Witt MG 50-2ME User manual

Copyright WITT-GASETECHNIK GmbH & Co KG, 2016, all rights reserved
Instruction Manual for
WITT Gas Mixer
MG 50,100,200-2ME
MG 50,100,200-2ME PvDu
MG 50,100,200-2ME GB
Issue: 29.04.2016
This issue is not subject to change management

Page 2 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
1 Table of contents
1Table of contents......................................................................................................... 2
2Notes on this manual.................................................................................................. 4
2.1 What does this manual contain?.........................................................................................................4
2.2 Structure of the manual.......................................................................................................................4
2.3 Rights to this manual...........................................................................................................................5
2.4 What symbols are used?.....................................................................................................................5
2.5 Terms (in alphabetical order) ..............................................................................................................6
3Safety instructions and precautionary measures .................................................... 8
3.1 General safety instructions..................................................................................................................8
3.2 Gas mixer with oxygen........................................................................................................................9
3.3 Liability.................................................................................................................................................9
4Description ................................................................................................................ 10
4.1 Types ................................................................................................................................................10
4.2 Applications for the gas mixer...........................................................................................................11
4.3 Functional description of the gas mixer.............................................................................................11
4.3.1 Technical data on the gas mixer............................................................................................11
4.4 Function of the alarm module............................................................................................................12
4.4.1 Technical data on the alarm module......................................................................................12
4.4.2 The terminal strip (rear)..........................................................................................................12
5Setting up and installation ....................................................................................... 13
5.1 Checking for transport damage.........................................................................................................13
5.2 Place for setting up............................................................................................................................13
5.3 Safety instructions for installation......................................................................................................13
5.4 Installation of the pipes......................................................................................................................14
5.5 Electrical installation..........................................................................................................................15
5.5.1 Connection of the floating contacts........................................................................................15
6Commissioning and operation................................................................................. 16
6.1 Safety instructions for commissioning and operation........................................................................16
6.2 Commissioning the gas mixer...........................................................................................................16
6.3 Operating the gas mixer....................................................................................................................17
6.3.1 Setting the mixing valve (24) on models MG200...................................................................17
6.4 The alarm module..............................................................................................................................18
6.4.1 Buttons and displays..............................................................................................................18
6.4.2 Inlet pressure monitoring alarm..............................................................................................18
6.5 Malfunctions and rectification............................................................................................................19
6.5.1 Malfunction table....................................................................................................................19
6.6 Taking out of operation......................................................................................................................21
6.7 Short interruption in work ..................................................................................................................21
7Servicing and maintenance...................................................................................... 22
7.1 Safety instructions for servicing and maintenance............................................................................22
7.2 Repair instructions.............................................................................................................................22
7.3 Checks and servicing tasks...............................................................................................................23
7.4 Checking inlet filters for blockages....................................................................................................24
7.4.1 Plug filters (for version MG 50, MG 100, MG 200).................................................................24
7.4.2 Screwed filters (for version MG 200, MG 500).......................................................................24
7.5 Functional check on the electrical equipment...................................................................................24
7.6 Setting the receiver pressure ............................................................................................................24
7.7 Reset of the temperature monitor for the mixed gas temperature (optional) .........................................25

Page 3 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
8Concise instructions on operation ..........................................................................26
8.1 Switching on.......................................................................................................................................26
8.2 Switching off.......................................................................................................................................26
9Appendices................................................................................................................27

Page 4 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
2 Notes on this manual
You have decided for a gas mixer from WITT-GASETECHNIK.
With this manual, we would like to provide you with all the information necessary for safe, correct
setting up and installation, commissioning, operation and checking of the gas mixing system.
2.1 What does this manual contain?
The operation and maintenance of the WITT gas mixer are described in this manual.
Observance of the manual helps avoid hazards, down times due to incorrect operation and to en-
sure long service and reliability of the gas mixer.
The handling of gases, particularly inflammable and/or toxic gases, requires a high degree of cau-
tion. To prevent incorrect operation this instruction manual must be fully read carefully, and under-
stood, prior to the installation and commissioning of the gas mixer. This manual must be available
to the operating personnel during the operation of the gas mixer. The operating personnel must be
familiar with the operation of the gas mixer and instructed by qualified personnel.
If unexpected malfunctions occur that you cannot rectify with the assistance of the instruction man-
ual, please contact us stating the device number on the rating plate (see also technical data, Sec-
tion 9) or fax us the first page of the technical data with a short description of the fault. Do not for-
get to state your company, your name, and your telephone number.
Our address is:
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8
D-58454 Witten
Tel.: [phone]
Fax: [phone]
You can of course also send us an e-mail (servi[email protected]) or visit our homepage at
http://www.wittgas.com.
In the case of modification to the gas mixing system this instruction manual ceases to be applica-
ble!
2.2 Structure of the manual
This manual is sub-divided into several sections:
In the “Notes on this manual” section the layout of the instruction manual is explained and
the terms and symbols used explained.
In the “Safety instructions and precautionary measures” section suggestions for safe us-
age of the gas mixer are listed. You should pay particular attention to this section as failure to
observe the information given here can result in equipment damage and physical injury.
In the “Description” section the function of the WITT gas mixer is explained based on the
function scheme.
The function of the integrated alarm module is addressed in the “Function of the alarm module”
section.
In the “Set up and installation” section you will find information on the correct location for set-
ting up the gas mixer and notes on both the gas and electrical installation.
In the “Commissioning and operation” section you will learn how you must proceed so that
mixed gas is produced and how you can change the composition of the mixed gas. Here you
will also find information on how to proceed if the alarm module signals insufficient inlet pres-
sure and the possible causes of this situation. You will also learn here how you can take the
gas mixer out or operation. e.g., for servicing tasks.

