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What is a suction roll and how they work
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Copyright © Bill Frawley 2001
Suction Roll Training
By
Bill Frawley
Copyright © Bill Frawley 2001
Objective
Types of rolls
Explain how each roll functions
Explain how seal strips work
Explore reasons for failure
Cost of proper Vs improper operation
Roll service life
Copyright © Bill Frawley 2001
Suction Rolls
Transfer sheet without an open draw
Remove water
Copyright © Bill Frawley 2001
Types of Suction Rolls
Suction Breast Roll: Is used to form the sheet on some tissue and other lightweight grades
Suction Forming Roll: This roll is used to help evacuate water from the topside fabric & the sheet on twin wire paper machines
Copyright © Bill Frawley 2001
Types of Suction Rolls
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
Suction Pickup Roll: This roll main function is to vacuum the sheet off the forming fabric and on the felt without an open draw
Copyright © Bill Frawley 2001
Types of Suction Rolls
Suction Press Roll: This roll is used to help pull water away from the nip and hold it in the felt
Suction Transfer Roll: This roll main function is to vacuum the sheet from one felt to another without an open draw
Copyright © Bill Frawley 2001
Types of Suction Rolls
Combi-Roll: This roll is a combination of a pickup roll and press roll
Suction Felt Roll: Used as an anti-blow box vacuums sheet to felt to stop flutter going in to a press
Suction wringer Roll: This roll is used like a uhle box to dry the felt
Copyright © Bill Frawley 2001
Types of Packings
1. Roll shell 2. Suction box3. Air load tubes4. Seal Strip
5. Silencer packing6. End deckle7. Lube / fog shower
Copyright © Bill Frawley 2001
How Seals Function
Define vacuum areaEnd deckle set widthAir load tubes move up & downLiquid ring seal In a perfect world strips wouldn’t wear.018 clearance from deckle to ID of shell
Copyright © Bill Frawley 2001
Suction Box Attitude
Suction box can rotate to control exactly where vacuum is applied
If misaligned air can reduce vacuum effect on nip
Rewetting and shadow mark sheet
Copyright © Bill Frawley 2001
Suction Box Attitude Early
If misaligned to early air can reduce the vacuums effect in nip & rewet exiting Example if zone A is set to far before nip air will bleed into vacuum box Zone C would then release water to early, rewetting and shadow mark the sheet
Copyright © Bill Frawley 2001
Suction Box Attitude Late
If the opposite were to happen and zone A was set to lateA puddle will form coming in to the first nip In zone C the vacuum and center roll will fight for control of the sheetIf the felt wins lookout the sheet is coming back
Copyright © Bill Frawley 2001
Why Strips Wear Out
Showers Shower pressure should be 25-45 psi
Air loading Normal operating level between 4-6 psi
Thermal expansion
Shell &/or box deflection
Surface of shell interior
Incorrect machining
Copyright © Bill Frawley 2001
Fog & Cleaning Showers
Only Invisible showers on machine
Fog shower 25-45 psi clean water
Flood/cleaning shower should be run whenever sheet is off & machine is running 100 psi
Copyright © Bill Frawley 2001
Air Load Tubes
Over loading is the #1 cause for strip wearOver loading causes heat from friction Over loaded strip will doctor lube water off shellCould cause cover failure
Copyright © Bill Frawley 2001
Dirt Trap
Appleton International Inc sketch of suction roll packing dirt trap. This is caused when the improper radius is machined into the strip.
Copyright © Bill Frawley 2001
Shell Interior Surface
Chemicals can corrode metal
Dirt, sand, fillers and Foreign objects can score shell
Flexing of shell can work harden metal
Copyright © Bill Frawley 2001
Shell and Box Deflection
Over loading press
Over crowing rolls
Exceeding vacuum levels in holding zones
Thin shell
Weak box
Thermal expansion
Copyright © Bill Frawley 2001
How to Read Worn Packings
Copyright © Bill Frawley 2001
Cost of Proper Vs Improper Operation
Over loading is slamming on the brakes this will cost thousands of dollars in horsepowerRunning dry can cause enough heat that cover bond can fail, and in worst case remove temper from shellAllowing holes to fill with dirt reduces vacuum capacity & machine efficiency Most expensive roll to service
Copyright © Bill Frawley 2001
Suction Roll Summary
Properly run rolls improve machine performance
Keep air loading as low as possible
Run fog showers always & cleaning shower whenever sheet is off & machine is running
Adjust box attitude to fine tune performance
Know which roll and roll zone dewater and which control sheet transfer