3 Series Gas Saver Spares FAQs
Practical answers on choosing, fitting and looking after the individual parts of a larger gas saver torch set-up.
Can I mix parts from different torch series or from another gas saver set?
Usually not. Collets, bodies, insulators, back caps and cups are made to fit one particular torch series, and parts from a different series, or from a standard set-up without a gas lens, often will not thread together or seal properly. Even a part that seems to fit can leave a small gap that lets air into the shielding gas.
Match every part to the torch series given in the torch manual or marked on the old part. When several parts need replacing, changing them as a matching group is the safest way to avoid mismatches.
What does the heat shield (insulator) do, and when should it be replaced?
The heat shield sits between the gas lens body and the cup. Its main job is to help seat the cup and seal the joint so shielding gas cannot escape or air be drawn in, and a missing or wrong insulating part can contaminate the shielding gas. Check the torch manual for exactly what it does on your torch.
Torch makers list separate heat shields for standard, short and large diameter gas lens set-ups, so they are not normally interchangeable. Inspect it whenever you change the cup, and replace it if it is cracked, crumbling, distorted or no longer seats the cup firmly, because a poor seal can let air into the gas.
How do I choose between short, medium and long back caps?
Back cap length is mainly about how much tungsten you need to fit and how much room you have behind the torch head. A long cap takes a full-length electrode, a medium cap is a general-purpose compromise, and a short cap helps in tight spaces but usually means the tungsten has to be cut shorter so that it fits.
Caps are made for a specific torch series, so match the series first and then pick the length. Whichever you choose, check that the cap has its O-ring and that it tightens fully without forcing.
Why does a back cap have an O-ring, and how do I know it needs replacing?
The O-ring seals the rear of the torch head so shielding gas cannot leak out and air cannot be drawn in. Heat and repeated tightening and loosening can make it dry out, crack or flatten.
Signs include a visible crack, a flattened or pinched ring, or porosity and discolouration in the weld that you cannot trace to gas flow, draughts or cleanliness. Use an O-ring that matches the cap and torch series, check that the groove is clean, and seat the ring so it is not pinched as the cap goes on. If in doubt, fit a new O-ring whenever you replace the back cap.