BOC Inverweld 110VRD User manual

BOC INVERWELD™
110VRD/140/140VRD
PRODUCTS THAT PERFORM
OPERATING MANUAL

2
Welcome to a better way of welding
Congratulations on purchasing a BOC Inverweld MMA and
GTAW welding machine.
The BOC manual metal arc range are Products that Perform with
reliability and the backing of Australia’s leading welding supplier.
This manual provides the basic knowledge required for MMA and TIG
welding, as well as highlighting important areas of how to operate the
machine. By following these steps, your BOC Inverweld machine will
provide years of trouble-free service,
Access to a wealth of experience and technical information, accumulated
over the years makes the BOC range of equipment a world leader.
BOC equipment and technical support is available through our national
BOC Customer Service Centre or contact your local Gas & Gear outlet.
BOC Customer Service Centre
AUSTRALIA
131 262
Email: [email protected]
Website: www.boc.com.au
NEW ZEALAND
0800 111 333
Email: [e-mail]
Website: www.boc.co.nz

Contents
3
1. Safety Precautions
1.0 Health Hazard Information 4
1.1 Personal Protection 4
1.2 Electric Shock 5
1.3 Use of Gas Cylinders 5
1.4 User Responsibility 5
2. Manual Metal ArcWelding Process (MMAW)
2.0 MMA Welding Principle 6
2.1 Fundamental Equipment Requirements 6
2.2 Control of the Process 7
2.3 Features of the Process 7
2.4 Application of MMA Welding 7
2.5 MMA Electrode Characteristics 7
2.6 Electrode types 8
2.7 Care of Electrodes 8
3. Gas Tungsten Arc Welding (GTAW)
3.0 Gas Tungsten Arc Welding (TIG) Principle 9
3.1 Equipment Requirements 9
3.2 Modes of Operation 9
3.3 Electrode Types and Preparation 10
3.4 Consumables 11
3.5 Control of the Process 11
3.6 Features of the Process 12
3.7 Application of GTAW 12
3.8 Technique 12
4. Shielding Gases
4.0 Overview 13
4.1 General Instructions for Pressure Regulators 13
5. Plant Specifications
5.0 Machine Specifications and Contents 14
6. Operating Controls
6.0 Diagram A 15
6.1 BOC Inverweld 110 VRD and 140 VRD
Operation 16
7. Periodic Maintenance
7.0 Power Source 17
8. Electrical Diagrams
8.0 Inverweld 140 18
8.1 Inverweld 110 VRD / 140 VRD 19
9. Machine Spare Parts
9.0 Diagram D – Machine Spare Parts 20
9.1 Machine Spare Parts List 21
10. Terms of Warranty
10.0 Terms of Warranty 22
10.1 Limitations on Warranty 22
10.2 Warranty Repairs 22
11. Glossary 23

1.0 Health Hazard Information
The actual process of MMA and TIG welding
is one that can cause a variety of hazards.
All appropriate safety equipment should be
worn at all times, i.e. headwear, hand and body
protection. Electrical equipment should be
used in accordance with the manufacturer’s
recommendations as "electric shock can kill".
Eyes:
The process produces ultra violet rays that can
injure and cause permanent damage. Fumes can
cause irritation.
Skin:
Arc rays are dangerous to uncovered skin.
Inhalation:
Welding fumes and gases are dangerous to the
health of the operator and to those in close
proximity.The aggravation of pre–existing
respiratory or allergic conditions may occur in
some workers. Excessive exposure may cause
conditions such as nausea, dizziness, dryness
and irritation of eyes, nose and throat. Shielding
Gases (Carbon Dioxide or inert gases) in high
concentrations when working in confined
spaces may lead to dangerous low levels of
oxygen, resulting in asphyxiation.
Ventilation and fume extraction should be
used to maintain exposure levels and are in
accordance with Australian Standards.The
operator should be trained to work in a
manner that minimises the exposure.
1.1 Personal Protection
Respiratory
Confined space welding should be carried out
with the aid of a fume respirator or air supplied
respirator as per AS/NZS 1715 and AS/NZS
1716 Standards.
• You must always have enough ventilation in
confined spaces. Be alert to this at all times.
• Keep your head out of the fumes rising from
the arc.
• Fumes from the welding of some metals are
bad for you. Don't breathe them in. If you are
welding on material such as stainless steel,
nickel, nickel alloys or galvanised steel, further
precautions are necessary.
• Wear a respirator when natural or forced
ventilation is not good enough.
Eye protection
A welding helmet with the appropriate welding
filter for the operation must be worn at all
times in the work environment.The welding arc
and the reflecting arc flash gives out ultraviolet
and infrared rays. Protective welding screen and
goggles should be provided for others working
in the same area.
Recommended filter shades for arc
welding
Less than 150 amps Shade 10*
150 to 250 amps Shade 11*
250 to 300 amps Shade 12
300 to 350 amps Shade 13
Over 350 amps Shade 14
*Use one shade darker for aluminium
4
1. Safety Precautions

