Tubes and pipes made from titanium, stainless steel, chrome/nickel steels are mostly required to be welded in a non-oxidised environment in order to achieve a metallurgically correct, zero colour weld. Best results are obtained by reducing the volume to be purged, with an inflatable Weld Purging System.
Leading the way in Weld Purging Technology, Huntingdon Fusion Techniques HFT® have developed PurgExtra®, for purging tube and pipe joints from 1 – 24” diameter that provide an extra gas purge hose to speed up the purging process even further.
Additional advantages of this design improvement are that the operator can use the extra purge gas supply for welding reactive metal joints in particular, such as those made from titanium and zirconium. In addition, the extra gas can be used for cooling welded joints faster than normal, where permissible.
Luke Keane, Technical Support for HFT® said: “The PurgExtra® Range complements the PurgElite® Series that has a single purging inlet and is more appropriate for stainless steel only. PurgExtra® however, allows the operator to purge at the recommended rates initially and then, when conditions are correct, to introduce the additional gas at high flow rates. This system is especially valuable for achieving the lower oxygen levels required for welding materials around 20 parts per million.”
When welding joints where interpass temperature control is necessary, PurgExtra® allows extra argon gas into the welding zone, helping to cool the weld zone dramatically. The extra gas also helps to remove the gases that are expelled by the outgassing, which occurs as the metal is being heated. The extra gas flow will prevent these expelled gases from combining with the hot metal and oxidising, which would otherwise cause the metal to discolour and lose its corrosion resistance and possibly introduce defects that would cause loss of joint integrity.
PurgExtra® comprises two inflatable dams connected by a heat resistant, highly flexible gas hose that has the unique IntaCal® gas release system. IntaCal® allows the dams to be inflated correctly and then releases the inert gas to safely purge the space between the dams. The low profile IntaCal® Valve replaces the old fashioned, bulky complicated valves and eliminates the need to make adjustments to flow rates.
The highly flexible spinal hose between the inflatable dams allows the PurgExtra® Systems to be pulled or pushed easily around bends and elbows. In the centre of the spinal hose a strip of RootGlo® material is adhered, allowing the welder to see clearly through the root gap, when the system has reached the correct position in the pipe. RootGlo® can be charged by exposing it to daylight for 10 minutes, after which it will provide up to 24 hours of bright illumination inside the pipe.
The innovative PurgeGate® Valve may be fitted to the PurgExtra® Systems as an accessory, to protect the inflatable dams from bursting due to accidental over pressurisation.
Heat Resistant Covers are also available for PurgExtra®, which fit onto the inflatable dams and allow operation with pre-heated and post-weld heat-treated pipe joints where the temperatures might reach 760°C.
The HFT® Weld Purge Monitors® are used to give precise oxygen values throughout the purging process.
Huntingdon Fusion Techniques HFT® are Weld Purging Innovators, Designers and Manufacturers with offices located globally.
Huntingdon Fusion Techniques HFT® invented the ‘Weld Purge Monitor®’ in 1975 and own all international intellectual property rights and registered trademarks.
Weld purging is the act of removing, from the vicinity of the joint, oxygen, water vapour and any other gases or vapours that might be harmful to a welding joint. Such gases may combine with the metal to form undesirable compounds that may reduce corrosion resistance or may be instrumental in creating cracks or other structural defects in metals.
Tungsten is a rare metallic element used for manufacturing gas tungsten arc welding (GTAW) electrodes. Tungsten Electrodes are available in a range of sizes and lengths and are made up of either pure tungsten or an alloy of tungsten and other rare-earth elements and oxides. Choosing an electrode depends on the base material type and thickness and whether you weld with alternating current (AC) or direct current (DC).
Each electrode is color-coded at the tip to eliminate confusion over its type. Unlike the red-tipped thoriated Tungsten Electrode, which contain 2% thoria, Huntingdon Fusion Techniques HFT®’s blue-tipped MultiStrike® Tungsten Electrodes contain a mix of non-radioactive rare earth elements, eliminating the risk to health posed by thoriated Tungsten Electrodes.
