seasoning ppt

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WOOD SEASONING WOOD SEASONING Dr.E.SREENIVASAN Dr.E.SREENIVASAN Technical Manager, R&D Technical Manager, R&D THE WESTERN INDIA PLYWOODS LTD THE WESTERN INDIA PLYWOODS LTD BALIAPATAM, BALIAPATAM, KANNUR-670010 KANNUR-670010 Ph:8289865990 Ph:8289865990 E-Mail: E-Mail: [email protected] [email protected]

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Page 1: Seasoning ppt

WOOD SEASONINGWOOD SEASONING

Dr.E.SREENIVASANDr.E.SREENIVASANTechnical Manager, R&DTechnical Manager, R&D

THE WESTERN INDIA PLYWOODS LTDTHE WESTERN INDIA PLYWOODS LTDBALIAPATAM,BALIAPATAM,

KANNUR-670010KANNUR-670010Ph:8289865990Ph:8289865990

E-Mail: [email protected]: [email protected]

Page 2: Seasoning ppt

INTRODUCTIONINTRODUCTION Seasoning means partial drying of wood.Seasoning means partial drying of wood. Wood from freshly felled trees contains a large quantity of Wood from freshly felled trees contains a large quantity of

moisture(100 to200 per cent). This has to be removed before moisture(100 to200 per cent). This has to be removed before the timber becomes fit for servicethe timber becomes fit for service

Water contained in wood is held in two forms: 1)as free water, Water contained in wood is held in two forms: 1)as free water, in cavities of cells and space around cells 2) as absorbed in cavities of cells and space around cells 2) as absorbed water, held in cell walls. water, held in cell walls.

"Free moisture" is the name given to the water in the cell cavities in timber, and the moisture saturating the cell walls is termed the "bound" or "combined“ moisture. Although the moisture is exactly the samein either position, its effect on the timber is quite different.

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OBJECTIVES

The objectives of any seasoning process are to dry the material to a low uniform moisture content with a minimum amount of degrade in a minimum amount of time with a minimum cost for operating expenses and equipment These objectives are not all compatible with one another, and one must often be sacrificed to satisfy another. The conditions of each situation must necessarily determine the relative emphasis placed on each objective Thus rate of drying must often be retarded to allow the wood to dry with a minimum of degrade.

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ADVANTAGESADVANTAGES Seasoning reduces gross weight and thereby subsequent

shipping and handling costs, imparts dimensional stability, increases most strength properties, increases fastener holding power and thereby joint strength,

increases electrical resistance, improves paintability and glueability, improves the thermal properties of wood. In addition to these advantages, drying wood below the fiber

saturation point renders it impervious to biological degradation so long as it is not re-wetted. Attack by wood destroying fungi is prevented.

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METHODSMETHODS Seasoning aims at drying a set quantity of

timber uniformly to the equilibrium moisture content required with a minimum of degrade in the shortest possible time.

There are many ways of seasoning or drying timber, but only two methods have been found satisfactory, principally for economic reasons.

They are air drying and kiln drying.

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AIR SEASONINGAIR SEASONING It is the simplest method pf drying woodIt is the simplest method pf drying wood Important points to be noted and taken care of: Important points to be noted and taken care of:

1.proper piling or stacking of the timber1.proper piling or stacking of the timber 2.protection of stack from hot winds, blazing 2.protection of stack from hot winds, blazing

sun and rainsun and rain

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VERTICAL STACKINGVERTICAL STACKING Usually in use for light timbers such as semul Usually in use for light timbers such as semul

((SalamaliaSalamalia) and salai () and salai (BosweliaBoswelia) used for ) used for packing casespacking cases

Sawn planks are made to stand in open air Sawn planks are made to stand in open air against a wall or a framework of wood or against a wall or a framework of wood or bamboosbamboos

The surface of planks dries rapidly thereby The surface of planks dries rapidly thereby avoiding mould-attacks and sap stainavoiding mould-attacks and sap stain