Clothing
Suitable clothing must be worn to prevent
excessive exposure to UV radiation and
sparks.An adjustable helmet, flameproof loose
fitting cotton clothing buttoned to the neck,
protective leather gloves, spats, apron and steel
capped safety boots are highly recommended.
1.2 Electrical Shock
• Never touch "live" electrical parts.
• Always repair or replace worn or damaged
parts.
• Disconnect power source before performing
any maintenance or service.
• Earth all work materials.
• Never work in moist or damp areas.
Avoid electric shock by:
• Wearing dry insulated boots.
• Wearing dry leather gloves.
• Never changing electrodes with bare hands or
wet gloves.
• Never cooling electrode holders in water.
• Working on a dry insulated floor where
possible.
• Never hold the electrode and holder under
your arm.
1.3 Use of Gas Cylinders
• Always use the recommended shielding gas
for the application.
• Always store cylinders in upright position and
securely chained to a trolley or support.
• Keep electrically "hot" parts away from
cylinders at all times.
• Cylinders must be at a safe distance away
from sparks or from any other heat source.
• Keep head and face away from the cylinder
valve when opening.
• Read and follow instructions on compressed
gas cylinders and associated equipment
AS2030 Parts1 & 2.
1.4 User Responsibility
• Read the Operating Manual prior to
installation of this machine.
• Unauthorised repairs to this equipment may
endanger the technician and operator and will
void your warranty. Only qualified personnel
approved by BOC should perform repairs.
• Always disconnect mains power before
investigating equipment malfunctions.
• Parts that are broken, damaged, missing or
worn should be replaced immediately.
• Equipment should be cleaned periodically.
When necessary, vacuum inside of wire feeder
and gearbox section.
PLEASE NOTE that under no circumstances
should any equipment or parts be altered
or changed in any way from the Standard
specification without written permission given
by BOC.To do so, will void the Equipment
Warranty.
Further information can be obtained
from Welding Institute of Australia
(WTIA) Technical Note No.7
"Health and Safety Welding" TN7-98.
Published by WTIA,
PO Box 6165 Silverwater NSW 2128
Phone [phone].
5
STOP

