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Issue Seven of Weld Purging World - July 2020

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Published by Huntingdon Fusion Techniques HFT®, 2020-07-13 03:50:00

Weld Purging World - July 2020

Issue Seven of Weld Purging World - July 2020

ISSUE 07: JULY 2020









Weld Purging Equipment 3
HFT® News 4-6
Product News 7-8

Technical Paper: Welding Zirconium 9 - 11
and its alloys


Dear Reader,

Welcome to the July Issue of Weld Purging World.

It seems like life is starting to take steps towards returning back to normal, although still a little
way to go. The Industry Shows that were cancelled due to the pandemic are setting new dates
and we’re delighted to confirm our Booth Number at Fabtech this year, which is N413. As usual,
we will be there supporting our USA Distributor Cob Industries. More on that in future issues.

In this month’s Weld Purging World we feature our Heat Tint
Chart for Titanium Welding, we take a look at our available
Weld Purging Equipment and in our Technical Article, we
discuss Welding Zirconium and its Alloys!

If you have any information that you would like to be
featured in this publication, please contact me. Perhaps a
photograph of a special weld that you have made, a product
that you find of interest or a question of some kind?

From everyone here at HFT®, thank you for reading and
stay safe!

Best wishes,
Michaela - Marketing and Social Media Manager
[email protected]



We have a range of Weld Purging Equipment are the perfect solution to achieving clean, bright,
oxide free stainless steel, titanium and zirconium welds.
Weld Purge Film®
Ideal for a variety of pipe sizes, Weld Purge Film® Kits
can be used on pipe diameters up to 900 mm (36”) and for
temperatures up to 300ºC (572ºF) without the material burning
or coming loose and losing the weld purge.
Weld Backing Tape®
Weld Backing Tape® is a common material used where manual

welding cannot control the weld root profile sufficiently, or when an
automatic weld process is unable to reach optimum speeds while still
obtaining satisfactory underbeads.
HFT Glass Fibre Backing Tape supports and protects the weld root
from oxidation. It will trap the inert gas from the weld torch to hold
the gas surrounding the weld pool, effectively providing a back purge
facility, available in four grades for use up to 600 Amps.
Weld Trailing Shields®
Providing an additional inert gas coverage during and after welding,
Trailing Shields® help to produce bright, shiny, oxide free welds time and
time again and eliminating the expensive post weld cleaning process.
Along with the new sleek design, our Trailing Shields® have a new unique
clip design, which means the welder can interchange different Trailing
Shield® sizes without having to change the welding torch.
With our name and logo stamped onto every new Trailing Shield®, you
can be sure the Shield you are using is a HFT design, we guarantee quality and 100% craftsmanship.
HFT® owns the Weld Trailing Shield® copyright and full Intellectual Property rights for more than
40 years.
Flexible Welding Enclosures®
Standard and specially made Welding Enclosures are available for a fraction
of the cost of a rigid welding chamber, providing a technically viable option to
the very expensive metal chambers and purge boxes.
The state of the art welding chamber, also known as an argon chamber, offers
many advantages over a rigid chamber, with rapid purge times down to as low
as 10 ppm.
This high quality piece of weld purging equipment has been highly rated by
customers worldwide in use within industries including aerospace, racecar,
titanium bicycle manufactures and wire arc additive manufacturers.



Heat Tint Recognition Chart For Titanium Welding

Oxidation colours have many different variations.
We have assembled a few here as guidelines.

1 2 3 67

Legend: Excellent gas coverage. Clean, silver looking welds 10 ppm O2 level.
1, 1a, 1b Weld slightly straw coloured shows higher oxygen level due to poor
2, 2a trailing shield gas coverage causing slight oxidation.
Weld and heat affected zone are now deeper straw and blue, showing
3, 3a, 3b higher oxygen level caused by faster speed losing trailing shield gas.
Weld blue and dark straw showing heavier oxide layer caused by
4, 4a, 5, 5a excessively high oxygen level.
6, 6a, 7, 7a, 7b Welds silvery to white with intolerable oxidation level.

1a 2a 3a 4 5

1b 2b 3b 4a 5a 6a 7a 7b
Oxidation colours need to be eliminated prior to additional welding.

Use a Weld Purge Monitor® to eliminate oxygen to prevent oxides from forming and
save this additional work load.

Use Argweld® PurgEye® Weld Purge Monitors® to detect oxygen levels down to
10 ppm to eliminate oxidation, weld reject and potential weld failure.

The hotter a Titanium weld becomes, the easier it is to oxidise, so the best solution is to
keep the purge level as close to 10 ppm oxygen as possible.

Huntingdon Fusion Techniques HFT® with over 40 years of high integrity, totally ethical business practices.
The only innovators and developers of Weld Purging Products.
The owners of the Weld Purge Monitor® Registered Trade Mark.



