 cordset between

the system power connector and a

suitable mains power socket.

Check that the DSMS is suitable for

the local supply. The voltage rating is

given on the serial number label.

The mains power socket must be easily 

accessible by the operator.

16. Install the MASsoft application by

following the instructions in the

Software Suite Installation Guide.

Refer to the Hiden Software Suite

Installation Guide.

Issue: C 19 DSMS Gas Analysis System

HIDEN ANALYTICAL
6 Operation

6.1 System start-up from atmospheric pressure

To start the DSMS system following assembly or shut down:

1. Ensure the inlet bypass isolation valve

is open.

2. Power up the system. Check the local supply is suitable for

the system.

Connect the system's mains

distribution block to the mains supply

and move the mains distribution power 

switch to the on position.

The switch will illuminate providing

mains power is available.

The Vacuum Control Unit display will

illuminate and show Pumps Off and

SP1 off.

3. Move the Vacuum Control Unit

Pumps switch to the ON position.

The scroll pump or backing and

bypass rotary pumps will start and the

turbo pump will start to accelerate.

The turbo pump vent valve will be

energised and will close.

Turbo pump speed is indicated

towards the bottom of the display. 

Before the turbo pump reaches full

speed the total pressure gauge will

switch on automatically.

4. When the pressure indicated by the

total pressure gauge is less than 9x10-5

mbar switch on the mass spectrometer

RC Interface unit.

The value of 9x10-5 mbar may vary

depending on system type. Systems

with mass spectrometers fitted with

Ion Counting detectors will typically

have the trip level set to 5x10-6 mbar.

Refer to the Contents Sheet supplied

with the system.

The VCU display will show SP1 OK

once the pressure has fallen below the

setpoint pressure.

5. Start MASsoft.

DSMS Gas Analysis System 20 Document Number: HAV-001-013

HIDEN ANALYTICAL
6.2 Sampling using the inlet system

CAUTION

1. The UHV housing pressure must not exceed 5x10-5 mbar during

sampling; the pressure should ideally be in the range 1x10-6 to

1x10-5 mbar.

2. When sampling reactive gases, the UHV housing pressure must

not exceed 2x10-6 mbar as measured on the total pressure gauge.

Note:

The total pressure gauge should be used in preference to the mass spectrometer for total

pressure measurement.

To sample:

1. Follow the start-up procedure. Refer to Section 6.1.

2. Ensure the pressure at the sampling

point is in the correct region for the

inlet system being used.

Refer to the capillary inlet manual.

3. Ensure the vacuum system is operating 

and that the pressure at the mass

spectrometer is below 1x10-6 mbar.

4. Ensure the bypass pump is operating. For scroll pumped systems bypass

pumping is via the backing line.

5. Ensure the bypass isolation/control

valve is fully open.

6. To operate the inlet system hot, apply

power to the heaters.

Allow 1⁄2 hour (minimum) for the inlet

to heat up.

7. Open the sample isolation valve.

CAUTION

If using the mass spectrometer multiplier detector, the maximum

pressure must not exceed 5x10-6 mbar.

Issue: C 21 DSMS Gas Analysis System

HIDEN ANALYTICAL
8. Monitor the sample pressure as

displayed on the mass spectrometer.

CAUTION

The bypass isolation/control valve must not be fully closed during

sampling.

9. If necessary, set the pressure at the

mass spectrometer to a maximum of

1x10-5 mbar for normal use, by

adjusting the bypass pumping using

the bypass isolation/control valve.

Slowly turn the valve clockwise to

increase the pressure at the mass

spectrometer.

To end sampling:

1. If used, switch off the heater.

2. Close the sample isolation valve.

3. Wait for a minimum of 1 minute, to

allow evacuation of the inlet.

4. Close the bypass/isolation valve.

6.3 Cryo-shield operation

Using the cryo-shield will reduce background levels by enhancing pumping in the ion

source region. This allows detection of lower partial pressures from the sample, thus

increasing the detection capability.

WARNING

Liquid nitrogen can burn.

The following procedures must be performed by suitably trained

and qualified personnel. 

Protective clothing and eye protection must be worn.

DSMS Gas Analysis System 22 Document Number: HAV-001-013

HIDEN ANALYTICAL
1. Ensure that the UHV housing is being

pumped by the turbo pump and is

under vacuum.

