Butt weld ball valves and maintenance
Butt weld end ball valves are welded permanently into the line, so they are normally 3 piece designs: the centre body can be unbolted and swung out to replace seats and seals without cutting the pipe. Remove the centre body or seats before welding the end caps, as PTFE seats will not tolerate welding heat.
See the 316 stainless steel 3 piece butt weld ball valve, the BV-L3000 range and the BV-L8000FS heavy duty range, and read 2 piece vs 3 piece ball valves for more on construction.