Why should you use Inert Gas Purging when welding Stainless Steel, Titanium and Nickel Alloys?
Preventing oxidation and thus avoiding discolouration and weld underbead discontinuities in tubes and pipes can be achieved readily by purging the inside with inert gas. This simple procedure saves both time and cost, both of which can be considerable. Consider the thoughts of one specialist.
'It's difficult persuading our supervisors to allow us to take the time to purge lines during the welding process! Instead, engineers weld the lines, then use a die grinder with a flapper wheel to clean the "grapes" off the inside of the pipe! What an incredible waste of time.
Purging really makes more sense in the long run, especially since products going through these lines get snagged or contaminated.
The troubleshooting process is confused because the pipe fitter may not see the correlation, nor does the machine operator unless there is good exchange of information!'
Greg Godek - Integrity Piping Solutions Inc
What is Weld Purging?
It’s a way of using inert gas to stop oxidation and is most easily done by sealing the weld region, in the case of tubes and pipes, using inflatable tube and pipe purging systems. Other techniques are available - expanding plugs, tapes and membranes are often used. The sealed region can then be filled with argon or helium and this prevents contamination during welding.
Inflatable purging system technology has advance by leaps and bounds in the last few years with Huntingdon Fusion Techniques leading the way with highly innovative developments that help the welder produce sound joints quickly and free from the defects that arise due to oxidation in unprotected joints.
A new series of purge systems incorporating advanced polymers in the construction and specialised gas valve technology has now been introduced to cover pipe diameters as small as 25 mm (1 inch). This is the HFT ‘PurgElite®’ range.
The collapsed purge system is inserted into the pipe to be welded. When the selected inert gas is admitted the dams will first inflate to a preset pressure at which point the gas will be diverted into the purge volume. Gas flow will continue until the correct oxygen level is read by the Weld Purge Monitor®, the weld started and completed and then cooled sufficiently to safely withdraw the purge system. This will only lead to turbulence and this in turn entraps air, leading to poor weld production.
Have a look at confirmed gas and time savings:
|Inefficient and DIY devices
Purge time to 0.1% (1000 ppm) - 26 mins
Flow rate 24 litre/min (50 cu ft/hr)
|PurgElite® Pipe Purging System
Purge Time to 0.01% (100 ppm) - 3 mins 6 secs
Flow rate 10 litre/min (21 cu ft/hr )
This exciting extension to the HFT product range is the world’s smallest fully integrated purging system. It can be used in pipes and tubes with a diameter of only 25 mm (1 inch). The recent development has been made possible through the use of innovative low profile gas valves.
Huntingdon Fusion Techniques' Argweld® Quick Purge® flagship weld purging range, designed as a fully integrated solution to purging that offers the worlds fastest method of producing high integrity joints. This system covers the pipe range from 200 to 1800 mm (8 to 72 inches).
What are the alternative HFT weld purge products?
The HFT purge family is extensive and has been developed progressively during the Company’s 35 year history to meet the demands of it s customers. Details of these products are available as Technical Notes Nos TN–8 to TN-13. See also TN-15 covering purge monitors to measure oxygen content.