2. Add liquid nitrogen to the cryo-shield

chamber through the vertical filling

port.

The liquid nitrogen will boil

vigorously at first; keep adding liquid

nitrogen until the boiling reduces.

3. Add more liquid nitrogen as necessary. This normally will be every few hours.

6.4 System shut down

The DSMS will need to be shut down for maintenance or if it is to be moved. The user

may wish to shut down the system if it is not to be used for some time.

CAUTION

If a cryo-shield is being used, ensure that cryo-shield chamber is

empty before the system is shut down; this avoids water condensing 

in the UHV housing.

To shut down the DSMS:

1. Switch off the mass spectrometer

filament(s) and shut down MASsoft.

Refer to the MASsoft manual.

2. Switch off the RC Interface unit.

3. If appropriate, switch off any heaters. Allow a minimum of 10 minutes for

the filaments to cool.

Allow an additional 20 minutes for the

heaters to cool.

4. Close the sample isolation valve and

the bypass line isolation valve as

appropriate.

5. Move the Vacuum Control Unit

Pumps switch to the OFF position.

The turbo pump is switched off and

starts to decelerate.

After a delay the vent valve opens and

the backing and bypass pumps are

switched off.

The total pressure gauge will be switch 

off automatically.

Wait for the system to vent.

Issue: C 23 DSMS Gas Analysis System

HIDEN ANALYTICAL
5. Move the rocker switch on the mains

distribution block to the off position.

Power to the Vacuum Control Unit

will be switched off.

7 Troubleshooting

CAUTION

The procedures described in this section must be performed by

suitably qualified personnel with experience of high vacuum

systems.

The procedures described in this section are for troubleshooting only; they are not

required for normal operation.

7.1 Fault finding guide

This section aims to help the user identify and resolve problems which may prevent the

DSMS from operating correctly.

7.1.1 Vacuum Control Unit

As soon as the DSMS system is powered on the Vacuum Control Unit display should

illuminate.

Symptom Fault Action

Display fails to

illuminate at

power on.

No mains supply to DSMS. Check the mains supply to the DSMS

mains distribution block.

Check the distribution block switch is

in the ON position. The switch should 

illuminate when switched on with

mains power present.

VCU mains cable

disconnected.

Check the mains cable to the VCU is

fully connected to both the mains

distribution block and the VCU rear

panel connector.

VCU unit has failed. The VCU unit will need to be

replaced.

Contact Hiden Analytical for advice.

DSMS Gas Analysis System 24 Document Number: HAV-001-013

HIDEN ANALYTICAL
7.1.2 Scroll pump

In DSMS systems the scroll pump acts as both the turbo backing pump and the inlet

bypass pump. It should start as soon as the system is started by moving the VCU Pumps

switch to the ON position. It should be obvious when the pump is running due to the

sound and vibration.

Symptom Fault Action

Scroll pump does

not run when

system started.

No mains supply. Check the mains cable to the pump is

fully connected to both the pump

mains inlet and the DSMS mains

distribution block.

Check mains power to the pump is

being provide by the DSMS mains

distribution block.

Temporarily try powering the scroll

pump directly from a mains power

outlet and see if it then runs.

No control signal. Check that the control cable

connecting the VCU to the scroll

pump 15 way D-type plug is

connected and both connectors are

correctly seated.

Pump fault. Contact Hiden Analytical for advice, a 

replacement pump may be needed.

Turbo pump fails

to reach full speed

and/or scroll pump 

making a louder

than normal noise.

Worn tip seals. Scroll pump requires servicing and tip 

seals replacing.

Test the pump, see Section 8.6.1.

Contact Hiden Analytical for advice.

7.1.3 Rotary pump

Note 

Some DSMS systems do not have a separate bypass rotary pump. Only follow this part if

the DSMS has two rotary pumps.

Start the bypass rotary pump. Some rotary pumps have a switch on the top of the pump

others just plug into the mains.

The bypass rotary pump is powered by the PSTU from the BACKING PUMP outlet via a 

Y-cable.

Check the pump is running by listening for the sound or feeling the vibration of the pump 

body.

Issue: C 25 DSMS Gas Analysis System

HIDEN ANALYTICAL
Symptom Fault Action

The rotary pump is 

not running.

It is not switched on. Check the switch on the top of the

pump is in the on position.