We recently manufactured a 110” (279 cm) Low Profile
Stopper within three weeks from receipt of order, with our
raw materials sourced from within the UK.

Pipe stopping where access is tight can pose challenges
for when duties such as repair work, leak testing and
weld purging are required.

Ron Sewell, Chairman at HFT® said: “The Low Profile
Stopper can fit into a pipe end that may be directly on an
elbow or just inside a flanged neck on a casting. Other
applications include blocking pipe ends to keep gases
inside or to keep debris and vermin out.”

“When used in a vertical mode, these Low Profile Stoppers have already been used to prevent
machine swarf or tools from falling into pipes, into an unrecoverable and dangerous situation, in
a nuclear power steam turbine.”

Manufactured from tough, robust fabric, these Low Profile Inflatable Stoppers are available in
sizes 6” (150 mm) diameter and provide excellent grip inside the pipe, with an effective airtight

The Pipestoppers® Inflatable Stoppers Range consists of:

- Cylindrical and Spherical Stoppers: an easy way to stop the flow of gas or liquid inside pipes
and ducts. Available up to 96” ø (2,440 mm). For higher temperatures, these Inflatable Stoppers
can also be manufactured with a Heat Resistant Cover for temperatures up to 300ºC (572ºF).

- PetroChem® Stoppers: manufactured from high-grade latex, they are used for stopping off
pipes with hydrocarbon gases and liquids inside.

- Inflatable Rubber Plugs: a wide diameter range and are tough, durable, can withstand chemicals
and hydrocarbons, for higher-pressure applications, with a long life.



TechniShow Adipec

1 - 4 September 2020 9 - 12 November 2020 18 - 20 November 2020

Utrecht, Netherlands Abu Dhabi, UAE Las Vegas, USA

OSEA 2020 TWI’s Welding & Joining Tube
7 - 11 December 2020
24 - 26 November 2020 3 December 2020 Düsseldorf, Germany

Marina Bay Sands, Singapore Cambridge, UK


1. Weld Purge Monitor for On-Site Conditions


We have featured part one and part two of our Welding Knowledge Series in previous issues of Weld
Purging World and we hope to bring you part three in next month’s issue.
These articles are aimed at explaining in engineering terms the principles of arc welding, the
properties of materials, the need for pre- and post- weld heating and other related issues.
Here is a look ahead at some topics to be covered in future issues.
Part 3: Small Tubes
Part 4: Corrosion
Part 5: Basic Metallurgy
Part 6: Welding Enclosures
Part 7: Wire Arc Additive Manufacturing

All issues of our Welding Knowledge Series are uploaded onto our Technical Papers section of our
website, so be sure to check them out if you have missed them!


Safe Pipe Repairs with Liquid Nitrogen Pipe Freezing

Scientific Developers of Weld Purging Technology and
Manufacturers of Weld Purging Products since 1975

Celebrating our 45th Anniversary



Protecting titanium and stainless steel welds from coming
into contact with air whilst they cool prevents oxidation, weld
defects and rework.
Leaders in Weld Purging Technology, Huntingdon Fusion
Techniques HFT® have launched their re-designed Weld
Trailing Shields®, which provide an additional inert gas
coverage during welding, preventing the hot metal from
coming into contact with air while it cools.
CEO Managing Director, Georgia Gascoyne said: “Along with the new sleek design, our Trailing
Shields® have a NEW Unique clip design, which means the welder can interchange different trailing
shield sizes without having to change the welding torch.”
“With our name and logo stamped onto every new Trailing
Shield, you can be sure the Shield you are using is a HFT
design. We manufacture our Weld Trailing Shields® right
here in the UK so we can guarantee quality and 100%
The low cost, lightweight Argweld® Trailing Shields® will
fit any make of TIG, MIG or Plasma (GTAW, GMAW, PAW)
welding torch for welding flat sheet or plate and the OD or
ID of tubes or pipes. For pipes and vessels the radiused
versions are manufactured to suit diameters from 25 mm
and upwards.
By using an Argweld® Trailing Shield® welds will be left bright and shiny and eliminate discolouration
and oxidation. The silicone (side skirt) gasket is resistant to temperatures up to 230ºC.
Titanium and stainless steels are chosen for their corrosion resistant properties in particular and if
they are then allowed to oxidise during the weld cycle, expensive post welding cleaning techniques
become necessary. Using a Trailing Shield® guarantees an oxide free, zero colour, bright shiny
weld, time and time again.


A great weld by Travis Field, with a little help from our
PurgEye® 100 Weld Purge Monitor®.
If you are using our products and would like to enter to
have your weld featured on our Instagram, simply tag us
in you photos and use the hashtag #HuntingdonFusion.
Extra points of if you can get our products in the photo too
... @huntingdon_fusion.



