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Issue Four of Weld Purging World - April 2020

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Published by Huntingdon Fusion Techniques HFT®, 2020-04-14 04:14:34

Weld Purging World - April 2020

Issue Four of Weld Purging World - April 2020

Issue 4: APRIL 2020

In April’s Issue:

• We are still open for business
• Ask The Expert: PurgEye® 600
• Product News: HotPurge®, TEG-1000 and Weld Purge Dams
• Technical Article: Welding Knowledge: Part 2

Weld Purging Products
Innovators, Manufacturers and
Internationally Renowned Specialist
Made in Wales ‘Manufacturer of the Year’ and Welsh
Business Awards – Exporter of the Year

Huntingdon Fusion Techniques HFT® are proud members of:

www.huntingdonfusion.com

2 CONTENT

WHAT’S IN THIS MONTH’S ISSUE

Open for Business 3

HFT® News 4 - 6

Product News 7-8
9 - 13
Technical Paper: Welding Knowledge
Part 2

A WELCOME FROM THE EDITOR

Dear Reader,

Welcome to the April Issue of Weld Purging World.

I write this month’s issue in what seems to be very strange and worrying times. We’d like to let all
of our Customers know that we are still continuing to receive and ship orders Worldwide and of
course, bring you all our latest news in the form of our monthly Weld Purging World.

In this month’s issue, we introduce our NEW Dew Point
Sensor, we ask the Experts some questions about our
unique PurgEye® 600 Weld Purge Monitor® and we feature
our latest Technical Article, following on from Part 1, Welding
Knowledge: Part 2.

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]

HFT® NEWS 3

4 HFT® NEWS

NEW PRODUCT: DEW POINT SENSOR

During purging welders need to measure the
oxygen content but also need to measure the ‘dew
point’.
The dewpoint is the temperature where
condensation begins and water will condense on
the material being welded. This can affect the weld
properties significantly.
We have recently added a Dew Point Sensor to
our range that can be used in conjunction with our
range of 10 ppm Weld Purge Monitors®, so rather
than purchasing a separate, expensive Dew Point
Meter, HFT®’s Dew Point Sensor that can be
connected to the Weld Purge Monitor® via the PurgeNet™ lead.
The dew point sensor is designed to fit any of our Weld Purge Monitors® that read down to 1ppm:
- PurgEye® 200
- PurgEye® Desk
- PurgEye® 600
- PurgEye® 1000
- PurgEye® Site

• Measurement Range (@20˚C and 100
mbara)
300 to 50,000 ppm(v)
(600 to 200,000 ppm(v) @ 50˚C*)
• Accuracy (@ 20˚C* and 1000mbara)
30 ppm + 10% of measured value #
• Response time (t90)
Minutes for decreasing dew point
Seconds for increasing dew point #
• Power Requirement 1 watts, powered from O2M (with PurgeNet™)]
• Output
Dew point data will be output to supporting Weld Purge Monitor® with PurgeNet™ for display (and
logging on compatible models)
* Medium temperature.
# This will be heavily dependent on pipe length, material, ambient temperature etc. (Pipe lengths
must be kept to a minimum). However, purge times will likely be significantly longer than the response
time.

HFT® NEWS 5

ASK THE EXPERT

This month, we ask our Experts some frequently asked questions regarding our all in one, colour
touch-screen PurgEye 600 with PurgeNet™ reads from atmospheric, down to 1 ppm oxygen
(accurate to 10 ppm).

Q. What is the intended applications for the Argweld®
PurgEye 600 Weld Purge Monitor®?
For weld quality control in “High Tech” industries such
as aerospace, semiconductor, pharmaceutical, vacuum,
biotech, food and drinks etc where pristine oxide and colour
free welds are demanded to prevent the risk of corrosion
and to eliminate mechanical polishing that can need to
surface imperfections with the risk of contamination. Also
for the welding of sensitive materials such as titanium,
zirconium, polished stainless steels for example

Q. What sort of sensor is used in the Argweld®
PurgEye® 600 Weld Purge Monitor®?
The PurgEye 600 Weld Purge Monitor® uses a solid-state
long life sensor of a unique design.

Q. Can Weld Purge Monitors® only be used when purging with argon?
The PurgEye® Weld Purge Monitors® measure the oxygen level within any gas or gas mixture. Not
only the inert weld shielding gases of argon and helium but also nitrogen and hydrogen mixes.