A customer in the UK recently said: "We have tested your MultiStrike® under production conditions where we need to make short lengths welds using the TIG process. On a batch of 50 components only 2 light re-grinds were required compared to 7 heavy regrinds when using thoriated electrodes. Even when the welder occasionally touched the work with the electrode there was no material change in performance whereas we would normally expect to have to re-grind. Better weld quality and finish was observed. We were particularly impressed with the health and safety aspects and have taken the decision to remove all thoriated electrodes from site."
MultiStrikes® can be used for welding aluminium with the AC process as well as steels and alloys with the DC process, which allows the welder to have just one type of Tungsten Electrode to weld all materials and reduce the amount of stocks and purchasing requisitions.
Other tungsten electrodes work at higher temperatures so their oxide additions (mostly radioactive) burn out, or evaporate much faster than those non-radioactive ingredients in MultiStrike®, so much so that they give at least 10 times more arc striking capacity of other tungsten electrodes, when tested under the same conditions.
With most tungsten electrodes in use still containing radioactive and carcinogenic 2% thorium oxide, MultiStrike® provide the TIG and Plasma welder with a safe and superior alternative.
Each packet comes with a traceability number to ensure that companies with a quality control procedure have traceability over another aspect of their joining processes.
MultiStrike® Tungsten Electrodes demonstration video is available at: https://youtu.be/bx1BeepVMaw
Huntingdon Fusion Techniques HFT® have a worldwide Exclusive Distributor network, which can be found at www.huntingdonfusion.com
Huntingdon Fusion Techniques HFT® are Weld Purging Innovators, Designers and Manufacturers with offices located globally
Weld Butts in Pipe Diameters up to 80” diameter can now be purged using the Argweld® QuickPurge®II Inflatable Pipe and Pipeline Weld Purging Systems.
QuickPurge®II Pipe Weld Purging Systems have been designed to dramatically reduce weld purging times and deliver bright shiny oxide free welds irrespective of the size and the volume of the pipe.
A central collar between the two inflatable dams reduces the volume to be purged to a small annulus.
Around the centre of the collar is a piece of ‘RootGlo®’ illuminating strip that allows operators to see the centre of the purging system. RootGlo® holds its illuminating charge for 24 hours after which it can be recharged simply by exposing it to daylight for ten minutes.
The PurgeGate® accessory is fitted to all QuickPurge®II Systems. PurgeGate® is a special device that prevents the purge gas input pressure to the Inflatable Pipe Weld Purging System from rising above 7.5 psi.
Even in the event that the gas pressure rises suddenly to 50 psi by error, only 7.5 psi can be allowed through to the inflatable dams so they are unlikely to burst due to over inflation.
Another new development from the HFT development team is the IntaCal®specially developed purge valve that does not need setting like previous systems.
So inert gas is fed into the PurgeGate® system which then passes through at 7.5 psi or less to the IntaCal® valve which allows inflation of the first dam, after which inflation of the second dam takes place before surplus purge gas is passed into the purge void to eliminate air from the trapped cavity.
Using a Weld Purge Monitor®, engineers can ascertain exactly when the amount of oxygen has been reduced to an adequate level for their applications.
Because of the low vapour pressure materials that have been selected for QuickPurge®II, it is possible with these System to reach an oxygen level of better than 10 ppm to ensure that bright shiny welds are created.
Even with this significantly reduced annulus having been designed, QuickPurge®II Systems are manufactured in sizes of 6” (150 mm) diameter and upwards to 96” (2440 mm).
Thick wall chrome steel pipe joints, as used in the power industry for high pressure high strength pipe work, need to be pre-heated for welding and probably need a post weld heat treatment too.
Weld joints of this nature need to be purged of oxygen and welded in an inert gas atmosphere, to prevent oxidation, slag formation etc., that leads to loss of corrosion resistance and undesirable change to the metallurgy.
With the high temperatures and length of time at temperature needed in the pre-heat, weld and post heat treat cycles, most weld purging systems are unsuitable.
