A paper machine (or paper-making machine) is an industrial machine
used in the
Pulp and paper industry
Pulp and paper industry to create paper in large
quantities at high speed. Modern paper-making machines are based on
the principles of the Fourdrinier Machine, which uses a moving woven
mesh to create a continuous paper web by filtering out the fibres held
in a paper stock and producing a continuously moving wet mat of fibre.
This is dried in the machine to produce a strong paper web.
The basic process is an industrialised version of the historical
process of hand paper-making, which could not satisfy the demands of
developing modern society for large quantities of a printing and
writing substrate. The first modern paper machine was invented in
Britain by Henry and Sealy Foudrinier, and patented in 1806.
The same process is used to produce paperboard on a paperboard
1 The process sections
2.1 Fourdrinier machine
2.2 Similar designs
2.3 Related inventions
3 Pulp types and their preparations
4 Stock (pulp) preparation
5.1 Forming section or wet end
5.2 Variations of the Fourdrinier forming section
5.3 Press section
5.4 Dryer section
8 See also
10 External links
The process sections
Paper machines usually have at least four distinct operational
Forming section, commonly called the wet end, is where the slurry of
fibres filters out fluid a continuous fabric loop to form a wet web of
Press section where the wet fibre web passes between large rolls
loaded under high pressure to squeeze out as much water as possible.
Drying section, where the pressed sheet passes partly around, in a
serpentine manner, a series of steam heated drying cylinders. Drying
removes the water content down to a level of about 6%, where it will
remain at typical indoor atmospheric conditions. Infra-red driers are
also used to supplement cylinder drying where required.
Calender section where the dried paper is smoothened under high
loading and pressure. Only one nip (where the sheet is pressed between
two rolls) is necessary in order to hold the sheet, which shrinks
through the drying section and is held in tension between the press
section (or breaker stack if used) and the calender. Extra nips give
more smoothing but at some expense to paper strength.
There can also be a coating section to modify the surface
characteristics with coatings such as china clay.
Before the invention of continuous paper making, paper was made in
individual sheets by stirring a container of pulp slurry and either
pouring it into a fabric sieve called a sheet mould or dipping and
lifting the sheet mould from the vat. While still on the fabric in the
sheet mould, the wet paper is pressed to remove excess water and then
the sheet is lifted off to be hung over a rope or wooden rod to air
Louis-Nicolas Robert of Essonnes, France, was granted a
patent for a continuous paper making machine. At the time Robert
was working for Saint-Léger Didot, with whom he quarreled over the
ownership of the invention. Didot thought that England was a better
place to develop the machine. But during the troubled times of the
French Revolution, he could not go there himself, so he sent his
brother-in-law, John Gamble, an Englishman living in Paris. Through a
chain of acquaintances, Gamble was introduced to the brothers Sealy
and Henry Fourdrinier, stationers of London, who agreed to finance the
project. Gamble was granted British patent 2487 on 20 October 1801.
The Fourdrinier Machine used a specially woven plastic fabric mesh
conveyor belt (known as a wire, as it was once woven from bronze) in
the forming section, where a slurry of fibre (usually wood or other
vegetable fibres) is drained to create a continuous paper web. The
original Fourdrinier forming section used a horizontal drainage area,
referred to as the drainage table.
With the help particularly of Bryan Donkin, a skilled and ingenious
mechanic, an improved version of the Robert original was installed at
Frogmore Mill, Apsley, Hertfordshire, in 1803, followed by another in
1804. A third machine was installed at the Fourdriniers' own mill at
Two Waters. The Fourdriniers also bought a mill at
St Neots intending
to install two machines there and the process and machines continued
Thomas Gilpin is most often credited for creating the first U.S
cylinder type papermaking machine at Brandywine Creek,
1817. This machine was also developed in England, but it was a
cylinder mould machine. The Fourdrinier machine wasn't introduced into
the USA until 1827.
