Technology News
N
ovember
2014
71
wire products during production.
For quality assurance of composite
pipes, manufacturers are using X-ray
technology, such as the X-Ray 6000
Pro. Depending on the requirements,
the device is installed directly after the
extruder (hot measurement) or at the
end of the line (final quality control).
The four-point online measurement
provides values for the wall thickness,
eccentricity, inner and outer diameter
and ovality immediately. These are
calculated and visualised in real time
with the Ecocontrol 6000 processor
system. The system measures up to
three different material layers. For
composite pipe these are the outer
diameter and wall thickness of the PE
inner pipe, the aluminium layer and the
PE outer pipe. With the Ecocontrol 6000
these measuring values, as well as the
eccentricity, are displayed numerically
and graphically as pipe cross sections
at eight points, and allow the operator to
centre the extrusion tool. The use of the
X-ray measuring system is especially
effective in combination with automatic
line speed or extruder rpm control. By
controlling the minimal value, only the
required amount of plastic material is
used, thus reducing costs. With the
use of the X-ray measuring system,
typically a reduction of 80µm of a 2mm
wall can be achieved. This means 4 per
cent of the material can be saved. This
represents a cost reduction of about
€100,000/per year (extruder output:
600kg/h, operating time: 6,000h/per
annual, material costs: €1.5/kg).
In extrusion lines in which the
measurement of only one material
layer is required, manufacturers are
using the X-ray measuring system
X-Ray 6000. A 7" TFT monitor, including
touchscreen operation, is directly
integrated in the X-Ray 6000 gauge
head, where all measuring values are
displayed graphically and numerically.
In combination with the processor
system Ecocontrol 6000, 1000 or 600,
the automatic control of the line speed
or extruder rpm is also possible with this
system.
The technology of the X-Ray 6000
Pro is based on an imaging method.
Two X-ray tubes, aligned at right angles
to each other, illuminate the pipe
transverse to its axis. A line sensor is
positioned opposite each of the X-ray
tubes and is equipped with a scintillator
that transforms received X-rays into
light. This creates an image of the pipe
within milliseconds. In this way, accurate
values are recorded continuously online
during the running production process.
The analysis is carried out directly from
the X-ray image and provides accurate
measuring values. A coupling medium
is not required, as it is for ultrasound
techniques. In addition, the technology
is not dependent on the temperature of
the measuring head.
The fundamental principle of the
X-ray measuring technique is the
different attenuation of materials based
on the periodic table of the elements.
The attenuation (µ) of the X-rays is
proportional to the atomic number to
the power of 3 (µ~Z3). The ethylene
monomer (PE) is made out of two
carbon and four hydrogen atoms. This
corresponds to a very small attenuation.
The metal aluminium has 13 protons
in its nucleus and, as a result, has
a stronger attenuation than PE. The
recording of materials with different
attenuations leads to a visible contrast of
each layer and provides measurements
of the pipe dimensions with greater than
micrometre precision.
For the production of composite
pipes, a three-axis measurement can be
an important tool for quality control. The
measurement in three planes allows for
a six-point wall thickness measurement
and, in combination with a high
measuring rate, the detection of defects
such as blisters between the aluminium
and the inside of the pipe, as they could
arise from a missing adhesive agent.
Blisters reduce the product quality and
eventually lead to scrapping of the pipe.
Composite pipes are typically produced
at 30m/min. At this speed, which
is 0.5m/sec, the Triax X-ray device
measures the pipe at up to 100Hz every
5mm. The smallest blisters and defects
in the pipe are reliably detected. A time-
intensive and cost-consuming ball test,
where a ball is shot through the pipe in
order to detect possible irregularities,
is unnecessary. Besides the wall
thickness, the outer and inner diameter
as well as the eccentricity of up to three
wall thicknesses, the system measures
the ovality of the pipe. The analysis and
controlling of the measuring values is
done in the same way as with the X-Ray
6000 Pro.
The available X-ray technologies
cover product diameters of 0.7mm
to 650mm. The X-ray measuring
system X-Ray 6000 Pro is used in the
production of large composite pipes of
63mm to 110mm. The X-Ray 6000, for
the measuring of one material layer, is
suitable for composite pipes of 14mm
to 63mm. The Triax X-ray is used for
products of 6mm to 65mm.
With the worldwide increasing
production of multi-layer composite
pipes, the quality requirements for the
products are also increasing.
Online quality control of composite
pipes by means of X-ray technology is
becoming more and more important.
With the use of the X-Ray 6000 Pro
directly after the extruder, the product
parameters of all three material layers
are controlled.
Sikora AG
– Germany
Email:
Website:
The different attenuation of the materials
leads to a visible contrast in the X-ray image
The measuring values of the X-ray system
are displayed at the processor system
