Webcast Weld Purging 2011 Ten best Practices

Webcast

Weld Purging 2011

Ten best Practices

ARGWELD ® Weld Purging – Ten best practices 2

1.0 Monitor Oxygen Content to save time and prevent bad welds

3.0 Use the correct materials for best purging results.

2.0 Enclose purge volume tightly

4.0 Introduce purge gas slowly at the bottom of the purge zone

5.0 Don’t start welding until the oxygen level has reached the value you need

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7.0 Cleanliness is critical to obtain a good weld purge

10.0 Avoid supply pipe leaks to prevent air getting into the purge lines

8.0 Purge tack welds to stop contamination of main weld pool

9.0 Use a high quality purge gas

6.0 Keep purge gas flowing until temperature has fallen below the

oxidation level



Don’t guess at weld purge time. Monitor it continuously.

Guessing can be time consuming and unnecessarily expensive.

Guessing can lead to

weld rejection.

Use a Weld Purge Monitor™



A PurgEye™ 100 Weld Purge Monitor will cut waiting periods enormously

and ensure weld quality.

The small cost of the instrument often provided payback in less than one

weld



Continued:

PurgEye™ 100, the 21st Century Weld Purge Monitor™ to ensure your welds

are made efficiently saving you money on every weld.

Push button calibration at atmosphere and the lowest oxygen level


2.0 Enclose the volume to be purged as tightly as possible with good materials

Reducing the volume to be purged will save you money.

The best product for confining the weld

zone must be chosen to match the

conditions ie level of cleanliness,

amount of heat generated,

length of time that heat is present

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Continued:

2.1 For tube and pipe welding - Inflatable Pipe Purging System Range

Simple inflatable systems

Heat resistant systems for

chrome steel pipework

HFT designed and developed

Argweld® Quick Purge™ range

2.0 Enclose the volume to be purged as tightly as possible. 8

The HFT concept of two inflatable dams placed either side of

the weld has proved to be the system of choice over a 35 year

period. Using in house advanced technology, HFT has

continued to develop designs and the use of low outgassing

rate materials to prevent weld contamination.

This ensures that the job is done quickly saving time and money

Inflatable system at either

end of a lobster back assembly

Don’t use makeshift devices,

use the proper tools for the job.


Continued:

2.2 For aerospace component and medical device welding

low cost welding enclosures are available

2.0 Enclose the volume to be purged as

tightly as possible

9

Components inserted using the wide opening zip

Enclosures can be collapsed to squeeze out residual air

Purging goes quickly down to 10 parts per million


3.0 Select materials carefully and wisely

Check with experts whether your materials are going to be acceptable for

the duty, allowing for heat generated, gas temperature, volume and

surface area etc

All materials have a vapour pressure and give off harmful gases into a weld

zone

Or choose ready made products that have been designed with these

scientific conditions in mind.



Paper is not good for a

weld purging environment

Provisional Dam Systems

ARGWELD ® Inflatable Pipe Purging Systems 11

Sponge or foam is very porous and

contains masses of air pockets that

contain water vapour as well as

oxygen

These materials should not be used!



Paper is not good for a

weld purging environment.

It has a high percentage of

Water and fibres that clog

filters



Water soluble weld purge film.

Transparent so that you can

see the weld root clearly


4.0 Introduce your purge gas slowly in the right place.

Helium is lighter than air and needs to be inserted at the top of a cavity.

Argon is heavier than air. Introduce it slowly at the bottom of the weld purge

space

The exhaust port should be at the highest point when using Argon.

(lowest when using Helium.)

Residual air will be pushed out of the exhaust, from where it can be

measured with your PurgEye™ Weld Purge Monitor™

By introducing the gas slowly and avoiding turbulence,

you will save enormous volumes of weld purge gas and

the costs resulting


4.0 Introduce Argon purge gas slowly and at the bottom of the purge zone created

A typical inflatable purge dam system


5.0 Wait until the oxygen level has stabilised at the reading you need

before you start to weld. Usually less than 0.1%

Today, welders no longer have to guess at the oxygen level, or use

archaic methods such as the extinguishing of a flame when the oxygen

level falls.

They can use a Weld Purge Monitor™

No more canaries in the box at the

end of a pipe to go to sleep when the

oxygen level falls


5.0 Wait until the oxygen level has stabilised at the reading you need

before you start to weld. Usually less than 0.1%

PurgEye™ 100 – atmosphere to 0.1%

PurgEye™ 300 – atmosphere to 10 ppm

PurgEye™ 500 – atmosphere to 10 ppm

with integral pump

For stainless steels, duplex steels, Titanium, Nickel alloys and other reactive metals


6.0 Keep the purge gas flowing until the material has cooled sufficiently.

Don’t stop the weld purge gas when the weld has finished !

Wait until the weld zone has cooled below the oxidation temperature.

Waiting that extra few minutes might save you days of work, cutting out a

badly oxidised weld for example

USING PROVISIONAL DAM SYSTEMS

19

Weld appearance when gas

shut off prematurelyWeld with longer wait period

6.1 Keep the purge gas flowing until the material being welded has fallen

below the oxidation temperature


7.0 Cleanliness is critical in obtaining a good weld purge

Before two components are placed together for tack

welding,

ensure that the area around the joint has been

thoroughly cleaned from machining fluids, finger

greases, grinding dust and any other contamination.


8.0 Purge tack welds to avoid contamination being dragged into the main weld pool

Even lightly oxidised tack welds allow the

oxidation to be dragged into critical weld pools

and contaminate them.

Tack welds must be clean.

The weld purging system may need

to be in place prior to tack welding


9.0 Use a quality Purge gas

Ensure the right quality of purge

gas is ordered, delivered and

connected

Use your PurgEye™ Weld

Purge Monitor to check gas

source before connection


10.0 Purge Gas leaks eliminated

There are many specialised fittings for making

leak tight joints in gas tubing for weld gas purging

lines

Check purge gas lines to ensure that there are no leaks

Leaks will draw air (Oxygen, Nitrogen and water vapour)

Into the weld zone


Thank You

2011

All photos courtesy of Huntingdon Fusion Techniques Limited, UK.

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Webcast Weld Purging 2011 Ten best Practices