Reprinted from American Laundry News • Published by American Trade Magazines, a division of Crain Communications Inc.,360 North Michigan Avenue, Chicago, IL 60601 — (312) 649-5200 © Copyright 2008 Crain Communications Inc. All Rights Reserved.

By Michael Reilly

Every laun-dry type, fromthe home tothe large com-mercial facili-ty, must dealwith the peskyproblem oflint collection.

Handlingand processing textiles fatiguesthe fibers and produces lint par-ticles. A clothes dryer or tumbleris the most obvious source oflint, which can be foundthroughout a textile processingfacility. Every step of processing— from washing to finishing —produces lint, but the greatestvolume comes from dryers.

This article summarizes com-mon lint-collection methods and empha-sizes the importance of lint col-lectors (or lint filters) for use inconjunction with clothes dryersand ironers.

Evolution of lint filtersA lint collector may be used

either as a primary filter or sec-ondary filter for a single machineor multiple machines. The appli-cation may vary from one smalldryer to a bank of dryers in acontinuous-batchwashing system. In any applica-tion, thereasons to use a lintcollector are typicallythe same: environmental con-cerns, meeting code require-ments, reducing fire risk and,most importantly, maximizingdryer performance.

For many years, textile manu-

facturers developed methods ofcapturing and reusing processedlint while laundries concentratedon containing the large amountsof lint produced by their high-capacity (200-600 pounds) dry-ers. Various containment meth-ods included homemade “chick-en coops” and machines thatused a powerful vacuum, com-pressed air, pressurized water,fabric rollers and, believe it ornot, even fire! These early con-traptions were large, bulky anddifficult to maintain, and weretypically located on the laundry’sroof.

Large, outdoor lint collectorswere introduced during the1970s. By the next decade, theywere standard additions for mostlarge-capacity industrial dryers.Energy prices skyrocketed, result-ing in the introductionof filters that were equipped withexhaust heat-recovery systems.This leads us to the 1990s, whenmore options became availablefrom dryer manufacturers as wellas after-market suppliers.

A more economical line of lintcollectors targeting smaller-capacity (30-150 pounds) dryershas emerged during the lastdecade. This has brought aboutthe collectionof “secondary lint,” making sec-ond-stagefiltering with multiple dryersmorecommonplace, especially insmalleron-premise laundries.

Today, manufacturers concen-trate on developing filtration sys-tems that require minimal spacewhile improving maximum effi-ciency by taking total airflow

design into account.

Dry or wet: What’s your type?Dry-type and wet-type are the

two common terms used indescribing methods of lint filter-ing. Most lint filters made todayare dry-type, but their designsvary.

A dry-type lint collector uses amesh screen to filter the lint fromthe exhaust. Some require manu-al screen cleaning while othersautomatically collect lint into a

container. The mesh screen ismade of high-temperature poly-ester or stainless steel, and itsholes range in size from 180 to300 microns — about the thick-ness of a human hair. Wet-typelint collectors use water to satu-rate the lint and filter it througha fine screen or a coarse bag.

Some various designs andmethods of lint collection usedtoday are:

• Manual Cleaning — Flatscreen; floating screen; cylindri-

Laundries turn to filtration systemsto capture lint, boost dryer efficiency

This lint filter is shown in a one-on-one, or inline, application with a dryer.

Reilly

cal screen.• Automatic Cleaning —

Cyclone design with cylindricalscreen and compressed air; cylin-drical screen with compressed airand scraper and suction; flatscreen with suction and othermechinism.

• Automatic Cleaning —Cyclone design with spray noz-zles; square-baffle design withspray nozzles or jets.

The inline cyclone lint collec-tor is heralded as the most effi-cient and economical means ofcontaining lint. The slenderdesign is common in many pro-cessing industries and naturallyassists in the separation of airand particles while providing lowresistance. It has a small footprintand improves screen longevity byspinning oncoming particles oflint, sand and foreign objectsaround the screen instead ofdirectly into it. These units areavailable in many capacities andcan be used for individual dryers(one-on-one) or in multiple-dryer applications.

When choosing a lint collector,the entire dryer-exhaust systemmust be properly designed toachieve the best results. As thelint filter is only one part of thesystem, considerations for resist-ance of the ductwork, includingpossible elbows, fan, damper,louver or weather cap, must bemade.

With the proper sizing of thefilter and ductwork, a large-capacity dryer may operate with-in specifications while having upto three 90-degree elbows and upto 30 feet of running duct. Therule of thumb for smaller dryersis that performance may bedecreased if there are more thantwo 90-degree elbows and morethan 20 feet of running duct.

When the static pressure in theexhaust-air system exceeds thedryer manufacturer’s recommen-dations, then an assist (or boost-er) fan should be considered.Such a fan can maintain constantairflow, improve dryer efficiency,prevent lint buildup and reduce

energy costs. Installing an assistfan requires proper engineeringto equalize the airflow properly orit may create negative results:longer drying times, higher main-tenance costs and additional lintpass-through.

Selecting a lint collectorOne must first determine how

much lint exhaust is acceptablewhen choosing a collector. Mostlint collectors are designedto collect at least 97% of exhaustlint. This is adequate in mostcommercial applications but it’simportant to consider the finaldryer-exhaust point. If there isany lint pass-through, it willcause a problem.

Too much lint passing througha filter can litter a parking lot,clog an air conditioner condens-ing unit, waft onto a neighbor’sproperty or scatter at theentrance of your building (snowin July). Even if your facility is in

an industrial area, the local firemarshal or your insurance loss-control consultant may requirebetter containment of lint.

Suggestions for matchingdryer and filter:

• New-dryer installation —The ideal situation would consistof one collector for every dryer,but space constraints and higherup-front costs don’t always makethis practical. The built-in filtersaves space but may sacrifice per-formance and boost maintenancecosts.

• Existing-dryer installation —A central lint collector, wheremultiple dryers are connected,can produce results that are simi-lar to a one-on-one installation,but ductwork design is impor-tant. An assist fan may berequired.

• When textiles contain sand,grit or foreign objects — Slowingdown the velocity of the exhaustair and deflecting particles

on approach to the filter’s screen,which are characteristic of theinline cyclone filter,will create the best results. Inmore abrasive applications, astainless-steel housing andfilter screen will result in longerlife.

• When 100% lint collection isnecessary — For highly sensitivesituations, a two-stage lint filterprocess is required. For this sce-nario, and when heavy solvents oroils are present, a wet-type lint fil-ter is more applicable.

There are many advantages inhaving a properly designeddryer-exhaust system, startingwith a lint collector.

Michael Reilly is president ofClean Cycle Systems, a division ofTQ Industries Ltd. He can bereached at 830-401-4400 or bye-mail at mike@tqind.com.ALN

This lint collector for an on-premise laundry can be installed either indoors or outdoors.

Photos courtesy Clean Cycle Systems