Weld Purging World - October 2020

ISSUE 09: OCTOBER 2020

IN THIS ISSUE:

HFT®

CELEBRATES 45 YEARS

WELDING STAINLESS STEEL
ALL THE LATEST HFT® NEWS

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

HFT® Celebrated 45 Years 3
HFT® News 4-6
Product News 7-9
10 - 11
Technical Paper: Seven Tips
for Weld Purging

A WELCOME FROM THE EDITOR

Dear Reader,

Welcome to the October Issue of Weld Purging World.

In August, HFT® officially turned 45 and to mark the official anniversary, we had a socially
distanced afternoon tea at our UK HQ. Read more about our 45 years in business on page 3.

This month’s issue of Weld Purging World is full of useful
welding tips, with our detailed article ‘Welding Stainless
Steel’ on pages 4 and 5 and our Technical Article ‘7 Tips for
Weld Purging’ on pages 10 and 11.

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

HFT® CELEBRATES 45 YEARS IN BUSINESS

August marked HFT®’s official 45th year in business and we celebrated by throwing a small,
socially distanced afternoon tea at our UK HQ.

Our CEO Georgia said: “Although 2020 has been quite a strange
year, we couldn’t let our 45th anniversary pass by without some sort
of celebration.”
“45 years in business is an incredible achievement and a huge
landmark for us. Our dedication to product development, long-
standing industry experience and loyal Distributor network are
key elements of our success,” comments Georgia Gascoyne,
HFT®’s CEO. “We are a family owned business and are proud of
our heritage. We have developed into a truly global business and
are looking forward to the next few years of continued business
expansion, enabling us to strengthen our position as the number
one manufacturer of Weld Purging Systems.”
“A key element of our success and one that we are very proud of is our long and enduring
relationships with our Distributors and Suppliers. Their loyalty, along with the commitment of our
staff means we are now embarking on what we anticipate will be some of the most exciting years
in business. Our success in identifying the high-potential niche markets around the world where
our technical capability and experience has been central to our longevity and will be critical to
our future.”

4 HFT® NEWS

WELDING STAINLESS STEEL

Avoiding loss of corrosion
Many industries rely on the corrosion resistance of stainless steels including the food, beverage,
pharmaceutical, semiconductor, petrochemical and nuclear.
It has become common practice in some applications to accept discolouration and remove it
post-welding, but this can be very expensive. It is time-consuming and, where access is limited,
difficult to achieve with any degree of success. Some methods require specialist equipment.
The expense of post-weld operations is often overlooked and not considered part of the
welding process. They are largely applied manually and thus prone to significant variations in
effectiveness. They are seen as an easy option but can easily exceed the welding costs.
The most effective method of preventing discolouration is to use a weld purging technique.
Purging involves eliminating oxygen from the heated weld zones by displacing the air with an
inert gas, usually argon.
Available Weld Purging methods:
Inflatable Systems are the only totally reliable and are the
most effective tube and pipe purging systems.
Considerable design effort has been applied to these
inflatable 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.
PurgElite® Systems • First ever 1” (25 mm) system size
available
• Range from 1 – 24” (25 – 610 mm)
• Special gas saving designs
• Flexible spinal hose with heat protection
• Heat Cover and PurgeGate® available as accessories
QuickPurge® Systems
• Central Sleeve with RootGlo®
• IntaCal® purge gas release system
• Reduces purge volume
• Sizes from 6 to 88” (152 – 2,235 mm)
HotPurge® Systems
• Heat resistant. Withstands 300ºC (572ºF) for up to 24 hours
• Suitable for pre-heated pipework
• Ideal for P91 and other chrome pipework in power stations and refineries
• With RootGlo®, IntaCal® and PurgeGate®

HFT® NEWS 5

WELDING STAINLESS STEEL

Monitoring of oxygen content in the purge gas
The fact that even very small amounts of oxygen in the purge gas can cause discolouration
around the weld underbead makes it desirable that specialised instruments be used to measure
residual oxygen. Recommended practice to ensure acceptable discolouration is to maintain an
oxygen level below 50 ppm (0.005%) for stainless steel.
Two essential characteristics of a suitable instrument are that it must have an adequate measuring
range and it must sample the purge gas inside the purge volume. The sensitivity should be such
that an oxygen level as low as 10 ppm can be detected. Instruments that only display down to
1000 ppm (0.1%) are totally unsuitable.
Weld Purge Monitor® Range:
• PurgEye® 100 IP65, low cost, dustproof and
waterproof hand held unit for reading down to 100 ppm.
• PurgEye® 200 with PurgeNet™ is our hand held,
rechargeable battery driven Weld Purge Monitor® for
reading very accurately down to 10 ppm complete with
electromechanical sampling pump.
• PurgEye® 300 Nano, the worlds first and only
super low cost, entry level, mains power driven Weld
Purge Monitor® measuring accurately down to 10 ppm.
• PurgEye® 500 Desk with PurgeNet™ uses an internal electromechanical pump to draw
the gas across the sensor. It also has the switching capabilities and the PurgeLog™ Software.
• PurgEye® 600 a computerised, touch screen model measuring very accurately from
atmospheric level down to 10 ppm, with high and low oxygen level switching capabilities, data
capture via USB using PurgeLog™ software for recording purging results for subsequent
evaluation and provision of a quality control document.
• PurgEye® 1000 monitor with PurgeNet™ has been developed for those instances where
the measuring point is more than 20 metres away from the monitor. The slow time for the gas to
travel and reach the sensor and the contamination of actual reading that can take place inside
the gas tube, leads to serious delays and erratic readings.
• PurgEye® 1500 Site with PurgeNet™, designed and manufactured in a robust, virtually
non-destructible case, perfect for dusty, hazardous, on-site conditions, measuring oxygen levels
from 1,000 ppm down to 10 ppm. IP68 rated with the lid closed.
What is PurgeNet™?
PurgeNet™ controls the welding power sources such as orbital welders and any other automatic
welding systems to switch on and off according to 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 Traffic Light System, which
gives a visual warning during welding in case of rising of falling oxygen levels.

