Can you weld stainless pipe without purge?

Yes, it is possible to weld stainless steel pipe without purging, but it comes with significant challenges and is generally not recommended for critical applications. Purging is a common practice in welding stainless steel to prevent oxidation and ensure a high-quality weld. However, there are some techniques to weld without purging:

Using Backing Gas Tape: A backing tape with an adhesive strip can be applied to the backside of the weld. The tape contains a strip of metal, usually aluminum, that provides a backing surface to prevent oxidation.

Solar Flux: This is a compound that can be applied to the backside of the weld area. It forms a protective layer that reduces oxidation.

Welding in a Controlled Environment: Performing the welding in an inert gas environment or using a trailing shield can help minimize oxidation without purging the inside of the pipe.

Short Welds: For very short welds, the time of exposure to the atmosphere can be so brief that oxidation is minimal.

Weld Seams: Carefully positioning the weld seams so that they can be welded with minimal exposure to air can sometimes allow welding without purging.

However, these methods may not provide the same level of protection as purging with an inert gas like argon, and the quality of the weld might be compromised. For critical applications, especially where corrosion resistance and mechanical strength are paramount, purging is strongly recommended.