A consolidation of highly respected British brands E R & F Turner, Christy & Norris and Miracle Mills, Christy Turner Ltd is renowned for quality British engineering and innovation in the milling industry. With flaking mills operational around the globe, the leading UK engineering firm talks us through their top tips for increasing the longevity and performance of your flaking rolls.

1. A
consolidation of highly respected
British brands E R & F Turner,
Christy & Norris and Miracle
Mills, Christy Turner Ltd is
renowned for quality British
engineering and innovation in
the milling industry. With flaking
mills operational around the globe,
the leading UK engineering firm
talks us through their top tips for increasing the longevity and
performance of your flaking rolls.
Christy Turner’s team of service engineers travel around the
world providing expertise and assistance with roll changes. Not
only skilled in Christy Turner machinery, the team can provide
grinding and fluting services for almost every make and model of
flaking mill, regardless of brand.
As Chris Jones, managing director of Christy Turner Ltd,
explains: “Part of our site here in Ipswich is dedicated to the
maintenance of our customer’s rolls. We have a busy in-house
roll grinding and fluting department where we receive rolls in a
variety of sizes and conditions from a wide range of roller and
flaking mills.
“On receiving the rolls, we remove, clean and assess the
condition of the bearings. What we are looking for is any pitting
or corrosion often caused by poor storage conditions after the
rolls are removed from the mill or for any bearing wear due
to under or over greasing. A report is generated advising our
customer on the condition and if replacements are recommended.
We assess the rolls themselves, paying particular attention to any
badly worn or damaged areas. We check the roll diameter and
chill depth and then grind to reveal a clean, flat surface to which a
new finish may be applied, fluted or matt.
“We are able to grind not just our own rolls, but also other
manufacturers chilled iron rolls with sizes from 250mm diameter
up to 660mm, with tapers if required.”
Offering a complete range of roll finishes suitable for all types
of flake production from breakfast cereal to animal feed through
and other non-food applications, Christy Turner can match the
finish on a roll to exact specifications. On the rare occasions that
rolls require more serious repairs, Christy Turner are able to refit
shafts and repair bearing journals to maximise the life of a roll.
Christy Turner only uses genuine parts for ultimate reliability
and performance, with all replacement parts manufactured
from the most suitable materials and to the correct dimensional
specification. The company maintains casting patterns for every
machine in its current range and all parts have full material
traceability, essential for any food or feed production.
Chris added: “We stock recommended spares for all of our mills
in service, which includes many mills over 40 years old. By using
genuine OEM parts compatibility is guaranteed.
“Naturally, over time, all rolls will require replacement and we
supply and fit a wide range, however, there is a great deal you can
do to enhance the life of your rolls, including regular re-grinding
and servicing.”
Christy Turner’s dedicated team of experienced engineers
support customers with site visits throughout the year to carry out
Howtomaximisethelifeof
yourflakingrolls
by Lyndsey Filby, Chris Turner & Ian Butcher for Christy Turner.
ROLLMAINTENANCE
44 | November 2016 - Milling and Grain
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2. repairs, servicing and maintenance.
Proper care greatly increases the
service life of flaking rolls and
decreases the whole life cost of
operating the mill according to
Christy Turner’s Service & Parts
Manager Ian Butcher Take a look
at his top tips for increasing the
longevity and performance of your
Chilled Iron Flaking Rolls...
The rules:
Do smear the entire surface of
both rolls liberally with edible oil
whenever the mill is stopped for
a continuous period of 3 hours or
more. The surplus oil should then
be removed prior to start-up. This
simple measure is most important
and should be done without fail,
as a matter of routine, to avoid
the onset of corrosion. Corrosion
is easier to control by totally
excluding it and not letting it gain a
foothold!
Do aspirate the mill by attaching
appropriate aspiration ducting into
the blanked off opening in the
feed roll unit (when fitted) This
helps to aspirate the atmosphere
above the rolls in cases where the
mill is closed in and flood fed.
For the same reason do not block
ventilation in any of the mill covers
around the rolls.
In addition, where a product
discharge conveyor is fitted below the rolls, there can be a
tendency for humidity to build up in the enclosed conveyor slot
and to subject the underside of the rolls to damp air. When these
conditions are present it is essential to aspirate the conveyor
slot. When conveyor slot aspiration is required we recommend a
locally mounted axial fan delivering approximately 0.3 m3/sec @
50 Pa.
Do remove the rolls from the mill for regrinding. Ideally the
rolls should be returned to specialists, such as Christy Turner,
so that the roll surface can be factory machined to its original
specification, which may include end tapers, matt finish or fluting.
It is not advisable to attempt to regrind the rolls while they are
still in the mill By products of grinding are not desirable in a food
or feed production environment.
In practice, the required accuracy, surface finish and
concentricity cannot be achieved in this way. Part of the reason
for this is the fact that when the rolls are mounted in the mill,
their location is subject to bearing “float”
Do purchase a spare pair of rolls with bearings so that the mill
can still be used in production while the worn roll surface is being
correctly and professionally repaired to its original specification.
This extra initial investment always proves to be beneficial in
successful production environments as it enables quick roll
changes, minimising down time and a spare set of rolls can be
used to service several mills.
Do ensure even feed is maintained across the full width of
the rolls. Uneven feed creates locally different thermal expansion
of the rolls, making it impossible to maintain a constant roll gap
Milling and Grain - November 2016 | 45
F

3. when fine flaking and, in the longer term, results in uneven wear
of the rolls and inconsistent product.
