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Issue Seven of Weld Purging World - November 2019

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Published by Huntingdon Fusion Techniques HFT®, 2019-11-11 05:34:54

Weld Purging World - November 2019

Issue Seven of Weld Purging World - November 2019

ISSUE 7 November 2019

In November’s Issue:

• Don’t miss us at FABTECH
• Ask the Expert: CEO Georgia Gascoyne
• Focus on Distributor: West Country Welding
• Product News: Qwik-Freezer, PurgEye® Desk and Steel Plugs
• Technical Article: Corrosion


Huntingdon Fusion Techniques HFT® are proud members of:



Fabtech 2019 3

HFT® News 4-6

Product News 7-8

Technical Paper: Corrosion 9 - 11


Dear Reader,

Welcome to November’s Weld Purging World.

There have been some amazing milestones achieved in the HFT® World recently, including us
reaching 10,000 followers on Instagram. WOW. I’d like to thank everyone who has interacted
with us on Instagram and to those amazing welders out there producing nothing short of perfect

Christmas is just around the corner and that can only mean
one thing, Fabtech and Adipec are here! Be sure to follow
our Instagram @huntingdon_fusion for up to the minute
videos and photos from both events!

This month, we ask CEO Georgia some questions on our
MultiStrike® Tungsten Electrodes, we also find out where
Technical Sales Manager Luke has been travelling to

If you have any news or would like to be featured in our
magazine, then please get in touch.

Thank you for reading!

Best wishes,

Marketing and Social Media Manager
[email protected]

FABTECH 2019 3


We will be exhibiting at Fabtech 2019 November 11 - 14 at McCormick Place, Chicago, IL, Booth No,
A4545. Georgia Gascoyne, CEO Managing Director for HFT® said: “We are once again delighted
to be joining our USA Partner COB Industries to take part in one of the biggest events within the
industry. We will be showcasing our entire product line at Fabtech 2019.”
“Our Weld Purging Technology is designed to achieve oxide free, zero colour welds. On display
at Fabtech will be our Tube and Pipe Weld Purging Systems, available in sizes 1” to 88”. These
ingenious devices are designed to localise a small volume of pipe section to purge, thus making
savings in time inert gas costs and eliminating post weld cleaning and oxide removal costs.”
HFT will also be showing a selection of their Weld Purge Monitors® that accurately measure the
amount of oxygen within the purge gas. Their PurgEye® 100 has become the monitor of choice
amongst the international welding fraternity, assisting welders to achieve zero colour welds.
The Family Range of Weld Purge Monitors® now includes seven 10 ppm monitors for a variety of
applications, including remote monitoring up to 1 km away from the weld and robust, heavy-duty
instruments for on-site conditions. HFT have also developed a line of accessories for use with our
Monitors such as light alarms and dew point sensing.
Standard and purpose designed Flexible Welding Enclosures® will be exhibited at the Show. These
low cost Enclosures are manufactured at a fraction of the cost of a rigid welding chamber, providing
a technically viable option to the very expensive metal chambers and purge boxes. They are also
widely in use throughout the Additive Manufacturing Industry where complete robot cells can be
placed inside or attached to the robotic arm itself.



CEO Georgia Gascoyne

In this month’s Weld Purging World, we continue to take your questions
to our experts! We ask CEO Georgia Gascoyne some questions about
our MultiStrike® Tungsten Electrodes.
Q. What is in MultiStrike® Tungstens Electrodes to make them so
MultiStrike® Tungstens contain a blend of rare earth dopants to replace
thoria. Our dopants are not radio-toxic and they are mixed in accurate
proportions using statistical proportional control procedures, fully
computerised to ensure that the tungstens are made to the same high
standards every time.

Q. Will you tell me what materials you use inside
MultiStrike® Tungstens Electrodes?
The exact ingredients of MultiStrike® Tungsten Electrodes
are part of our intellectual property gained by extensive
research and development to bring a quality product to the
market place that is totally traceable, reliable and repeatable.
Q. I’m worried about the dust generated when I grind
MultiStrike® Tungsten Electrodes.
Because MultiStrike®’s do not contain thoria or any other radiotoxic materials, the dust generated is
not carcinogenic. However, any local health and safety standards about the generation and collection
of dust should be observed.


