TPT-January-2015

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Technology News
48 January 2015
Producing and testing stainless
steel tube to meet rising demands
MAGNETIC Analysis Corp (MAC)
Echomac® ultrasonic inspection
systems are being used by a number
of tube manufacturers who supply steel
tube for heat exchanger applications. A
recent installation at Ratnamani Metals
& Tubes Ltd, a steel tube producer in
India, is testing welded stainless steel
heat exchanger tube to meet industry
standards.
The system incorporates an Echomac
ultrasonic instrument with an ultrasonic
rotary containing eight transducers – two
for detecting longitudinal defects, two for
transverse, three for wall thickness and
OD/ID measurement, and one for water
temperature compensation to enable
dimensional measurement. This is the
second system of this type that MAC
has supplied to the company. Both are
operating very satisfactorily, according
to the company.
MAC has also supplied several
ultrasonic test systems to Schoeller Werk
in Germany, to inspect heat exchanger
tubing made of stainless steel and
titanium alloys. In addition to detecting
defects, the company uses these test
systems to provide quick feedback to the
operators on any changes taking place
in the welding process. One system
incorporates seven ultrasonic channels,
while the other includes 14 channels.
MAC also supplied a complete inlet table
and outlet conveyor.
Eddy current test systems are also
generally required to inspect any tubing
that is to be used for fluid transmission.
When using eddy current technology,
care must be taken when testing 300
series welded tube. Generally, the 300
series is close to being non-magnetic,
while the 400 series is much closer to
being magnetic. However, where 300
series tube is being welded, the weld
can become ‘delta ferritic’, which creates
permeability noise that will interfere
with an eddy current test. This problem
can be solved by ‘saturating’ the tube
by means of a direct current coil, which
MAC can supply. When this is done, the
permeability becomes relatively uniform
and the noise is minimised. It is also
possible to avoid the permeability noise
by testing the product after it has been
annealed.
Magnetic Analysis Corp – USA
Email:
Website:
Echomac ultrasonic
inspection system