Cooked Feathers, Cooked the Conveyor!
Guest Article by John Stoltzfus of J. S. Machines
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What's the difference between uncooked feathers and cooked
feathers?
Let's start at the beginning. We have a customer who
renders approximately 650,000 chicken scraps per week in their Pennsylvania plant.
The feathers from the chickens are discharged from cookers hot, at 150 to 180 ºF, and
then dropped into a live bottom feeder, which delivers the cooked feathers to an inclined
screw conveyor.
This tortured screw conveyor is the subject of our story.
It's 9-inches in diameter, 17 feet long and constructed with a carbon steel, screw
and stainless steel trough. The screw conveyor was supplied with a hanger bearing in
the center of the unit.
The screw conveyor had only been in service only a little
over 12 months when major failures occurred!
The difference between uncooked feathers and cooked feathers
is like night and day. After feathers are cooked they become acidic and very abrasive,
such that the first failure was at the pipe coupling on the other side of the hanger. We
determined that the cooked feathers were had build up on the coupling and that the acidic
nature of the material corroded the pipe in half.
Our first approach was to replace the screw with a one-piece
construction, plastic flighted conveyor; the plastic material was designed for 150 ºF
temperatures and very abrasion resistant, (Or so we thought!)
This new plastic screw has a square center pipe 1/8-inch
thick wall x 2-inches. While the new screw appeared to work well, 6 months later the
customer called and said the screw broke half, again! We immediately made a stronger
center tube using a 1/4-inch thick wall of the same polymer. This worked fine for another
7 months, but the screw broke a third time!
Back to square one! Our engineers evaluated the entire
operation and came up with this theory.
- Hot feathers would softened the plastic, which in turn
affected polymer's abrasion resistance. This wore down the screw, mostly in the center.
- With the smaller center, the hot cooked feathers jammed
allowing build up to lift the screw in it's trough.
- Rotating the screw and the resultant eccentric motion. caused
the screw to fail!
With our second try, getting tough, we installed a heavy-duty
screw fabricated of stainless steel schedule 80 pipe center, AR 250 flights and AR wear
plate strips on the bottom of the u-trough. This screw lasted approximately 18
months before our customer started to see major corrosion problems again.
Better,
but not right.
Our third shot at solving the problem was when our customer
decided to replace this screw with another of the same material. We recommended an
all new stainless steel screw. Surely our troubles would be over now! Why?
Because we bet on the heavy construction, corrosion and abrasion resistance this new
stainless steel.
Guess what? Six months after the installation our customer
called back. "We are having problems on the inclined conveyor
again," he said, "the stainless steel flights were wearing down in the center
and the material was building up in the center, same as before!"
Back to the drawing board again!
Finally we added changeable flighting shoes and wear strips
made out of AR 450. The idea was that the same materials would wear against each
other. Our persistence paid off! We were finally able to provide a
reliable piece of equipment to our customer. Ah, the sweet sound of a satisfied
customer!
Our thanks to John Stoltzfus of J S Machines for this
week’s article. J. S. Machines specializes in new processes and finding better
ways to handle or move different products most would typically walk away from.
These include: candy, eggs, coal, ground & cooked grains, plastic, feathers, chicken
scrap, wood waste, ground rubber, paper sludge and other difficult materials.
Help others by posting your comments, suggestions and
experiences with bulk solids feeding or any other materials handling concerns you may have
on our On-Line Help Forum. For
past Ask Joe ! Articles, visit the Ask Joe! Archived Articles.
Guest articles for the Ask Joe! Column are always welcome,
for more information please contact Joe Marinelli directly at his email address:
joe@solidshandlingtech.com.
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