Records show Charles Kinsey of
Paterson, NJ had already patented a
continuous process papermaking machine in 1807. Kinsey’s machine was
built locally by Daniel Sawn and by 1809 the Kinsey machine was
successfully making paper at the Essex Mill in Paterson. Financial
stress and potential opportunities created by the Embargo of 1807
eventually persuaded Kinsey and his backers to change the mill’s
focus from paper to cotton and Kinsey's early papermaking successes
were soon overlooked and forgotten.
Gilpin's 1817 patent was similar to Kinsey's, as was the John Ames
patent of 1822. The Ames patent was challenged by his competitors,
asserting that Kinsey was the original inventor and Ames had been
pilfering other peoples' ideas, their evidence being the employment of
Daniel Sawn to work on his machine.
The method of continuous production demonstrated by the paper machine
influenced the development of continuous rolling of iron and later
steel and other continuous production processes.
Pulp types and their preparations
Main article: Pulp (paper)
The plant fibres used for pulp are composed mostly of cellulose and
hemi-cellulose, which have a tendency to form molecular linkages
between fibres in the presence of water. After the water evaporates
the fibres remain bonded. It is not necessary to add additional
binders for most paper grades, although both wet and dry strength
additives may be added.
Rags of cotton and linen were the major source of pulp for paper
before wood pulp. Today almost all pulp is of wood fibre.
is used in speciality grades, usually in printing paper for such
things as resumes and currency.
Sources of rags often appear as waste from other manufacturing such as
denim fragments or glove cuts. Fibres from clothing come from the
cotton boll. The fibres can range from 3 to 7 cm in length as
they exist in the cotton field. Bleach and other chemicals remove the
colour from the fabric in a process of cooking, usually with steam.
The cloth fragments mechanically abrade into fibres, and the fibres
get shortened to a length appropriate for manufacturing paper with a
cutting process. Rags and water dump into a trough forming a closed
loop. A cylinder with cutting edges, or knives, and a knife bed is
part of the loop. The spinning cylinder pushes the contents of the
trough around repeatedly. As it lowers slowly over a period of hours,
it breaks the rags up into fibres, and cuts the fibres to the desired
length. The cutting process terminates when the mix has passed the
cylinder enough times at the programmed final clearance of the knives
Another source of cotton fibre comes from the cotton ginning process.
The seeds remain, surrounded by short fibres known as linters for
their short length and resemblance to lint. Linters are too short for
successful use in fabric. Linters removed from the cotton seeds are
available as first and second cuts. The first cuts are longer.
The two major classifications of pulp are chemical and mechanical.
Chemical pulps formerly used a sulphite process, but the kraft process
is now predominant. Kraft pulp has superior strength to sulphite and
mechanical pulps. Both chemical pulps and mechanical pulps may be
bleached to a high brightness.
Chemical pulping dissolves the lignin that bonds fibres to one
another, and binds the outer fibrils that compose individual fibres to
the fibre core. Lignin, like most other substances that can separate
fibres from one another, acts as a debonding agent, lowering strength.
Strength also depends on maintaining long cellulose molecule chains.
The kraft process, due to the alkali and sulphur compounds used, tends
to minimize attack on the cellulose and the non-crystalline
hemicellulose, which promotes bonding, while dissolving the lignin.
Acidic pulping processes shorten the cellulose chains.
Kraft pulp makes superior linerboard and excellent printing and
Groundwood, the main ingredient used in newsprint and a principal
component of magazine papers (coated publications), is literally
ground wood produced by a grinder. Therefore, it contains a lot of
lignin, which lowers its strength. The grinding produces very short
fibres that drain slowly.
Thermomechanical pulp (TMP) is a variation of groundwood where fibres
are separated mechanically while at high enough temperatures to soften
Between chemical and mechanical pulps there are semi-chemical pulps
that use a mild chemical treatment followed by refining. Semi-chemical
pulp is often used for corrugating medium.