2.0 MMAWelding Principle
Manual Metal Arc (MMA*) welding is a fusion
welding process which uses the heat of an arc
formed between the consumable electrode and
the workpiece to melt the joint area.The arc
and the weld pool are shielded by gases and
slags that result from the decomposition of the
coating material that surrounds the electrode.
The electrode material is transferred across the
arc to fill the joint and must be continuously
fed forward by the operator to maintain a
constant arc length.The principle of the process
is illustrated below.
MMA welding applications
Manual metal arc welding is used for:
• structural steel work
• steel bridges
• pressure vessels
• tanks
• general fabrication
• earth moving equipment
2.1 Fundamental Equipment
Requirements
The basic arrangement of the MMA welding
system is shown in figure 2 and consists of:
• a welding power source
• electrode holder
• welding cables
Basic arrangement of DC MMAW
equipment
Note:
The electrode may be connected to either the
positive (+) or the negative (–) connection on
the BOC Inverweld front panel.
Connecting the electrode to the positive
(DCEP) and the work clamp to the negative
will result in deeper weld metal penetration.
Connecting the electrode to the negative
(DCEN) and the work clamp to the positive
will result in a flatter and wider weld bead
profile with less penetration than the electrode
positive connection.
6
2. Manual Metal Arc Welding (MMAW)
*Commonly referred to as Stick Welding.
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2.2 Control of the Process
The main control parameters for the MMA
process are:
• current and
• operator technique
The current range is determined by the
electrode type and size. Deposition rate
increases with current for a given electrode
diameter but the maximum current is limited by
the coating material and the ability to control
both the weld pool and the molten slag.
Increasing the current also increases the level of
fume and the arc radiation.A high level of manual
dexterity is required to coordinate the movement
of the electrode to match the burn-off rate and
maintain a constant arc length. Some electrodes
are designed for 'touch' or contact welding (the
electrode coating rests on the workpiece during
welding) and this simplifies the production of
fillet welds.Additional skills are required to
control fusion characteristics and bead profile
(electrode angle, travel speed and weave patterns
must be carefully chosen), particularly for
positional welding.
2.3 Features of the Process
The most important characteristic of the
MMAW process is its overall flexibility.The wide
range of electrode types allows the weld metal
to be matched to the application, which may be
particularly useful in repair and jobbing shop
environments. Relatively simple equipment is
required and the capital cost is low.
The quality of the welded joint depends almost
entirely on the welder, and availability of
suitably qualified welders may cause production
bottlenecks. In addition the process is
intermittent, as the electrode must be changed
at regular intervals, placing a natural limit on the
productivity of the process.
2.4Applications of MMAWelding
The process is applied widely in the fabrication
and repair of plain carbon and low alloy steels.
It has been used in the construction of power
stations, pipelines and offshore structures.
Stainless steel, inconel, nickel and a wide
range of surfacing electrodes are available, and
these may be used in low volume production,
maintenance and repair situations.
2.5 MMA Electrode
Characteristics
The characteristics of the MMAW process are
largely determined by the electrode coating
material that controls the following important
features:
Arc
Certain chemicals may be added to the coating
material to stabilise the arc (e.g. rutile or potassium
silicate), improve metal transfer and reduce spatter.
These additions also provide a useful reduction
in the operating voltage required for the electrode.
Shielding
Shielding is provided by gases generated by the
decomposition of constituents such as calcium
carbonate or cellulose and by liquid slags which
protect the weld pool surface.
Weld pool control
The slag fluidity is usually the factor that
determines the ease of positional welding. Rapidly
freezing slags may be used to provide support
for the weld pool in vertical and overhead welding.
Alloying
The coating material can provide a useful source
of alloying elements or additions that control the
weld metal chemistry (such as deoxidisers).This
enables a wide range of weld metal properties to
be achieved by modifying the coating whilst using
a standard core wire.
7

