A very interesting quotation from one of our Weld Purging Best Practices Group members has been posted.  This raises additional reasons for not using foam. Colin’s comments are: “Some pipe welding companies I’ve worked for buy in sheets of thick foam and the dams then have to be hand made (sometimes badly).” “The rubber seal type always give a better seal and are more durable to heat.” “Burning foam dams release fumes that are not healthy for a high purity weld or the welder. ” “More than once I’ve seen welders burn their hands whilst hurriedly removing a foam dam which had caught fire.” “Masking tape used in their place can often start peeling off whilst the welder is oblivious ” “Foam dams can fall out during welding – a real sickener when you lift your hood to inspect your work. ” Colin Sherriffs In addition to Colin’s comments,

• Foam is highly porous and will be full of voids containing air, water vapour and maybe even hydrocarbons that will outgas as the dams become warm from the welding process.
• There are return on investment charts available, showing how purging with modern products can save many thousands of dollars in gas costs on large stainless steel construction projects.

Typical modern Pipe Weld Purge System