Bales of recycled paper (normally old corrugated containers) for
unbleached (brown) packaging grades may be simply pulped, screened and
cleaned. Recycling to make white papers is usually done in a deinking
plant, which employs screening, cleaning, washing, bleaching and
Deinked pulp is used in printing and writing papers and in
tissue, napkins and paper towels. It is often blended with virgin
At integrated pulp and paper mills, pulp is usually stored in high
density towers before being pumped to stock preparation. Non
integrated mills use either dry pulp or wet lap (pressed) pulp,
usually received in bales. The pulp bales are slushed in a [re]pulper.
Stock (pulp) preparation
Stock preparation is the area where pulp is usually refined, blended
to the appropriate proportion of hardwood, softwood or recycled fibre,
and diluted to as uniform and constant as possible consistency. The pH
is controlled and various fillers, such as whitening agents, size and
wet strength or dry strength are added if necessary. Additional
fillers such as clay, calcium carbonate and titanium dioxide increase
opacity so printing on reverse side of a sheet will not distract from
content on the obverse side of the sheet.
Fillers also improve
Pulp is pumped through a sequence of tanks that are commonly called
chests, which may be either round or more commonly rectangular.
Historically these were made of special ceramic tile faced reinforced
concrete, but mild and stainless steels are also used. Low consistency
pulp slurries are kept agitated in these chests by propeller like
agitators near the pump suction at the chest bottom.
In the following process, different types of pulp, if used, are
normally treated in separate but similar process lines until combined
at a blend chest:
From high density storage or from slusher/pulper the pulp is pumped to
a low density storage chest (tank). From there it is typically diluted
to about 4% consistency before being pumped to an unrefined stock
chest. From the unrefined stock chest stock is again pumped, with
consistency control, through a refiner. Refining is an operation
whereby the pulp slurry passes between a pair of discs, one of which
is stationary and the other rotating at speeds of typically 1,000 or
1,200 RPM for 50 and 60 Hz AC, respectively. The discs have
raised bars on their faces and pass each other with narrow clearance.
This action unravels the outer layer of the fibres, causing the
fibrils of the fibres to partially detach and bloom outward,
increasing the surface area to promoting bonding. Refining thus
increases tensile strength. For example, tissue paper is relatively
unrefined whereas packaging paper is more highly refined. Refined
stock from the refiner then goes to a refined stock chest, or blend
chest, if used as such.
Hardwood fibres are typically 1 mm long and smaller in diameter
than the 4 mm length typical of softwood fibres. Refining can
cause the softwood fibre tube to collapse resulting in undesirable
properties in the sheet.
From the refined stock, or blend chest, stock is again consistency
controlled as it is being pumped to a machine chest. It may be refined
or additives may be added en route to the machine chest.
The machine chest is basically a consistency levelling chest having
about 15 minutes retention. This is enough retention time to allow any
variations in consistency entering the chest to be levelled out by the
action of the basis weight valve receiving feedback from the on line
basis weight measuring scanner. (Note: Many paper machines mistakenly
control consistency coming out of the machine chest, interfering with
basis weight control.)
There are four main sections on this paper machine. The forming
section makes the pulp into the basis of for sheets along the wire.
The press section, which removes much of the remaining water via a
system of nips formed by rolls pressing against each other aided by
press felts that support the sheet and absorb the pressed water. The
dryer section of the paper machine, as its name suggests, dries the
paper by way of a series of internally steam-heated cylinders that
evaporate the moisture. Calenders are used to make the paper surface
extra smooth and glossy. In practice calender rolls are normally
placed vertically in a stack.
Diagram showing the sections of the Fourdrinier machine
Forming section or wet end
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A worker inspecting wet, bleached wood pulp on an old-fashioned
Hollander pulper or "beater".