2.6 Electrode Types
A range of well established electrode types are
available for the welding of ferrous materials,
and these are usually classified in the following
groups:
• cellulosic
• rutile
• basic, iron powder,
• others
Cellulosic electrodes contain over 30%
organic material (e.g. cellulose) in the coating.
This decomposes in the arc to generate
hydrogen and carbon dioxide. High arc forces
are formed in the arc and these depress the
weld pool and produce deep penetration
characteristics.The arc force may also be used
to generate a 'keyhole' effect that may be used
to complete single sided root runs, particularly
in pipe. It is usually these types of electrodes
that are use in the "Stovepipe" method of
welding.
Rutile electrodes contain the principal alloying
element titanium dioxide (TiO2i.e. rutile).
This addition gives excellent arc stability, low
voltages, low spatter and easily controlled self-
detaching slag.These characteristics make the
rutile electrode the most common general-
purpose electrode type.
Basic (Low Hydrogen) electrodes usually
contain calcium carbonate (CaCO3) and
calcium fluoride (CaF2).The hydrogen content
of the coating is controlled by the absence of
minerals containing combined water and careful
baking procedures. In general, the arc running
characteristics of these electrodes are inferior
to those of the rutile types described above, but
the mechanical properties of the weld metal are
superior.These electrodes are used on ferritic
steels when resistance to hot and cold cracking
is required.
Iron powder may be added to any of the above
coating types to increase the 'recovery' or the
amount of filler material produced when the
electrode is used.The addition of iron powder
also increases the deposition rate and usually
reduces the arc voltage requirement.
Iron oxide/silicate electrode formulations
may be used for general purpose mild steel
welding in the flat and HV positions but these
types have largely been superseded by rutile
coatings.
In addition to electrodes for plain carbon, low
alloy and high alloy steels a range of surfacing
and non-ferrous alloy electrodes are available.
2.7 Care of Electrodes
The performance of MMA electrodes and
the quality of the resultant weld depend on
the type of electrode and its condition. If the
mineral coating is damaged or chipped, poor
arc stability and inadequate shielding may
result. Most coating materials absorb moisture
if not properly protected and this may result
in deterioration of the coating and hydrogen
pick up in the weld bead. Particular care must
be taken with controlled hydrogen electrodes
that should be stored and if necessary re-dried
according to the manufacturers instructions.
Poor electrode condition will often be indicated
by increased spatter, striking difficulties, weld
bead porosity, and 'harsh' arcing characteristics.
8

3.0 Gas Tungsten Arc Welding
(TIG) Principle
Gas Tungsten Arc Welding (GTAW) utilises
the heat of an arc that is formed between a
non-consumable tungsten electrode and the
workpiece to fuse the joint material.The arc
area is shrouded in inert gas that protects the
weld pool and the electrode from contamination
while allowing a stable arc to be maintained.
TIG welding applications
• light fabrication
• general engineering
• welds most metals, particularly stainless steel
and other non-ferrous metals
3.1 Equipment Requirements
The basic requirements for the GTAW
process are:
• a welding power source
• TIG torch
• a gas supply system
TIG power sources may have an alternating or
direct current output, and depending on the
application and provision for controlling the gas
flow, initiating the arc is usually required.The
BOC Inverweld has a direct current output.
The torch design will depend on the application
but it is required to provide a uniform shield or
inert gas and is often water cooled to reduce
size and protect the operator.
Equipment set-up
• Install the welding machine as near as possible
to the mains power to keep the primary
power cable short.The primary power cable
carries dangerously high voltages.
• Inspect all cables for damage
• Use welding cables that are fully insulated
• Make sure the electrode holder is insulated
from the bench. Hang it on an insulated hook
• Switch off when not in use
3.2 Modes of Operation
The process may be operated in one of the
following modes
• DC electrode negative
• DC electrode positive
DC electrode negative
In this mode the electrode remains relatively
cool whilst the workpiece is effectively heated.
(The normal estimate of heat distribution in the
GTAW process is 1/3 at the negative (cathode)
and 2/3rds at the positive (anode).This is the
most common mode of operation for ferrous
materials, copper, nickel and titanium alloys.
DC electrode positive
With DC electrode positive there is a tendency
for the electrode to overheat and fusion, of the
workpiece is poor.The advantage of this mode
of operation is the cathodic cleaning effect that
removes the tenacious oxide film from the
surface of aluminium alloys.
9
3. Gas Tungsten Arc Welding (GTAW)

