Weld Purging World - June 2020

ISSUE 06: JUNE 2020

IN THIS ISSUE:

HFT® PROVIDES SUPPORT FOR

SPACEX

FOCUS ON ADDITIVE MANUFACTURING
HEAT TINT CHARTS OPEN FOR BUSINESS

WELD PURGING PRODUCTS
INNOVATORS, MANUFACTURERS AND
INTERNATIONALLY RENOWNED SPECIALISTS
MADE IN WALES ‘MANUFACTURER OF THE YEAR’ &
WELSH BUSINESS AWARDS – EXPORTER OF THE YEAR

WWW.HUNTINGDONFUSION.COM

2 CONTENT

WHAT’S IN THIS MONTH’S ISSUE

Spacex Launch 3

HFT® News 4-6

Product News 7-8
9 - 13
Technical Paper: Welding in the
Power Industry

A WELCOME FROM THE EDITOR

Dear Reader,

Welcome to the June Issue of Weld Purging World.

The past month has definitely been incredible for us with our USA Distributor and Sub-Contractors
supporting Spacex with the build of their spacecraft ... read the article in full on page 3.

In this month’s Weld Purging World we feature our Heat Tint Chart for Stainless Steel Welding,
we Focus on Additive Manufacturing and our Technical
Article highlights welding technology challenges in the
Power Industry.

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

SPACEX LAUNCH

On Saturday 30th May, Spacex launched its first private spacecraft into orbit, which shortly afterwards
docked at the International Space Station.
Huntingdon Fusion Techniques HFT®’s Exclusive Partner in the USA, COB Industries, supported
Spacex throughout the build of the spacecraft.
Spacex purchase HFT® Weld Purging
Equipment through COB Industries,
including QuickPurge® Inflatable Weld
Purging Systems, Weld Purge Monitors®,
Weld Trailing Shields®, Flexible Welding
Enclosures® and Aluminium Plugs.
COB Industries also supply Spacex sub-
contractors, which are all based in and
around the launch pad area.
CEO Georgia Gascoyne for HFT® said:
“What a spectacular event on Saturday!
Huntingdon Fusion Techniques HFT® are
proud to be a supplier to Spacex via our Exclusive Distributor. This photo was taken by COB on the
beach close to the launch pad and such terrific news to see them docking on the ISS.”

WE REMAIN OPEN FOR BUSINESS

We are open for business during this difficult time and have continued to remain open to support our
Exclusive Distributors and Customers. We have faced many challenges during this time but above
all we have been here to ensure that you, the customer, continues to receive our products without
delay or compromised quality.

CEO Managing Director Georgia Gascoyne
said: “It’s been an incredibly tough few
months for everyone.”
“As we have been identified as being in the
‘Critical Key Workers Essential to Business
Category’, we will remain open to serve
you as our valued customers throughout
these challenging times.”
For support or enquiries, please contact us
on +44 1 554 836 836 or +1 800 431 1311
or email [email protected].

4 HFT® NEWS

HEAT TINT CHART

Heat Tint Recognition Chart For Stainless Steel Welding

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

1a 1b 1c 1d 1e 1f 1g

Pictures 1a to 1 g provided by Norsok for the Norsok Standard M-601 Welding and Inspection of Piping (Edition 5 April 2008) (Annex B).

Legend:

1a Excellent gas coverage (Norsok).
1b Acceptable gas protection (Norsok).
1c Acceptable providing that blue areas are intermittent (Norsok).
1d Acceptable providing brown areas close to the weld are narrow and light coloured (Norsok).
1e, 1f and 1g Poor back purge not acceptable.

2a 2b 2c 2d 2e 2f
12 ppm 60 - 70 ppm 70 - 90 ppm 200 ppm 250 ppm 500 ppm

Oxygen level Oxygen level Oxygen level Oxygen Oxygen Oxygen
unacceptable unacceptable unacceptable

2018: These are the results of HFT® research using Argweld® Weld Purge Monitors®.