From the machine chest stock is pumped to a head tank, commonly called
a "head tank" or stuff box, whose purpose is to maintain a constant
head (pressure) on the fiber slurry or stock as it feeds the basis
weight valve. The stuff box also provides a means allowing air bubbles
to escape. The consistency of the pulp slurry at the stuff box is in
the 3% range. Flow from the stuff box is by gravity and is controlled
by the basis weight valve on its way to the fan pump suction where it
injected into main flow of water to the fan pump. The main flow of
water pumped by the fan pump is from a whitewater chest or tank that
collects all the water drained from the forming section of the paper
machine. Before the fiber stream from the stuff box is introduced, the
whitewater is very low in fiber content. The whitewater is constantly
recirculated by the fan pump through the headbox and recollected from
the wire pit and various other tanks and chests that receive drainage
from the forming wire and vacuum assisted drainage from suction boxes
and wet fiber web handling rolls. On the way to the head box the pulp
slurry may pass through centrifugal cleaners, which remove heavy
contaminants like sand, and screens, which break up fibre clumps and
remove over-sized debris. The fan pump ultimately feeds the headbox,
whether or not any centrifugal cleaners or screens are present.
The purpose of the headbox is create turbulence to keep the fibers
from clumping together and to uniformly distribute the slurry across
the width of the wire. Wood fibers have a tendency to attract one
another, forming clumps, the effect being called flocculation.
Flocculation is lessened by lowering consistency and or by agitating
the slurry; however, de-flocculation becomes very difficult at much
above 0.5% consistency. Minimizing the degree of flocculation when
forming is important to physical properties of paper.
The consistency in the headbox is typically under 0.4% for most paper
grades, with longer fibres requiring lower consistency than short
fibres. Higher consistency causes more fibres to be oriented in the z
direction, while lower consistency promotes fibre orientation in the
x-y direction. Higher consistency promotes higher calliper (thickness)
and stiffness, lower consistency promotes higher tensile and some
other strength properties and also improves formation (uniformity).
Many sheet properties continue to improve down to below 0.1%
consistency; however, this is an impractical amount of water to
handle. (Most paper machine run a higher headbox consistency than
optimum because they have been sped up over time without replacing the
fan pump and headbox. There is also an economic trade off with high
pumping costs for lower consistency).
The stock slurry, often called white water at this point, exits the
head box through a rectangular opening of adjustable height called the
slice, the white water stream being called the jet and it is
pressurized on high speed machines so as to land gently on the moving
fabric loop or wire at a speed typically between plus or minus 3% of
the wire speed, called rush and drag respectively. Excessive rush or
drag causes more orientation of fibres in the machine direction and
gives differing physical properties in machine and cross directions;
however, this phenomenon is not completely avoidable on Fourdrinier
On lower speed machines at 700 feet per minute, gravity and the height
of the stock in the headbox creates sufficient pressure to form the
jet through the opening of the slice. The height of the stock is the
head, which gives the headbox its name. The speed of the jet compared
to the speed of the wire is known as the jet-to-wire ratio. When the
jet-to-wire ratio is less than unity, the fibres in the stock become
drawn out in the machine direction. On slower machines where
sufficient liquid remains in the stock before draining out, the wire
can be driven back and forth with a process known as shake. This
provides some measure of randomizing the direction of the fibres and
gives the sheet more uniform strength in both the machine and
cross-machine directions. On fast machines, the stock does not remain
on the wire in liquid form long enough and the long fibres line up
with the machine. When the jet-to-wire ratio exceeds unity, the fibers
tend to pile up in lumps. The resulting variation in paper density
provides the antique or parchment paper look.
Two large rolls typically form the ends of the drainage section, which
is called the drainage table. The breast roll is located under the
flow box, the jet being aimed to land on it at about the top centre.
At the other end of the drainage table is the suction (couch) roll.
The couch roll is a hollow shell, drilled with many thousands of
precisely spaced holes of about 4 to 5 mm diameter. The hollow
shell roll rotates over a stationary suction box, normally placed at
the top centre or rotated just down machine. Vacuum is pulled on the
suction box, which draws water from the web into the suction box. From
the suction roll the sheet feeds into the press section.
Down machine from the suction roll, and at a lower elevation, is the
wire turning roll. This roll is driven and pulls the wire around the
loop. The wire turning roll has a considerable angle of wrap in order
to grip the wire.