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HORIZONTAL STACKINGHORIZONTAL STACKING Most common practice and is suitable for all Most common practice and is suitable for all

kinds of sawn materialkinds of sawn material Stacking with the help of battens or crossesStacking with the help of battens or crosses Different species and different thicknesses Different species and different thicknesses

should be stacked separatelyshould be stacked separately

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HORIZONTAL STACKINGHORIZONTAL STACKING

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PROTECTION OF STACKPROTECTION OF STACK The amount of protection required depends on: The amount of protection required depends on: a. the species of timber,a. the species of timber, b. thickness of the material, and b. thickness of the material, and c. climatic conditions. Therefore, the provision of an c. climatic conditions. Therefore, the provision of an

air-seasoning shed is desirable as otherwise it is not air-seasoning shed is desirable as otherwise it is not possible to regulate the factors affecting the rate of possible to regulate the factors affecting the rate of drying (temperature, humidity, air circulation)drying (temperature, humidity, air circulation)

Three seasoning sheds by FRI: Shed type1,2 and 3Three seasoning sheds by FRI: Shed type1,2 and 3

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SHED TYPE 1SHED TYPE 1 For refractory species ie, those species which are very For refractory species ie, those species which are very

liable to crack, split and warp. Eg.liable to crack, split and warp. Eg. Anogeissus Anogeissus latifolialatifolia (Axle wood), (Axle wood), Madhuca indicaMadhuca indica (Mahua), (Mahua), Diospyros melanoxylonDiospyros melanoxylon (Ebony), (Ebony),Syzygium cuminiSyzygium cumini (Jamun), (Jamun), Lagerstroemia lanceolataLagerstroemia lanceolata (Benteak), (Benteak), Terminalia paniculataTerminalia paniculata (Kindal), (Kindal), Xylia xylocarpaXylia xylocarpa (Irul) and (Irul) and Palaquium ellipticumPalaquium ellipticum (Pali) (Pali)

A closed shed provided with open space for A closed shed provided with open space for ventilation in walls just below the roof and above the ventilation in walls just below the roof and above the groundground

It should have a central passage for loading and It should have a central passage for loading and unloading or removable side wallsunloading or removable side walls

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SHED TYPE 2SHED TYPE 2 For medium refractory species Eg.For medium refractory species Eg.AcaciaAcacia arabica arabica

(Babul), (Babul), Adina cordifoliaAdina cordifolia (Haldu), (Haldu), Albizia lebbekAlbizia lebbek (Kokko), (Kokko), CedrelaCedrela toonatoona(Toon), (Toon), Dalbergia latifoliaDalbergia latifolia (Rosewood), (Rosewood), Dalbergia sissoDalbergia sisso(Sisso), (Sisso), Dipterocarpus Dipterocarpus spsp.(Gurjan), .(Gurjan), Pterocarpus marsupiumPterocarpus marsupium (Bijasal), (Bijasal), Tectona grandisTectona grandis (Teak) (Teak)

Shed open on one side and closed on three sidesShed open on one side and closed on three sides Open side should have sufficient overhang of the roof Open side should have sufficient overhang of the roof

to protect the stack from direct sun and rainto protect the stack from direct sun and rain

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SHED TYPE 3SHED TYPE 3 For non-refractory species ie, for timbers which can For non-refractory species ie, for timbers which can

stand rapid seasoningstand rapid seasoning Also recommended for species liable to staining, Also recommended for species liable to staining,

mould and decay during seasoningmould and decay during seasoning A simple shed open on all sides and provided with a A simple shed open on all sides and provided with a

roof sufficiently overhanging for protection against roof sufficiently overhanging for protection against rain and direct sunrain and direct sun

Eg.Abies pindrow(Eg.Abies pindrow(Fir), Fir), Salamalia malabaricaSalamalia malabarica (Semul), (Semul), Boswellia serrata(Boswellia serrata(Salai), Salai), Cedrus deodaraCedrus deodara (Deodar), (Deodar), Mangifera indica(Mangifera indica(Mango), Mango), Morus albaMorus alba (Mulberry), (Mulberry), Picea smithiana(Picea smithiana(Spruce), Spruce), Pinus Pinus roxburghiiroxburghii (Chir) and (Chir) and Vateria indica(Vateria indica(VellapineVellapine))