CURRENT TYPE DCEN DCEP
Electrode polarity Negative Positive
Electron & ion flow
Penetration characteristics
Oxide cleaning action No Yes
Heat balance in the 70% at work end 30% at work end
arc (approx.) 30% at electrode end 70% at electrode end
Penetration Deep, narrow Shallow, wide
Electrode capacity Excellent e.g. 3.2mm, 400A Poor e.g. 6.4mm, 120A
3.3 Electrode Types and
Preparation
Originally, pure tungsten was used as the
electrode material.Tungsten is a refractory
metal, with a high melting point (3380°C)
and has relatively good electrical and thermal
conductivity. It was discovered, however,
that arc stability, tip shape retention and arc
initiation could be improved by adding small
amounts of thorium oxide, thoria, or zirconium
oxide, zirconia, to the electrode.
More recently, it has been found that improved
performance can be obtained by alloying the
electrodes with oxides of lanthanum, yttrium
or cerium, particularly in automatic or orbital
TIG welding where consistency of operation is
important.
Traditionally,‘thoriated’ electrodes have tended
to be used for DC operation and ‘zirconiated’
electrodes for AC. However, scares regarding
the potential health effects due to inhalation of
radioactive thorium oxide dust have resulted
in some users changing to ‘ceriated’ or
‘lanthaniated’ electrodes in place of ‘thoriated’.
Whilst not ‘consumed’ to form weld metal,
tungsten electrodes are used up over a period
of time due to repeated grinding of tips and due
to some erosion by the arc during welding.They
may also be accidentally consumed by being
dipped into the weld pool and melting into it.
The electrode diameter is determined by the
current and polarity. Recommended diameters
are given in the table below.
Recommended diameter for electrodes
ELECTRODE CURRENT
DIAMETER (mm) DC – DC +
0.5 0 – 20
1.0 21 – 80
1.6 81 – 150 0 – 17
2.4 151 – 230 18 – 25
3.2 231 – 350 26 – 35
4.0 351 – 475 36 – 50
4.8 476 – 650 51 – 67
6.3 651 – 950 68 – 100
8.0
10
Figure 3. Effects of current type.

Electrode Sharpening
Tungsten alloy electrodes offer improved
• arc striking
• arc stability
• current capacity
Tungsten alloy electrodes for DCEN
• Thoriated,AWS colour code RED(2%)
• Lanthanium,AWS colour code BLACK(1%)
• Cerium oxide,AWS colour code ORANGE(2%)
3.4 Consumables
The consumables used in the GTAW process
include the shielding gas and the filler material.
The shielding gas must be essentially inert
(i.e. argon or helium) although very small
amounts of active gases may be used in certain
applications.
This is because active (oxidising) gases like CO2
and Oxygen react to tungsten.
The process may be used without filler material
addition, but if a filler is required this is added
in the form of a rod that is introduced into the
leading edge of the weld pool, either manually
or by a wire feed mechanism
A filler is added in the form of a rod introduced
into the leading edge of the weld pool, either
manually or by a wire feed mechanism.
3.5 Control of the Process
The main control parameters for the GTAW
process are:
• current
• travel speed
• filler wire addition
The current is increased to enable higher
travel speeds to be obtained (for a given plate
thickness or weld size) although at high current
levels the arc may become very fierce and
undercut may occur. In single electrode GTAW
applications the occurrence of undercut limits
the maximum speed and current. Filler wire may
be used to cool the weld pool and this may be
beneficial for complex positional joints and for
surfacing applications.
11
Shape of tungsten electrode tip – DCEN
Safety glasses and
respirator are worn
Silicon carbide
grinding wheel
Electrode held firmly in hands, resting on tool rest.
Hands well clear of grinding wheel.