There is no mains supply to 

the pump.

Check the pump is plugged in to the

DSMS mains distribution block or

Y-cable.

Check the mains supply is present.

Check the mains supply is correct for

the pump. There will be a rating plate

on the pump body.

Check the mains fuses.

Check the circuit breaker on the

DSMS mains distribution block.

Temporarily try powering the pump

directly from a mains power outlet

and see if it then runs.

The bypass rotary pump is

faulty.

The bypass rotary pump may need to

be replaced. Please contact Hiden

Analytical for advice.

Rotary pump oil

on the floor or

base of system.

Spillage from an oil

change.

Clean up and check if more oil

appears.

Rotary pump shaft seal has

failed.

Check the pump for signs of oil

dripping from the oil sump/motor

housing seal.

Follow the manufacturers instructions

to replace the seal. Contact Hiden

Analytical for advice.

DSMS Gas Analysis System 26 Document Number: HAV-001-013

HIDEN ANALYTICAL
7.1.4 Turbo pump fails to reach full speed

Symptom Fault Action

There is a large air leak 

on the system.

There is a leak on one of

the vacuum seals.

Check all the bolts are tight on the

CF fittings.

Check the clamps are tight on the

KF fittings.

No backing pump. Check the backing pump is

running.

Worn scroll pump seal. Worn tip seals generally cause

louder than normal running noise.

See Section 7.1.2.

The air admittance valve

is leaking.

Check whether air is being sucked

in through the automatic vent

valve.

Check that 24V DC is being

supplied to the valve by the turbo

pump. If it is not there could be a

fault with the cable.

Try replacing the automatic vent

valve with a manual vent vale (one

is supplied with the system).

The automatic vent valve will need 

to be replaced if it is leaking.

Also please refer to the manufacturers documentation of fault finding information.

7.1.5 Total pressure gauge

The DSMS mass spectrometer vacuum chamber will be fitted with either an Edwards

AIM-XL cold cathode gauge or an Edwards AIGX-S active ion gauge. The type of gauge 

fitted is recorded in the configuration section of the Contents Sheet.

The gauge head is connected to the G1 connector on the VCU rear panel. The pressure

reading is shown on the VCU display as G1. In addition to displaying the chamber total

pressure this gauge provides the mass spectrometer over-pressure trip signal to protect the 

filaments and detector.

When the system is started and before the turbo pump reaches full speed the total

pressure gauge will be switched on and the pressure will be displayed. This pressure will

typically be in the 10-5 mbar region and will be falling rapidly.

Please refer to the manufacturers documentation in addition to the following sections.

Issue: C 27 DSMS Gas Analysis System

HIDEN ANALYTICAL
Symptom Fault Action

VCU display is blank

where pressure

reading should be

shown.

Gauge head not connected. Check the cable is plugged into

the gauge head and the VCU unit.

Try an alternative cable.

Pressure displayed is

lower than normal.

Capillary inlet is blocked. Remove any adapters and sample

ambient air and monitor the

pressure.

A mass spectrum with an absence

of nitrogen and oxygen as the

main peaks when sampling air

indicates a blockage.

Pressure displayed is

higher than normal.

Leak on the system. Check all the vacuum seals

particularly any that have recently

been disturbed.

Increase in gas sample

pressure.

Disconnect the capillary from the

gas sample source and sample

ambient air, look for a change in

pressure.

Worn scroll pump tip seals. Scroll pump requires servicing

and tip seals replacing.

Test the pump, see Section 8.6.1.

Contact Hiden Analytical for

advice.

7.1.6 Edwards AIGX-S ion gauge

The gauge has a tri-coloured LED which gives some status information.

Off No power to gauge or a fault.

Amber Power on, gauge disabled.

Green Emission on.

Red Over-pressure trip.

Refer to the manufacturers documentation for further information.

DSMS Gas Analysis System 28 Document Number: HAV-001-013

HIDEN ANALYTICAL
7.1.6.1 Edwards AIM-XL cold cathode gauge

Symptom Fault Action

VCU displays

Striking 

The cold cathode gauge has

not started.

Try un-plugging and plugging in

the gauge head cable.

The cold cathode gauge

requires servicing. 

Please contact Hiden Analytical

for advice.

VCU displays

pressure as 8.5x10-3. 