Do not overcool the surface of the roll by using cooling water
which is at a lower temperature than is strictly necessary. We
recommend when possible that the roll surface temperature is
maintained at a minimum of 35 Degrees Celsius. In most cases
this temperature will ensure that the roll surface remains above
dew point, though not in all cases. If there is any doubt, the dew
point of the air in close proximity to the rolls must be checked in
order to determine the safe operating temperature for the rolls.
Do not run cooling water through the rolls when they are
not in use. Running cooling water when the mill is shut down
will invariably cause the roll temperature to descend below
dew point and cause water to condense on the roll surface and
risk corrosion. The best arrangement is to operate the cooling
water with electrical solenoid operated valves, linked in with the
starting and stopping of the mill itself.
In addition, do not run cooling water unless the rolls are
rotating. If cooling water is run through the rolls when they
are stationary, it cools the mass of the iron unevenly and can
temporarily distort the rolls slightly into an “egg shape”. If and
when this happens by mistake, the rolls need to be left for some
time without flaking and without running any cooling water so
that the temperature is evened up throughout the roll body.
Do not attempt to extend the periods between roll regrinds
until the surface is seriously damaged. The nature of chilled iron
is such that the rolls will give a better flaking performance and
actually last longer if they are reground at regular intervals and at
a frequency which allows each regrind to be light.
When, on the other hand the rolls are left in operation until
deeper and more serious damage has to be repaired, it is normally
necessary to grind the entire roll surface down to a level well
clear of the deepest visual problem. This has to be done in order
to free the roll structure of any fissures and work hardening.
Therefore the depth of material removed is likely to be greater, so
fewer such extensive regrinds will be possible before the rolls are
scrapped.
The rule of regrinding chilled iron rolls is little and often;
though unfortunately the actual optimum frequency depends
upon individual operating parameters and product being flaked so
cannot usefully be generalised.
Do not weld chilled iron rolls under any circumstances in an
attempt to repair the surface. Welding will totally disrupt the
structure and effectively extend the damaged zone, rather than
repair it!
Do not allow foreign bodies to pass through the roll nip.
Any hard objects, for example pieces of metal or stones, passing
through will cause damage to the surface of the roll. All E R &
F Turner flaking mills are designed in such a way as to allow the
rolls to part, and therefore to limit the magnitude of the total nip
force generated in a situation where a foreign object accidentally
passes through the roll nip.
However the necessarily high weight and inertia of chilled
iron rolls inevitably causes high local pressures to be generated
by the foreign object on the roll surface before the roll gap is
opened. Sometimes, chilled iron will become “bruised” in such
an accident. This means that damage may take place beneath the
surface even if none is visible, in such a way that pieces of the
roll surface may become dislodged at a later date. The best policy
here is prevention rather than cure!
Do not use any scraper blades other than genuine parts.
This applies equally to re-grindable and disposable scraper types.
The genuine article is manufactured at an optimum hardness level
designed to strike a careful balance between maximising scraper
life and minimising wear caused by the scrapers to the rolls. It is
possible to make the scrapers both harder and softer, but neither
will be fully satisfactory.
Do not use more pressure than necessary in applying the
scrapers to the rolls. This principle applies to both manually and
pneumatically operated scrapers. In other words, whilst flaking,
gradually increase the application pressure until a satisfactory
performance is obtained. At the point when further increases in
pressure make no further improvement to flaking performance,
reduce pressure back as far as possible without performance
being reduced again.
Excess pressure only creates unnecessary wear on the scraper
blades and the rolls. Christy Turner recommend pneumatically
operated scrapers as they maintain a constant scraper pressure,
irrespective of the roll position, and can be easily switched off
when no feed is present. This system is available as an upgrade
on our older mills.
DO NOT ALLOW THE ROLLS TO RUN TOGETHER in
the flaking position unless product is present. Running the rolls
together without flaking causes unnecessary roll wear and this
wear is increased when there is a roll speed differential.
COMPANY BACKGROUND
In 2012, Christy Turner, celebrated 175 years of supplying
high quality robust and reliable Flaking Mills, Hammer Mills,
Pulverizers, and associated plant for the human foods, animal
feed, biomass, waste recycling, minerals, chemicals and
pharmaceuticals industries around the world.
Machines of choice in the breakfast cereal market - over 90
percent of the machines used by UK cereal giant Weetabix at
Burton Latimer & Corby sites are E R & F Turner’s flaking
mills.
Building upon manufacturing skills and expertise since E R
& F Turner started production in 1837, while making the most
of modern technological advances, Christy Turner continue
to produce machines of choice for manufacturers around the
globe.
TECHNICAL INFO: Chilled iron roll cross section
Chilled iron is a form of cast iron, which has a structure rich
in iron carbide, referred to as white iron, to a minimum depth
of some 20 – 25 mm for spun cast or 6-8 mm for static cast,
whilst the interior becomes grey iron. This depth of white iron
is known as the ‘chill depth’.
White iron is an extremely hard, abrasion resistant material,
largely due to its iron carbide content, whilst grey iron is softer
with high load-bearing capacity. The two materials can be
identified by colour difference as their names suggest and this
can be clearly seen in the above photograph, which illustrates
an end section of a rough-turned chilled iron roll body.
46 | November 2016 - Milling and Grain
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4. 02 - 06 NOV
STAND C5-10
13 - 16 NOV
STAND 39