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Up Topic Welding Industry / Technical Discussions / Measuring the dew point at the welding source.
- - By Tevis Date 11-06-2015 02:26
Got a question regarding dew point. I have a customer with a specification requirement to measure the dew point at the source (welding torch).
Anybody familiar with this and how do you do it? The process is GTAW using Argon as a shielding gas.Thanks.
Parent - By fschweighardt (***) Date 11-06-2015 19:43
Use a PPM moisture analyzer, you can make an adapter to screw into the head of the torch and run the gas down to the analyzer.  Its way tougher with GMAW, as there is not a real good way to capture the gas at the end of the torch.  I have an adapter here somewhere.
Parent - - By jd369 (**) Date 11-26-2015 12:20
Instead of measuring dew point is there an allowance to use titanium strike test? We were allowed to demonstrate the argon quality using titanium strike plates at the end of each argon line in the plant.
Parent - - By Lawrence (*****) Date 11-27-2015 14:28
Hey JD,

Please say more about titanium "strike plates" and the procedures you brought up.

Never heard of it, and a Google search just links to gun stuff :(
Parent - - By 803056 (*****) Date 11-28-2015 18:49
We used to refer to the piece of scrap as a "getter". The idea was if the purge was inadequate the weld would discolor.

Parent - - By Lawrence (*****) Date 11-28-2015 19:28 Edited 11-28-2015 19:34
That is exactly what worries me about a titanium "getter" or GTAW "Strike Plate"

The amount of oxygen, or nitrogen for that matter, it takes to render a titanium weldment rejectable via embrittlement through the entire thickness of the weld can be introduced with the color of the weld face remaining perfectly silver or any of the other shades that are used to judge titanium..   This does not even take into account the phenomena of "Alpha Case" layers at the surface and root.

All these words meaning; the color of a titanium strike plate, provides zero quality assurance if the weldment is actually titanium.

So shortcuts for gas purity testing are resisted for very good reasoning in my opinion when exotics are being joined.  Those extra steps in process control are pretty much a requirement if a higher level of gas purity is stated in the controlling documents or standard practices by the OEM.

Back in the 1990's In Everett Washington, the Boeing titanium tube shop would keep a constant 2 CFH running through their GTAW torch lines even during scheduled downtime, feeling that the risk of moisture or atmospheric contamination warranted such an expensive countermeasure.
Parent - - By 803056 (*****) Date 11-28-2015 20:31
I should have mentioned the welding was being performed in a plastic bag.

The purity of the gas supply and purity at the torch has little to do with the purity in a chamber. If the chamber is contaminated, the weld is likely to be contaminated.

Parent - - By Lawrence (*****) Date 11-28-2015 21:19
Even so Al,

If titanium is the base metal in question...

Would not could not In a bag,

Would not could not with a box,

Would not could not with a fox,

Would not strike test here, Would not strike there, would not strike test anywhere :)

Gas surrounding molten Ti can produce perfect color and still make a brittle weld... That is the thing that should strike fear into your heart.
Parent - - By 803056 (*****) Date 11-29-2015 00:51
You lost me.

Parent - - By waqasmalik (**) Date 04-22-2023 16:09
Then how to measure the dew point at the place of welding?
Parent - By 803056 (*****) Date 04-30-2023 03:42
Good question Waqas.

Up Topic Welding Industry / Technical Discussions / Measuring the dew point at the welding source.

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