This is the maximum

pressure reading and could

mean the gauge is

contaminated with metal

deposits.

The gauge requires servicing

please contact Hiden Analytical

for advice.

Refer to the manufacturers documentation for further information.

7.1.7 Mass spectrometer

Providing the pressure indicated by the total pressure gauge controller is below 9x10-5

mbar the mass spectrometer can be switched on and used to leak check the DSMS

system.

Move the switch on the RC Interface to the ON position. The switch should be

illuminated and the RC Interface should emit a short beep. 

Symptom Fault Action

The RC Interface

switch does not

illuminate when in the

ON position.

Mains cable not plugged in. Check the mains cable is

plugged into the DSMS mains

distribution board and RC

Interface unit.

No mains supply to the

DSMS.

Check the mains supply is

present and the correct voltage

for the RC Interface.

Check the mains fuse.

Check the circuit breaker on

the DSMS mains distribution

block.

Try connecting the RC

Interface to an external mains

supply.

The RC Interface is faulty. Please contact Hiden

Analytical for further

assistance.

Issue: C 29 DSMS Gas Analysis System

HIDEN ANALYTICAL
There is no beep sound 

made by the RC

Interface.

The RC Interface has a fault. Please contact Hiden

Analytical for further

assistance.

The RC Interface emits 

a long and continuous

beep to indicate that

the RC Interface is

detecting an external

trip.

The trip signal from the total

pressure gauge control is not

connected.

Check the 15 way D-Type

connector is plugged into the

TRIPS connector on the rear

panel of the RC Interface.

The over-pressure trip signal

from the mass spectrometer

RF Head is not connected.

Check the 37 way D-Type

connector is plugged into the

RF HEAD connector on the

rear panel of the RC Interface.

The chamber pressure is

above the total pressure gauge 

set point.

A trip condition is indicated by

the VCU SP 1 showing as

blank rather than OK.

The total pressure

gauge controller

indicates a trip

condition. 

The chamber pressure is

above the total gauge set

point.

If the total pressure gauge

controller indicates a pressure

below 9x10-5 mbar the total

pressure gauge set point may

be incorrect.

The set point will usually be set 

to 9x10-5 mbar for analogue

instruments and 5x10-6 for

pulse counting instruments.

Refer to the Contents Sheet for

the correct setting.

The chamber pressure is

above the total pressure gauge 

set point and the set point is

correct.

The chamber pressure is in the

region between 1x10-4 mbar

and the set point (9x10-5 mbar). 

Fit the linking plug. Refer to

the text below and the total

pressure gauge manual. 

If the total pressure gauge switches on, the pressure must be below its internal trip level,

set by Hiden to 1x10-4 mbar. 

The total pressure gauge set point is set by Hiden to 9x10-5 mbar (5x10-6 mbar for

RC-PIC instruments) and the relay output is used to trip the RC Interface, thereby

protecting the filaments and the electron multiplier. Neither the filaments or the multiplier 

can be switched on if the external trip (provided by the total pressure gauge) is active.

In the small pressure region of 8x10-5 mbar to 1x10-4 mbar with care the mass

spectrometer may be used to leak check the system to locate any air leaks which will be

the most likely cause of high mass spectrometer chamber pressure.

DSMS Gas Analysis System 30 Document Number: HAV-001-013

HIDEN ANALYTICAL
The external trip may be disabled by un-plugging the cable from the TRIPS connector on

the rear panel of the RC Interface and fitting a linking plug. Alternatively, the total

pressure gauge set point may be adjusted, refer to the total pressure gauge documentation

for a description of adjusting the set point.

Hiden Analytical supplies a linking plug. Alternatively, refer to the over-pressure

protection section in the mass spectrometer manual.

Using the SEM at high pressure will dramatically reduce its useful operating life.

7.1.8 Emission Failure

When a MASsoft recipe is run (when leak checking for instance) a filament is switched

on and the correct emission current (flow of electrons from the filament to the source

cage) is established. When operating correctly the Filament 1 and/or Filament 2,

Emission and Run LEDs on the RC Interface front panel should all be illuminated. 

Symptom Fault Action

The Emission LED is

flashing.

There is an open circuit

on the filament circuit.

Check the RF cable is properly

connected to both the RF Head and

RC Interface.

Check the RF Head is connected to

the probe and the connector is fully 

pushed on to the probe.