Weld Purging large diameter pipework made from stainless,
duplex and chrome steels, titanium or zirconium can be expensive,
with requirements to have the oxygen level well below 100 ppm
during the welding cycle.
As it is not cost effective to completely fill pipework with expensive
inert gas, Huntingdon Fusion Techniques HFT® have developed
QuickPurge® Systems to dramatically reduce the space that
needs to be purged.
Ron Sewell, Chairman for HFT® said: “Welders can often spend up to half a day purging pipes,
which will cost a considerable amount in time and gas costs. With the help of QuickPurge®, large
diameter pipes can be purged down to 100 ppm ready for welding in just a short time. The dramatic
savings in time and argon pay for the system in just one weld!”
Huntingdon Fusion Techniques, HFT®’s innovative design of the reusable QuickPurge® Systems
means that zero colour welds will be achieved and there will be no loss of corrosion resistance
caused by oxidation.
QuickPurge® has an additional gas input line, which means extra purge gas can be introduced for
applications such as this, thereby achieving a much faster purge, down to the lowest oxygen levels,
which is perfect for larger diameter pipes where quality welds are required.
1. Weld Purge Monitor for On-Site Conditions


Companies currently facing system downtime can drastically reduce pipe and valve repair and
maintenance costs with Accu-Freeze™ available from the Pipestoppers® Division of Huntingdon
Fusion Techniques HFT®.
Georgia Gascoyne, CEO for HFT® said: “Pipe freezing is a simple and efficient way of sealing a
pipe or system while pipe repairs or general pipework maintenance is carried out, without the need

to drain the system.”
Accu-Freeze™ works by reducing the pipe fluid to a temperature
below its freezing point and developing a freeze plug. This
controlled method of pipe freezing uses liquid nitrogen (LN2)
to freeze stationary liquids in a section of pipe or tubing. The
nitrogen is passed through a coil surrounding the pipe producing
a frozen plug inside and hence preventing flow through the part
to be removed.
The ice plug only forms beneath the Accu-Freeze™ coil wrap,
jacket or aluminium clam jacket. The system is effective on 6 - 12” (150 to 300 mm) pipe or tube.
The ice plug does not expand outside of the range of the jacket or coil.
The LN2 injections are automated which reduces the operators’ workload and the amount of LN2
consumed, keeping operating costs low. Accu-Freeze™ can also be operated remotely, which makes
it ideal for use inside ‘hot’ nuclear areas where personal exposure must be kept below certain limits.



Zirconium and its principal alloy zircaloy possess physical properties unmatched by most other
metallic materials. The combination of mechanical strength, corrosion resistance and their high
temperature stability make them attractive for use in sectors as diverse as biochemical, nuclear,
aerospace and petrochemicals.
More specifically, zircaloy is used in the manufacture of
pressure vessels and heat exchangers. The alloy has
excellent resistance to most organic and inorganic acids,
salt solutions, strong alkalis, and some molten salts and
these properties makes it suitable for use in pumps where
strength coupled with corrosion resistance is mandatory.
Zirconium alloys are biocompatible, and therefore can be
used for body implants: a Zr-2.5Nb alloy is used in knee
and hip implants.
By far the most significant applications however are in
nuclear power plant. Zirconium alloys are widely used
in the manufacture of fuel rods especially in pressurised
water reactors 1.
Figure 1. Zirconium alloy welded with effective inert gas protection showing no discolouration.
Preparation for welding
Zirconium is highly sensitive to contamination by active gases such as oxygen, nitrogen and hydrogen
and absorption of these materials can have a significant effect on mechanical, chemical and thermal
properties 2. The joint and filler wire must be carefully and completely cleaned and remain free of all
foreign material throughout the welding process. The metal surfaces must be protected using inert
gas shielding until the weld metal cools from its 1,835⁰C melting point to below 315⁰C.
Electron Beam (EBW) and Gas Tungsten Arc (GTAW) processes are both used for zirconium welding.
EBW is undertaken under vacuum so the requirement for environmental protection is not necessary.
Welding-grade argon ie 10 parts per million (ppm) other gases (99.999 percent argon) is essential
for primary, secondary, and backup shielding during GTAW, as well as for purging. Argon provides
excellent arc stability and because it is heavier than air, it blankets the weld and provides protection.
Argon and argon/helium mixtures can also be employed for backup shielding and purging, in which
helium’s low density can effectively purge blind spaces. Gas dew point should be not more than
In a high proportion of these application areas fusion welding is an essential requirement but care is
necessary to ensure that reproducible weld quality is achieved.
All the conventional welding processes can be used and the basic technical aspects have been
understood for many years. It is however essential to ensure that contamination does not occur—
zirconium alloys can be particularly susceptible to cracking and porosity if the welding environment
is not properly controlled.
Machining or vigorous stainless steel wire brushing followed by thorough degreasing with a suitable
solvent is necessary prior to welding, with the welding taking place within about eight hours to
reduce the risk of contamination.