1 2 3 4 5 6 7 8 8 10
10 ppm 25 ppm 50 ppm 100 ppm 200 ppm 500 ppm
(0.01%) (0.02%) (0.05%) 1,000 ppm 5,000 ppm 12,500 ppm 25,000
(0.1%) (0.5%) (1.25%) ppm (2.5%)

Heat Tint AWS-D18.2_1999 Guide for weld discolouration levels inside Austenitic Stainless Steel Tube

Oxidation colours need to be eliminated for most applications today.
Use a Weld Purge Monitor® to eliminate oxygen to prevent oxides from forming and save the additional

work load involved in removing the oxide film.
Use Argweld® PurgEye® Weld Purge Monitors® to detect oxygen levels down to 10 ppm to eliminate

oxidation, weld reject and potential weld failure.

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.

HFT® NEWS 5

FOCUS ON ADDITIVE MANUFACTURING

“Additive Manufacturing (AM) is the industrial production name for 3D printing, a computer
controlled process that creates three dimensional objects by depositing materials, usually in
layers.” – The Welding Institute.
The advantages:
Additive Manufacturing allows for the creation of bespoke parts, design flexibility, rapid product
development and very little wastage. Parts and products can be made directly from design data
by adding layers of material to achieve the final shape.
Welding:
There are many types of Additive Manufacturing. Wire Arc Additive Manufacturing (WAAM)
uses arc welding power sources and manipulators to build 3D shapes through arc deposition.
This method of Additive Manufacturing is usually performed using five axes computer numerical
control or robots.
Industries:
Many industries are now involved with AM and WAAM. The Aerospace Industry uses WAAM to
produce parts for aircraft and aircraft engines.
The Healthcare Industry manufactures equipment using Additive Manufacturing.

The Automotive Industry has also reported success in AM technologies.

6 HFT® NEWS

1. Weld Purge Monitor for On-Site Conditions

FOCUS ON ADDITIVE MANUFACTURING

During WAAM, reactive alloys such as titanium and stainless steels must be protected using an inert
gas environment.
The use of Flexible Welding Enclosures has helped to keep
an inert gas shield around the titanium and other reactive
alloy components. Our Standard Enclosures were quickly
found to be too small for the tooling and size of component
being manufactured so we started to manufacture Special
Enclosures. Since then, we have built a large number of all
shapes and sizes, each one having it’s own identity with the
varied numbers of glove ports and dimensions right up to a
complete robot system being placed inside of a 27 cubic ft
model.
To accurately measure the oxygen level inside the Welding
Enclose, The revolutionary PurgEye® Desk monitors oxygen
levels from 1,000 ppm, right down to levels as low as 1 ppm
(accurate to 10 ppm).
One huge addition to the PurgEye® Desk is 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 and even give dew point measurements.

PRODUCT NEWS 7

LOW COST MONITOR FOR WELDING TITANIUM AND STAINLESS STEEL

Titanium and stainless steel are both reactive alloys. When they are heated during the welding
process, they will react with any air that is present, causing oxidation, which can lead to a loss of
corrosion resistance properties. Shielding the metal with an inert gas is therefore crucial and one

way to measure the oxygen content within the welding
zone is by using a Weld Purge Monitor®.
Leading the way in Weld Purging Technology, Huntingdon
Fusion Techniques HFT®’s PurgEye® Nano is ideal for
welding titanium and high end stainless steel, where
oxygen levels are required to be as low as 10 ppm.
Luke Keane, Technical Sales Manager for HFT® said:
“By knowing the exact level of oxygen inside the pipe
at all times, the welder knows when to start welding for
high quality results. The PurgEye® Nano is our basic
entry level 10 ppm Monitor, which means it is perfect for restricted budgets. It’s a simple plug and
play monitor, ideal for welding titanium, stainless steel and other reactive metals such as zirconium.”
With leak-tight connectors for weld purge hoses, the lightweight PurgEye® Nano can be used with
optional accessory hand pump and gas sampling probe. The PurgEye® Nano has been developed
for weld purging where data logging, alarms and machine control are not necessarily required.
The monitor has been developed with a unique long life sensor that has a warm up time under 60
seconds.
Ron Sewell, Chairman for HFT® said: “All of our Weld Purge Monitors® and Inflatable Tube, Pipe
and Pipeline Weld Purging Systems as well as our inflatable welding enclosures are manufactured
in the UK. We do not sacrifice on quality and guarantee 100% craftsmanship.”
1.