Q. What is PurgeNet™?
The PurgeNet™ facility allows a series of accessories to be added to the Weld Purge Monitor®.
One accessory allows control of automatic welding systems to switch the welding process on and off
according to pre-set oxygen levels. PurgeNet™ can be used with PurgeLog™ Software to transfer
weld purge data for quality control of welds. PurgeNet™ connects to other smart accessories for
weld purging, including the external, distance light system, which gives a visual warning during
welding in case of rising or falling oxygen levels.
1.

CALENDAR: EVENTS IN THE INDUSTRY

Fabtech Mexico Fabtech Canada WIN Eurasia - HALL 12 A160
18 - 21 June
12 - 14 May 2020 16 - 18 June 2020 İstanbul, Turkey

Mexico City, Mexico Toronto, Canada Fabtech
18 - 20 November 2020
Las Vegas, USA
TechniShow Adipec

1 - 4 September 2020 9 - 12 November 2020

Utrecht, Netherlands Abu Dhabi, UAE

Tube

7 - 11 December 2020

Düsseldorf, Germany

6 HFT® NEWS

1. Weld Purge Monitor for On-Site Conditions

RUBBER STOPPERS FOR SUPER YACHTS

The Pipestoppers® Division at Huntingdon Fusion Techniques
HFT® have launched new Rubber PetroChem Stoppers, for
pipe stopping on Super Yachts where access is difficult.
CEO Managing Director, Georgia Gascoyne said: “We were
recently tasked with the challenge of sealing various holes on
a Super Yacht. The seachest inlets needed to be blocked off
to prevent ingress of seawater so valves and valveseats could
be cleaned. Deck cleaning is also made easier by using these
plugs by blocking off the scupper holes.”
“Each Stopper has a longer length than diameter, which prevents them from tipping over and losing
their seal inside the pipe. They are also manufactured with a ribbing
to prevent slipping.”
The Stoppers are manufactured from high quality materials, ensuring
a long life span and are resistant to a large number of chemicals and
petrochemicals.
The Stoppers are available in five sizes, which will seal pipes from 2”
to 12” (50 mm – 300 mm). Each Stopper is inflated simply using the
Schräder Valve.

Accu-Freeze™

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

www.huntingdonfusion.com

PRODUCT NEWS 7

WELD PURGING OF HEAT-TREATED PIPEWORK

Some high strength steels need to be pre-
heated prior to welding and may also require
a post-weld heat-treatment.
Both pre- and post- weld heat treatment
is necessary to prevent cracking, but
temperatures up to 300ºC (572ºF) must be
maintained for lengthy periods. To prevent
oxidation, the inside of piping needs to be
purged continuously using a specialised pipe
weld purging system.
HotPurge® has been developed by
International Weld Purging Specialists
Huntingdon Fusion Techniques HFT®. It is an
Inflatable Pipe Purging System for use with High Strength Steel Pipe Joints where pre-and post-
weld heating temperatures might be as high as 300ºC (572ºF) for lengthy periods.
Manufactured in sizes 6 to 88” (150 to 2,235 mm), HotPurge® Systems can be used repeatedly
for weld purging and can keep the oxygen levels below 100 parts per million (ppm) throughout the
welding cycle, ensuring oxidation-free welds, without the metallurgical imperfections caused due to
rapid heating and cooling.
Luke Keane, Technical Sales Manager for HFT® said: “HotPurge® allows the purge to be safely
continued for up to 24 hours whilst pre-heating, welding and post weld heat-treating with the purge
system remaining in place. Furthermore, the addition of PurgeGate® prevents the risk of dams
bursting due to increased pressure.”

“Along with all of our Inflatable Pipe Purging
Systems, our HotPurge® Systems are all
manufactured in the UK, with scientific knowledge
and research invested in each of our products.
We do not save on quality. You can be sure to
achieve perfect welds, time and time again.”
Once positioned in the pipe and inflated with an
inert gas supply, the HotPurge® System seals
inside the pipe with inert gas supply displacing the
oxygen from within the weld purging zone ready
for pre-heating and welding. Each HotPurge®
System is manufactured with a Weld Purge
Monitor® connection for viewing the oxygen
level throughout the welding process.
Each HotPurge® System features PurgeGate®, a revolutionary device to prevent over inflation of,
and damage to the inflatable dams. The innovative HotPurge® System also incorporates RootGlo®,
a central band for easy positioning inside the pipe, which will illuminate inside the dark pipe for up
to 20 hours.