6 HFT® NEWS

HFT® NEWS

Latest News Headlines from HFT®:
ILnadrugsetryInflatable Stopper for the Offshore

A 52’’ Inflatable Stopper manufactured by the
Pipestoppers® Division.
Technical Sales Manager for HFT®, Luke Keane
said: “This large Inflatable Stopper was manufactured
specifically for an offshore application.”
The 52” Stopper was manufactured with a special heat
resistant covers to protect it against high temperatures
of up to 300ºC (572ºF), ensuring the Stopper is not
damaged when exposed to high temperatures.”

Sizewell C Consortium
Huntingdon Fusion Techniques HFT® are proud to announce that we are a part of the Sizewell C
Consortium.
CEO Managing Director for HFT® Georgia
Gascoyne said: “We are excited to be part of the
Sizewell C Consortium.
This is a group of businesses that are behind
getting Sizewell C constructed, lobbying the
government and ensuring that the majority of
services, goods, supplies are procured from UK
businesses.”
We are very much looking forward to getting
involved.
1.

CALENDAR: EVENTS IN THE INDUSTRY

Postponed to 2021 - Date TBC Tube WIN Eurasia
OSEA 2020 7 - 11 December 2020 10 - 13 March 2021

24 - 26 November 2020 Düsseldorf, Germany Istanbul, Turkey
Marina Bay Sands, Singapore

Fabtech Adipec TechniShow
13 - 16 September 2021 8 - 11 November 2021 March 2022
Netherlands
Chicago, USA Abu Dhabi, UAE

PRODUCT NEWS 7

REPLACE CERAMIC BACKING TAPE FOR SUPPORTED WELD ROOTS

Luke Keane®, Technical Sales Manager for Huntingdon Fusion Techniques HFT® said: “Achieving
clean welds is easy with Argweld® Weld Backing Tape® available up to 600 amps. Weld Backing
Tape® with help protect and support the backside or under side of the joint during welding.”
Suitable for stainless, carbon, duplex and chrome steels, as well as other reactive alloys, Weld

Backing Tape® is used for manual and
automatic welding. It can help achieve
higher welding speeds and dramatically
reduce the amount of post weld cleaning
required.
Each tape consists of a 3” (75mm) wide
aluminium adhesive tape, in the centre of
which is a 1” (25mm) wide band of woven
glass fibre. The glass fibre matting has
differing thicknesses to match the welding
current in use.
Save gas and down time with the simple
addition of Argweld® Weld Backing
Tape®.

EASY PIPE WELDING

Typically for closure welds, tight bends, T piece joints and dome end connections where a conventional
Tandem Weld Purging System cannot be used, a range of low cost, single ended Inflatable Weld
Purge Dams is available for pipe diameters from 6 to 88 inches (150 mm up to 2,235 mm).
Weld Purge Dams from Huntingdon Fusion Techniques HFT® offer a great, lightweight solution
where access is difficult, are easy to inflate and heat resistant up to 80oC (176oF).
Ron Sewell, Chairman at Huntingdon Fusion Techniques HFT® said: “Even today, many companies
are still allowing their technicians to spend many hours fabricating temporary dams made of foam,
cardboard, adhesive tape, wood and so on. Like paper, these materials contain a high percentage
of water, which is very undesirable to have in the presence of a weld.
“As these old fashioned, poor quality dams and
materials are warmed by the welding operation,
they start to outgas their water vapour, which starts
to circulate around the weld joint and combine
with the weld pool to cause porosity and oxidation,
leading to metallurgical defects.”
Each of the HFT® Dams are made of low vapour
pressure materials specially selected for optimum
weld purging results to provide the lowest quality
oxygen reading in the fastest possible time with the
minimum use of expensive argon gas.

8 PRODUCT NEWS

WELD PURGING WITH PREHEAT

In the power generation and nuclear industry,
low and medium alloy steels such as SA 213
T91 and SA 335 P91 are chosen for their high
strength, but are often prone to cracking during
welding. Pre-heating and post-heating reduces
the crack sensitivity.

In order to meet the requirements of inert gas
purging when temperatures exceed 200ºC
(392ºF). The use of purge systems capable of
withstanding such high temperatures for lengthy
periods is necessary

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.