CALENDAR: EVENTS IN THE INDUSTRY



TechniShow Adipec Fabtech

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

8 PRODUCT NEWS

DELIVERING THE HIGHEST QUALITY GAS

High quality Argon Gas Feed Hose provides welders with a
method of delivering non-contaminated argon gas into their
welding zone.
Huntingdon Fusion Techniques HFT®, Global Weld Purging
Manufacturing Company, produce tailor made Inert Gas Feed
Hoses, suitable for use for TIG welding where argon and other
inert gas is used.
Georgia Gascoyne, CEO for HFT® said: “Our high quality Argon
Gas Feed Hose is manufactured of a special low outgassing rate rubber feed hose, which comes
complete with a regulator and can directly connect to any range of Inflatable Tube and Pipe Weld
Purging Systems at one end and to the gas source at the other. Designed to help keep welding
zones purged of oxygen.”
Conforming to British Standard BS EWN 599 Quality Standard, the Inert Gas Feed Hoses each
have a temperature range from -30º up to 80ºC and a safety factor of three times working pressure
20 bar (300 psi).
A selection of leak tight adaptors is provided for attaching the inert gas regulator whilst the pre-fitted
other end joins up with all HFT® Argweld® Pipe Weld Purging Systems. All of these high quality
fittings will eliminate welding connection difficulties that welders might experience on site.
1. Weld Purge Monitor for On-Site Conditions

INFLATABLE PIPE STOPPERS FOR SEALING, BLOCKING AND TESTING

Single Ended Inflatable Dams are readily available in a variety of shapes and sizes for a range of
applications including sealing, blocking, pressure testing and isolation.
Pipe stopping equipment from the Pipestoppers® Division from Huntingdon Fusion Techniques HFT®
gives the user the opportunity to isolate a section of pipeline to carry out repair and maintenance
work.

Luke Keane, Technical Support Manager for HFT® said: “We
design and manufacture a range of standard and non-standard
Inflatable Stoppers for tanks, chambers, tubes, pipes and pipework
fabrications, offering a range of pipe stopping and blocking
requirements for a variety of sealing problems.”
“We recently added new Rubber PetroChem Stoppers to our
range, an easy way to stop the flow of gas or liquids along a pipe
or duct. 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.”
All Inflatable Stoppers are manufactured with a strong internal latex balloon covered in a waterproof
polyurethane coated nylon bag for low friction and to prevent the production of static electricity or
accidental sparking.

