If the arc wanders and you believe arc blow is the culprit, wrap the welding lead around the part several times and use DC at high amperage. Polarity can be switched if the arc blow isn't diminished. The polarity of AC can be switched by reversing the cables at the welding machine terminals.
Sugaring on the root side of the weld is due to "burning out all the carbon" thus weakening the metal. Corrective action on the part of the welder is to blacken the root surface (if accessible) with an acetylene flame after back grinding and rewelding over the carbon black. The carbon will be drawn into the arc and alloy with the decarburized base metal.
Titanium welds that are discolored (straw to blue) should be wire brushed before the inspector sees it. The resulting silver weld is better than new.
Hydrogen is a figment of the inspector's imagination. If you can't see it, taste it, smell it, or feel it, it doesn't exist. If the inspector throws a hissy fit, burn the "hydrogen" out with the next weld pass.
Any metal can be welded in a pinch with stainless rod if there is enough nickel in it. Even titanium.
As the number of the stainless steel alloy (304, 308, 309, 310, etc.) increases, so does the chrome content. You can tell if the metal is stainless steel if the magnet won't stick to it and it is shiny. But if it isn't heavy, it is aluminum.
All metals should be preheated to drive out moisture. This includes all steels, titanium, aluminum, etc. The preheat temperature is job dependent. You never know what it will be until you start heating the metal up. You can stop when the water stops bleeding from the pores. You'll know when it hot enough. Preheating should be completed just before morning coffee break so that it will be ready to weld when the break is over. Preheating is not required if it is a hot day or if the boss is in a hurry. Preheating is never necessary before tack welding.
When in doubt, always call for X-ray. If the weld doesn't pass X-ray, do some research to find a code that isn't as stringent. If it still won't pass, get the owner to declare the weld to be non-structural.
When purging pipe, purge long enough to feel the gas come out of the pin hole. Taping open root joints is wasteful of argon and is not necessary. A good gas filter is required with argon purchased in high pressure cylinders and bulk liquid tanks to remove all lumps and foreign materials.
There is no such thing as an excessive root opening. A wider backing bar will fix it. When a backing bar is not available, any piece of metal will do. Extension tabs are a waste of time, material, and money.
Most welding inspectors don't know jack about welding. When a weld is rejected or if the inspector tries to tell you to do something that is different, challenge him to show you how to weld it. That will shut most of them up. You can always use the argument that the engineer is overly conservative and nothing you've welded has ever broken before. That's why there are safety factors built into the design codes.
At least the turkeys can breath a little easier for a couple of weeks even if the Farm Code inspectors can't.
Best regards - Al