Page 5 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
Information on servicing tasks that you can perform yourself is given in the “Servicing and
maintenance“ section. Here you will also find notes on what you should check if, at some
point, a feature does not function correctly.
The “Concise operating instructions” provide you with information on the operation of the
gas mixer in short steps.
As an appendix to this manual you will find the technical data on the WITT gas mixer, the
schemes given in the technical data, along with drawings and a list of symbols. This provides a
short overview on the function and the controls on the gas mixer. You will also find the num-
bers for the symbols on the function scheme on the components themselves. With the aid of
the list of symbols and function scheme, you can identify components in the gas mixer.
2.3 Rights to this manual
This manual is the copyright of WITT-GASETECHNIK GmbH & Co KG.
Without the prior written agreement of WITT-GASETECHNIK GmbH & Co KG the manual is not
permitted to be duplicated or used in a manner contrary to the company’s due interests.
It is only permitted to pass this manual on to third parties in conjunction with the provision of the gas
mixer.
2.4 What symbols are used?
The attention symbol indicates hazards for man or the system.
It is imperative that these instructions are observed and followed.
The word “Caution!” is placed in front of information indicating risk of injury- and potentially
fatal hazards.
The word “Attention!”is placed in front of hazards for the system.
Note!
The pointing hand marks general notes that explain operating procedures.
The “dot” marks actions to be performed.
This symbol is used for a list.
This symbol indicates that you should turn the page.
This symbol indicates sections that only apply to the PvDu and GB versions.
PvDu
GB

Page 6 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
2.5 Terms (in alphabetical order)
In this section the terms necessary to understand this manual are explained.
*These terms are explained in more detail in the following text.
Alarm module :
The alarm module is on the separate control housing. It signals insuf-
ficient gas inlet pressure* and indicates the corresponding gas.
Constant pressure (Pm) :
The individual gases are reduced to the constant pressure by the
constant pressure regulator unit*. The constant pressure is the pres-
sure of the individual gases from the dome or double dome loaded
pressure regulators.
Constant pressure
regulator unit :
The constant pressure regulator unit comprises dome or double dome
loaded pressure regulators and a p
ilot pressure regulator*. The gases
to be mixed are regulated to the required constant pressure* by the
constant pressure regulator unit.
Dome loaded pressure
regulator :
A dome loaded pressure regulator functions similarly to a spring-
loaded pressure reg
ulator, however in this case the force from the
spring is replaced by the pilot gas pressure on a membrane. If several
dome loaded pressure regulators are subjected to the same pressure-
regulated pilot gas, then the same constant pressure* is established a
t
each of the dome loaded pressure regulators.
Double dome loaded
pressure regulator :
A double dome loaded pressure regulator* can be considered as two
single dome loaded pressure regulators*. Both chambers in the dome
loaded pressure regulator are subje
cted here to a gas, the pilot gas*;
this results in exactly the same pressures being established at the
outlets of the dome loaded pressure regulator. Together with the pilot
pressure regulator*, the dome and double dome loaded pressure
regulators in a gas mixer form the constant pressure regulator unit*.
Gas inlet pressure (Pv) :
The pressure provided by the supplies for the individual gases is
termed the gas inlet pressure. A differentiation is made between static
and dynamic pressure. If no mixed gas is
produced, no gas flows. The
pressures now present at the inlet to the gas mixer are static pres-
sures. However, if mixed gas is produced, the gas inlet pressure
drops to the dynamic pressure as a function of the sizing of the gas
supply.
The static pressu
re is always higher that the dynamic pressure. The
static pressure (without mixed gas production) must not exceed the
maximum permitted inlet pressure. The dynamic pressure (during the
production of mixed gas) must not drop below the minimum required
gas inlet pressure (in the case that inlet pressure monitoring is acti-
vated, this would result in the triggering of the alarm).
Inlet pressure
monitoring :
The inlet gas pressure monitoring comprises pressure switches*
or
pressure transmitter* and an alarm mo
dule*. It is used to check for the
minimum gas inlet pressure required. The inlet pressure is only moni-
tored to check if the inlet pressure drops below the min. inlet pressure
given in the technical data.
Mixed gas output (QM) : The mixed gas output is t
he mixed gas flow that the gas mixer can
produce in the normal operating state (P=1
bar; T=15 °C). The mixed
gas output will depend on the mixture this value relates to air.