3.6 Features of the Process
The most important characteristics of the
GTAW process are that:
• it is chemically inert,
• the energy density of the arc is high,
• the process is very controllable,
• joint quality is usually high, and
• joint completion rates are usually low.
In spite of the low speed of the process its
ability to produce high quality joints in a wide
range of materials has made it an attractive
proposition for more demanding applications.
The process is not normally considered
economics for thicker sections or for low
integrity joints in plain carbon steels.
3.7 Application of GTAW
Common applications of the process include
high quality fabrications in stainless steel,
aluminium alloys, copper and nickel alloys and
reactive metals such as titanium and zirconium.
GTAW is used extensively in the nuclear and
aerospace industries as well as in the fabrication
of chemical process plant, pipework, brewery
and food processing vessels.
Notes
1) The process is also known by several other
names, i.e.:Argonarc and Heliarc, the original
trade names for the process. GTAW is the
Australian and New Zealand terminology
that is also used in many other countries,
although the acronym TIG (Tungsten Inert
Gas) welding is also used.
2) The terms 'straight' and 'reverse' polarity
are sometimes used to describe the mode
of operation of the process.These terms are
best avoided and the actual polarity of the
tungsten electrode should be stated.
3.8 Technique
The filler wire and torch needs to be at differing
angles depending on the position of the-weld.
See diagrams below.
12
A= Torch travel angle – forehand technique
– push angle 10°-20° (to the vertical)
B= Work angle: 90°
C= Filler metal feed angle: 10°-20°
D= Arc length: 1-1.5 x electrode diameter
Flat position (1G) Vertical position (3G)
Upwards progression
Horizontal position (2G)
Torch and filler metal manual control guidelines

13
4.0 Overview
Shielding gases forTIG welding are important for
keeping the arc stable and protecting the molten
weld metal from contamination during welding.
The major function of a shielding gas is to
surround the weld zone with a protective shroud
of non-reactive shielding medium.This removes
harmful elements from the atmosphere (oxygen,
nitrogen gas) which would give a poor quality
weld deposit if they contacted the molten metal.
The TIG process cannot use a shielding gas that
has an oxidising agent in it i.e. CO2or O2.This
is due to the reaction with tungsten and will
cause immediate particle disintegration of the
tungsten.
The gases that can be used are Argon by itself
or additions of helium.The use of helium has
the effect of increasing the heat in the arc, or
molten pool and therefore more penetration
and a molten pool that remains fluid for longer
periods of time and allows contaminants to
'boil' off before freezing.The recommended
flow rate is from 5 l/min to 10 l/min depending
on the amperage being used.
One of the major causes of contaminated
welds/tungstens is the operator removing or
turning off the gas flow before cooling past the
critical level has taken place. For example when
finishing a weld the torch should be held at
the end until the pool has cooled past the 'red'
stage.This is also the case for the tungsten, as it
will turn to a blue colour (oxide) if shielding is
removed prior to cooling.
4.1 General Instructions for
Pressure Regulators
Before mounting the regulator
1. Step aside and open the cylinder valve.This
is called "cracking the cylinder" and by doing
this you will release any dirt that may be
trapped in the valve of the bottle.
Regulator connection
1. Fit the regulator "bull-nose" into the cylinder
valve and tighten the nut (do not over
tighten)
2.Turn the regulator bonnet in an anti clockwise
rotation, so that there is no pressure on the
regulator diaphragm.This is the fully off/no
flow position.
3.Attach hose nut/nipple to the regulator outlet.
4. Connect the gas hose to the nipple with the
supplied hose clamp.
5. Connect the other end of the hose into the
machine wire feeder quick connection nipple.
Setting the regulator
1. Open the valve of bottle slowly
2.The high pressure gauge will show the
pressure in the bottle.
3. Open the regulator bonnet until the desired
pressure is achieved on the low pressure
gauge (12 to 20 L/min usually).
4. Pull the torch trigger to simulate a welding
condition, and readjust the regulator bonnet
to the desired pressure that will be required
while welding (it is normal for the gas
delivery gauge to drop back while in use due
to pressure drop when in the static position).
Close the valve of the cylinder after welding
has stopped. If the machine will be out of
use for a long period of time, you should
unscrew the regulator bonnet screw to act as a
secondary valve.
4. Shielding Gases