Supporting the wire in the drainage table area are a number of
drainage elements. In addition to supporting the wire and promoting
drainage, the elements de-flocculate the sheet. On low speed machines
these table elements are primarily table rolls. As speed increases the
suction developed in the nip of a table roll increases and at high
enough speed the wire snaps back after leaving the vacuum area and
causes stock to jump off the wire, disrupting the formation. To
prevent this drainage foils are used. The foils are typically sloped
between zero and two or three degrees and give a more gentle action.
Where rolls and foils are used, rolls are used near the headbox and
foils further down machine.
Approaching the dry line on the table are located low vacuum boxes
that are drained by a barometric leg under gravity pressure. After the
dry line are the suction boxes with applied vacuum. Suction boxes
extend up to the couch roll. At the couch the sheet consistency should
be about 25%.
Variations of the Fourdrinier forming section
The forming section type is usually based on the grade of paper or
paperboard being produced; however, many older machines use a less
than optimum design. Older machines can be upgraded to include more
appropriate forming sections.
A second headbox may be added to a conventional fourdrinier to put a
different fibre blend on top of a base layer. A secondary headbox is
normally located at a point where the base sheet is completely
drained. This is not considered a separate ply because the water
action does a good job of intermixing the fibers of the top and bottom
layer. Secondary headboxes are common on linerboard.
A modification to the basic fourdrinier table by adding a second wire
on top of the drainage table is known as a top wire former. The bottom
and top wires converge and some drainage is up through the top wire. A
top wire improves formation and also gives more drainage, which is
useful for machines that have been sped up.
The Twin Wire Machine or Gap former uses two vertical wires in the
forming section, thereby increasing the de-watering rate of the fibre
slurry while also giving uniform two sidedness.
There are also machines with entire Fourdrinier sections mounted above
a traditional Fourdrinier. This allows making multi-layer paper with
special characteristics. These are called top Fourdriniers and they
make multi-ply paper or paperboard. Commonly this is used for making a
top layer of bleached fibre to go over an unbleached layer.
Another type forming section is the cylinder mould machine using a
mesh-covered rotating cylinder partially immersed in a tank of fibre
slurry in the wet end to form a paper web, giving a more random
distribution of the cellulose fibres. Cylinder machines can form a
sheet at higher consistency, which gives a more three dimensional
fibre orientation than lower consistencies, resulting in higher
calliper (thickness) and more stiffness in the machine direction (MD).
High MD stiffness is useful in food packaging like cereal boxes and
other boxes like dry laundry detergent.
Tissue machines typically form the paper web between a wire and a
special fabric (felt) as they wrap around a forming roll. The web is
pressed from the felt directly onto a large diameter dryer called a
yankee. The paper sticks to the yankee dryer and is peeled off with a
scraping blade called a doctor. Tissue machines operate at speeds of
up to 2000 m/min.
Granite press roll at a granite quarry site
The second section of the paper machine is the press section, which
removes much of the remaining water via a system of nips formed by
rolls pressing against each other aided by press felts that support
the sheet and absorb the pressed water. The paper web consistency
leaving the press section can be above 40%.
Pressing is the most efficient method of de-watering the sheet as only
mechanical action is required. Press felts historically were made from
wool. However, today they are nearly 100% synthetic. They are made up
of a polyamide woven fabric with thick batt applied in a specific
design to maximise water absorption.
Presses can be single or double felted. A single felted press has a
felt on one side and a smooth roll on the other. A double felted press
has both sides of the sheet in contact with a press felt. Single
felted nips are useful when mated against a smooth roll (usually in
the top position), which adds a two-sidedness—making the top side
appear smoother than the bottom. Double felted nips impart roughness
on both sides of the sheet. Double felted presses are desirable for
the first press section of heavy paperboard.
Simple press rolls can be rolls with grooved or blind drilled surface.
More advanced press rolls are suction rolls. These are rolls with
perforated shell and cover. The shell made of metal material such as
bronze stainless steel is covered with rubber or a synthetic material.
