"Randy Zimmerman" wrote in message
news:Q01Ie.100937$5V4.49675@pd7tw3no...
Don,
You will find that the wrinkle bends whould be limited to 15 degrees
each.
To do a 90 you should have six wrinkles. I first stumbled on to
this
procedure in an old Union Carbide gas welding textbook. The
procedure works
with any size pipe and if you follow the 15 degree rule there is no
appreciable reduction in cross sectional area so fluids are not
restricted.
On really big pipe a com-a-long is needed to maintain bending force
as you
heat the pie section.
As you mention cooling off after each heat is necessary so that
you can
locate the wrinkle accurately.
Randy


I have a "Copper and Brass Pipe and Tube Bending Handbook", published
in 1954 by the Copper & Brass Research Association, that has 8 pages
of text, tables, and photos devoted to the subject of wrinkle bending.
Maybe I'll scan them and post to my personal page...