8 PRODUCT NEWS

HIGH PRECISION TUNGSTEN ELECTRODE GRINDER

To produce optimum arc stability, improve arc starting and
subsequently weld quality, a dedicated Tungsten Electrode
Grinder should be used for sharpening all Tungsten Electrodes
during TIG welding.
Huntingdon Fusion Techniques HFT® state-of-the-art TEG-1000
Tungsten Electrode Grinder will ensure the grinding of each
Tungsten Electrode results in clean and smooth finishes, with
no splintering and eliminating arc jumping. The reliability of the
equipment means that tip consistency is guaranteed and this is
especially important with automated welding operations.
Unstable arcs are most likely down to the sharpening of the Tungsten Electrode. An incorrectly
ground Tungsten Electrode tip may drop into the weld pool and create a tungsten inclusion that
could lead to a weld cut-out or reject, either way, leading to additional welding costs and lost time. It
can also result in a huge reduction in tip life and changes in arc voltage.
Manufactured with a diamond wheel, the TEG-1000 Grinder will give repeatable Tungsten Electrode
points every time, enabling consistent arc performance and welding results. Sizes 1.0 to 3.2 mm can
be ground as standard, with other sizes catered for on request.
The design of the TEG-1000 is such, that the diamond wheel grinds the Tungsten Electrodes
longitudinally, preventing arc flicker or wander caused by circumferential lines or ridges found on
electrodes, which have been ground incorrectly.
1. Weld Purge Monitor for On-Site Conditions

STAINLESS STEEL PIPE WELDING MADE EASY

Welders often face difficulties when welding stainless steel T piece joints, dome end connections
and closure welds, where a tandem Inflatable Pipe Purging System is unsuitable.
Weld Purge Dams from Huntingdon Fusion Techniques HFT® offer a great solution, available for
pipe sizes 6 to 88” (150 – 2,235 mm).
Georgia Gascoyne, CEO for HFT® said: “Weld Purge Dams are a more effective alternative to foam
or cardboard dams that are still frequently handmade by welders, which can often be unsuitable for
Weld Purging. Restricting the pipe volume has proven to be the most cost effective solution and Weld
Purge Dams offer a great solution where Tandem Weld Purging Systems are not practical, especially
welding metals such as stainless steels, titanium and zirconium.”
“Displacing the oxygen with an inert gas before, during and after
welding helps to create welds that are free from oxidation. Once the
Dam is inflated using the purge gas and seals all around the internal
circumference of the pipe, the excess inert purge gas spills out and
purges the space around the weld joint. The air (oxygen) is then released
out and into the pipe length through a series of venting exhausts on the
dam.”

TECHNICAL ARTICLE - WELDING KNOWLEDGE PART 2 9

WELDING KNOWLEDGE - PART 2

Introduction to Stainless Steels
It comes as a surprise to many that ‘stainless steel’ is not stainless. Discolouration is not uncommon
and salt water environments in particular can give rise to corrosion: this is even noticeable at domestic
level where dark spots appear caused by the mild salt solutions used during automatic
dishwashing cycles.
The importance of stainless steel one is best reflected by the worldwide annual consumption which
was reported at over 50 million tonnes in 2019. Generally recognised for its corrosion properties the
material range is also widely used where strength coupled with elevated temperature resistance to
oxidation.
The most common alloying elements include chromium, nickel, manganese carbon and molybdenum
and these may be added for corrosion and high temperature oxidation resistance, or to improve
mechanical properties. Varying proportions of alloying elements give rise to different phase structures
in the steels, generally classified as austenitic, ferritic and martensitic.
To preserve continuity, references to steel grades and classifications in this publication will use the
SAE System two.
In the 1930s the American Iron and Steel Institute (AISI) and Society of Automotive Engineers (SAE)
were both involved in efforts to standardise the numbering system for steels. These efforts were
similar and overlapped significantly and in 1995 the AISI turned over future maintenance of the
system to SAE International.
The diversities in alloy balance require different approaches to welding. Most of the problems arising
during fabrication have been resolved, but attention to filler metal composition and welding technique
is essential if high quality joints are to be produced.
Principle applications arise in the
domestic, architecture, transport,
chemical, pharmaceutical, oil
and gas, medical, food and drink
sectors, but these alloys are also
widely used in the manufacture of
fasteners and wire.
Austenitic alloys
Austenitic stainless steels are
classified in the SAE 200 and SAE 300 series, with 16% to 30% chromium and 2% to 20% nickel.
Other metals such as molybdenum, nitrogen may be added to improve corrosion and mechanical
strength. Together they constitute 75% of the world stainless steel market.
With care all the stainless steels can be welded using all the principal arc (GTAW, GMAW and
SAW) processes.