An open day was recently held in
partnership with Balfour Beatty. HFT®
Technical Sales Manager Luke was
on there, showcasing our full product
range with Exclusive Distributor General
Luke said: “It was a fantastic event
centered around new technology,
showing innovation and quality to help
product assembly and improve onsite



West Country Welding Supplies LTD are a premier UK based
welding supplies Distributor. They have been supplying the
welding industry for over 30 years and have been the main HFT
Distributor in the South West of England for over 25 years.
By employing staff that understand the industry they have great
knowledge of all types of welding so can offer advice and training
on purging, alloy welding, stainless welding, titanium welding and

They were the industry pioneer along with HFT in designing and
building the early Robotic Adaptive Manufacturing Enclosures
and still hold the record for designing the largest inflatable
chamber with 22 glove ports.
Holding over 5000+ products in stock and having an on-site
workshop, West Country Welding supply, repair and hirer
quality branded products to all welding industries.

Craig Elliott, managing director commented, “Exciting times are ahead, Talking to most of the current
Hinkley Point PowerStation contractors we are expecting to showcase The HFT product range in
abundance over the next 5 years.”
West Country welding supplies have a huge technical expertise, mixed with the best brands on the
market, making West Country Welding Supplies the go to distributor for welding products.


Exhibiting! 26 - 28th November
11 - 14 November Stainless Steel World
Fabtech MECC Maastricht, The Netherlands
McCormick Place, Chicago, IL, USA
Distributor Exhibiting! 11 - 14 November
27 - 28 November Adipec
MetalMadrid Adnec, Abu Dhabi
Ifema, Madrid, Spain

Distributor Exhibiting!

30 March - 03 April 2020
Tube Düsseldorf
Düsseldorf, Germany


1. Weld Purge Monitor for On-Site Conditions


Technical Sales Manager Luke attended a Welsh Government Trade Mission to Singapore and
Malaysia recently, which allowed a great opportunity to catch up with our Asian Distributor Leeden
Nox and discuss the current projects we have within Asia as well as meeting new and existing
customers in different sectors across the region.

Luke and new to HFT®, Ffion also attended the International Business Culture Event, which is
centred around doing business in China.

Luke (centre) catching up Business Networking Reception at the Luke and Ffion at the
with Leeden Nox British High Commissioner’s Residence International Business

Culture Event



Avoiding the requirement to drain down
pipelines for repair work or to carry out
maintenance can save a considerable amount
of time and potential loss of product.

Qwik-Freezer™ Pipe Freezing System
eliminates the need to drain pipework by
creating a freeze plug. Available from the
Pipestoppers® Division of Huntingdon Fusion
Techniques HFT® Qwik-Freezer is a very cost
effective and quick way to perform pipeline
maintenance without draining the system,
meaning very little or no system downtime.

Luke Keane, Technical Sales Manager for HFT® said: “Qwik-Freezer™ is a simple, low cost method
for pipe repairs. A flexible jacket is wrapped around the pipe at the point where the freeze is required.
A nozzle in the jacket is then coupled to a cylinder of low cost liquid carbon dioxide by means of a
high-pressure hose. When the CO2 is injected into the space between the jacket and the pipe, at
a temperature of -78oC, the pipe contents freeze and a secure ‘ice plug’ is formed, which seals the

“The ‘ice plug’ forms only in a section of the pipe covered by
the jacket, so the resulting rise in pressure is very small and
there is no damage to the pipe. The technique can be used
safely on steel, iron, lead, stainless steel, copper, brass and
plastic pipe. After the work is carried out, the ice plug is
simply thawed and the line is restored to full operation.”

Qwik-Freezer™ is
in use Worldwide in
industry sectors such
as petrochemical,
building and maintenance services, food and beverage,
hospitals, water treatment, shipping and aerospace. It is also
extremely beneficial for pipework where valves need to be
changed. By not having to drain systems of liquids to make
repairs, the savings made are able to justify the low relative
cost of the Qwik-Freezer™ System.

Larger pipe diameters than 8” and the use of anti freeze and rust inhibitors can create the need for
tbheearliiqnugidfreneitzroegpelung(.LN2) temperatures of the Accu-Freeze™ System in order to create a pressure

A Qwik-Freezer™ video demonstration is available on our YouTube Channel.