Both shell and cover are drilled throughout the surface. A stationary
suction box is fitted in the core of the suction roll to support the
shell being pressed. End face mechanical seals are used for the
interface between the inside surface of the shell and the suction box.
For the smooth rolls, they are typically made of granite rolls.
The granite rolls can be up to 30-foot (9.1 m) long and 6 feet
(1.8 m) in diameter.
Conventional roll presses are configured with one of the press rolls
is in a fixed position, with a mating roll being loaded against this
fixed roll. The felts run through the nips of the press rolls and
continues around a felt run, normally consisting of several felt
rolls. During the dwell time in the nip, the moisture from the sheet
is transferred to the press felt. When the press felt exits the nip
and continues around, a vacuum box known as an Uhle Box applies vacuum
(normally -60 kPa) to the press felt to remove the moisture so that
when the felt returns to the nip on the next cycle, it does not add
moisture to the sheet.
Some grades of paper use suction pick up rolls that use vacuum to
transfer the sheet from the couch to a lead in felt on the first press
or between press sections. Pickup roll presses normally have a vacuum
box that has two vacuum zones (low vacuum and high vacuum). These
rolls have a large number of drilled holes in the cover to allow the
vacuum to pass from the stationary vacuum box through the rotating
roll covering. The low vacuum zone picks up the sheet and transfers,
while the high vacuum zone attempts to remove moisture. Unfortunately,
at high enough speed centrifugal force flings out vacuumed water,
making this less effective for dewatering. Pickup presses also have
standard felt runs with Uhle boxes. However, pickup press design is
quite different, as air movement is important for the pickup and
dewatering facets of its role.
Crown Controlled Rolls (also known as CC Rolls) are usually the mating
roll in a press arrangement. They have hydraulic cylinders in the
press rolls that ensure that the roll does not bow. The cylinders
connect to a shoe or multiple shoes to keep the crown on the roll
flat, to counteract the natural "bend" in the roll shape due to
applying load to the edges.
Extended Nip Presses (or ENP) are a relatively modern alternative to
conventional roll presses. The top roll is usually a standard roll,
while the bottom roll is actually a large CC roll with an extended
shoe curved to the shape of the top roll, surrounded by a rotating
rubber belt rather than a standard roll cover. The goal of the ENP is
to extend the dwell time of the sheet between the two rolls thereby
maximising the de-watering. Compared to a standard roll press that
achieves up to 35% solids after pressing, an ENP brings this up to 45%
and higher—delivering significant steam savings or speed increases.
ENPs densify the sheet, thus increasing tensile strength and some
other physical properties.
Dryer section of an older Fourdrinier-style paper-making machine.
These narrow, small diameter dryers are not enclosed by a hood, dating
the photo to before the 1970s.
The dryer section of the paper machine, as its name suggests, dries
the paper by way of a series of internally steam-heated cylinders that
evaporate the moisture.
Steam pressures may range up to 160 psig.
Steam enters the end of the dryer head (cylinder cap) through a steam
joint and condensate exits through a siphon that goes from the
internal shell to a centre pipe. From the centre pipe the condensate
exits through a joint on the dryer head. Wide machines require
multiple siphons. In fast machines centrifugal force holds the
condensate layer still against the shell and turbulence generating
bars are typically used to agitate the condensate layer and improve
The sheet is usually held against the dryers by long felt loops on the
top and bottom of each dryer section. The felts greatly improve heat
transfer. Dryer felts are made of coarse thread and have a very open
weave that is almost see through, It is common to have the first
bottom dryer section unfelted to dump broke on the basement floor
during sheet breaks or when threading the sheet.
Paper dryers are typically arranged in groups called sections so that
they can be run at a progressively slightly slower speed to compensate
for sheet shrinkage as the paper dries. The gaps between sections are
The drying sections are usually enclosed to conserve heat. Heated air
is usually supplied to the pockets where the sheet breaks contact with
the driers. This increases the rate of drying. The pocket ventilating
tubes have slots along their entire length that face into the pocket.
