Mill and Calender Safety

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Mill and Calender Safety

• Presenters Name

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Agenda

• General Overview of Mill
• Mill Operation Video
• Stopping Distances
• Other Safety Requirements
• Calender Safety
• Mill Rescue Video
• Overview of Rescue Procedures
• Accident Scenario
• Mill Emergency Kit
• Summary and Questions

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General Overview of Mill

• Personnel Safety
• Paramount issue in mill/calender operation
• Must be operated with care and respect for the
  hazards that a mill poses
• No substitute for proper training in safety
  operation
• Continuous training required for safety awareness

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• Lighting
• Good lighting is essential
• Lighting installations should be planned with
  care to avoid shadows and glare

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• Ventilation
• Certain polymer stocks in use today produce
  noxious or irritating smoke and fumes when milled
  or calendared.
• Consider this factor and provide adequate
  exhaust ventilation
• Such equipment usually takes the form of a
  ventilation hood or enclosure located over the
  machinery

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• Maintenance
• Good preventative maintenance is integral to
  safety
• Braking equipment, safety switches and actuating
  devices should be tested at a regular scheduled
  time every week
• Requiring periodic attention are stock guides,
  roll adjustment screws (lubrication), lights, and
  ventilation

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Stopping Distance

• The width of the danger zone above the nip point
  is defined in terms of the roll speed- the faster
  the roll speed, the wider the danger zone

• This requirement keeps the operators hands out of
  a defined danger zone above the feed nip (where
  the two rolls come together)

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• Workers fail to realize that more people are
  injured on the small lab-scale mills than the
  larger process mills because the work area is
  closer to the nip point
• Mills and calenders must meet certain minimum
  stopping distances, measured in travel of surface
  of the roll after the safety stop has been
  actuated

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Stopping Limits

• Stopping limits for mills are 1 ½ of the roll
  speed
• Stopping limits for calenders are 1¾ of the
  roll speed
• EXAMPLE If the roll speed is 100 foot per minute
  then the maximum stopping distance allowed is 18
  inches

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Mill Check Procedure

1. Front and back mill must be empty and running at
   the maximum operating speed. (The front roll is
   considered to be the roll on the same side as the
   adjustment screws.)
2. Simultaneously pull the safety cable and place
   the crayon down onto the mill so that a mark is
   drawn.
3. When the roll has completely stopped, measure the
   crayon line

• to the nearest quarter inch.
• Record the results along with the date, shift,
  and your initials on the inspection form.
• If the actual stopping distance is greater than
  the maximum stopping distance allowed for the
  roll, run a second test to verify your initial
  results.
• If the second check is still too high, notify
  your supervisor immediately.

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Inspection Sheet of Safety Stops(To Be Checked
Prior to Each Shift)
MILL 60_
__ LOCATION 3 Banbury __ Front
Roll Surface Speed 124RPM
Date Tested Shift Maximum Stopping Distance Allowed (Inches) -------------- Front Roll Actual Stopping Distance (Inches) ----------- Front Roll Initials Comments
22.0
22.0
22.0
22.0
22.0
22.0
22.0
22.0
22.0
22.0
22.0
22.0
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Safety Check Requirements

• Perform these checks at the beginning of each
  before the mill man works the mill
• The only exception is when continuous stops are
  running and the mill cannot be completely
  emptied, you are then required to perform the
  check at the first opportunity to clear the mill
• Clipboards at each mill are required to record
  the data
• The most important reason to record these
  distances is to monitor the stopping distance in
  case of change which may indicate a brake problem
  that can be corrected prior to exceeding the
  maximum allowable limit

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• The two roll mill is and extremely flexible and
  versatile piece of equipment

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Other Safety Requirements

• Install mills so the distance from the surface
  the operator stands upon is not less than 50
  inches below the top of the rolls to meet
  requirements
• Install body bars on both sides of the mill,
  arranging the bars so the operator cannot reach
  in to the danger zone without pressing hard
  enough at the body bar to trip the emergency stop
  switch at no more than 40 pounds of pressure. Be
  certain that the bars work reliably with both
  inward and upward pressure.

