suction rolls

Copyright © Bill Frawley 2001

Suction Roll Training

By

Bill Frawley


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


Suction Rolls

Transfer sheet without an open draw

Remove water


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



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



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



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


Types of Packings

1. Roll shell 2. Suction box3. Air load tubes4. Seal Strip

5. Silencer packing6. End deckle7. Lube / fog shower


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


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


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


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


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


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


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


Dirt Trap

Appleton International Inc sketch of suction roll packing dirt trap. This is caused when the improper radius is machined into the strip.


Shell Interior Surface

Chemicals can corrode metal

Dirt, sand, fillers and Foreign objects can score shell

Flexing of shell can work harden metal


Shell and Box Deflection

Over loading press

Over crowing rolls

Exceeding vacuum levels in holding zones

Thin shell

Weak box

Thermal expansion


How to Read Worn Packings


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


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

suction rolls

Documents

press roll suction felt

suction roll summary

suction roll training

pickup roll

felt suction transfer

expensive roll

roll functions

center roll