However, Huntingdon Fusion Techniques, HFT®, has now developed “HotPurge™” Pipe Purging Systems, for use up to 300ºC (572ºF) for 24 hours. (The material used is rated up to 700ºC (1,292ºF)
HotPurge™ is based on the company’s world famous Quick Purge®II design that has been in wide use for many years, but adapted for use at high temperatures.
This system is available for pipe internal diameters (i.d.) from 4 – 96” (100 – 2,500 mm). Each Hotpurge™ is made to size and has a tolerance of +/- ½” (12 mm) because of the restrictions of heat proofing material.
Features of the HotPurge™
1.0 The central large collar that dramatically reduces the space to be purged and makes it easier to reach the lower oxygen levels faster.
2.0 Four pull handles are securely attached to each dam, secured with the Kevlar thread that will withstand a pulling force of 1.000 lbs on each handle.
3.0 The most stunning feature of the the HotPurge™ system is the PurgeGate® to prevent over inflation.
PurgeGate® is a clever, world wide patented invention that allows users to simply connect the Hotpurge™ system to any source of compressed inert gas and simply turn it on to whatever flow or pressure they wish.
PurgeGate® will protect the dams from over inflation or bursting and allow the user to deliver whatever flow they like, using the one gas source.
No matter how high the user raises the pressure in order to deliver more flow, PurgeGate® prevents the pressure going to the inflatable dams, but allows the increased flow to make a faster purge.
PurgeGate® is guaranteed for life.
HotPurge™ Pipe Purging Systems can be used over and over again for specialist weld purges on power industry piping, that will keep the oxygen levels below 100 parts per million throughout the welding cycle.
For a stainless steel pipe welding job with just under 17,000 joints from 6 – 36” diameter, it was found that a gas savings of almost 7 million litres of Argon were made, when comparing old fashioned weld purging products with modern day products like the QuickPurge® II System.
A return on investment document has been created showing savings, weld by weld, so that operators can extrapolate to make their own calculations.
With such dramatic savings, operators can apply their own Argon or Helium gas costs to assess the savings that they could make with the QuickPurge® II system.
The full ROI (Return on Investment) analysis document is available on request from Huntingdon Fusion Techniques Limited.
Coinciding with Fabtech 2013 in Chicago, Huntingdon Fusion Techniques (HFT®) is launching the most revolutionary Pipe Weld Purging System ever QuickPurge® II.
The original QuickPurge® concept was devised between HFT® and Mitsui Babcock just over ten years ago for the Isle of Grain stainless steel pipeline across the south of England.
Now, after the phenomenal success of this concept of weld purging, HFT® has added a whole new raft of improvements.
Probably the most significant development ever for inflatable weld purge systems is PurgeGate™. This extremely clever device will prevent the inflatable dams from ever bursting due to over inflation. In the real world of pipe and pipeline weld purging, operators come and go and the opportunity to read instruction manuals rarely arises. Technicians will therefore look at weld purging systems, assess how easy they think it is to use them and will inevitably over inflate and burst dams at some time or other.
Now PurgeGate™ eliminates this problem entirely.
No matter how much pressure or flow the operator puts into the system, PurgeGate™ will deliver the right amount, eliminating the need for setting up, trials and probably the bursting of dams at some time or other.
Low volume annulus
With new heat resistant materials, it has been possible to create a lower volume annulus between the inflatable dams, so that the space to purge has been further decreased leading to faster purge times.
Now with PurgeGate™ and the new heat resistant materials, welders can have their joint purged and ready for welding before welders with other weld purge devices have even finished their set-up procedure.
Extra Purge Gas Hose
QuickPurge® II sizes up to 20 inch diameter are provided as standard with three hoses.