14
5. Plant Specifications
This package includes:
• BOC Inverweld
• Electrode holder
• Welding cable
• Work cable
• Work clamp
• Primary power cable
DESCRIPTION INVERWELD 110 VRD INVERWELD 140 INVERWELD 140 VRD
Part No. B610211101 B6102141 B610214101
Welding Application General MMA and TIG* fabrication, repair and maintenance.
Standards IEC 60974-1 / EN 50199
Input Voltage 1 Phase 50/60Hz 240 V
Duty Cycle 35% - 140A 140A
50% 110A - -
100% 80A 100A 100A
Primary plug 10 A 15 A 15 A
Welding current range (MMA) 10A / 20.5V to
110A / 24.4V
10A /20.5V to
140A / 25.6V
10A /20.5V to
140A / 25.6V
Electrode diameter (mm) 1.5 to 2.5 1.5 to 3.5 1.5 to 3.5
Voltage step capacity Stepless
Open-circuit (no-load) voltage < 31V 90 V < 31V
Power factor 0.60 (110A / 24.4V) 0.60 (140A / 25.5V) 0.60 (140A / 25.5V)
Protection IP23
Temperature class B (130ºC) / H (180ºC)
Range of working temperature - 20 to + 40 ºC
Range of storage temperature - 40 to + 60 ºC
VRD built-in factory fitted Yes No Yes
VRD peak to no-load time 100ms N/A 100ms
VRD on load voltage < 31V N/A < 31V
VRD welding circuit activation
resistance
20ohms N/A 20ohms
Power generator minimum capacity 6 kVA
External dimensions LxHxW (mm) 305 x 250 x 123 mm
Weight (kg) 4.2 kg
* Additional equipment not supplied with the Inverweld required for TIG welding.

15
6. Operating Controls
ITEM DESCRIPTION
1 Negative (–) dines connection
2 Positive (+) dines connection
3 Overload protection indicator
4 Welding current regulator
5 Main power switch and signal light
6 Carry strap
7 Selector switch for welding process
8 Machine body
9 Workclamp and cable
10 Electrode holder and cable
11 VRD fitted as standard on 110VRD and 140 VRD
6.0 Diagram A
h
e
d
g
c
b
a
j
f
ik

6.1 BOC Inverweld 110 VRD and 140 VRD Operation
16
General
The new BOC Inverweld 110VRD and 140
VRD welding machines are fitted with an
internal VRD (Voltage reducing device) circuit
fulfilling AS 1674.2 safety requirements forVRD
operation.
The no-load voltage is required to be reduced
to 35V DC (peak) or less within 300ms time
after the weld when the load resistance
exceeds 20ohms.The BOC Inverweld with
VRD fitted does this and more.The Inverweld
VRD automatically reduces the no-load voltage
to below 31volts in 100ms when the external
welding circuit resistance is 20ohms.
The green LED-light on the front panel indicates
that the VRD is active and the unit is in the safe
mode. If the light is on the no-load voltage is
safe. During welding the green light may flicker,
which is normal.
Actual operation
The Inverweld VRD is designed as an integral
part of the unit and therefore the performance
of the Inverweld is not compromised by the
VRD functionality.
The VRD function is fully automatic and should
the green light not be on or flash in the on-load
state (i.e. when the power is on you are not
welding) please contact your nearest BOC or
BOC service technician.

The working environment or amount of use
the machine receives should be taken into
consideration when planning maintenance
frequency of your BOC welder.
Preventative maintenance will ensure trouble-
free welding and increase the life of the machine
and its consumables.
7.0 Power Source
• Check electrical connections of unit at least
twice a year.
• Clean oxidised connections and tighten.
• Inner parts of machine should cleaned with a
vacuum cleaner and soft brush.
• Do not use any pressure-washing devices.
• Do not use compressed air as pressure may
pack dirt even more tightly into components.
• Only authorised electricians should carry
out repairs.
17
7. Periodic Maintenance

18
8. Electrical Diagram
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Only authorised electricians should carry out repairs
8.0 Diagram B – Inverweld 140

19
Only authorised electricians should carry out repairs
8.1 Diagram C – Inverweld 110 VRD / 140 VRD

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9.0 Diagram D – Machine Spare Parts
20
9. Machine Spare Parts
Only authorised electricians should carry out repairs