BLACK CLAWSON LTD.
Black Clawson Turbo Former.
Black Clawson has further developed the Bristol Former and introduced it to a short wire loop to
enhance fibre distribution and water drainage. The result has produced the Turbo Former.
This machine is able to operate with improved fibre distribution on a moving wire with faster
machine speeds to allow the operator to maximise formation and drainage.
Overview and General Description.
Octopus Header
The Black Clawson Octopus Header was designed to control the cross machine basis weight
profile by providing each lateral of the Octopus with an even distribution stock at a constant
velocity. This design allows for the addition of a water dilution system (manual or automatic)
that can be used to influence the cross machine basis weight profile of the final sheet. Flexible
distribution tubes connect the Octopus to the Turbo Former that permit the Former to be raised
for cleaning or lowered for operation.
Micro-turbulence
It has always been understood that creating micro-turbulence is the key to maintaining
deflocculated fibres. Therefore the new design Turbo Former has incorporated step diffusers that
generate micro-turbulence. This turbulence generator then makes a gradual change of cross
section to a full cross machine rectangular shape to create the optimum intensity of microturbulence
prior to the stock entering the triangular mixing (explosion) chamber.
The Mixing Chamber
The mixing (explosion) chamber has been developed through pilot plant studies on the effect of
shear forces on fibrous suspensions. The relationship between the size of the mixing chamber
and its distribution tubes relative to the flows through the head box have a large influence on the
distribution of fibres.
Bottom Lip
The bottom lip forms the base of the mixing chamber and provides the stability to provide a
controlled throat gap whilst also making light contact with the moving wire as it rotates with the
cylinder mould. This bottom lip is a wear item that is manufactured from high density
polyethylene and designed to be removed easily from the machine during maintenance shuts.
Top Slice Lip
The top slice lip is a fabricated beam that has been accurately machined and polished to a very
high standard and forms part of the triangle that is described as the mixing chamber. The
dimensional stability of this curved lid is of paramount importance in resisting the hydraulic
pressures of the Turbo Former. The gap between the top lip and the bottom lip is called the
Throat gap.
Throat Gap
The throat gap is adjustable from 5mm to 25mm and provides a major tool for the papermaker.
This gap controls the velocity of the stock passing through the throat gap and onto the wire and
will greatly influence the final sheet properties. The resultant throat gap /efflux ratio can be
adjusted whilst the machine is running by using the indicator hand wheel at the front side of the
machine.
Slice Gap
The slice gap provides a major tool for the papermaker and is normally set prior to operation but
can be altered whilst the machine is running. The range gap during operation varies typically
from 0.5mm to 1.5mm (depending on GSM and machine speed). The resultant size of this
opening will affect the drainage rate and back pressure of the system.
The slice gap is measured under the top slice lip at the point that the formed web exits the lip.
The gap produced between the machined and polished top slice lip and the cylinder mould will
be accurate across the full width of the machine. Profiling of the slice gap may be necessary
depending on the quality of the cylinder moulds being used. The opening or closing of this gap
is undertaken by using the slice adjustment at the front and rear side of the machine.
The Formed Web
The formation of the web on the short making wire loop takes place over the rotating cylinder
mould and under the Top Lip and is complete upon exiting the slice gap.
The properties of the web will have been influenced by the Throat Gap, Slice Gap, Furnish,
Cylinder Mould Air Extraction, Wire Mesh, etc.
Further dewatering can take place over the vacuum assisted multi compartment dewatering box.
By controlling the amount of vacuum in this box the dry line can be established.
Some additional dewatering will occur with the action of ply bonding during the transfer of the
web from the making wire.
Benefits of the TURBO FORMER
a) Improved sheet formation.
b) Reduction in top liner usage.
c) Improved sheet smoothness.
d) Excellent basis weight profile.
e) Extremely flexible in operation – will accommodate a wide range of operating parameters.
f) Quick grade changes.
g) Operator friendly – minimum training period.
h) Increase in production potential.
i) Repeatability.
Applications.
• High quality folding boxboard (coated and uncoated with waste paper or all chemical
mechanical pulp).
• Double lined folding boxboard (food packaging liquid containers).
• Solid bleach multi-ply F.B.B (food packaging).
• Test liner.
• Fluting Medium.
• Plasterboard/lath board
• Chipboard (heavy packaging).
• Tube board.
• Filter boards/papers.
Typical Conditions:
1. Furnish: Chemical pulp, Mechanical pulp, Waste paper or combinations of furnish.
2. Basis Weight: 30 gsm to 100 gsm.
3. Speed: 50 metres/minute to 350 metres/minute.
4. Consistency – 0.3% - 1.3%
5. Freeness range 20º S.R to 70º S.R.
Turbo Former Controls are:
a) Lift and load control (lowers Turbo Former for operation or lifts for shutdown or
cleaning).
b) Total flow of thin stock through Turbo Former.
c) Consistency of stock in Turbo Former.
d) Speed of machine.
e) Throat gap adjustment for rush/drag control that can be changed whilst the machine is in
operation.
f) Slice gap adjustment for controlling dewatering through the Turbo Former (can be done
whilst the machine is in operation).
g) Amount of vacuum (Cubic metres/hour) passing through the dewatering boxes.
h) The amount of loading used to transfer and ply bond the web.