The dryer hoods are usually exhausted with a series of roof mounted
hood exhausts fans down the dryer section.
Additional sizing agents, including resins, glue, or starch, can be
added to the web to alter its characteristics.
Sizing improves the
paper's water resistance, decreases its ability to fuzz, reduces
abrasiveness, and improves its printing properties and surface bond
strength. These may be applied at the wet (internal sizing) or on the
dry end (surface sizing), or both. At the dry end sizing is usually
applied with a size press. The size press may be a roll applicator
(flooded nip) or Nozzle applicator . It is usually placed before the
last dryer section. Some paper machines also make use of a 'coater' to
apply a coating of fillers such as calcium carbonate or china clay
usually suspended in a binder of cooked starch and styrene-butadiene
latex. Coating produces a very smooth, bright surface with the highest
Paper leaving the machine is rolled onto a reel for further
Main article: Calender
A calender consists of two or more rolls, where pressure is applied to
the passing paper. Calenders are used to make the paper surface extra
smooth and glossy. It also gives it a more uniform thickness. The
pressure applied to the web by the rollers determines the finish of
After calendering, the web has a moisture content of about 6%
(depending on the furnish). It is wound onto a roll called a tambour
or reel, and stored for final cutting and shipping. The roll hardness
should be checked, obtained and adjusted accordingly to insure that
the roll hardness is within the acceptable range for the product.
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broke: waste paper, either made during a sheet break or trimmings. It
is gathered up and put in a repulper for recycling back into the
consistency: the percent dry fibre in a pulp slurry.
couch: French meaning to lie down. Following the couch roll the sheet
is lifted off the wire and transferred into the press section.
dandy roll: a mesh covered hollow roll that rides on top of the
Fourdrinier. It breaks up fibre clumps to improve the sheet formation
and can also be used to make an imprint, as with laid paper. See also
fan pump: the large pump that circulates white water from the white
water chest to the headbox. The flow may go through screens and
cleaners, if used. On large paper machines fan pumps may be rated in
tens of thousands of gallons per minute.
felt: a loop of fabric or synthetic material that goes between press
rolls and serves as a place to receive the pressed out water. Felts
also support the wet paper web and guide it through the press section.
Felts are also used in the dryer section to keep the sheet in close
contact with the dryers and increase heat transfer.
filler: a finely divided substance added to paper in the forming
Fillers improve print quality, brightness and opacity. The
most common fillers are clay and calcium carbonate. Titanium dioxide
is a filler but also improves brightness and opacity. Use of calcium
carbonate filler is the process called alkaline sizing and uses
different chemistry than acid sizing. Alkaline sized paper has
superior ageing properties.
formation: the degree of uniformity of fiber distribution in finished
paper, which is easily seen by holding paper up to the light.
headbox: the pressure chamber where turbulence is applied to break up
fibre clumps in the slurry. The main job of the headbox is to
distribute the fiber slurry uniformly across the wire.
nip: the contact area where two opposing rolls meet, such as in a
press or calender
pH: the degree of acidity or alkalinity of a solution. Alkaline paper
has a very long life. Acid paper deteriorates over time, which caused
libraries to either take conservation measures or replace many older
size: a chemical (formerly rosin derived but now a different chemical)
or starch, applied to paper to retard the rate of water penetration.
Sizing prevents bleeding of ink during printing, improving the
sharpness of printing.
slice: the adjustable rectangular orifice, usually at the bottom of
the headbox, through which the whitewater jet discharges onto the
wire. The slice opening and water pressure together determine the
amount and velocity of whitewater flow through the slice. The slice
usually has some form of adjustment mechanism to even out the paper
weight profile across the machine (CD profile), although a newer
methods is to inject water into the whitewater across the headbox
slice area, thereby using localized consistency to control CD weight
stock: a pulp slurry that has been processed in the stock preparation
area with necessary additives, refining and pH adjustment and ready
for making paper
web: the continuous flow of un-dried fibre from the couch roll down
the paper machine
white water: filtrate from the drainage table. The white water from
the table is usually stored in a white water chest from which it is
pumped by the fan pump to the headbox.
wire: the woven mesh fabric loop that is used for draining the pulp
slurry from the headbox. Until the 1970s bronze wires were used but
now they are woven from coarse mono-filament synthetics similar to
fishing line but very stiff.
