October Newsletter

VOLUME 27 NO. 10

Look underneath most old carbon steel fryer kettles and you will see chunks of black polymer.  This polymer is a product of hot frying oil reacting with air at elevated temperatures to form the polymer.  Wherever the polymer is visible, at one time there was a leak.  There is a very good chance that this leak was the result of corrosion, which was probably caused by clean-up chemicals.  For many fryers the first step of the clean-up cycle is to circulate a caustic solution through the system to clean out oil, carbon and any other unwanted material present.  Next, an acid solution is circulated through the system to neutralize the caustic, followed by fresh water to flush out the acid.  Because of concern that the acid may be the major contributor to the corrosion, some plants have stopped using the acid.  There is one other contributor to this corrosion.  Usually the corrosion starts in a pin hole, crack or some other depression that retains a minute amount of corrosive clean-up chemicals after the clean-up cycle is complete.  The corrosive material reacts with the metal until the clean-up chemical is gone.  While not much metal is removed in each cycle, after a few years enough metal can be removed to produce a leak.  With the frying oils used until recently, this was not a very big problem.  The polymer that formed plugged the hole.

Unfortunately, some of the healthy oils being used today do not form a hole plugging polymer.  This is probably only one of the factors that is placing more emphasis on manufacturing frying systems that are less likely to leak.  For several years this company has been putting more effort to produce fryer kettles that are less likely to leak.  Since most kettles can be manufactured in a sequence that allows inspection of both inside and outside the weld, this effort has produced positive results.  Until recently, Gem Equipment had no way of inspecting welds inside a pipe that were very far from an opening.  Recently this company obtained optical devices that allow welds located up to 20 feet from the nearest opening to be inspected from inside the pipe.  Gem Equipment’s new standard is that all welds on fryer piping will be inspected from both inside and outside.  So far 3 Gem employees are approved to perform final inspection of fryer piping welds.  Each one has more than 20 years experience with this company. 

Their experience has developed the knowledge to qualify these 3 to evaluate the finished welds.  Ideally, the weld inside frying system piping should have exactly the same inside diameter as the inside of the pipe. It must be free of pinholes, cracks and any other topography that would allow minute pools of corrosive liquids to remain after clean-up.  Proper welding procedure will assure relatively smooth welds without pinholes and cracks.  Producing a weld with a diameter exactly the same as the inside diameter of the pipe is not quite as achievable.  In practice, the welds will be allowed to intrude up to 1/16 inch inside the pipe.  A vertical weld that sticks too far into a horizontal run of pipe will form a dam.  (A weld prepared for X-ray inspection will intrude as much as ¼ inch into the pipe.)  The seam found in cheaper grades of pipe is another potential cause of failure in fryer piping.  For that reason Gem is now specifying seamless pipe for all carbon steel fryer piping.