WELDING TECHNOLOGY IN POWER INDUSTRY 9

TECHNICAL ARTICLE

The planned surge in new electricity power generation plant and refits across the world over the
next two decades will provide outstanding opportunities for the fabrication sector. Recent innovative
developments in welding equipment will support the drive towards the production of consistently
better quality joints, many of which are in the safety critical class.
Over 300 nuclear reactors have been proposed of which 136 will be in China, 24 in the USA and
23 in Russia. India’s massively delayed nuclear power programme will see a resurrection after
Électricité de France (EDF), the world’s biggest electricity company, agreed to build six nuclear
plants in the country. The Indian Jaitapur project is expected to become the world’s biggest nuclear
contract and one of the world’s largest nuclear sites. The 10,000 MW project will have six reactors
of 1650 MW each.
Fossil fuel powered generators are still expected to play a major part in the ever-increasing global
demand for electricity. An estimated 1000 GW of new coal fired power stations will be built in the
next 20 years. Half of these will be in China, but with significant programmes in South Africa and
India. Most of the global coal-fired installations are old and maintenance programmes will need to be
implemented coupled with the introduction of CCS retrofitting (carbon capture and storage).
All the programmes involve extensive fabrication of steel pipes and tubes, the welding of which
presents particular challenges.
Stainless steels are used extensively in the construction of nuclear power plant, primarily for their
corrosion resistance. Core and secondary parts of most reactor types in service today such as
PWR/VVER, BWR, CANDU, AGR and fast breeder reactors are built from stainless steel, as are
reprocessing plants and research reactors. The nuclear decommissioning and waste storage industry
is also a prime user of high quality stainless for different types of transport or storage canisters and
boxes for low- to high level waste.
The high pressures and temperatures used in steam generation circuits necessitate the use of creep
resistant steels such as those based on chromium/molybdenum/vanadium alloys. These materials
provide improved oxidation and corrosion resistance together with high strength and are widely
used in both fossil fuel and nuclear power plants.
The demand for quality in all these safety critical joints is reflected in the stringent regulations laid
down in welding procedures. Nevertheless some welding practices can result in significant reduction
both in corrosion resistance and mechanical strength.
Welding of high pressure steam pipe
Some engineering alloys are prone to cracking during welding. Industry sectors having to overcome
this problem are principally in the power generation sector. The materials include low and medium
alloy steels that have been specially developed for their high strength. Metallurgists have learned that
heating the joint prior to and after welding (pre-heating and post-heating) can reduce the sensitivity
to cracking quite significantly. These processes involve temperatures in the region of 200°C (392°F)
although this may be much higher for certain materials.
An example of a commonly used alloy benefiting from this treatment is SA 213 T91 or SA 335 P91.
This is a ferritic alloy steel that meets the condition of creep resistance required in high temperature
steam generating plant. The material, often simply referred to as P91, has been in successful use
for the last two decades in power plant service.

10 WELDING TECHNOLOGY IN POWER INDUSTRY

Pipe welding is one process that is widely used during manufacture. This affects the micro-structure.
Preheating, maintaining inter-pass temperatures, and post-weld heat treatment procedures are very
critical for P91 and similar alloys. Failure to follow the procedures can result in catastrophic failures
in service.

Other high temperature creep resistant ferrous alloys requiring this type of heat treatment are;

ASTM A389 grade C24 A356 grade 9 DIN 21CrMoV 5-11 15CrMoV 5-10
GS-17CrMoV 511 EN G17CrMoV5-10 GE B50A224

The preferred welding procedures in this type of fabrication are GTAW and GMAW and these offer
protection of the exposed upper fusion zone.

The joint around the underbead however needs to be protected simultaneously by purging away
the air that could be in contact with this underbead (known as the root weld) - thus protecting the
exposed metal by using an inert gas envelope.

Meeting the requirements of inert gas purging when temperatures exceeding 200ºC are involved
necessitates the use of purge systems capable of withstanding these temperatures throughout the
heating and welding cycles. Typical thermal cycles can exceed 2 hours and it may be necessary to
maintain the purge system in place throughout.

Specially engineered purge products have been designed over the past five years that are capable
of withstanding the temperatures involved whilst at the same time maintaining excellent gas sealing
characteristics. They are also rugged enough to survive multiple-use applications.

Few manufacturers are able to supply weld purging systems that can be used at the high temperatures
prevailing during pre- and post-heating. The range of equipment designed by Huntingdon Fusion
Techniques HFT® meets the requirement for thermal stability and operational reliability.

Fig 1. HotPurge® systems cover the diameter range from 6” to 88” (152 to
2,235 mm).

These systems are capable of withstanding temperatures up to 300ºC / 572ºF
for 24 hours.

• The inflatable seals are manufactured from flexible, thermally resistant engineering materials.
• Anti burst.
• Guaranteed seal and purge.
• Volume reducing sleeve to keep purge time down and to keep gas costs low.
Welding of Stainless Steels
One area of production receiving little attention is during pipe and tube fabrication where welding is
widely used.
Unless strict welding schedules are adhered to, however, not only will discolouration (heat tint) take
place but corrosion resistance can be significantly reduced.

WELDING TECHNOLOGY IN POWER INDUSTRY 11

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 chromium 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:
• Crevice corrosion
• Pitting corrosion
• Stress corrosion cracking
• Microbiologically induced corrosion (MIC)

Crevice Corrosion
Localised corrosion of a metal surface attributable to 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.