Ron Sewell, Chairman for HFT® said: “We are the only manufacturer that has studied materials and
designed products suitable for use in weld purging at the high temperatures required during pre- and
post-heating.”

“The inflatable seals at each end of HotPurge® systems are manufactured from flexible, yet thermally
resistant materials and the central collar is also
temperature resistant.”

HotPurge® systems are manufactured in sizes
6 to 88” (150 to 2,235 mm) and 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.

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.

PRODUCT NEWS 9

PurgEye® 1000 Remote

Weld Purge Monitor® with PurgeNet™

Monitor Your Weld Purge at a Distance

Scientific Developers of
Weld Purging Technology and

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

www.huntingdonfusion.com

10 TECHNICAL ARTICLE

SEVEN TIPS FOR WELD PURGING

Effective weld purging is only achieved by making sure that oxygen is displaced from the purge zone
prior to and during welding. Any residual oxygen can cause significant loss of corrosion resistance
and a reduction in joint strength. It is therefore essential to seal the pipe either side of the joint and
maintain this seal throughout the process. The residual level of oxygen in the purge zone needs to
be consistent with the welding procedure so continuously monitoring to ensure compliance is crucial.
1 Choose a dependable sealing material
The cheapest is seldom the best so examine the options available.
Don’t be tempted to use sealing discs made from polystyrene foam, wood and cardboard - at best
they leak or emit contaminants and at worst they catch fire during the hot weld cycle.

Fig 1. These examples from the QuickPurge® 1 range are
representative of proven purge systems. They employ
components made from materials that are stable, thermally
resistant, durable and non-toxic. They cover the entire pipe
size range between 150 and 2400 mm diameter giving an
effective seal in each case and a low purge volume.

2 Use a complete purging system
Don’t try to economise by making use of whatever happens to be around at the time. Separate seals
for the pipe and rubber tubing for the inert gas, all held together with bits of tape seldom succeeds.
Invariably this is time consuming and can only be used once.
Find systems using inflatable dams. Commercial equipment is now available in which gas flow
and pressure and purge gas quality are all pre-set. Complete monitoring instrumentation can be
incorporated to ensure a high level of quality control. These systems have been designed for multiple
use and are rugged enough to cope with site conditions whilst still reducing overall purging and
welding time very significantly.

Fig 2. These PurgElite® 1 systems employ the latest advances
in technology and are fully integrated to keep purge times and
cost to a minimum. Sizes between 25 and 600 mm diameter
are available. The hoses are completely flexible and allow the
systems to transverse 90º bends.

3 Establish what level of oxygen in the purge gas is acceptable
There is plenty of published information available that establishes what the maximum oxygen content
needs to be to prevent loss of mechanical and physical properties in the weld. This depends on the
material being welded but generally, some stainless steel welding requires a low level whereas most
carbon steels are much less sensitive.

TECHNICAL ARTICLE 11

4 Take care with gas flow
Whatever system is selected ensure that the inert gas enters gas slowly. Argon is heavier than air
so introduce it slowly at the bottom of the weld purge space and discharge from the highest point.
Helium is lighter than air and needs to be inserted at the top of a cavity and removed at the base.

Fig 3. Inflated system in place showing gas flow.

5 Don’t rush into the welding sequence
Wait until all the air has been displaced before welding. For many metals this means ensuring a
residual oxygen level below 100 ppm.
Traditionally, and a practice still followed even by major fabricators, this is based a pure guesswork.
If the oxygen content is too high, or varies during welding, oxidation occurs and this often means
rejection with the expense of re-machining, and therefore production delays. It can also lead to loss
of corrosion resistance in stainless steels.
6 Use a purge gas oxygen monitor
Don’t assume that allowing ‘plenty of time’ for purging to remove all the oxygen. If there are leaks
in the system, turbulence or simply poor quality purge gas then oxygen levels could be way above
those necessary to prevent contamination. The best solution is to use a device capable of accurate
and reliable measurement of oxygen level.

Fig 4. Purge gas oxygen monitor. These instruments
have been specially designed for rugged use during
site welding and can measure oxygen content as low
as 10 ppm. They may be hand held, desk mounted or
boxed for “ON SITE” use.

7 Read published information about purging
There’s plenty of it and examples are shown below. Learn from the experience of others rather than
using trial and error methods that could cost time and necessitate re-welding.
References:
Argweld products from www.huntingdonfusion.com
Developments in weld purge gas oxygen monitoring technology. Stainless Steel World. March 2015.
Guide to weld discoloration levels in stainless steel. American Welding Society. AWS D18.2:1999
Choosing an effective weld purging technique. Stainless Steel World. May 2013
Danger of Corrosion when Welding Stainless Steel Food Safety Magazine Digest Nov 2014 www.
foodsafetymagazine.com
Major Advances in Weld Purge Technology World Pipelines 2014
Latest developments in weld purging www.energyglobal.com

Weld Purge Film®

Successful Low Cost Weld Purging

Scientific Developers of
Weld Purging Technology and

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

www.huntingdonfusion.com