Check the filaments are not open

circuit. Refer to the

Trouble-shooting chapter in the

mass spectrometer manual to check

the filaments. If the filaments are

open circuit they will need to be

changed, refer to 8.2.

Neither Filament LED

is illuminated.

The MASsoft recipe is

not switching the filament 

on.

In the MASsoft recipe Global RGA

box check that a filament is

selected.

Issue: C 31 DSMS Gas Analysis System

HIDEN ANALYTICAL
7.2 Leak checking

To operate correctly the only gas entering the DSMS and being detected by the mass

spectrometer probe must be through the DSMS inlet valve assembly. A leak on the mass

spectrometer vacuum chamber would, at best, give an air background spectrum that

would limit the instrument’s performance. At worst a large leak could prevent the system

from operating at all.

If there is a leak one or more of the following symptoms may be observed:

1. The turbo pump fails to reach full speed.

2. The total pressure gauge gives a higher reading than expected.

3. A persistent air background spectrum is observed.

An air spectrum would have mass 28 and mass 32 peaks in the ratio 5 to 1.

The mass spectrometer’s ability to detect gas species is used to find any leaks in the

DSMS vacuum system. The mass spectrometer is configured to monitor a probe gas

(helium is the most common leak checking gas) which is carefully sprayed over the

vacuum system. Any signal detected by the mass spectrometer will be due to the leak

check gas entering the system through the leak.

A helium cylinder fitted with a regulator and a length of hose is required to leak check

the system. 

Another gas such as argon can be used if helium is not available. Any grade of gas may

be used.

To leak check:

1. Start MASsoft.

2. Select Leak Detect from the Gallery.

3. Set the Mass: to 4 (if using helium) or an appropriate mass for the leak checking gas

(mass 40 for argon). Refer to the Leak Detect scan section in the MASsoft User’s

Manual for further details regarding the configuration of MASsoft.

4. Adjust the helium cylinder regulator to give a gentle flow of gas. Spraying large

amounts of helium over the vacuum system will make it difficult to precisely locate

any leaks.

5. Spray helium over the vacuum chamber paying particular attention to the vacuum

seals as these are the most likely source of a leak. Start at the top and work down the

system.

DSMS Gas Analysis System 32 Document Number: HAV-001-013

HIDEN ANALYTICAL
8 Maintenance

WARNING

The procedures described in this section must be performed by

suitably qualified personnel with experience of high voltage and

high vacuum systems.

Procedures described in this Section are for system maintenance only; they are not

required for normal operation.

8.1 Maintaining System safety

The following points should be checked every two years in order to maintain safe

operation of the equipment:

Item Test Pass condition

1. Mains lead(s)

and connectors.

a) Visual inspection. No damage to cable or

connectors.

b) Mains plug. Correct fuse fitted.

c) Attempt to pull the cable

from the IEC connector.

No movement.

Note:

If the lead or one of its connectors is damaged it must be discarded and replaced by a

suitably approved cordset with a moulded IEC 320 socket and mains plug; the cable must

contain a double layer of insulation and must have an adequate current capacity for the

application.

2. Mains on/off

switch

Visual inspection. Correct operation, no damage.

3. Conducting cases

and metalwork.

a) Visual inspection. No damage.

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b) Using an earth tester which

will check resistance and

pass a current of at least

twice the fuse rating, check

between the mains plug

earth, and the DSMS

metalwork.

Earth resistance must be less

than 0.1 ohm.

c) High voltage insulation

500 V a.c. minimum test,

check between the mains

plug live and earth.

No fault indicated after

5 seconds.

4. Accessible fuse

holders.

Visual inspection. No damage.

The above information has been derived from the United Kingdom Health and Safety

Executive Guidance Note PM32.

8.2 Filament renewal

The mass spectrometer ionisation source filament lifetime depends on operating

conditions and may be up to several years. Two filaments are fitted to the mass

spectrometer ionisation source so that when one fails the other filament may be used. 

Follow the instructions below to renew the filaments; also refer to the instructions in the

mass spectrometer manual.

1. Shut down the system. Follow the procedure described in

Section 6.4.

2. Remove the RF Head and secondary

electron multiplier detector cable (if

fitted).

3. Make a note of the mass spectrometer

probe feedthrough flange orientation.