10 TECHNICAL ARTICLE - WELDING KNOWLEDGE PART

Welding
Their single-phase structure means that hardening does not occur during cooling so no post-weld
heat treatment is necessary. Joints exhibit good toughness. However, some of the compositions
are prone to ‘sensitisation’. During cooling, chromium carbides form at grain boundaries so the
chromium content of the alloys is reduced leaving the grain boundaries at risk of corrosion. This
sensitisation can be reduced by adding small additions of titanium and/or niobium.
Filler metals to match the parent alloys are available for most of the austenitic range of alloys.
Prominent exceptions are type 304 for which a type 308 filler metal is commonly used and type 321
which may be welded using a type 347 filler.

Ferritic Alloys
All falling within the SAE 400 series of alloys, ferritic
stainless steels contain 10.5 to 27 percent chromium
and some of these metals may contain molybdenum,
aluminium and titanium. The nickel content is small and
this accounts for them being much less expensive than
austenitic grades.
Confusion often arises because some of the SAE 400
grades can have a martensitic structure. Typical ferritic
alloys are SAE 409, 430, 434 and 446. SAE 400 alloys are magnetic. Together they constitute 20%
of the world stainless steel market.
Welding
Although less corrosion-resistant than austenitic alloys, ferritic grades generally have better
mechanical properties. Many are readily weldable, but care needs to be exercised since some are
prone to sensitisation within the heataffected zone and to weld metal hot cracking, particularly in
thicker sections.
Austenitic filler metals, particularly the low carbon SAE 309 alloy are the most commonly used. The
higher chromium content helps to prevent too much chromium dilution, and hence
a reduction in strength and corrosion resistance.
Martensitic alloys
The most common martensitic steels are SAE 410, 420, 422 and 431 and these contain up to 18%
chromium with additions of carbon and manganese. The combination of elements coupled with
heat treatment result in the production of martensitic rather than ferritic structures and these exhibit
superior mechanical properties. They are widely used for their creep strength combined with erosion
and corrosion resistance.
Welding
Fusion welding presents some challenges. Most require pre- and post- weld heating to avoid weld
cracking problems and to provide a tough, but ductile joint. Filler metals with similar composition to
the base alloys are most suitable and these are readily available. Some contain additions of nickel
so that the weld ferrite content is kept low to avoid loss of mechanical strength.

TECHNICAL ARTICLE - WELDING KNOWLEDGE PART 2 11

Duplex Stainless steels
The concept of duplex alloys was to develop materials with corrosion resistance coupled with
strength. Only from the 1980s however were satisfactory production techniques developed.
The alloys are complex and demand specialist manufacturing skills so that production has been
limited to intrinsic steelmaking operations.
For this reason, many of the duplex alloys are not categorised internationally but named commercially.
Sandvik’s hyper-duplex alloys are representative of materials with the best combinations of strength,
corrosion resistance and weldability.
These typically offer;
• Double the design strength of austenitic and ferritic stainless steels
• A wide range of corrosion resistance to match application
• Good toughness down to minus 80ºC
• Weldability in thick sections
They are however more difficult to form and machine than austenitic alloys and have limited high
temperature applications. Duplex stainless steels are now used extensively in the offshore oil and
gas industry and in the petrochemical sector for pipework systems and pressure vessels.
Welding
Duplex steels can be complex materials, relying on their properties for a careful balance of differing
microstructures. Thermal cycles experienced during welding and any heat treatment can make
significant differences to mechanical strength and tendency to cracking.
Filler metals are generally formulated to contain more nickel than the parent alloy in order to maintain
an adequate balance of austenite in the weld metal. Up to 7% nickel is typical, but as much as 10%
may be required in the super duplex materials.
General Welding Precautions
Dissimilar metals
Filler metals need to be selected to maintain an optimum weld metal that meets the need to
accommodate any differences in expansion co-efficient and maintain acceptable mechanical
properties. Matching filler alloys with the martensitic composition are often satisfactory but the
nickel-based Inconel 625 is useful if a close match with the coefficient of expansion is mandatory.
Purging
Loss of chromium during welding because of oxidation can reduce the corrosion resistance
significantly so it is essential to protect the molten weld metal using a shield of inert gas. The upper
bead protected by the arc shield but special attention to protecting the weld root is essential.
References
1. British Stainless Steel Association. https://www.bssa.org.uk
2. AISI Steel grades, SAE and Werkstoff numbers - Steel Express.
https://www.steelexpress.co.uk › aisi-sae

PurgElite®

Inflatable Pipe Weld Purging Systems
Drastically Restrict Weld Purge Volumes

Scientific Developers of
Weld Purging Technology and

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

www.huntingdonfusion.com


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