The Welding Institute states that “Titanium is a reactive metal; it will burn in pure oxygen at 600°C
and in nitrogen at around 800°C. Oxygen and nitrogen will also diffuse into titanium at temperatures
above 400°C raising the tensile strength but embrittling the metal. Despite this reactivity titanium is
used extensively in chemical processing, offshore and aerospace applications.”
In critical welding applications, it is therefore crucial that the oxygen level surrounding the weld is
purged of oxygen to 50 ppm or lower. Measuring the oxygen level is the most efficient way to know

exactly when to commence welding.

The PurgEye® Desk is leading the way in inert gas purging
technology by reading oxygen levels from 1,000 ppm, right
down to levels as low as 1ppm (highly accurate to 10 ppm),
ensuring titanium welders achieve perfect oxide free, zero
colour welds time and time again.

Manufactured by Huntingdon Fusion Techniques HFT®, the
PurgEye® Desk is equipped with HFT®’s revolutionary PurgeNet™, for the in-line connection of
additional accessories that allows the Weld Purge Monitor® to control welding systems based upon
oxygen level as well as to provide indications of high and low oxygen levels.


Heavy-duty pipe blocking and stopping is easy with the Steel Plugs Range from Pipestoppers®.

Pipestoppers®, a division of Huntingdon Fusion
Techniques HFT®, manufacture Steel Plugs, which have
been the favoured heavy-duty plug for applications such
as leak testing, pipe stopping and blocking for their sealing
effectiveness and durability.

HFT Pipestoppers® Steel Plugs can be used for low
pressure testing and plugging all pipes, pipelines and pipe
work between 2 to 48” (50 to 1,200 mm) diameter.

Luke Keane, Technical Sales Manager for HFT® said: “Plugging challenges are a thing of the past
with our Steel Plugs range. They provide a strong, leak-free seal with each plug having a long life

“Where plugs might be required to work close to the top of their pressure range and to hold seals
longer than would be the case with single plugs, we also manufacture Double Steel Plugs, which
increases the capability of the plug.”



During heat treatment surface oxide layers, usually called heat tints, are formed on precipitation-
hardening nickel-based alloys like UNS N07718. These oxide layers are composed of elements that
have been selectively oxidised from the base metal, principally nickel, chromium and iron.
The same phenomenon has been intensively studied on austenitic stainless steels. It is well known
that the region beneath the oxide layer is depleted in one or more of the elements that are involved
in the scale formation.
Consequently, reduced corrosion resistance can be expected.
Causes, consequences and prevention of corrosion during welding of nickel based alloys. We have
all seen the effect of welds carried out without adequate gas coverage, the hot metal simply oxidises
in contact with air. It comes as a surprise to most that oxygen contents as low as 50 ppm (0.005%)
may produce discolouration or heat tint in stainless steels. Reduction in corrosion resistance can be
significant 1 - 5.
Whilst it is not too difficult to protect the outside surface of a weld by using an inert gas as coverage,
preventing oxidation and loss of corrosion resistance on the inside is often overlooked.
The technique of inside protection is known as ‘weld purging’ and uses inert gas to flush out air and
thus oxygen before and during welding.

Fig 1.The result of unprotected Fig. 2 Even relatively low oxygen Fig. 3 To ensure no heat tint occurs
underbead. Some operators still content in the purge gas can lead to the oxygen content needs to be
tolerate this and absorb the cost ‘heat tint’. This example is the result reduced to 20 ppm (0.002).

of removing it after welding. of using an oxygen content as low as
50 ppm.

The Mechanism of Corrosion

Stainless steels owe their resistance to corrosion to the formation of a very thin (10-5 mm), transparent
surface layer of chromum oxide. This provides a passive film that acts as a barrier to penetration
by an invasive environment. When heated to a high temperature in the presence of oxygen this
film increases in thickness until it becomes visible – the colour becomes darker with increasing film

At a critical film thickness the film becomes unstable and begins to break down. The fractured zones
created offer sites for localised corrosion.