- The inert gas inflation and purge hose (black)
- An auxiliary purge/exhaust hose (blue) and
- A 6mm polycarbonate tube (red) that can be connected directly to the Weld Purge Monitor®
For pipe diameters about 20 inch, the systems have:
- the inert gas inflation and purge hose (black)
- two auxiliary purge/exhaust hoses (blue) and
- a 6mm polycarbonate tube (red) that can be connected directly to the Weld Purge Monitor®
For weld purge readings that can be taken from the end of the QuickPurge® II system, the red tube on the Weld Purge Monitor® should be joined to the red tube on the QuickPurge® II by a single quick fit connection thus avoiding the leaks that are so common with other systems having to adapt connections and that lead to erroneous readings.
(The residual oxygen readings are mostly taken through the root gap using the manual pump connected to the Weld Purge Monitor®).*
As mentioned previously, HFT® has chosen new higher temperature resistant materials, for the annulus and ends of dam systems, that are heat resistant up to 700 ºC and the surfaces in contact with the pipe are now covered with a 50% heavier gauge of nylon making them tougher to resist tearing and giving good friction free travel characteristics when being pulled through pipelines and pipe assemblies.
All older and inferior yellow and red materials have now been replaced and the only genuine
QuickPurge® II Pipe Weld Purging systems are those with the grey and black materials.
Previously, there was only a small length of RootGlo® luminescent material placed on the topside of the Quick Purge systems for alignment purposes.
However, now with QuickPurge® II we have been able to place the RootGlo® material all around the circumference, to give welders the ability to align the QuickPurge® II system from any position around the pipe.
In addition this extra high degree of light allows welders to see all parts of the weld root through the remaining joint gap.
RootGlo® gives off its luminescence for up to 12 hours and recharges when in daylight.
Although the material is expected to last the life of the QuickPurge® II systems, if the performance does deteriorate, the RootGlo® material can be quickly and easily replaced.
Working hand in glove with PurgeGate™, IntaCal® produces the correct flow rate to inflate both inflatable end dams equally, offering a great improvement over earlier models where one dam inflates before the other, increasing the purge time unnecessarily.
As the operator turns on the inert gas supply valve to the recommended level or above, IntaCal® and PurgeGate™ deliver only the flow and pressure necessary for fast but gentle inflation and purging.
Each end of every QuickPurge® II system is fitted with four pull loops for precise positioning and pulling into position. Each loop is double stitched with high temperature, very strong Nomex thread that allows a breaking strain of 1,000 lbs (446 kg) per loop.
QuickPurge® II has been designed and manufactured with greater flexibility in mind. These systems can now be dragged around and set up in 90º bends, something that has been impossible previously.
QuickPurge® II joins the family of inflatable pipe purging systems, including the PurgElite® Tube and Pipe Purging range from 1 – 24” systems, the HotPurge™ inflatable pipe purging systems for pre-heated pipework, capable of resisting temperatures up to 700º C (1300ºF) for 24 hours and the Argweld® single ended inflatable purge dams.
This family of systems will typically be suitable for welding all stainless and duplex steels, chrome steel pipework such as P91 and P92 etc, nickel alloy pipework, titanium pipework and even aluminium and carbon steel when extra high quality is required from welded joints.
Ten years on, from the original development for the Isle of Grain, LNB pipeline, in August 2013, there was a call from a contactor working on the Isle of Grain LNG site, who had been suffering from the bursting of inflatable dams, from an inferior product supplied by a Welding Product reseller.
It seems that the LNG contractors there had stopped using HFT® systems and had brought cheaper copies from another Company.
As the cheaper supplier was unable to help with the problem, the contractor contacted HFT® who
sent a technician the next day with replacement product fitted with PurgeGate™.
Samples tested positive and the Company was thrilled with the addition of PurgeGate™ and is going to purchase from HFT® once again.
Interesting how a new demonstration has completed a circle after all these years from original design and supply to replacing a cheaper alternative.
* On the spot purge quality readings may be taken through the pipe root gap using a hand pump or a Weld Purge Monitor® with an electric pump.
Continuous, high quality purge readings can be made inside lengthy pipe runs at the immediate exhaust point using the ‘Torpedo’ unit attached to the Weld Purge Monitor® at distances up to several hundred metres if required.