Fig 2. Crevice corrosion adjacent to stainless steel pipe weld

Pitting corrosion
This produces attacks in the form of spots or pits
and takes place at points where the passive layer
might be weakened: 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.

Fig 3. Extensive penetration following pitting corrosion in
stainless steel pipe.

Stress Corrosion Cracking
Characterised by cracks propagating either through or 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.
Microbiologically induced corrosion
Corrosion promoted or caused by microorganisms, usually referred to by the acronym ’MIC’ and is
common in welded sections.

12 WELDING TECHNOLOGY IN POWER INDUSTRY

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 is to
prevent heat tinting during the welding process by using an inert environment to protect the surface.
Removal of Heat Tint
Bright annealing or acid pickling can remove light discolouration 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.

Fig 4. Even very low oxygen content of protective gas can
cause discolouration in stainless steel.

Fig 5. In order to eliminate discolouration oxygen content of
protective gas must be reduced to 20 ppm (0.002%)

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, during and after welding while waiting for the joint to cool below its oxidation temperature.
Weld Purging Techniques
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 6” to 88” (152 to 2,235 mm).
The most effective devices are those based on connected inflatable dams and shown in Fig 6.

Fig 6. The inert gas weld purging concept can be illustrated
using the QuickPurge® systems.

These are 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 materials and
are thus suitable for use with oil and gas pipelines and
processing plant where elimination of contamination is
essential.

WELDING TECHNOLOGY IN POWER INDUSTRY 13

Fig 7. PurgElite® range of fully integrated systems covering
the 1” to 24” (25 to 610 mm) thin wall tube and pipe range.

Purge gas oxygen content can be controlled by using
special oxygen monitoring instruments called Weld
Purge Monitors®.
These instruments not only measure oxygen levels
but will inhibit welding if the PPM level is above that
set by the operator. Recording and analysing software
provides information for quality control purposes.

Fig 8. Weld Purge Monitor® designed specifically for use in
a welding environment. The PurgEye® range is capable of
measuring residual oxygen content down to 1 ppm (accurate
to 10 ppm). This model (PurgEye® 200) with PurgeNet™
allows connection of accessories to run automatic machines
such as orbital welders.

Conclusion

Even very low oxygen concentrations in weld gases can give rise to discolouration, loss of corrosion
resistance and reduction in mechanical strength. Controlling oxygen level in purge gas can be
effected simply and efficiently using contemporary integrated purge systems.

References

World Nuclear Power Reactors & Uranium Requirements, World Nuclear Association, November 2016.
Analysis of Globally Installed Coal Fired Power Plant, Finkenrath et al, International Energy Agency,2012.
BS EN ISO 13916:1997: ‘Welding: Guidance on the measurement of preheating temperature, British Standards Institution, 1997.
BS EN 1011-2: 2001: ‘Welding: Recommendations for welding of metallic materials. Arc welding of ferritic steels’, British Standards Institution, 2001.
The Welding Institute. Technical-knowledge series.
Bailey, N. Weldability of Ferritic Steels. The Welding Institute, 1995.
Huntingdon Fusion Techniques Ltd, UK. www.huntingdonfusion.com.
Eastwood et al. 1993. Welding stainless steel to meet hygienic requirements. Document 9. European Hygienic Engineering Design Group (EHEDG).
Microbiologically influenced corrosion of stainless steel. Jörg-Thomas Titz. 2nd symposium on orbital welding in high purity industries, La Baule,
France.
Effects of purge gas purity and Chelan 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. Dr B. K. Henon, Arc Machines,
Inc. Stainless Steel America conference 2008.
Heat Tint Guide with references from Norsok, AWS, and Huntingdon Fusion Techniques own research. (https://www.huntingdonfusion.com/index.php/
en_gb/technical-support/technical-material/heat-tint-charts).

PurgEye® 100 Weld Purge Monitor®

Accurate Oxygen Monitor for
Weld Purging Stainless Steel

Scientific Developers of
Weld Purging Technology and

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

www.huntingdonfusion.com