Welds sweating
Welds sweating
(OP)
We have a carbon steel vacuum tank with stainless steel and carbon steel connections. Under a high vacuum condition we have witnessed the carbon-carbon welds and HAZ "sweating". The stainless-carbon welds do not exhibit this same phenomenon. The welds are fillet only and FCAW. Has anyone had a similar experience? What could be causing the sweat?
Thank you.
Thank you.





RE: Welds sweating
RE: Welds sweating
The tank is empty. Is is simply under high vacuum, ~50 microns, and is sitting at room temperature.
RE: Welds sweating
Could this be cooling from expansion at a nozzle entering the tank? If not too hot feel the line and tank for a quick comparison.
Adding to this is the tank normally cooler that the surrounding area?
To check for any physical problems a quick test during a period of sweating is to wipe the sweat off and quickly apply some Dye Penetrant Developer or if not available some chalk dust like that used in chalk line.
RE: Welds sweating
http://www.welding-advisers.com/
RE: Welds sweating
Things have evolved somewhat in that I was told the welds in question were actually phisically colder than the surrounding metal. This would explain the localized condensation. As things stand right now the sweating has stopped and we have reached some kind of steady state condition.
So now my question has changes to "what would cause carbon steel welds, subject to full vacuum on one side, to be phisically colder than the surrounding material?"
RE: Welds sweating
(Just a thought.......maybe ????)
RE: Welds sweating
You may be quite right as the phenomenon has not returned. I suppose that the HAZ would be also affected by the colder weld metal.
We will be building more of these tanks so I will keep my eyes open and let you know if similar issues come up.