The probe will need to be fitted in the

same orientation. The radial M3 screw

and metalised feedthrough pin may be

used for reference.

4. Remove the mass spectrometer probe. Remove the six or eight M6 or M8 bolts 

using 10mm or 13mm spanners.

5. Follow the filament renewal procedure

detailed in the mass spectrometer

manual.

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6. Refit the mass spectrometer probe onto

the vacuum chamber using a new

copper gasket seal.

Refer to the "Assembling Conflat-type

flange joints" section in the mass

spectrometer manual.

7. Refit the RF Head.

8. Re-start the DSMS system. Refer to Section 6.1

9. Leak check the DSMS system. Refer to Section 7.2.

8.3 Inlet assembly

8.3.1 Removal

WARNING

Protective gloves and face mask must be worn when removing the

unit's cover.

The cover must be removed to carry out maintenance operations such as replacing the

molecular leak as described in this section. When removing the cover and carrying out

work on internal parts of the unit a face mask and protective gloves must be worn.

The Heated Molecular Leak Assembly incorporates ceramic paper insulation which may

pose a long term health risk due to sub six micron filament size fibres in the material.

For further information and Safety Data Sheets please contact Hiden Analytical Limited.

Refer to Figure 5.

To remove the inlet assembly from the mass spectrometer vacuum housing:

1. Remove the knobs from the bypass

isolation/control valve and the sample

isolation valve.

Each knob is secured by two grub

screws.

2. Remove the M3 cap head screws

(4-off) retaining the outer cover.

3. Remove the outer cover.

4. Unscrew the tapped spacers (4-off)

retaining the inner cover.

5. Remove the inner cover.

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Mounting flange type DN-35-CF

with integral molecular leak

Inner cover

Outer cover

Heaters

Bypass pumping connection

port DN-10-KF

Sampling capillary connection

point [1⁄4 inch (6.35 mm) o.d.]

Sample 

isolation 

valve

Bypass isolation/control 

valve

Tapped spacer

Swagelok

nut

M3 cap head 

screw

Enclosure fixing screws

Figure 5 Heated Molecular Inlet Assembly interior
6. Loosen the heater clamped around the

mass spectrometer vacuum housing

mounting flange and slide the heater

off the flange joint.

7. Remove the mounting flange fixing

bolts.

8. Remove the heated inlet assembly

from the mounting flange.

8.3.2 Fitting the inlet

Refer to Figure 5.

To fit the inlet assembly to the mass spectrometer vacuum housing:

1. Mount the Heated Molecular Inlet

Assembly onto the mass spectrometer

vacuum housing mounting flange.

A new copper gasket must be used in

the flange. The copper gasket is used

as the sealing medium, the seal being

formed when the flange knife-edges

embed in the copper as the fixing

screws are tightened.

It is essential that the flanges are

tightened uniformly:

First tighten diametrically opposite

screws finger-tight only, then tighten

the remaining screws finger-tight only.

Each screw is then tightened

progressively, a little at a time, until all 

screws exhibit strong resistance. It is

not necessary to achieve

flange-to-flange contact. The normal

tightening torque required to achieve a

good seal is 7 to 9 Nm; over-tightening 

can cause later problems with gasket

removal.

2. Refit the heater around the mounting

flange.

3. Refit the inner cover.

4. Refit and tighten the tapped spacers

(4-off) to secure the inner cover.

5. Refit the outer cover. Do not fit the screws at this stage.

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6. Refit the knobs to the bypass

isolation/control valve and the sample

isolation valve and tighten their grub

screws.

The outer cover will need to be pushed 

away from the knobs to gain access to

the grub screws.

7. Refit and tighten the four M3 cap head 

screws to secure the outer cover.

WARNING

The Heated Molecular Inlet Assembly must be earthed.

8. Use a suitable earth tester to check that 

the Heated Molecular Inlet Assembly

is connected to the DSMS system

earth.

See also Section 8.1.

8.3.3 Replacing the molecular leak

To renew the molecular leak/flange assembly:

1. Follow the steps detailed in

Section 8.3.1.

2. Undo the Swagelok nut connecting the 

inlet fittings to the molecular leak

assembly.

3. Remove the enclosure fixing screws

from the flange.

4. Remove the molecular leak/flange

assembly.

5. Fit the new molecular leak/flange

assembly.

6. Fit the enclosure fixing screws to the

flange.