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• Make sure the body bar will not bounce and reset
  itself
• Operators come in many shapes and sizes, make
  certain that the short ones are not working under
  or inside the bar. If the operator happens to be
  a former basketball center, check to be positive
  that he can NOT reach the danger zone

Danger Zone
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• In general, emergency stop devices, including
  body bars, pull cables, and emergency stop push
  buttons, must be of the maintained position type
  (requiring that they be manually reset before the
  equipment can be restarted)
• Such switches should be double-pole and should
  break both the hat and the neutral side of the
  run circuit

• The use of pull cables in conjunction with body
  bars is strongly recommended

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• Emergency stop devices must be retested on a
  regular basis
• Plant personnel should be schooled to avoid
  misuse or abuse of the emergency stop system
• A routine stop should be made using the normal
  stop button on the operators control station to
  avoid undue wear and tear
• General guarding is also a safety requirement
  all gearing should be enclosed with guards to
  prevent unauthorized personnel from putting hands
  or other objects into the gear mesh

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Calender Safety

• The problem of protecting calenders is considered
  different from that of protecting mills
• The accident exposure is greater due to increased
  number of bites
• Guarding the point wear stock feeds into the
  calender is extremely difficult
• Hazards are greatly reduced by employing feed
  conveyors, preferably an oscillating type
• Stock tables located just below and close to the
  face of the rolls also reduces exposure

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Calender Safety Controls

• A safety trip rod or cable is needed across each
  pair of in-running rolls extending the length of
  the rolls. It must be readily accessible and
  operate whether pushed or pulled.
• A safety trip rod or cable must be connected to
  the safety trip at the end of the face of the
  rolls. They must be located no more than 12
  inches out from the rolls, not less than 2 inches
  form the calender frame and extend within 6
  inches of the floor.

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• A calender installed so operators cant reach
  through, over, under, or around the roll bite or
  be caught between the rolls or an adjacent object
  are not required to have safety devices.
• Again, all trip and emergency switches require
  manual resetting.

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• The full calender view shows the safety bar in
  position at the fabric feed bite and also
  illustrates the recommended location for safety
  trip cables which are required in addition to the
  interlocked bite bar. The letters in this drawing
  indicate the following items

B- Safety trip cable switch C- Vertical safety
trip cable D- Adjustable clamp for horizontal
safety trip bar E- Horizontal safety trip bar
F- Double action electrically interlocked bite
bar J- Safety trip cable screw eye tension
adjustment K- Safety trip cable guide pulley L-
Calender control switch
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Location of Double-Action Interlocked Safety Bar
at Fabric Feed Bites of Calenders
View A-A in this drawing illustrates the
recommended location of the interlocked safety
bar at the fabric feed bites of calenders. The
dimensions shown are the maximum allowable for
safe operation. Distance X will vary in
accordance with the roll diameter, but must
always be great enough to insure that no part of
the operators hand can reach the bite without
tripping the bar.
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Accident ScenarioAccident in the Mill Room
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George is an experienced mill operator at BWC
Rubber Company. While at his work station milling
rubber, Georges arm is caught in the mill.
George activates the safety cable but his arm is
pulled into the mill up to his shoulder before
the mill stops rotating.
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George screams for help. John, hears George and
quickly responds to the sound of his voice. John
calls for additional help and retrieves a blanket
form the mill rescue box. John then places the
blanket between the hot mill roll and George.
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Other employees quickly arrive to Georges
work station and retrieve tools from the mill
rescue box. One of the mill rescue team members,
Steve, climbs below the mill to cut away the
rubber. The other rescue team workers open to
crack the mill and begin to free George from the
rolls. They utilize pry bars to separate the
rolls and hooks to pull the rubber out from
between the mill rolls.
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• Mill Emergency Kit

• 2 Porta-power pumps (hydraulic pumps)
• Blood-born pathogen kit
• First Aid Kit
• Latex gloves

• Thermal blanket
• Rubber knives
• Flashlights
• Pry bars
• 2 Sledge hammers
• 2 Wedges
• Rubber hooks
• Clean rag
• Mill gloves

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Summary and Questions
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