Foam sponge in Weld Purging is widely used. To those people welding stainless steel for garden gates or other decorative applications, satisfactory is something where oxide discolouration has little to no importance.
On the other hand, those needing defect free structures or oxide free welds, there are different standards to be complied to.
The food and drinks, pharmaceutical, semiconductor industries are three of many that cannot permit discolouration or oxidation of materials or joints.
Discolouration and oxidation is caused by oxygen entering the molten weld pool or being in the vicinity of the heat affected zone.
This can only be prevented by the use of purging devices that can provide an atmosphere of 10 ppm oxygen or less.
This cannot be done by using foam sponge in weld purging as the material is porous and will allow oxygen and water vapour to pass through it to prevent oxide free welds from being produced.
When purging an environment such as a welding space in a pipe, the use of argon to push all of the air out, will effectively provide a vacuum of oxygen.
When there is a vacuum inside an enclosed space, the components confining that space will be under a pressure of oxygen from the air outside. If the confining components are not vacuum tight, they will allow oxygen to leak in.
Foam sponge is not vacuum tight so oxygen and water vapour will pass through it very easily, into the confined space and contaminate the weld.
Here at Huntingdon Fusion Techniques HFT® we have over 40 years of Weld Purging experience. We invest our resources and scientific knowledge to develop our products to the highest of quality.
For more information on our line of Weld Purging Equipment, please visit our website.