The Mechanism of Corrosion
Stainless steels owe their resistance to corrosion to the formation of a very thin (10 to -5 mm),
transparent surface layer of chromum oxide. This provides a passive film that acts as a barrier to
penetration by an invasive environment. When heated to a high temperature in the presence of
oxygen this film increases in thickness until it becomes visible – the colour becomes darker with
increasing film thickness. At a critical film thickness the film becomes unstable and begins to break
down. The fractured zones created offer sites for localised corrosion.
Four principle mechanisms are involved:
Pitting corrosion.
Stress corrosion cracking.
Crevice corrosion.
Microbiologically Induced Corrosion (MIC).
Pitting corrosion.
Pitting corrosion is a form of localised corrosion. It produces attacks in the form of spots or pits. This
type of corrosion attacks most often take place at points where the passive layer might be weakened
and it occurs in stainless steels where oxidation has reduced the passivity. Once the attack has
started, the material can be completely penetrated within a short time.
Stress Corrosion Cracking
Stress corrosion cracking is characterised by cracks propagating either transgranularly (through) or
intergranularly (along) grain boundaries. It results from the combined action of tensile stresses in
the material and the presence of a corrosive medium. It can be induced in some stainless steels by
adverse heat treatments such as those occurring in weld heat affected zones.
Crevice Corrosion
Localised corrosion of a metal surface that is attributable to close proximity of another metal such
as a weld. It is a locally accelerated type of corrosion and is one of the major corrosion hazards in
stainless steels.
Microbiologically induced corrosion
Corrosion promoted or caused by micro-organisms, typically in industries related to food, beverage
and chemical processing. It is usually referred to by the acronym ’MIC’ and is common in welded
To avoid these forms of corrosion it is essential that heat tints are properly removed before the
stainless steel equipment or piping is exposed to aggressive or aqueous environments.
The alternative to removal, often costly or difficult, is to prevent heat tinting during the welding
process by using an inert environment to protect the surface.
Removal of Heat Tint
Light discolouration can be removed by bright annealing or acid pickling but heavier deposits may
require machining such as grinding and polishing. Removal clearly requires access to the area in
question, not only for treatment but also for debris removal. Even when access is available none of
these treatments is easy and most can be very expensive.


Weld Purging
The alternative to potentially time-consuming, difficult and expensive cleaning of heat tint is to avoid
it during the welding process. This can be undertaken by protecting the joint from oxidation by using
an inert gas such as argon. The upper side of the joint is protected by the inert gas used in the torch.
The underside, known as the underbead, needs separate treatment. This technique is referred to as
weld purging. (Fig. 4).
Seals are inserted on either side of the weld root and inert gas is admitted to displace air in the
space between them. A wide range of options for sealing are available but the only totally reliable
and sufficiently versatile systems are those based on inflatable seals.

Fig. 4 The
inert gas
weld purging

Equipment has been developed over the past decade to make purging much easier. Currently
available systems are robust and suitable for multi-use applications. They can be supplied to cover
the size range between 25 and 2,235 mm diameter.
The most effective devices are those based on connected inflatable dams. These can be programmed
to control gas flow and pressure during inflation and purging and once placed in position require
little more input from an operator. The dams are fabricated using advanced engineering polymers
and are thus suitable for use where elimination of contamination is essential. Purge gas oxygen
content can be controlled by using an oygen monitor. These instruments not only measure oxygen
levels, but can be programmed to stop the welding process if the level rises above that set by the
procedure. Recording and analysing software provides information for quality control purposes.
Considerable design effort has been applied by the designers and manufacturers of these solutions
over the past decade or so and currently available systems address the problems of controlled inert
gas pressure and flow, the need for easy and rapid deployment and removal to limit overall welding
time, thermal resistance and leak-tight access for oxygen monitoring equipment. They also provide
a large pipe contact area and therefore excellent and reliable sealing.
Coupled with these advantages comes flexibility to allow access and removal through pipe bends,
abrasion resistance and the use of materials that meet food, semiconductor and nuclear compliance
Clearly a knowledge of the oxygen level in the purge gas is essential, recognising that a level as low
as 20ppm may be necessary. This can be accommodated with a weld purge oxygen monitor and
advanced versions of these have been developed for the welding industry.

Microbiologically influenced corrosion of stainless steel - 2nd symposium on orbital welding in high purity industries, La Baule, France
Effects of purge gas purity and Chelant passivation on the corrosion resistance of orbitally welded 316L stainless steel tubing. Pharmaceutical
Engineering. Vol 17 Nos 1 & 2 1997
Considerations for Orbital Welding of Corrosion Resistant Materials to the ASME Bioprocessing Equipment Standard. Stainless Steel America
conference 2008
Heat Tint Poses Corrosion Hazard in Stainless Steel. Welding Journal December 2014
ASM International. Corrosion in Weldments. 2006

Weld Purge

For small or odd diameter pipes where purge
systems may not be available or practical.



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