Progress,  page 61
May 2005
The seams around the edge of each roof section - where the parapet flashing meets the field
sheet - are welded with this "hair-dryer-on-wheels".  It runs off 220 volts and provides a stream
of hot air that melts the membrane and then rolls the seam together.  You can just barely see the
blade with the hot air at the bottom of the gray cyclinder on the side, just in front of the wheels.  
Both the temperature and the rolling speed are electronically controlled.  The membrane itself
has a tear strength of 7200 psi, and the welds are virtually as strong.
The seams at the corners and the tricky detail spots that can't be reached with the larger machine
get welded by hand.  The heat weld is essentially the same process, but it takes some experience
to get a reliable seam with the hand gun.  Our roof is rather complicated with all the various
sections and uneven parapet heights, so there is LOTS of detail work to be done.