The presence of nitrogen in the shielding gas can give rise to porosity so care must be taken to
ensure that the weld area is sufficiently protected and this is particularly relevant in site welding
applications. With the gas shielded processes, gas purity and the efficiency of the gas shield needs
careful monitoring. Gas hoses should be checked for damage and leaks at regular intervals and,
with the GTAW process, as large a ceramic shroud as is available should be used together with a
gas lens.
It goes without saying that gas purging of the root is essential when depositing a GTAW root
pass. Failure to control purging can result not only in the introduction of weld metal inclusions, but
also reduce corrosion resistance if left on exposed surfaces. Post weld cleaning to remove these
undesirable contaminants can be time-consuming and expensive.
Controlling Purge Gas Coverage
A wide range of ancillary equipment is available specifically to ensure optimised coverage of the
weld zone with inert purge gas. From simple expandable plugs to fully integrated inflatable devices
the products can accommodate pipe sizes from 10 to 2,500 mm.
Expandable Plugs are a popular choice and these are available with nylon, steel and aluminium
bodies. Surrounding each body is a flexible seal that can be expanded by applying a radial force
through a manually operated wing nut on the shaft.
These mechanical plugs can be used for purging pipework fabrications where a variety of openings
are present and where it is easier to purge the complete assembly.
Inflatable Weld Purging Systems have been developed to help speed up the welding process for
engineers involved in the fabrication of pipes and tubes.
The revolutionary PurgElite® range, manufactured by Huntingdon Fusion Techniques, is a robust,
easy to use, welding ancillary that offers considerable savings in time and inert gas.
Two inflatable dams are connected by a synthetic flexible hose that will not scratch the inside of
polished tube or pipe work. The hose is made of a self-sealing intumescent material that resists
even hot metal being dropped on it and will not disturb the purge gas flow.
The QuickPurge® Family of Inflatable Tube, Pipe and Pipeline Systems have been designed for
pipe welding between 6 and 88” (150 and 2,235 mm). Both PurgElite® and QuickPurge® products
are multi-use systems and include high temperature options for pre- and post- weld operations up
to 300oC.
Weld Trailing Shields®
Expandable plugs and inflatable purge systems meet the requirements for protection of the weld
root during tube and pipe welding: trailing shields are available for the topside.
They can provide a high level of additional inert gas shielding to supplement that supplied by the
basic welding torch. Shields are available to match a wide variety of forms from flat to diameters as
small as 25 mm. Both internal and external models are available
Flexible Welding Enclosures®
For component welding, Flexible Enclosures overcome all the disadvantages of glove boxes and
vacuum systems but at a fraction of the cost. They occupy considerably less floor space and all
parts of the welded component finish bright and shiny with no oxidation or discolouration. Argon gas
costs are reduced significantly and cleaning costs are eliminated.


Figure 2. The most efficient method of ensuring high quality inert gas coverage is to use flexible
enclosures. They are available in sizes approaching 30 cubic metres with residual oxygen content
as low as 10 parts per million.
Controlling Purge Gas Quality
Using specialised weld purging equipment does not guarantee defect free welds. Control of the
oxygen content of the purge gas is crucial to success and a monitor that measures residual oxygen
content reliably and accurately at the low levels considered is necessary when welding zirconium
These instruments are capable of measuring oxygen content accurately as low as 10 ppm - more
than adequate to satisfy the residual oxygen recommended for zirconium alloy welding.
Developments in End Closure Welding Technology for Zircaloy Clad Fuel
Elements. Amota I and Carena G, Energia Nucleari 17 (1970)
Welding zirconium and zirconium alloys
Sutherlin R, Tube and Pipe Journal, September 2016
Further information
Welding of zirconium alloys
Komuro K, Welding International, 1994 (2)
Guide for the fusion welding of zirconium and zirconium alloys
AWS G2.5/G2.5M: 2012, January 2012
Huntingdon Fusion Techniques Ltd in the UK can provide the following detailed information on
Technical Notes; Expandable Plugs, PurgElite® Systems, Trailing Shields, QuickPurge® Systems,
Flexible Welding Enclosures®, Weld Purge Monitors®.
The company has also published White Papers on topics including Flexible Enclosures, Advanced
Purge Monitor Technology, Trailing Shields, Principles of Tube and Pipe Welding and Orbital Weld

Flexible Welding Enclosures®

for Titanium Parts and
Wire Arc Additive Manufacturing

Scientific Developers of
Weld Purging Technology and

Manufacturers of
Weld Purging Products since 1975
Celebrating our 45th Anniversary

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