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SHEDSSHEDS

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PROTECTION OF ENDS OF PROTECTION OF ENDS OF TIMBERTIMBER

A common problem during air seasoning is the A common problem during air seasoning is the checking or splitting at the ends of boards or plankschecking or splitting at the ends of boards or planks

The best way to protect is to coat the ends with any of The best way to protect is to coat the ends with any of the following moisture proof compositions up to a the following moisture proof compositions up to a distance of about 8cm for the ends: distance of about 8cm for the ends:

1.Thick coal tar or bituminous paint1.Thick coal tar or bituminous paint 2.Rosin and lamp black(10:1),melted,mixed and 2.Rosin and lamp black(10:1),melted,mixed and

applied hot applied hot 3.Hardened gloss oil3.Hardened gloss oil 4.Molasses and lime(3:1)4.Molasses and lime(3:1)

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PREVENTION OF DRYING OF PREVENTION OF DRYING OF LOGSLOGS

If logs cannot be cut immediately, their drying should If logs cannot be cut immediately, their drying should be reduced by storing them under waterbe reduced by storing them under water

Barks on the logs should be removed before they are Barks on the logs should be removed before they are stored in waterstored in water

When storage under water is not possible,logs should When storage under water is not possible,logs should be stored on land preferably under shade over be stored on land preferably under shade over foundations which are slightly raised above groundfoundations which are slightly raised above ground

Apply one of the compositions for moisture-proof Apply one of the compositions for moisture-proof coatingcoating

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MOISTURE CONTENT MOISTURE CONTENT FOR DIFFERENT USESFOR DIFFERENT USES

The final moisture content to which timber shall be The final moisture content to which timber shall be seasoned before use depends upon the service seasoned before use depends upon the service requirements of the finished articles and the climatic requirements of the finished articles and the climatic conditions of the locality where it is to be usedconditions of the locality where it is to be used

For this purpose, India has been divided into 4 zones:For this purpose, India has been divided into 4 zones: Zone I: less than 40% average annual RHZone I: less than 40% average annual RH Zone II: ,, ,, 40-50% ,, ,, ,,Zone II: ,, ,, 40-50% ,, ,, ,, Zone III: ,, ,, 50-67% ,, ,, ,,Zone III: ,, ,, 50-67% ,, ,, ,, Zone IV: ,, ,, above 67% ,, ,, ,,Zone IV: ,, ,, above 67% ,, ,, ,,

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MOISTURE CONTENTMOISTURE CONTENTMAXIMUM PERMISSIBLE (%)MAXIMUM PERMISSIBLE (%)

No.No. ProductsProducts ZoneZoneII

ZoneZoneIIII

ZoneZoneIIIIII

ZoneZoneIVIV

11 Beams& raftersBeams& rafters 1212 1414 1717 2020

22 Doors& windowsDoors& windowsi. less than 50mm i. less than 50mm in thicknessin thicknessii.50mm&aboveii.50mm&above

88

1010

1010

1212

1212

1414

1414

161633 FurnitureFurniture 1010 1212 1414 1515

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KILN SEASONINGKILN SEASONING Kiln drying of lumber is perhaps the most effective and economical

method available Drying rates in a kiln can be carefully controlled and defect losses reduced to a minimum. Length of drying time is also greatly reduced and is predictable so that dry lumber inventories can often be reduced. Where staining is a problem, kiln drying is one n the only reasonable method that can be used unless chemical dips are employed

Kilns are usually divided into two classes-progressive and compartment. In the progressive kiln, timber enters one end and moves progressively

through the kiln much as a car moves through a tunnel Temperature and humidity differentials are maintained throughout the length of the kiln so that the lumber charge is progressively dried as it moves from one end to the other. Progressive kilns may be further subdivided into natural draft kilns in which heated air is allowed to rise through the material by natural convection, and forced draft kilns in which fans are employed to force the air through the wood