Page 7 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
Mixing valve : Mixing valves are only used in gas mixers for more than two gases.
The percentage portion of the related gas type is set on the mixing
valves. It must be noted that the total of all portions set must always
add up to 100%.
Non-return valve : The non-
return valves prevent the gases from each individual phase
flowing back into the other gases.
Outlet pressure (Ph) : The outlet pressure is the mixed gas pressure in the mixed gas re-
ceiver on the outlet of the gas mixer.
Pilot gas :
One of the gases used in the mixing process is defined as the pilot
gas and is used as the m
edium to be applied to the dome loaded
pressure regulators (via the pilot pressure regulator). If the supply of
the pilot gas is lost, the production of gas mixture is also lost com-
pletely. The pilot gas must therefore always be connected with suffi-
cient g
as inlet pressure, even if it is not used in the mixing process
itself.
Pilot pressure regulator :
The pressure to be applied to the dome loaded pressure regulator* is
adjusted on the pilot pressure regulator. In the dynamic condition, the
pilot pressure is slightly higher than the constant pressure.
Pressure switch /
Pressure transmitter :
The pressure switches or pressure transmitter
monitor the required
gas inlet pressures for the gases supplied. Together with the alarm
module, this then forms the inl
et pressure monitoring*. The pressure
switches only monitor the minimum inlet pressure required, and not
the maximum inlet pressure.
Proportional mixing
valve :
A proportional mixing valve is only found on gas mixers for two gases.
Here the percentage po
rtion of the gas named on the adjusting knob
is set. If the portion of a gas is increased, then portion of the other gas
is automatically reduced.
Receiver pressure (Pb) :
The receiver pressure is the pressure of the mixed gas in the mixed
gas receiver. It fluctuates between the minimum and maximum re-
ceiver pressure that is set on the pressure switch.
Supply gas :
All gases that are mixed including the pilot gas are termed supply
gases.

Page 8 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
3 Safety instructions and precautionary measures
It is imperative that the following safety instructions and precautionary measures are observed and
followed. They are intended to avoid hazards that can arise during the use of the system.
In addition, the applicable national health and safety regulations and safety regulations from the
trade associations are to be observed. For example, in Germany:
Health and safety regulations from the trade associations
a) DGUV Regulation 1 Grundsätze der Prävention (principles of prevention)
b) DGUV Regulation 3 Elektrische Anlagen und Betriebsmittel
(Electrical Systems and Equipment)
c) BGR 500 Sec. 2.33 Gase (Gases)
d) BGR 500 Sec. 2.32 Sauerstoff (Oxygen) - if used as a supply gas
The Pressure Devices Regulations and appropriate technical regulations
a) TRB 600 Aufstellung der Druckbehältern (Installation of Pressurised Vessels)
b) TRB 404 Ausrüstung der Druckbehälter, Ausrüstungsteile
Equipment for Pressurised Vessels, Equipment Parts)
c) TRB 700 Betrieb von Druckbehältern (Operating Pressurised Vessels)
must be observed.
No claim is made that this list is absolute.
Along with the instruction manual and the health and safety regulations applicable in the country
and place of use, recognised engineering regulations for safe and correct working are to be ob-
served.
The operating organisation must ensure that only authorised persons work on or with the system.
The gas mixer is built to the state of the art and is safe to operate. Hazards can be produced by the
gas mixer if it is used incorrectly by untrained personnel, or is not used for the purpose intended.
3.1 General safety instructions
Caution!
Only persons who have been instructed on the operation of the system and who have read
and understood this manual are permitted to use the system.
Observe national technical regulations on the handling of gases, e.g. applicable health and
safety regulations.
Any unauthorised modifications or changes to the system are forbidden for safety reasons.
Malfunctions arising during operation may only be rectified by trained personnel.
Maintenance- and repair tasks may only be performed by trained personnel.
During all maintenance- and repair tasks ensure that the gas mixer is isolated from mains elec-
tricity (also observe external voltage, e.g. via floating contacts) and is de-pressurised.
All supply pipes to and from the gas mixer are to be designed for the maximum permitted gas
pressure. If this is not possible for the system following the gas mixer, then it must be ensured
that the maximum permitted pressure for the following system cannot be exceeded by means
of the installation of suitable fittings, e.g., bursting discs or safety valves.
The material for the gas pipes (pipes from the gas supply to the inlets on the gas mixer), all fit-
tings installed there (e.g. shut-off valves, gauges, etc.) and all sealing elements there must be
designed for the related type of gas.
The material for the gas outlet pipe (pipe from the outlet on the gas mixer to the load), all fit-
tings installed there (e.g. shut-off valves, gauges, etc.) and all sealing elements there must be
designed for all the related types of gas.
The maximum gas inlet pressures in the technical data must not be exceeded. If necessary
this is to be ensured by the installation of safety valves or bursting discs.
Check the connections and joints for leaks to atmosphere at regular intervals (e.g. at every
commissioning) with inert gas and document this check. For this purpose only use suitable
leak detection methods. Never check using a naked flame! If you find leaks, rectify them im-
mediately; the applicable safety regulations are to be observed during this process.

