Shield Gas Contamination

By sloppyjoe86 Date 02-18-2005 17:41

We run 90Ar/10CO2 at our facility. This mixture is supplied throughout the plant from a bulk tank. We believe that we may be getting air in the mixture at the point of use in some of our robot cells. We have a Thermco Model 6900 portable gas analyzer that is capable of giving us a percent Argon and CO2, but does not take into account any air that may be entering through holes/leaks in the gas line plumbing. What is the easiest/best way to verify whether or not we are getting air in our gas mixture?

By ajoy

Date 02-24-2005 06:01

Dissolved oxygen meters are available. They are easy to use and capable of detecting oxygen from 0.01 % in the gas mixture. They generally find application in checking the purging gas composition during welding of exotic alloys like super duplex ss or inconel etc.

By backpurge (*)

Date 02-26-2005 16:35

You could check the actual gas mix using a purge atmosphere monitor as has been suggested, Dansensor do one that goes down to 1ppm or why not carry out a pressure drop test on the pipeline to check for leaks. If air can get in the shield gas can get out.

The other thing that could cause the problem is the material any flexible hoses are made from, most are permeable to some degree or another