Wash pass!
Wash pass!
(OP)
Can you describe to me? And which the purpose?
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RE: Wash pass!
RE: Wash pass!
RE: Wash pass!
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Plymouth Tube
RE: Wash pass!
RE: Wash pass!
I think the term wash pass originated in the early days of TIG welding when it was being groomed for welding SS. In the early days Heliarc (He Shielding) it was almost a universal requirement to use only stringers. This was a carry over form SMAW weld procedures that only allowed stringers. It was almost given that a good welder would use a wash pass to even out the stingers in the cover. This practise ended when a figure 8 weave was allowed in TIG welding. This happened almost simultaneously with the change to Ar shielding.
The term wash pass was also used with SMAW welding of SS when stringers were the norm. The flux on the electrodes was normally Titania based which only made pretty welds in the hands of a very skilled welder. TIG welding of the root pass wasn't allowed so when you put in a root and hot pass it generally wasn't pretty so the weld availed himself of a TIG rig and smoothed out the existing weld.
A wash pass was also used to to correct the root of welds where one has access to the backside of the weld.
A wash pass normally means that the arc is used sans filler metal.
RE: Wash pass!
In making heavy wall stainless pipe and tube we often weld with plasma (keyhole). This can leave a rougher weld than we want, so we use a 20-30% penetration TIG pass to re-melt the cap and smooth the weld.
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Plymouth Tube
RE: Wash pass!
My father in law said they used the term in the defense factories during WWII, in the '40's. Much the same reasons as you express as it was imperative that the welds 'looked good' for the inspectors...with all the implications that statement entails. I've worked a few gov't jobs and can attest to some of the tricks that I have seen.
I personally used the term for cleaning up open root welds when I was permitted to do so as far back as 1962, my Corp of Engineers test for the Atlas missile sites in NM. It's a crutch for bad welders, in most cases I am aware of, myself included. I was not very good when I started.
Rod
RE: Wash pass!
They got very good at 'wash passes'. They would basically do the minimum weld to hold the armour together and then make it look pretty. Idea being the welds would fail the first time it took a hit.
KENAT, probably the least qualified checker you'll ever meet...
RE: Wash pass!
This technique is used when welding brass or copper, to get enough heat into the part to start the weld, when you do not have a preheat torch.
B.E.