7. Tighten the Swagelok nut connecting

the inlet fittings to the molecular leak

assembly.

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8. Follow the steps detailed in

Section 8.3.2. to refit the inlet.

8.4 Bake-out

CAUTION

1. The RF head and all cables must be removed from the gauge

head prior to bake-out.

2. The system must be under vacuum during bake-out.

3. The maximum bake-out temperature for the UHV housing and

gauge head is 250 °C.

4. The maximum bake-out temperature for the bypass inlet system

will depend on its construction and seal materials;

Vespel/metal-sealed systems may be baked to 200 °C, PTFE/Kel

F-sealed systems may be baked to 80 °C.

5. Wrap the feed-through flange in aluminium foil prior to baking; 

this avoids damage to the feed-through due to sudden

temperature changes.

6. The UHV housing temperature must not be increased or

decreased at more than 2 °C/min.

7. The cold cathode gauge head must be partially dismantled

before bake-out; refer to the manufacturer’s instruction manual.

8. The turbo pump must not be subjected to excessive

temperatures; refer to the manufacturer’s instruction manual.

9. A minimum of two hours must be allowed for cooling after

bake-out, before venting the system or reconnecting the

electronics to the system.

Note:

The bypass inlet system fitted to standard DSMS systems uses all metal valves and Vespel 

ferrules; unheated sampling lines may include PTFE ferrules.

The relevant parts of the system may be cleaned by heating under vacuum. Heating tapes 

may be wrapped around the parts, or they may be enclosed in a purpose-built oven.

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8.5 Rotary pumps

Renew the rotary pump oil according to the instructions in the pump manufacturer’s

operating manual.

When pumping corrosive species it is recommended that the frequency of oil changes be

increased above the manufacturer’s standard recommendations. The increased frequency

will be determined by the user, based on the nature of the pumped species and any effect

on the pump fluids.

Standard DSMS systems use mineral oil, corrosive systems use a silicone oil. Oil must be 

replaced with the same type. Refer to the Contents Sheet for the oil type.

WARNING

Protective gloves and safety glasses should be worn when changing

the rotary pump oil.

Material Safety Data Sheets for both mineral oil and silicone oil are available from Hiden

Analytical and the pump manufacturer.

WARNING

Used rotary pump oil may contain harmful contaminants.

Normally, the user will be aware of any potentially dangerous contaminants in the pump

oil due to sampling hazardous gases. 

Any necessary safety precautions must be taken.

8.5.1 Testing the pump

Rotary pumps can develop oils leaks over time. Usually, oil will seep from the joint

between the casing and the motor housing due to a worn shaft seal. Consult the

manufacturer's documentation for further information.

To test if a rotary pump is working seal the inlet using a total pressure gauge. A Pirani

gauge or a baratron are suitable types of gauge. Switch on the pump. The gauge should

read less than 1 mbar within 1 minute from starting the pump. If it does not the pump

may need servicing.

8.6 Scroll pumps

The pump tip seals will wear in time and eventually need replacing. Refer to the

manufacturers instructions to do this.

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8.6.1 Testing a scroll pump

To test if a scroll pump is working seal the inlet using a total pressure gauge. A Pirani

gauge or a baratron are suitable types of gauge. Switch on the pump. The gauge should

read less than 50 mbar within one minute from starting the pump. If it does not the pump

may need servicing.

8.7 Diaphragm pumps

A small number of DSMS systems use one or two diaphragm pumps. Renew pump

diaphragms and flap valves in accordance with the manufacturer’s instructions.

8.7.1 Testing a diaphragm pump

To test if a diaphragm pump is working seal the inlet using a total pressure gauge. A

Pirani gauge or a baratron are suitable types of gauge. Switch on the pump. The gauge

should read less than 10 mbar within 30 seconds from starting the pump. If it does not the 

pump may need servicing.

8.8 Turbo pumps

The turbo pump bearings will typically require replacement every two to three years.

This task must be performed by the pump manufacturer; this can be arranged through

Hiden Analytical if preferred.

8.8.1 Testing the turbo pump

Modern turbomolecular pumps are far more reliable than the older models. The three

most likely causes of failure are:

• Faulty drive electronics

• Worn bearings

• Foreign object in the turbine stack jamming the rotor

Refer to the manufacturers documentation.

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