Page 9 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
Also check cables for damage, as well as the supply pipes to the gas mixer and the gas mixer
to the load for leaks.
When using toxic or corrosive gases, for your safety continuously monitor the atmosphere in
the workplace using a gas warning system.
The gas mixer must be used in a well ventilated area. If there is any doubt regarding the venti-
lation then the area should be monitored for minimum oxygen levels and maximum CO2or
flammable gas levels if they are part of the mixture.
A wrong gas mixture may be generated either when the gas mixing unit is started or possibly
as a result of a functional fault during operations, or as a result of the process in the down-
stream system, and for this reason the downstream consumer must be suitable for operations
with wrong gas mixtures. If this is not the case, the gas mixture must be permanently moni-
tored at a suitable place by an analyser to prevent the gas mixture entering a wrong area with-
out having been monitored.
The use of the gas mixer for a purpose other than that intended involves safety risks. Usage for a
purpose other than that intended includes, for example:
Use with gases other than those listed in the technical data.
Operation of the gas mixer with liquids.
The use of the gas mixer in ambient temperatures outside the temperature range specified in
the technical data.
The use of the gas mixer with gases at temperatures outside the temperature range specified
in the technical data.
The installation and operation of the gas mixer in areas with an explosion hazard.
In the case of unauthorised, unapproved changes, modifications, or conversions to the gas mixer,
the guarantee is void.
3.2 Gas mixer with oxygen
Caution!
In the case of the usage of oxygen, the German health and safety regulations BGR 500 Sec.
2.32 must be observed. In particular, the following applies:
The supply pipe for oxygen may only be installed in the connection provided for this purpose.
The oxygen connection must be kept oil-free and grease-free, and also free of soiling.
A vent pipe must be fitted to the safety valve on the receiver (if fitted); this must be designed
such that any gas escaping can flow out without hazard. The vent pipe must be designed such
that the required mass flow rate can be reliably and safely drawn off and the function of the
safety valve is not impaired.
A wrong gas mixture (e.g. pure oxygen) may be generated either when the gas mixing unit is
started or possibly as a result of a functional fault during operations, or as a result of the pro-
cess in the downstream system, and for this reason the downstream consumer must be suita-
ble for operations with wrong gas mixtures (e.g. pure oxygen). If this is not the case, the gas
mixture must be permanently monitored at a suitable place by an analyser to prevent the gas
mixture entering an undefined range without having been monitored.
Observe the maximum control pressure in the technical data.
3.3 Liability
The liability for the function of the unit passes in all cases to the owner or operating organisation as
far as the unit is operated by persons who do not belong to WITT Service, is incorrectly maintained
or repaired, or if the unit is used in a manner that does not comply with the intended usage of the
unit, or is contrary to the applicable regulations.
WITT-GASETECHNIK GmbH & Co KG is not liable for damages arising from failure to observe
these instructions.

Page 10 of 27
WITT-GASETECHNIK GmbH & Co KG
Salinger Feld 4-8

: [phone]
www.wittgas.com
Gas Safety- & Control Equipment
D-58454 Witten
Fax: [phone]
[e-mail]
4 Description
4.1 Types
The MG series comprises as standard the types MG 50, MG 100, MG 200 and MG 500. The differ-
ences between the types lie in the mixed gas outputs.
The gas mixer is specified in more detail by further additions. Please see the information in the en-
closed technical data for the specification of your gas mixer (see Section 9).
MG
50
100
200
500
-2
-3
-4
ME
GB
PvDu
PmDü
A
Ex
Ex Ex-Version (ATEX)
A Analysis
GB Inlet pressure monitoring,
solenoid valve closes on alarm
PvDu Inlet pressure monitoring
PmDü Pilot pressure monitoring
ME elec. pressure switch / solenoid valve
combination
Number of gases
Mixed gas output
Big gas mixer (Gross-Mischer)