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KILN SEASONINGKILN SEASONING Compartment kilns differ from progressive kilns in that the timber is Compartment kilns differ from progressive kilns in that the timber is

loaded into the kiln and remains in place throughout the drying process loaded into the kiln and remains in place throughout the drying process These kilns are usually smaller than progressive kilns, and because of their These kilns are usually smaller than progressive kilns, and because of their construction the temperature and humidity conditions within them can be construction the temperature and humidity conditions within them can be closely controlled .Consequently, they are often used to dry expensive closely controlled .Consequently, they are often used to dry expensive material or woods which are difficult to dry. It may be either forced or material or woods which are difficult to dry. It may be either forced or natural just as with progressive kilns. natural just as with progressive kilns.

Drying conditions cannot be controlled as closely in natural draft Drying conditions cannot be controlled as closely in natural draft compartment kilns, however, as in forced draft kilns, and the rate of drying compartment kilns, however, as in forced draft kilns, and the rate of drying is also slower For these reasons kilns built today are of the forced draft is also slower For these reasons kilns built today are of the forced draft type and many of the old natural draft types have been convertedtype and many of the old natural draft types have been converted

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PILING OF TIMBER IN KILNPILING OF TIMBER IN KILN The mode of arrangement of sawn timber for The mode of arrangement of sawn timber for

air seasoning is equally good for kiln air seasoning is equally good for kiln seasoningseasoning

The crossers should be placed at more frequent The crossers should be placed at more frequent intervals and in good alignment, in order to intervals and in good alignment, in order to avoid greater stresses during dryingavoid greater stresses during drying

The ends of planks should not be left The ends of planks should not be left unsupportedunsupported

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TYPES OF KILNSTYPES OF KILNS Internal fan, reversible circulation, steam Internal fan, reversible circulation, steam

heated kilnheated kiln Indirect heated, thermal circulation, furnace Indirect heated, thermal circulation, furnace

kilnkiln Hor air kilnHor air kiln Electrically heated kilnElectrically heated kiln Special methodsSpecial methods

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SEASONING DEFECTS&THEIR SEASONING DEFECTS&THEIR CONTROLCONTROL

Checks: Rupture of wood along the grain. There are two types: End checks Checks: Rupture of wood along the grain. There are two types: End checks and surface checks. Control: In air seasoning, both kinds of checking can and surface checks. Control: In air seasoning, both kinds of checking can be decreased by creating conditions which will cause evaporation of be decreased by creating conditions which will cause evaporation of moisture at a slow uniform rate. Surface checking can be reduced by moisture at a slow uniform rate. Surface checking can be reduced by cutting down the speed of circulating air and end checking can be cutting down the speed of circulating air and end checking can be minimized by using moisture resistant coatings. In kin seasoning, it can be minimized by using moisture resistant coatings. In kin seasoning, it can be retarded by regulating temperature, humidity and circulating airretarded by regulating temperature, humidity and circulating air

Warping: a kind of deformation or distortion from the true plane in a piece Warping: a kind of deformation or distortion from the true plane in a piece of woodof wood

1.Bowing1.Bowing 2.Crooking or splitting2.Crooking or splitting 3.Cupping3.Cupping 4.Twisting4.Twisting 5.Diamonding5.Diamonding Case hardening: develops in wood on rapid dryingCase hardening: develops in wood on rapid drying Collapse: This is due to abnormal and irregular shrinkage.Collapse: This is due to abnormal and irregular shrinkage.

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SPECIAL METHODS Chemical seasoning (McMillen, 1960) High frequency di-electric heating (McMillen& James, 1961) Resistance heating; emersion in hot liquid metal, boiling in

oily liquids (McMillen,1956) Infra-red radiation; vacuum drying and Vapour drying Solvent seasoning (McMillen,1956) High temperature drying by solar radiation Forced air drying with unheated (Stevens,1965) Heated air (Kimbal and Torgeson, 1959) Note: A few of these methods are of commercial importance;

some are apparently impractical ; others at present are uneconomical

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THANK YOUTHANK YOU