April Newsletter

VOLUME 28 NO. 4

Volume 28 No. 2 of Gem Memo published 2 months ago was devoted to the effort this company was making (and still is) to upgrade fryer piping systems.  Changes made include using seamless pipe instead of welded steel pipe for all carbon steel fryer piping, upgrading welding and use of viewers and a camera to inspect welds from inside the pipe up to 20 feet from the nearest opening.  It was also reported that a materials testing lab had recommended use of corrosion resistant (stainless steel) filler wire for the root pass on carbon steel pipe.  At the time this was written, weld tests had been performed, leading to the conclusion that the stainless steel root pass was going to be a viable alternative for welds on carbon steel pipe. 

Unfortunately, further testing revealed that it was very difficult to control the weld process using stainless steel wire.  A good weld surface could not be consistently produced inside the pipe.  In addition, using stainless steel filler wire for the root pass requires more heat to achieve a satisfactory weld surface.  Since corrosion often occurs in the heat effected zone, addition of more heat could be counterproductive.  Fryers have been observed after several years of operation, that had a pipe weld heat effected zone corroded to the point of failure with the weld still intact.  As a result of these tests and observations, fryer piping welds will be made using carbon steel filler wire.  It does appear, however, that stainless filler wire is a viable alternative for welds on the fryer return ducting.  The return ducting is rectangular and the material is thinner than the piping.

The welds on a duct are straight and can be made in the same position for the full length of the weld.  A vertical weld on a horizontal run of pipe, forces the welder to continuously change position as he welds around the pipe.  And if that isn’t tough enough, part of the weld is overhead.  Another way of stating this is that when he is welding at the bottom of a horizontal pipe, the welder has to place hot metal into the weld from underneath the weld.  On smaller sections of piping, overhead welding can be avoided in the manufacturing plant by using a weld positioner, which rotates the pipe avoiding overhead welding.  Since the pipe can’t be rotated for making large weldments in the plant and most pipe welding in the field,  overhead welding is part of the job.

One other area had to be upgraded.  For at least half a century, where a header pipe was feeding several spray pipes, holes were cut in the header to accommodate the outside diameter of the spray pipes, which were normally smaller diameter than the header.  A fillet weld fastened the spray pipes to the header.  The disadvantage of this approach is that it is impossible to get a satisfactory root pass with this configuration.  Not having a satisfactory root pass provides an opening on the inside of the weld that will furnish a protected area for corrosive clean-up chemicals to start their dirty work and cause premature failure.    Gem Equipment will not use this approach in the future for carbon steel fryer piping.  Either pipe fittings will replace the drilled hole or the job will be set up so the root pass can be made from inside the pipe