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Suction Rolls

What is a suction roll and how they work

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Suction Rolls

  1. 1. Suction Roll Training By Bill Frawley
  2. 2. Objective <ul><li>Types of rolls </li></ul><ul><li>Explain how each roll functions </li></ul><ul><li>Explain how seal strips work </li></ul><ul><li>Explore reasons for failure </li></ul><ul><li>Cost of proper Vs improper operation </li></ul><ul><li>Roll service life </li></ul>
  3. 3. Suction Rolls <ul><li>Transfer sheet without an open draw </li></ul><ul><li>Remove water </li></ul>
  4. 4. Types of Suction Rolls <ul><li>Suction Breast Roll: Is used to form the sheet on some tissue and other lightweight grades </li></ul><ul><li>Suction Forming Roll: This roll is used to help evacuate water from the topside fabric & the sheet on twin wire paper machines </li></ul>
  5. 5. Types of Suction Rolls <ul><li>Suction Couch Roll: The suction couch roll is used to remove water from the sheet. The suction couch roll is used to join multiple ply sheets together on some machines </li></ul><ul><li>Suction Pickup Roll: This roll main function is to vacuum the sheet off the forming fabric and on the felt without an open draw </li></ul>
  6. 6. Types of Suction Rolls <ul><li>Suction Press Roll: This roll is used to help pull water away from the nip and hold it in the felt </li></ul><ul><li>Suction Transfer Roll: This roll main function is to vacuum the sheet from one felt to another without an open draw </li></ul>
  7. 7. Types of Suction Rolls <ul><li>Combi-Roll: This roll is a combination of a pickup roll and press roll </li></ul><ul><li>Suction Felt Roll: Used as an anti-blow box vacuums sheet to felt to stop flutter going in to a press </li></ul><ul><li>Suction wringer Roll: This roll is used like a uhle box to dry the felt </li></ul>
  8. 8. Types of Packings <ul><li>Roll shell </li></ul><ul><li>Suction box </li></ul><ul><li>Air load tubes </li></ul><ul><li>Seal Strip </li></ul>5. Silencer packing 6. End deckle 7. Lube / fog shower
  9. 9. How Seals Function <ul><li>Define vacuum area </li></ul><ul><li>End deckle set width </li></ul><ul><li>Air load tubes move up & down </li></ul><ul><li>Liquid ring seal </li></ul><ul><li>In a perfect world strips wouldn’t wear </li></ul><ul><li>.018 clearance from deckle to ID of shell </li></ul>
  10. 10. Suction Box Attitude <ul><li>Suction box can rotate to control exactly where vacuum is applied </li></ul><ul><li>If misaligned air can reduce vacuum effect on nip </li></ul><ul><li>Rewetting and shadow mark sheet </li></ul>
  11. 11. Suction Box Attitude Early <ul><li>If misaligned to early air can reduce the vacuums effect in nip & rewet exiting </li></ul><ul><li>Example if zone A is set to far before nip air will bleed into vacuum box </li></ul><ul><li>Zone C would then release water to early, rewetting and shadow mark the sheet </li></ul>
  12. 12. Suction Box Attitude Late <ul><li>If the opposite were to happen and zone A was set to late </li></ul><ul><li>A puddle will form coming in to the first nip </li></ul><ul><li>In zone C the vacuum and center roll will fight for control of the sheet </li></ul><ul><li>If the felt wins lookout the sheet is coming back </li></ul>
  13. 13. Why Strips Wear Out <ul><li>Showers </li></ul><ul><ul><li>Shower pressure should be 25-45 psi </li></ul></ul><ul><li>Air loading </li></ul><ul><ul><li>Normal operating level between 4-6 psi </li></ul></ul><ul><li>Thermal expansion </li></ul><ul><li>Shell &/or box deflection </li></ul><ul><li>Surface of shell interior </li></ul><ul><li>Incorrect machining </li></ul>
  14. 14. Fog & Cleaning Showers <ul><li>Only Invisible showers on machine </li></ul><ul><li>Fog shower 25-45 psi clean water </li></ul><ul><li>Flood/cleaning shower should be run whenever sheet is off & machine is running 100 psi </li></ul>
  15. 15. Air Load Tubes <ul><li>Over loading is the #1 cause for strip wear </li></ul><ul><li>Over loading causes heat from friction </li></ul><ul><li>Over loaded strip will doctor lube water off shell </li></ul><ul><li>Could cause cover failure </li></ul>
  16. 16. Dirt Trap
  17. 17. Shell Interior Surface <ul><li>Chemicals can corrode metal </li></ul><ul><li>Dirt, sand, fillers and Foreign objects can score shell </li></ul><ul><li>Flexing of shell can work harden metal </li></ul>
  18. 18. Shell and Box Deflection <ul><li>Over loading press </li></ul><ul><li>Over crowing rolls </li></ul><ul><li>Exceeding vacuum levels in holding zones </li></ul><ul><li>Thin shell </li></ul><ul><li>Weak box </li></ul><ul><li>Thermal expansion </li></ul>
  19. 19. How to Read Worn Packings
  20. 20. Cost of Proper Vs Improper Operation <ul><li>Over loading is slamming on the brakes this will cost thousands of dollars in horsepower </li></ul><ul><li>Running dry can cause enough heat that cover bond can fail, and in worst case remove temper from shell </li></ul><ul><li>Allowing holes to fill with dirt reduces vacuum capacity & machine efficiency </li></ul><ul><li>Most expensive roll to service </li></ul>
  21. 21. Suction Roll Summary <ul><li>Properly run rolls improve machine performance </li></ul><ul><li>Keep air loading as low as possible </li></ul><ul><li>Run fog showers always & cleaning shower whenever sheet is off & machine is running </li></ul><ul><li>Adjust box attitude to fine tune performance </li></ul><ul><li>Know which roll and roll zone dewater and which control sheet transfer </li></ul>