Stainless steels are used extensively in the Pulp and Paper
industry for two primary reasons, to avoid iron contamination of
the product and their corrosion resistance to the various chemicals
used in the paper making process. Type 316 stainless steel is a common
material used in paper machines.
Wikimedia Commons has media related to Pulp and paper mill machines.
Cutting stock problem
^ Larousse, Éditions. "Encyclopédie Larousse en ligne – les
frères Robert". www.larousse.fr.
^ Hills, Richard, "
Papermaking in Britain 1488–1988", Athlone Press,
^ a b Bidwell, John (2013). American
Paper Mills, 1690–1832: A
Directory of the
Paper Trade with Notes... Dartmouth College Press.
pp. 154–155. ISBN 978-1-58465-964-8.
^ "Historic American Engineering Record Essex Mill NJ-6" (PDF).
National American Engineering Record. National Park Service Department
of the Interior Washington D.C. 20240: 3. The Essex Mill is historic
as the first new mill site leased by the Society for Establishing
Useful Manufacturers, and as the scene of some of the earliest
experiments with continuous paper manufacture in the United
^ Misa, Thomas J. (1995). A Nation of Steel: The Making of Modern
America 1965–1925. Baltimore and London: Johns Hopkins University
Press. p. 243. ISBN 978-0-8018-6502-2.
^ Technical Association for the Pulp and
Paper Industry; Various
(2005). Wet End Operations Short Course Notes. TAPPI Press.
^ Results from dynamic material balance sensitivity analysis: The
timing for the basis weight control loop is much slower than that of a
consistency loop. Also, varying pressure of the consistency control
dilution water will introduce swings in consistency. This can be and
should be verified for any particular system using dynamic material
balance software such as CADSIM Plus. Run model by creating a sharp
consistency change ~ 1/2% and observe system stability. 
^ Technical Association for the Pulp and
Paper Industry; Various
Paper Machine Operations Short Course Notes. TAPPI
^ Technical Association for the Pulp and
Paper Industry; Various.
Paper Machine Wet End, The. TAPPI Press.
^ Technical Association for the Pulp and
Paper Industry; Various
(2005). Wet End Operations Short Course Notes. TAPPI Press.
^ Technology choice in a global industry : the case of the
twin-wire in Canada, Ofori-Amoah, Benjamin, 1989 Thesis (Ph.D.) –
Simon Fraser University, 1990, http://ir.lib.sfu.ca/handle/1892/6373
Paper Machine Clothing: Key to the
Paper Making Process Sabit
Adanur, Asten, CRC Press, 1997, p. 120–136,
^ a b Technical Association for the Pulp and
Paper Industry; Various.
Paper Machine Dry End, The. TAPPI Press.
^ "Papermaking: Papermachine – Pressing" (PDF). UBC Fibre Lab: 2, 3,
12, 13. Retrieved 25 August 2014.
^ Richter, Dorothy A. (1987). "Barre granite quarries, Barre,
Vermont". Geological Society of America Centennial Field
Guide—Northeastern Section. access-date= requires url=
^ A. H. Tuthill (2002). "Stainless Steels and Specialty Alloys for
Modern Pulp and
Paper Mills". Nickel Institute.
Patent for Louis-Nicolas Robert
Technical Association of the Pulp and
Paper Science and Technology at Georgia Tech
Fourdrinier machine description from
Paper Manufacturing in the United
Henry Fourdrinier from Dictionary of National Biography,
British Association of
Video: Frogmore Mill in Apsley; Victorian era Fourdrinier machine
Quality Control System QCS
Units of paper quantity
Surface chemistry of paper
Manufacture and process
Bleaching of wood pulp
Environmental impact of paper
In the United States
List of paper mills